Compounds and electrolytic compositions for use in energy storage devices

Abstract

This invention relates to the use of a class of redox-active, nitrogen-containing compounds, and electrolytic compositions thereof, comprising at least a redox-active molecular core and at least one side chain, for use in energy storage devices, particularly redox flow batteries. The invention also relates to methods of making a redox flow battery comprising the compounds and / or compositions disclosed herein.

Description

[0001]SP3159 - 1 - COMPOUNDS AND ELECTROLYTIC COMPOSITIONS FOR USE IN ENERGY STORAGE DEVICES Field of the Invention This invention relates to the use of redox-active, nitrogen-containing compounds, and electrolytic compositions thereof, for use in energy storage devices, 5 particularly redox flow batteries. Background of the Invention Large-scale energy storage devices are essential elements to overcome electrical grid power supply imbalances. This is particularly the case in respect of 10 the transition to renewable energy sources, such as wind and solar, which may not be available for constant power generation and as such require energy storage for use in maintaining steady, uninterrupted power supply. Batteries are a common technology for energy 15 storage, and may be engineered to store different amounts of energy, as per the technological requirements for a particular application. Important parameters relating to battery engineering include ease and cost of manufacture, total energy storage capacity (kWh) and power production 20 (kW). The ease and cost of manufacture substantially relate to the materials used, their availability and toxicity / corrosivity. Redox flow batteries (RFBs) are one form of battery which offer the ability to scale power production and 25 total energy storage capacity independently. Because power and energy can be scaled separately, as the energy capacity of RFBs is increased, the normalised cost per unit energy ($ / kWh) decreases. This renders RFBs good candidates for long duration and large-scale energy 30 storage with advantages over other technologies, such as lithium-ion batteries for which the ability to alter the power and energy capacity ratio is severely limited. RFBs comprise at least two liquid electrolyte solutions, each of which contains a redox-active compound, 5 which together make up an electrochemical redox couple, in which chemical energy is stored. The chemical energy is converted into electrical energy in a closed external circuit when the redox couple is allowed to undergo a redox reaction. An ion-selective membrane separating the 10 two electrolyte solutions allows selective passage of ions, completing the electrical circuit. The two electrolyte solutions comprise a negative charge storage electrolyte, or anolyte, and a positive charge storage electrolyte, or catholyte. 15 For RFBs the total energy storage capacity (kWh) relates to the product of the redox potential and concentration of the redox-active compounds in the anolyte and catholyte. Inorganic materials have typically been used for RFB 20 redox couples. Organic materials offer advantages over inorganic materials in that they may be cheaper and their pertinent properties, including redox potential and solubility, may be more easily tailored using organic synthetic techniques. 25 Anthraquinones, benzoquinones, and phenazines are exemplary families of redox-active organic molecules which have been demonstrated for use in RFBs for anolyte compositions. However, such redox-active cores are limited by how their redox potentials may be tuned to satisfy 30 application requirements. Their relatively large, flat aromatic cores also limit solubility, especially in aqueous solvent, which in turn substantially limits the upper energy storage capacity of RFBs comprised thereof. Additionally, the limited global supply of anthraquinones, benzoquinones, and phenazines limits their real-world applicability to meet global energy supply demands. There exists a current need to find new organic materials suitable for use as redox-active compounds for 5 energy storage devices and particularly for RFBs. Summary of the Invention The present invention provides the use of a compound as a redox-active component in a redox flow battery, wherein the compound has the structural Formula I, II, or 10 III, or a salt thereof: wherein and R12are as defined herein. The present invention also provides the use of a compound as a redox-active component in a redox flow 15 battery, wherein the compound has the structural Formula II, III, or IV, or a salt thereof: wherein and R12are as defined herein. The present invention also provides an electrolytic 20 composition for use as an anolyte in a redox flow battery comprising at least a compound as defined herein. The present invention also provides a redox flow battery comprising an electrolytic composition as defined herein. The present invention also provides a method for making a redox flow battery comprising an electrolytic composition as defined herein. Within the scope of this application, it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and / or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and / or features of any described embodiment can be combined with other embodiments in any way and / or combination, unless such features are incompatible. Brief Description of the Drawings Figure 1 illustrates cyclic voltammogram data performed on the blank electrolyte solution, HClaq (1 M) at a scan rate of 20 mV / s against a Ag / AgCl reference electrode; Figure 2 illustrates cyclic voltammogram data performed on the blank electrolyte solution, KOHaq (1 M), at a scan rate of 20 mV / s against a Hg / HgO reference electrode; Figure 3 illustrates cyclic voltammogram data performed on the blank electrolyte solution, KClaq(1 M), at a scan rate of 20 mV / s against a Ag / AgCl reference electrode; Figure 4 illustrates a cyclic voltammogram data of the second scan performed on an aqueous solution of N- [(pyrazin-2-yl)methyl]formamide (1 mM) in KClaq (1 M) (top) at a scan rate of 20 mV / s against a Ag / AgCl reference electrode; Figure 5 illustrates a cyclic voltammogram data of the second scan performed on an aqueous solution of N- [(pyrazin-2-yl)methyl]formamide (1 mM) in KOHaq(1 M) at a scan rate of 20 mV / s against a Hg / HgO reference electrode; Figure 6 illustrates cyclic voltammogram data of successive scans (scans 2, 50, 100, 250, 500 and 1000) performed on an aqueous solution of N-[(pyrazin-2- yl)methyl]formamide (1 mM) in KOHaq(1 M) at a scan rate of 20 mV / s against a Hg / HgO reference electrode; Figure 7 illustrates a cyclic voltammogram data of the second scan performed on an aqueous solution of (2- aminoethyl)[(pyrazin-2-yl)methyl]amine dihydrochloride (1 mM) in KClaq (1 M) at a scan rate of 20 mV / s against a Ag / AgCl reference electrode; Figure 8 illustrates a cyclic voltammogram data of the second scan performed on an aqueous solution of (2- aminoethyl)[(pyrazin-2-yl)methyl]amine dihydrochloride (1 mM) in KOHaq (1 M) at a scan rate of 20 mV / s against a Hg / HgO reference electrode; Figure 9 illustrates a cyclic voltammogram data of the second scan performed on an aqueous solution of 1H- imidazole-4-carboxylic acid (1 mM) in HClaq (1 M) at a scan rate of 20 mV / s against a Ag / AgCl reference electrode; Figure 10 illustrates calibration curve data using UV-vis spectroscopy used for determining the maximum solubility of N-[(pyrazin-2-yl)methyl]formamide in KOHaq(1 M); Figure 11 illustrates calibration curve data using UV-vis spectroscopy used for determining the maximum solubility of N-[(pyrazin-2-yl)methyl]formamide in KClaq (1 M); Figure 12 illustrates calibration curve data using UV-vis spectroscopy used for determining the maximum solubility of sodium pyridazine-3-sulfonate in KClaq (1 M); Figure 13 illustrates calibration curve data using UV-vis spectroscopy used for determining the maximum solubility of 1H-imidazole-4-carboxylic acid in KClaq(1 M); Figure 14 illustrates calibration curve data using UV-vis spectroscopy used for determining the maximum 5 solubility of 1H-imidazole-4-carboxylic acid in HClaq (1 M). Detailed Description of the Invention In general terms the present invention provides compounds and electrolytic compositions for use in energy 10 storage devices, particularly for use in anolytes for redox flow batteries, and methods for making a redox flow battery comprising the compounds and compositions disclosed herein. The methods comprise constructing a redox flow 15 battery, comprising at least an anolyte comprising at least a compound or composition of the present disclosure. Definitions: Unless defined otherwise, all technical and scientific terms used herein have the same meaning as 20 commonly understood by one of ordinary skill in the art (e.g. in organic, physical or theoretical chemistry; or physics; or engineering). Unless otherwise indicated, the practice of the present disclosure employs conventional techniques in 25 chemistry and chemical methods, which are within the capabilities of a person of ordinary skill in the art. Such techniques are also described in the literature cited herein. All documents cited in this disclosure are herein incorporated by reference in their entirety. 30 Prior to setting forth the detailed description of the various aspects and embodiments, a number of definitions are provided that will assist in the understanding of the disclosure. For the purpose of the following disclosure, the term ‘anolyte’ or ‘negolyte’ refers to the electrolyte which contacts the negative electrode in an electrochemical cell, which may be a redox flow battery, and is herein referred to as the anode; the term ‘catholyte’ or ‘posolyte’ refers to the electrolyte which contacts the positive electrode in an electrochemical cell, which may be a redox flow battery, and is herein referred to as the cathode. In accordance with this disclosure, the terms ‘molecule’ or ‘molecules’ are used interchangeably with the terms ‘compound’ or ‘compounds’, and sometimes the term ‘chemical structure’. The scope of this disclosure also includes various acceptable salt forms of Formula I, Formula II, Formula III, or Formula IV. Examples of acceptable salt forms include, but are not limited to, sodium salts, potassium salts and ammonium salts where the compound includes an anionic functional group such as a sulfonate group (-SO3Na, -SO3K, -SO3NH4), a phosphonate group (-PO3Na, -PO3K, - PO3NH4), or a carboxylate group (-COONa, -COOK, -COONH4), or combinations thereof. Further examples of acceptable salt forms include acid salt forms where the compound includes a protonatable functional group, such as an amine (-NH2.HCl, -NH2.H2SO4, -NMeH.HCl, -NMeH.H2SO4, -NRH.HCl, - NRH.H2SO4), or combinations thereof. The term ‘alkyl’ refers to a monovalent, optionally substituted, saturated aliphatic hydrocarbon radical. Any number of carbon atoms may be present, but typically the number of carbon atoms in the alkyl group may be from 1 to about 20, from 1 to about 12, from 1 to about 6 or from 1 to about 4. Usefully, the number of carbon atoms is indicated, for example, a C1-C12 alkyl refers to any alkyl group containing 1 to 12 carbon atoms in the chain. An alkyl group may be a straight chain (i.e. linear), or branched chain. ‘Lower alkyl’ refers to an alkyl of 1 to 6 carbon atoms in the chain, and may have from 1 to 4 carbon atoms, or 1 to 2 carbon atoms. Thus, 5 representative examples of lower alkyl radicals include methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, isopropyl, isobutyl, isopentyl, amyl (C5H11), sec-butyl, tert-butyl, sec-amyl, tert-pentyl, 2-ethylbutyl, 2,3- dimethylbutyl, and the like. ‘Higher alkyl’ refers to10 alkyls of 7 carbons and above, including n-heptyl, n- octyl, n-nonyl, n-decyl, n-dodecyl, n-tetradecyl, n- hexadecyl, n-octadecyl, n-eicosyl, and the like, along with branched variations thereof. A linear carbon chain of say 4 to 6 carbons would refer to the chain length not 15 including any carbons residing on a branch, whereas in a branched chain it would refer to the total number. Optional substituents for alkyl and other groups are described below. The term ‘alkenyl’ refers to a monovalent, 20 optionally substituted, unsaturated aliphatic hydrocarbon radical containing at least one carbon-carbon double bond. Any number of carbon atoms greater than one may be present, but typically the number of carbon atoms in the alkenyl group may be from 2 to about 20, from 2 to about 25 12, from 2 to about 6 or from 2 to about 4. Usefully, the number of carbon atoms is indicated, for example, a C2-C12 alkenyl refers to any alkenyl group containing 2 to 12 carbon atoms in the chain. An alkenyl group may be a straight chain (i.e. linear), or branched chain. ‘Lower 30 alkenyl’ refers to an alkenyl of 2 to 6 carbon atoms in the chain, and may have from 2 to 4 carbon atoms. Thus, representative examples of lower alkenyl radicals include ethenyl, n-propenyl, n-butenyl, n-pentenyl, n-hexenyl, isobutenyl, isopentenyl, sec-butenyl, tert-butenyl, tert- pentenyl, 2-ethylbutenyl, 2,3-dimethylbutenyl, and the like. ‘Higher alkenyl’ refers to alkenyls of 7 carbons and above, including n-heptenyl, n-octenyl, n-nonenyl, n- decenyl, n-dodecenyl, n-tetradecenyl, n-hexadecenyl, n- 5 octadecenyl, n-eicosenyl, and the like, along with branched variations thereof. A linear carbon chain of say 4 to 6 carbons would refer to the chain length not including any carbons residing on a branch, whereas in a branched chain it would refer to the total number. 10 The term ‘alkynyl’ refers to a monovalent, optionally substituted, unsaturated aliphatic hydrocarbon radical containing at least one carbon-carbon triple bond. Any number of carbon atoms greater than one may be present, but typically the number of carbon atoms in the 15 alkynyl group may be from 2 to about 20, from 2 to about 12, from 2 to about 6 or from 2 to about 4. Usefully, the number of carbon atoms is indicated, for example, a C2-C12 alkynyl refers to any alkynyl group containing 2 to 12 carbon atoms in the chain. An alkynyl group may be a 20 straight chain (i.e. linear), or branched chain. ‘Lower alkynyl’ refers to an alkynyl of 2 to 6 carbon atoms in the chain, and may have from 2 to 4 carbon atoms. Thus, representative examples of lower alkynyl radicals include ethynyl, n-propynyl, n-butynyl, n-pentynyl, n-hexynyl, 25 isopentynyl, 4,4-dimethyl-2-pentynyl, and the like. ‘Higher alkenyl’ refers to alkenyls of 7 carbons and above, including n-heptynyl, n-octynyl, n-nonynyl, n- decynyl, n-dodecynyl, n-tetradecynyl, n-hexadecynyl, n- octadecynyl, n-eicosynyl, and the like, along with 30 branched variations thereof. A linear carbon chain of say 4 to 6 carbons would refer to the chain length not including any carbons residing on a branch, whereas in a branched chain it would refer to the total number. The term ‘alkoxy’ or ‘alkoxyl’ refers to a monovalent radical of the formula -OR, where R is any alkyl, alkenyl or alkynyl as defined herein. Alkoxy groups may be optionally substituted by any of the 5 optional substituents described herein. ‘Lower alkoxy’ has the formula -OR, where the R group is a lower alkyl, alkenyl or alkynyl. Representative alkoxy radicals include methoxy, ethoxy, n-propoxy, n-butoxy, n-pentyloxy, n-hexyloxy, isopropoxy, isobutoxy, isopentyloxy, amyloxy, 10 sec-butoxy, tert-butoxy, tert-pentyloxy, and the like. Preferred alkoxy groups are methoxy and ethoxy. The term ‘carbocyclyl’ as used herein refers to a cyclized alkyl ring having the indicated number of carbon atoms in a specified range. Thus, for example, ‘C3-C6 15 carbocyclyl’ encompasses each of cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl. The term, ‘carbocyclyl’, as used herein refers to a monovalent radical of from about 3- to about 15- ring carbon atoms, and preferably 3-, 4-, 5-, 6-, 7-, 8-, 9- or 20 10- ring members. A carbocyclyl group may have only one individual ring or may comprise one or more fused rings comprising carbon atoms. It may be fully saturated or fully unsaturated or partially unsaturated containing at least one unsaturated carbon-carbon bond, and may be 25 substituted or unsubstituted. Representative examples of saturated carbocyclyl rings are cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl and cyclooctyl. Representative examples of unsaturated carbocyclyl rings are cyclopropenyl, cyclobutenyl, cyclopentenyl, 30 cyclohexenyl, cycloheptenyl and cyclooctenyl. The terms ‘heterocycle’ or ‘heterocyclic group’ or ‘heterocyclyl’ as used herein refer to a monovalent radical of from about 3- to about 15- ring atoms, and preferably 3-, 4-, 5-, 6-, 7-, 8-, 9- or 10- ring members. Generally, the heterocyclic group contains one, two or three heteroatoms, selected independently from nitrogen, oxygen and sulphur. A preferred heteroatom is N. Another preferred heteroatom is O. Another preferred heteroatom is 5 S. A heterocyclyl group may have only one individual ring or may comprise one or more fused rings in which at least one ring contains a heteroatom. It may be fully saturated or partially saturated and may be substituted or unsubstituted as in the case or aryl and heteroaryl 10 groups. Representative examples of unsaturated 5-membered heterocycles with only one heteroatom include 2- or 3- pyrrolyl, 2- or 3-furanyl, and 2- or 3-thiophenyl. Corresponding partially saturated or fully saturated radicals include 3-pyrrolin-2-yl, 2- or 3-pyrrolindinyl,15 2- or 3-tetrahydrofuranyl, and 2- or 3- tetrahydrothiophenyl. Representative unsaturated 5- membered heterocyclyl radicals having two heteroatoms include imidazolyl, oxazolyl, thiazolyl, pyrazolyl, and the like. The corresponding fully saturated and partially 20 saturated radicals are also included. Representative examples of unsaturated 6-membered heterocycles with only one heteroatom include 2-, 3-, or 4-pyridinyl, 2H-pyranyl, and 4H-pryanyl. Corresponding partially saturated or fully saturated radicals include 2-, 3-, or 4-piperidinyl, 25 2-, 3-, or 4-tetrahydropyranyl and the like. Representative unsaturated 6-membered heterocyclic radicals having two heteroatoms include 3- or 4- pyridazinyl, 2-, 4-, or 5-pyrimidinyl, 2-pyrazinyl, morpholino, and the like. The corresponding fully 30 saturated and partially saturated radicals are also included, e.g. 2-piperazine. The heterocyclyl radical is bonded through an available carbon atom or heteroatom in the heterocyclyl ring directly to the entity or through a linker such as an alkylene such as methylene or ethylene. The term, ‘oxo’, as used herein refers to a substituent comprising to a double-bonded oxygen atom. Suitably, the oxo substituent is double-bonded to a carbon atom, such as in R2C=O, where R is a suitable chemical 5 group. The term ‘substituted’ means that one or more hydrogen atoms (attached to a carbon or heteroatom) is replaced with a selection from the indicated group of substituents, provided that the designated atom’s normal 10 valency under the existing circumstances is not exceeded. The term, ‘polyalkylether’ as used herein refers to a substituent comprising the chemical unit formula, - (CH2CH2O)n-Me, or -(CH2CH2O)n-H, where ‘n’ may be any suitable number. For example, ‘n’ may typically be 1, or 15 2, or 3, or 4, or 5, 6, or 7, or 8, or 9, or 10, 11, or 12, or 13, or 14, or 15, 16, or 17, or 18, or 19, or 20, or greater than 20, or greater than 30, or greater than 40. Compounds: 20 Compounds described herein are characterised in that they comprise at least one of three redox-active 5- or 6- membered heteroaromatic cores. The redox-active 5- or 6- membered heteroaromatic cores are selected from pyrazine, pyridazine and imidazole. The compounds of the invention 25 offer distinct advantages over other organic molecules disclosed in the prior art for use in energy storage technologies, particularly redox flow batteries, including for example anthraquinones, in that they have less propensity for intermolecular stacking and are more 30 soluble in aqueous and non-aqueous solvents. Of particular advantage is their increased solubility in aqueous solvents and ability to undergo stable and reversible reduction and oxidation. Some compounds of the invention are advantageously liquids at room temperature facilitating increased energy density when used in electrolytic compositions due to higher achievable concentrations compared to compounds which are solids at technology operating temperatures and which therefore 5 require a solvent. The more localised aromatic electron densities of the compounds disclosed herein offer further advantage over the prior art in that they are more susceptible to electronic polarisation by substituent effects. Control 10 over the polarizability of the redox-active heteroaromatic cores of the compounds may be used to tune the redox potentials and solubilities of the compounds of the invention, particularly in aqueous solvents, via the addition of electron-donating groups, electron-withdrawing 15 groups and / or side-chains. Saturated carbon atom spacers may be used to separate electron-donating and / or electron- withdrawing groups from the redox-active cores to further control the degree of electron donation and / or withdrawal and polarizability. 20 Electron-withdrawing groups, such as sulfonic acid groups, phosphonic acids, carboxylic acids, nitro groups, halogen groups, and ammonium groups, chemically bonded directly to the electrochemical core may increase the reduction potential of the compounds of the invention; 25 while electron-donating groups, such as alkoxy groups, hydroxy groups and amino groups, impart the opposite effect. The extent to which these groups influence the electrochemical properties of the redox-active core can be further tailored by adding saturated or unsaturated alkyl30 group ‘spacers’ between the core and the active electron- donating / withdrawing group. One group of redox active compounds disclosed herein are compounds with the structural Formula I, II, or III, and salts thereof: wherein R11are each independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, -NO2, -X, -OR13, -NR14R15, -NHCOR16, - COOR17, -COR18, -CONR19R20, -COONHR21, Q1, Q2, and Q3; R12is selected from the group consisting of H, -SO3H, - PO3H, -COOH, -OR13, -NR14R15, -NHCOR16, -COOR17, -COR18, - CONR19R20, -COONHR21, Q4, Q5, and Q6; each R13and R22is independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, -COH, Q7, Q8, and Q9; each R14, R15, R23and R24is independently selected from the group consisting of H, -OH, -SO3H, -PO3H, -COOH, -COH, Q10, Q11, and Q12; each R16and R25is independently selected from the group consisting of H, -NH2, Q13, Q14, and Q15; each R17and R26is independently selected from the group consisting of -NR30R31, Q16, Q17, and Q18; each R18and R27is independently selected from the group consisting of H, -NR30R31, -SO3H, -PO3H, -COOH, Q19, Q20, and Q21; each R19, R20, R28, and R29is independently selected from the group consisting of H, -OH, -SO3H, -PO3H, -COOH, and Q22; each R21is independently selected from the group consisting of H, -SO3H, -PO3H, -COOH; and Q23; each R30and R31is independently selected from the group consisting of H and C1-C6 alkyl; each Q1and Q4is independently selected from C1-C6alkyl, C2-C6alkenyl, C2-C6alkynyl, and C2-C13polyalkylether, each optionally substituted with one or more groups independently selected from -SO3H, -PO3H, -NO2, -X, -OR22, - NR23R24, -NHCOR25, -COOR26, -COR27, -CONR28R29, oxo (=O), C1-C6alkoxyl, saturated or unsaturated 3- to 6-membered carbocyclyl and saturated or unsaturated 3- to 6-membered heterocyclyl, wherein the alkoxyl is optionally substituted with one or more groups independently selected from -SO3H, -PO3H, -COOH, -NO2, -X, -OR22, -NR23R24, -NHCOR25, -COOR26, -COR27, -CONR28R29, and oxo (=O), and the carbocyclyl and heterocyclyl are each optionally substituted with one or more groups independently selected from C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, C2-C13 polyalkylether, C1-C6 alkoxyl, -SO3H, -PO3H, -COOH, -NO2, - X, -OR22, -NR23R24, -NHCOR25, -COOR26, -COR27, -CONR28R29, and oxo (=O); each Q2and Q5is independently selected from saturated or unsaturated 3- to 6-membered carbocyclyl, optionally substituted with one or more groups independently selected from C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, C2-C13 polyalkylether, C1-C6alkoxyl, -SO3H, -PO3H, -COOH, -NO2, - X, -OR22, -NR23R24, -NHCOR25, -COOR26, -COR27, -CONR28R29, and oxo (=O); and each Q3and Q6is independently selected from saturated or unsaturated 3- to 6-membered heterocyclyl having one or more heteroatoms selected from N, O and S, optionally substituted with one or more groups independently selected from C1-C6alkyl, C2-C6alkenyl, C2-C6alkynyl, C2-C13polyalkylether, C1-C6 alkoxyl, -SO3H, -PO3H, -COOH, -NO2, - X, -OR22, -NR23R24, -NHCOR25, -COOR26, -COR27, -CONR28R29, and oxo (=O); each Q7is independently selected from C1-C6 alkyl, C2-C6 alkenyl, C2-C6alkynyl, and C2-C13polyalkylether, all optionally substituted with one or more groups independently selected from -SO3H, -PO3H, -COOH, -NO2, -X, -NR23R24, -NHCOR25, -COOR26, -COR27, -CONR28R29, oxo (=O), -OH, C1-C6 alkoxyl, saturated or unsaturated 3- to 6-membered carbocyclyl, and saturated or unsaturated 3- to 6-membered heterocyclyl, wherein the carbocyclyl and the heterocyclyl are each optionally substituted with one or more groups independently selected from C1-C6 alkyl, C2-C6 alkenyl, C2- C6 alkynyl, or C2-C13 polyalkylether, C1-C6 alkoxyl, -SO3H, - PO3H, -COOH, and -OH; each Q8, Q10, Q13, Q16and Q19is independently selected from saturated or unsaturated 3- to 6-membered carbocyclyl, optionally substituted with one or more groups independently selected from C1-C6 alkyl, C2-C6 alkenyl, C2- C6 alkynyl, C2-C13 polyalkylether, C1-C6 alkoxyl, -SO3H, - PO3H, -COOH, and -OH; each Q9, Q11, Q14, Q17and Q20is independently selected from saturated or unsaturated 3- to 6-membered heterocyclyl having one or more heteroatoms selected from N, O and S, optionally substituted with one or more groups independently selected from C1-C6 alkyl, C2-C6 alkenyl, C2- C6alkynyl, C2-C13polyalkylether, C1-C6alkoxyl, -SO3H, - PO3H, -COOH, and -OH; each Q12is independently selected from C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, and C2-C13 polyalkylether, each optionally substituted with one or more groups independently selected from -SO3H, -PO3H, -COOH, -NO2, -X, -NR30R31, -NHCOR25, -COOR26, -COR27, -CONR28R29, oxo (=O), -OH, C1-C6alkoxyl, saturated or unsaturated 3- to 6-membered carbocyclyl, and saturated or unsaturated 3- to 6-membered heterocyclyl, wherein the carbocyclyl and the heterocyclyl are each optionally substituted with one or more groups independently selected from C1-C6 alkyl, C2-C6 alkenyl, C2- C6alkynyl, or C2-C13polyalkylether, C1-C6alkoxyl, -SO3H, - PO3H, -COOH, and -OH; each Q15is independently selected from C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, and C2-C13 polyalkylether, all optionally substituted with one or more groups independently selected from -SO3H, -PO3H, -COOH, -NO2, -X, -NR30R31, -COOR26, -COR27, -CONR28R29, oxo (=O), -OH, C1-C6 alkoxyl, saturated or unsaturated 3- to 6-membered carbocyclyl, and saturated or unsaturated 3- to 6-membered heterocyclyl, wherein the carbocyclyl and heterocyclyl are each optionally substituted with one or more groups independently selected from C1-C6alkyl, C2-C6alkenyl, C2- C6 alkynyl, C2-C13 polyalkylether, C1-C6 alkoxyl, -SO3H, - PO3H, -COOH, and -OH; each Q18and Q21is independently selected from C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, or C2-C13 polyalkylether, all optionally substituted with one or more groups independently selected from -SO3H, -PO3H, -COOH, -NO2, -X, -NR30R31, -CONR28R29, oxo (=O), -OH, C1-C6 alkoxyl, saturated or unsaturated 3- to 6-membered carbocyclyl, and saturated or unsaturated 3- to 6-membered heterocyclyl, wherein the carbocyclyl and heterocyclyl are each optionally substituted with one or more groups independently selected from C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, C2-C13 polyalkylether, C1-C6 alkoxyl, -SO3H, -PO3H, -COOH, and -OH; each Q22is independently selected from C1-C7 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, and C2-C13 polyalkylether, all optionally substituted with one or more groups independently selected from -SO3H, -PO3H, -COOH, -NO2, -X, -NR30R31, oxo (=O), -OH, C1-C6alkoxyl, saturated or unsaturated 3- to 6-membered carbocyclyl, and saturated or unsaturated 3- to 6-membered heterocyclyl, wherein the carbocyclyl and heterocyclyl are each optionally substituted with one or more groups independently selected from C1-C6alkyl, C2-C6alkenyl, C2-C6alkynyl, C2-C13polyalkylether, C1-C6alkoxyl, -SO3H, -PO3H, -COOH, and -OH; each Q23is independently selected from C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, and C2-C13 polyalkylether, each optionally substituted with one or more groups independently selected from -SO3H, -PO3H, -COOH, -NO2, -X, -NR30R31, oxo (=O), -OH, C1-C6 alkoxyl, saturated or unsaturated 3- to 6-membered carbocyclyl, and saturated or unsaturated 3- to 6-membered heterocyclyl, wherein the carbocyclyl and heterocyclyl are each optionally substituted with one or more groups independently selected from C1-C6alkyl, C2-C6alkenyl, C2-C6alkynyl, C2-C13polyalkylether, C1-C6 alkoxyl, -SO3H, -PO3H, -COOH, and -OH; each -X is a halide (e.g. Cl, F, Br, or I, preferably Cl or F); wherein at least one of R1, R2, R3and R4is not H; wherein if one of R1, R2, R3or R4is -COOH, then at least one of the remaining R1, R2, R3and R4groups is not H or - COOH; wherein if one of R1, R2, R3or R4is C1 alkyl, then at least one of the remaining R1, R2, R3or R4groups is not H or C1 alkyl; wherein if one of R1, R2, R3or R4is Cl, then at least one of the remaining R1, R2, R3or R4groups is not H; wherein if one of R1, R2, R3or R4is -OMe, then at least one of the remaining R1, R2, R3or R4groups is not H; wherein if one of R1, R2, R3or R4is -CONH2, then at least one of the remaining R1, R2, R3or R4groups is not H; and wherein if one of R1, R2, R3or R4is C2alkenyl, then at least one of the remaining R1, R2, R3or R4groups is not H. In embodiments, each Q1is independently selected from C1-C6 alkyl and C2-C13 polyalkylether, each optionally substituted with one or more groups independently selected from -SO3H, -PO3H, -COOH, -NO2, -X, -OR22, -NR23R24, -NHCOR25, -COOR26, -COR27, -CONR28R29, oxo (=O), C1-C6alkoxyl, saturated or unsaturated 3- to 6-membered carbocyclyl and saturated or unsaturated 3- to 6-membered heterocyclyl, wherein the carbocyclyl and heterocyclyl are each optionally substituted with one or more groups independently selected from C1-C6alkyl, C2-C13polyalkylether, C1-C6 alkoxyl, -SO3H, -PO3H, and -COOH; each Q2is independently selected from saturated or unsaturated 3- to 6-membered carbocyclyl, optionally substituted with one or more groups independently selected from C1-C6alkyl, C2-C13polyalkylether, C1-C6alkoxyl, - SO3H, -PO3H, -COOH, and -NR23R24; and each Q3is independently selected from saturated or unsaturated 3- to 6-membered heterocyclyl having one or more heteroatoms selected from N, O and S, optionally substituted with one or more groups independently selected from C1-C6 alkyl, C2-C13 polyalkylether, C1-C6 alkoxyl, - SO3H, -PO3H, -COOH, and -NR23R24. In embodiments, each Q1is independently selected from C1- C6 alkyl and C2-C13 polyalkylether, each optionally substituted with one or more groups independently selected from -SO3H, -PO3H, -COOH; -X, -OR22, -NR23R24, -NHCOR25, - COOR26, -COR27, -CONR28R29, and oxo (=O); each Q2is independently selected from saturated or unsaturated 3- to 6-membered carbocyclyl optionally substituted with one or more groups independently selected from -NR23R24; and each Q3is independently selected from saturated or unsaturated 3- to 6-membered heterocyclyl having one or more heteroatoms selected from N, O and S. In embodiments, each Q4is independently selected from C1-C6 alkyl and C2-C13 polyalkylether, each optionally substituted with one or more groups independently selected from -SO3H, -PO3H, -NO2, -X, -OR22, -NR23R24, -NHCOR25, - COOR26, -COR27, -CONR28R29, oxo (=O), C1-C6alkoxyl, saturated or unsaturated 3- to 6-membered carbocyclyl and saturated or unsaturated 3- to 6-membered heterocyclyl, wherein the carbocyclyl and heterocyclyl are each optionally substituted with one or more groups independently selected from C1-C6alkyl, C2-C13polyalkylether, C1-C6alkoxyl, - SO3H, -PO3H, and -COOH; each Q5is independently selected from saturated or unsaturated 3- to 6-membered carbocyclyl, optionally substituted with one or more groups independently selected from C1-C6alkyl, C2-C13polyalkylether, C1-C6alkoxyl, - SO3H, -PO3H, -COOH, and -NR23R24; and each Q6is independently selected from saturated or unsaturated 3- to 6-membered heterocyclyl having one or more heteroatoms selected from N, O and S, optionally substituted with one or more groups independently selected from C1-C6 alkyl, C2-C13 polyalkylether, C1-C6 alkoxyl, - SO3H, -PO3H, -COOH, and -NR23R24. In embodiments, each R12is independently selected from the group consisting of, H, -COOR17, -COR18, -CONR19R20, -COONHR21, C1-C6 alkyl, C2-C13 polyalkylether, saturated or unsaturated 3- to 6-membered carbocyclyl, and saturated or unsaturated 3- to 6-membered heterocyclyl having one or more heteroatoms selected from N, O and S, wherein the alkyl is optionally substituted with one or more groups independently selected from -SO3H, -PO3H, -COOH, and oxo (=O). In embodiments, each R12is independently selected from H and C1-C3alkyl. In embodiments, each R13is independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, -COH, C1-C6 alkyl, saturated or unsaturated 3- to 6-membered carbocyclyl, and saturated or unsaturated 3- to 6-membered heterocyclyl having one or more heteroatoms selected from N, O and S, wherein the alkyl is optionally substituted with one or more groups independently selected from -SO3H, -PO3H, -COOH, -X, -NR23R24, oxo (=O), and -OH. In embodiments, each R13is independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, -COH, C1-C4alkyl, wherein the alkyl is optionally substituted with one or more groups independently selected from -OH. In embodiments, each R14and R15is independently selected from C1-C6 alkyl, saturated or unsaturated 3- to 6-membered carbocyclyl, and saturated or unsaturated 3- to 6-membered heterocyclyl having one or more heteroatoms selected from N, O and S, wherein the alkyl is optionally substituted with one or more groups independently selected from -SO3H, -PO3H, -COOH, -COOR26, -COR27, -X, -NR30R31, oxo (=O), and -OH. In embodiments, each R14and R15is each independently selected from the group consisting of H, -SO3H, -PO3H, - COOH, -COH, -OH, and C1-C4alkyl, wherein the alkyl is optionally substituted with one or more groups selected from -SO3H, -PO3H, -COOH, -X, -NH2, oxo (=O), and -OH. In embodiments, each R14is H. In embodiments, each R16is independently selected from the group consisting of H, -NH2, C1-C6alkyl, saturated or unsaturated 3- to 6-membered carbocyclyl, saturated or unsaturated 3- to 6-membered heterocyclyl having one or more heteroatoms selected from N, O and S, wherein the alkyl is optionally substituted with at one or more groups independently selected from -SO3H, -PO3H, - COOH, -NR30R31, and -OH. In embodiments, each R16is independently selected from the group consisting of H, -NH2 and C1-C4 alkyl optionally substituted with one or more groups independently selected from -OH. In embodiments, each R17is independently selected from the group consisting of -NR30R31, C1-C6alkyl, saturated or unsaturated 3- to 6-membered carbocyclyl, and saturated or unsaturated 3- to 6-membered heterocyclyl having one or more heteroatoms selected from N, O and S, wherein the alkyl is optionally substituted with one or more groups independently selected from -SO3H, -PO3H, - COOH, -X, -NR30R31, and -OH. In embodiments, each R17is independently selected from the group consisting of -NH2 and C1-C4 alkyl optionally substituted with one or more groups independently selected from -NH2, and -OH. In embodiments, each R18is independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, - NR30R31, C1-C6 alkyl, saturated or unsaturated 3- to 6- membered carbocyclyl, and saturated or unsaturated 3- to 6-membered heterocyclyl having one or more heteroatoms selected from N, O and S, wherein the alkyl is optionally substituted with one or more groups independently selected from -SO3H, -PO3H, -COOH, -X, -NR30R31, and -OH. In embodiments, each R19and R20is independently selected from the group consisting of H, -OH, -SO3H, -PO3H, -COOH, C1-C7 alkyl, saturated or unsaturated 3- to 6- membered carbocyclyl, and saturated or unsaturated 3- to 6-membered heterocyclyl having one or more heteroatoms selected from N, O and S, wherein the alkyl is optionally substituted with one or more groups independently selected from -SO3H, -PO3H, -COOH, -NR30R31, and -OH. In embodiments, each R19and R20is independently selected from the group consisting of H, -OH, -SO3H, -PO3H, -COOH, and C1-C7alkyl, wherein the alkyl is optionally substituted with one or more groups independently selected from -NH2 and -OH. In embodiments, each R19is H. In embodiments, each R21is independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, and C1-C6alkyl, wherein the alkyl is optionally substituted with one or more groups independently selected from -SO3H, -PO3H, -COOH, -NR30R31, oxo (=O), and -OH. In embodiments, each R22is independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, -COH, C1-C6 alkyl, saturated or unsaturated 3- to 6-membered carbocyclyl, and saturated or unsaturated 3- to 6-membered heterocyclyl having one or more heteroatoms selected from N, O and S, wherein the alkyl is optionally substituted with one or more groups independently selected from -SO3H, -PO3H, -COOH, -NR23R24, and -OH. In embodiments, each R22is independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, -COH, and C1-C4 alkyl, wherein the alkyl is optionally substituted with one or more groups independently selected from the group consisting of -NR23R24, and -OH. In embodiments, each R23and R24is independently selected from the group consisting of H, -OH, -SO3H, -PO3H, -COOH, -COH, and C1-C6 alkyl, wherein the alkyl is optionally substituted with one or more groups independently selected from -SO3H, -PO3H, -COOH, -NR30R31, - X, oxo (=O), and -OH. In embodiments, each R23and / or each R24is H. In embodiments, each R25is independently selected from the group consisting of H, -NH2, C1-C6 alkyl, saturated or unsaturated 3- to 6-membered carbocyclyl, and saturated or unsaturated 3- to 6-membered heterocyclyl having one or more heteroatoms selected from N, O and S, wherein the alkyl is optionally substituted with one or more groups independently selected from -SO3H, -PO3H, -COOH, -NR30R31, and -OH. In embodiments, each R25is independently selected from the group consisting of H, -OH, -NH2, and C1-C4alkyl, wherein the alkyl is optionally substituted with one or more groups independently selected from -NH2, and -OH. In embodiments, each R26is independently selected from the group consisting of -NR30R31, C1-C6 alkyl, saturated or unsaturated 3- to 6-membered carbocyclyl, and saturated or unsaturated 3- to 6-membered heterocyclyl having one or more heteroatoms selected from N, O and S, wherein the alkyl is optionally substituted with one or more groups independently selected from -SO3H, -PO3H, - COOH, -X, -NR30R31, oxo (=O), and -OH. In embodiments, each R26is independently selected from C1-C4 alkyl optionally substituted with one or more groups independently selected from -OH. In embodiments, each R27is independently selected from the group consisting of H, -NR30R31, -SO3H, -PO3H, -COOH, C1-C6 alkyl, saturated or unsaturated 3- to 6-membered carbocyclyl, and saturated or unsaturated 3- to 6-membered heterocyclyl having one or more heteroatoms selected from N, O and S, wherein the alkyl is optionally substituted withone or more groups independently selected from -SO3H, - PO3H, -COOH, -X, -NR30R31, oxo (=O), and -OH. In embodiments, each R27is independently selected from the group consisting of H, -OH, -NH2, and C1-C4 alkyl, wherein the alkyl is optionally substituted with one or more groups independently selected from -OH, and -NH2. In embodiments, each R28and R29is independently selected from the group consisting of, H, -OH, -SO3H, -PO3H, -COOH, C1-C6alkyl, saturated or unsaturated 3- to 6-membered carbocyclyl, and saturated or unsaturated 3- to 6-membered heterocyclyl having one or more heteroatoms selected from N, O and S, wherein the alkyl is optionally substituted with one or more groups independently selected from -SO3H, -PO3H, -COOH, -X, -NR30R31, oxo (=O), and -OH. In embodiments, each R28and R29is independently selected from the group consisting of H and C1-C4alkyl, wherein the alkyl is optionally substituted with one or more groups independently selected from -SO3H, -PO3H, - COOH, -OH, and -NH2. In embodiments, each R28and / or each R29is H. In embodiments, each R30and R31is independently selected from the group consisting of H and C1-C2 alkyl. In embodiments, each R30and / or each R31is H. In embodiments, each R30and R31is H. In embodiments, R1, R2, R3, R4, R5, R6, R7, R8, R9, R10and R11are each independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, -NO2, -X, -OR13, - NR14R15, -NHCOR16, -COOR17, -COR18, -CONR19R20, -COONHR21, Q1, Q2, and Q3; each Q1is independently selected from C1-C6 alkyl and C2- C13 polyalkylether, each optionally substituted with one or more groups independently selected from -SO3H, -PO3H, - COOH; -X, -OR22, -NR23R24, -NHCOR25, -COOR26, -COR27, - CONR28R29, and oxo (=O); each Q2is independently selected from saturated or unsaturated 3- to 6-membered carbocyclyl optionally substituted with one or more groups independently selected from -NR23R24; each Q3is independently selected from saturated or unsaturated 3- to 6-membered heterocyclyl having one or more heteroatoms selected from N, O and S; each R12is independently selected from H and C1-C3 alkyl; each R13is independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, -COH, C1-C4alkyl, wherein the alkyl is optionally substituted with one or more -OH; each R14, R19, R23, R28, R29, R30and R31is H; each R15is each independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, -COH, -OH, and C1-C4alkyl, wherein the alkyl is optionally substituted with one or more groups selected from -SO3H, -PO3H, -COOH, -X, - NH2, oxo (=O), and -OH; each R16is independently selected from the group consisting of H, -NH2 and C1-C4 alkyl optionally substituted with one or more groups independently selected from -OH; each R17is independently selected from the group consisting of -NH2and C1-C4alkyl optionally substituted with one or more groups independently selected from -NH2, and -OH; each R18is independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, -NR30R31, C1-C6 alkyl, saturated or unsaturated 3- to 6-membered carbocyclyl, and saturated or unsaturated 3- to 6-membered heterocyclyl having one or more heteroatoms selected from N, O and S, wherein the alkyl is optionally substituted with one or more groups independently selected from -SO3H, -PO3H, - COOH, -X, -NR30R31, and -OH; each R20is independently selected from the group consisting of H, -OH, -SO3H, -PO3H, -COOH, and C1-C7alkyl, wherein the alkyl is optionally substituted with one or more groups independently selected from -NH2 and -OH; each R21is independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, and C1-C6 alkyl, wherein the alkyl is optionally substituted with one or more groups independently selected from -SO3H, -PO3H, - COOH, -NR30R31, oxo (=O), and -OH; each R22is independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, -COH, and C1-C4 alkyl, wherein the alkyl is optionally substituted with one or more groups independently selected from the group consisting of -NR23R24, and -OH; each R24is independently selected from the group consisting of H, -OH, -SO3H, -PO3H, -COOH, -COH, and C1-C6 alkyl, wherein the alkyl is optionally substituted with one or more groups independently selected from -SO3H, - PO3H, -COOH, -NR30R31, -X, oxo (=O), and -OH; each R25is independently selected from the group consisting of H, -OH, -NH2, and C1-C4 alkyl, wherein the alkyl is optionally substituted with one or more groups independently selected from -NH2, and -OH; each R26is independently selected from C1-C4alkyl optionally substituted with one or more groups independently selected from -OH; and each R27is independently selected from the group consisting of H, -OH, -NH2, and C1-C4 alkyl, wherein the alkyl is optionally substituted with one or more groups independently selected from -OH, and -NH2. In embodiments, R1, R2, R3, R4, R5, R6, R7, R8, R9, R10and R11are each independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, -NO2, -X, -OR13, - NR14R15, -NHCOR16, -COOR17, -COR18, -CONR19R20, -COONHR21, Q1, and Q2. In embodiments, each Q1is independently selected from C1-C6 alkyl and C2-C13 polyalkylether, wherein the alkyl is optionally substituted with one or more groups independently selected from -SO3H, -PO3H, -COOH; -X, -OR22, -NR23R24, -NHCOR25, -COOR26, -COR27, -CONR28R29, and oxo (=O). In embodiments, each R15is each independently selected from the group consisting of H, -SO3H, -PO3H, - COOH, -COH, -OH, and C1-C4 alkyl, wherein the alkyl is optionally substituted with one or more groups selected from -COOH, -X, -NH2, oxo (=O), and -OH. In embodiments, each R18is independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, - NR30R31, C1-C6alkyl, saturated or unsaturated 3- to 6- membered carbocyclyl, and saturated or unsaturated 3- to 6-membered heterocyclyl having one or more heteroatoms selected from N, O and S, wherein the alkyl is optionally substituted with one or more groups independently selected from -NR30R31, and -OH. In embodiments, each R21is independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, and C1-C6 alkyl, wherein the alkyl is optionally substituted with one or more groups independently selected from -NR30R31and -OH. In embodiments, each R24is independently selected from the group consisting of H, -OH, -SO3H, -PO3H, -COOH, - COH, and C1-C6 alkyl, wherein the alkyl is optionally substituted with one or more groups independently selected from -NR30R31, oxo (=O), and -OH. In embodiments, each R25is independently selected from -OH and C1-C4 alkyl. In embodiments, each R26is independently selected from C1-C4 alkyl. In embodiments, each R27is independently selected from the group consisting of H, -OH, -NH2, and C1-C4alkyl. In embodiments, R1, R2, R3, R4, R5, R6, R7, R8, R9, R10and R11are each independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, -NO2, -X, -OR13, - NR14R15, -NHCOR16, -COOR17, -COR18, -CONR19R20, -COONHR21, Q1, and Q2; each Q1is independently selected from C1-C6alkyl and C2- C13polyalkylether, wherein the alkyl is optionally substituted with one or more groups independently selected from -SO3H, -PO3H, -COOH; -X, -OR22, -NR23R24, -NHCOR25, - COOR26, -COR27, -CONR28R29, and oxo (=O); each Q2is independently selected from saturated or unsaturated 3- to 6-membered carbocyclyl optionally substituted with one or more groups independently selected from -NR23R24; each R12is independently selected from H and C1-C3 alkyl; each R13is independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, -COH, C1-C4 alkyl, wherein the alkyl is optionally substituted with one or more -OH; each R14, R19, R23, R28, R29, R30and R30is H; each R15is each independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, -COH, -OH, and C1-C4alkyl, wherein the alkyl is optionally substituted with one or more groups selected from -COOH, -X, -NH2, oxo (=O), and -OH; each R16is independently selected from the group consisting of H, and C1-C4 alkyl optionally substituted with one or more groups independently selected from -OH; each R17is independently selected from the group consisting of -NH2 and C1-C4 alkyl optionally substituted with one or more groups independently selected from -NH2, and -OH; each R18is independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, -NR30R31, C1-C6 alkyl, saturated or unsaturated 3- to 6-membered carbocyclyl, and saturated or unsaturated 3- to 6-membered heterocyclyl having one or more heteroatoms selected from N, O and S, wherein the alkyl is optionally substituted with one or more groups independently selected from -NR30R31, and -OH; each R20is independently selected from the group consisting of H, -OH, -SO3H, -PO3H, -COOH, and C1-C7 alkyl, wherein the alkyl is optionally substituted with one or more groups independently selected from -NH2 and -OH; each R21is independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, and C1-C6alkyl, wherein the alkyl is optionally substituted with one or more groups independently selected from -NR30R31and -OH; each R22is independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, -COH, and C1-C4 alkyl, wherein the alkyl is optionally substituted with one or more groups independently selected from the group consisting of -NR23R24, and -OH; each R24is independently selected from the group consisting of H, -OH, -SO3H, -PO3H, -COOH, -COH, and C1-C6 alkyl, wherein the alkyl is optionally substituted with one or more groups independently selected from -NR30R31, oxo (=O), and -OH; each R25is independently selected from -OH and C1-C4 alkyl; each R26is independently selected from C1-C4 alkyl; and each R27is independently selected from the group consisting of H, -OH, -NH2, and C1-C4 alkyl. In embodiments, R1, R2, R3, R4, R5, R6, R7, R8, R9, R10and R11are each independently selected from the group consisting of H, -SO3H, -COOH, OR13, -COR18, Q1, and Q2. In embodiments, each Q1is independently selected from C1- C6 alkyl substituted with one or more groups independently selected from -COOH, -X, -NR23R24, and oxo (=O); and each Q2is independently selected from saturated or unsaturated 3- to 6-membered carbocyclyl substituted with one or more groups independently selected from -NR23R24. In embodiments, each R12is H. In embodiments, each R13is -COH. In embodiments, each R18is independently selected from C1-C6alkyl and saturated or unsaturated 3- to 6- membered heterocyclyl having one or more heteroatoms selected from N, O and S, wherein the alkyl is optionally substituted with one or more groups independently selected from -NR30R31. In embodiments, each R24is independently selected from C1-C6alkyl substituted with one or more groups independently selected from -NR30R31and oxo (=O). In embodiments, R1, R2, R3, R4, R5, R6, R7, R8, R9, R10and R11are each independently selected from the group consisting of H, -SO3H, -COOH, -OR13, -COR18, Q1, and Q2; each Q1is independently selected from C1-C6 alkyl substituted with one or more groups independently selected from -COOH, -X, -NR23R24, and oxo (=O); each Q2is independently selected from saturated or unsaturated 3- to 6-membered carbocyclyl substituted with one or more groups independently selected from -NR23R24; each R12, R23, R30and R31is H; each R13is -COH; each R18is independently selected from C1-C6 alkyl and saturated or unsaturated 3- to 6-membered heterocyclyl having one or more heteroatoms selected from N, O and S, wherein the alkyl is substituted with one or more groups independently selected from -NR30R31; and each R24is independently selected from C1-C6 alkyl substituted with one or more groups independently selected from -NR30R31and oxo (=O). In embodiments, R1, R2, R3, R4, R5, R6, R7, R8, R9, R10and R11are each independently selected from the group consisting of H, -SO3H, -COOH, and Q1; each Q1is independently selected from C1-C6 alkyl substituted with one or more groups independently selected from -NR23R24; each R23is H; and each R24is independently selected from C1-C6 alkyl substituted with one or more groups independently selected from -NH2. In embodiments, the compound is a compound of formula I. In embodiments of the compound of formula I, R1, R2, R3and R4are each independently selected from the group consisting of H, -COOH, -OR13, and Q1; each Q1is independently selected from C1-C6alkyl substituted with one or more groups independently selected from -COOH, -X, -NR23R24, and oxo (=O); each R13is CHO; each R23is H; and each R24is H. In embodiments of the compound of formula I, one, two or three of R1, R2, R3, and R4are H. In embodiments of the compound of formula I, two or three of R1, R2, R3, and R4are H. In embodiments, the compound is a compound of formula II. In embodiments of the compound of formula II, R5, R6, R7and R8are each independently selected from the group consisting of H, -COOH, -COR18, Q1and Q2; each Q1is independently selected from C1-C6 alkyl substituted with one or more groups independently selected from -COOH, -X, -NR23R24, and oxo (=O); and each Q2is independently selected from saturated or unsaturated 3- to 6-membered carbocyclyl substituted with one or more groups independently selected from -NR23R24; each R18is independently selected from C1-C6 alkyl and saturated or unsaturated 3- to 6-membered heterocyclyl having one or more heteroatoms selected from N, O and S, wherein the alkyl is substituted with one or more groups independently selected from -NR30R31; and each R23, R24, R30, R31is H. In embodiments of the compound of formula II, one, two or three of R5, R6, R7, and R8are H. In embodiments of the compound of formula II, two or three of R5, R6, R7, and R8are H. In embodiments of the compound of formula II, three of R5, R6, R7, and R8are H. In embodiments, the compound is a compound of formula III. In embodiments of the compound of formula III, R9, R10, and R11are each independently selected from H and - COOH; and R12is H. In embodiments of the compound of formula III, one or two of R9, R10, and R11are H. In embodiments of the compound of formula III, two of R9, R10, and R11are H. Another group of compounds disclosed herein are compounds with the structural Formula II, III, or IV, and salts thereof: wherein are selected from the group consisting of H, -SO3H, -PO3H, - NO2, -F, -OR13’, -NR14R15, -NHCOR16, -COOR17, -COR18’, - COONHR21, Q2, Q3, Q24or Q25; each R13’is independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, -COH, Q7, Q8, and Q9; each R18’is independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, Q19, Q20, and Q21; each Q7is independently selected from C2-C6alkyl, C2-C6alkenyl, C2-C6alkynyl, and C2-C13polyalkylether, all optionally substituted with one or more groups independently selected from -SO3H, -PO3H, -COOH, -NO2, -X, -NR23R24, -NHCOR25, -COOR26, -COR27, -CONR28R29, oxo (=O), -OH, C1-C6 alkoxyl, saturated or unsaturated 3- to 6-membered carbocyclyl, and saturated or unsaturated 3- to 6-membered heterocyclyl, wherein the carbocyclyl and the heterocyclyl are each optionally substituted with one or more groups independently selected from C1-C6 alkyl, C2-C6 alkenyl, C2- C6alkynyl, or C2-C13polyalkylether, C1-C6alkoxyl, -SO3H, - PO3H, -COOH, and -OH; each Q24is independently selected from C1 alkyl substituted with one or more groups independently selected from -SO3H, -PO3H, -NO2, -X, -OR22, -NR23R24, -NHCOR25, - COOR26, -COR27, -CONR28R29, C1-C6alkoxyl, saturated or unsaturated 3- to 6-membered carbocyclyl and saturated or unsaturated 3- to 6-membered heterocyclyl, wherein the alkoxyl is optionally substituted with one or more groups independently selected from -SO3H, -PO3H, -COOH, -NO2, -X, -OR22, -NR23R24, -NHCOR25, -COOR26, -COR27, -CONR28R29, and oxo (=O), and the carbocyclyl and heterocyclyl are each optionally substituted with one or more groups independently selected from C1-C6 alkyl, C2-C6 alkenyl, C2- C6 alkynyl, C2-C13 polyalkylether, C1-C6 alkoxyl, -SO3H, - PO3H, -COOH, -NO2, -X, -OR22, -NR23R24, -NHCOR25, -COOR26, - COR27, -CONR28R29, and oxo (=O); each Q25is independently selected from C2-C6alkyl and C2- C13 polyalkylether, each optionally substituted with one or more groups independently selected from -SO3H, -PO3H, -NO2, -X, -OR22, -NR23R24, -NHCOR25, -COOR26, -COR27, -CONR28R29, oxo (=O), C1-C6 alkoxyl, saturated or unsaturated 3- to 6- membered carbocyclyl and saturated or unsaturated 3- to 6- membered heterocyclyl, wherein the alkoxyl is optionally substituted with one or more groups independently selected from -SO3H, -PO3H, -COOH, -NO2, -X, -OR22, -NR23R24, -NHCOR25, -COOR26, -COR27, -CONR28R29, and oxo (=O), and the carbocyclyl and heterocyclyl are each optionally substituted with one or more groups independently selected from C1-C6alkyl, C2-C6alkenyl, C2-C6alkynyl, C2-C13polyalkylether, C1-C6alkoxyl, -SO3H, -PO3H, -COOH, -NO2, - X, -OR22, -NR23R24, -NHCOR25, -COOR26, -COR27, -CONR28R29, and oxo (=O); and each of R12, R14, R15, R16, R17, R21, R25, R26, R27, R28, R29, Q2, Q3, Q7, Q8, Q9, Q19, Q20, Q21, and X are as defined herein. In embodiments of the compound of formula IV, each Q24is independently selected from C1 alkyl substituted with one or more groups independently selected from -SO3H, -PO3H, - COOH, -NO2, -X, -OR22, -NR23R24, -NHCOR25, -COOR26, -COR27, - CONR28R29, C1-C6alkoxyl, saturated or unsaturated 3- to 6- membered carbocyclyl and saturated or unsaturated 3- to 6- membered heterocyclyl, wherein the carbocyclyl and heterocyclyl are each optionally substituted with one or more groups independently selected from C1-C6 alkyl, C2-C13 polyalkylether, C1-C6 alkoxyl, -SO3H, -PO3H, and -COOH; each Q25is independently selected from C2-C6alkyl and C2- C13 polyalkylether, each optionally substituted with one or more groups independently selected from -SO3H, -PO3H, - COOH, -NO2, -X, -OR22, -NR23R24, -NHCOR25, -COOR26, -COR27, - CONR28R29, oxo (=O), C1-C6 alkoxyl, saturated or unsaturated 3- to 6-membered carbocyclyl and saturated or unsaturated 3- to 6-membered heterocyclyl, wherein the carbocyclyl and heterocyclyl are each optionally substituted with one or more groups independently selected from C1-C6 alkyl, C2-C13 polyalkylether, C1-C6 alkoxyl, -SO3H, -PO3H, and -COOH; each Q2is independently selected from saturated or unsaturated 3- to 6-membered carbocyclyl, optionally substituted with one or more groups independently selected from C1-C6 alkyl, C2-C13 polyalkylether, C1-C6 alkoxyl, - SO3H, -PO3H, -COOH, and -NR23R24; and each Q3is independently selected from saturated or unsaturated 3- to 6-membered heterocyclyl having one or more heteroatoms selected from N, O and S, optionally substituted with one or more groups independently selected from C1-C6 alkyl, C2-C13 polyalkylether, C1-C6 alkoxyl, - SO3H, -PO3H, -COOH, and -NR23R24. In embodiments of the compound of formula IV, each Q24is independently selected from C1 alkyl substituted with one or more groups independently selected from -SO3H, -PO3H, -COOH; -X, -OR22, -NR23R24, -NHCOR25, -COOR26, -COR27, and -CONR28R29; each Q25is independently selected from C2-C6alkyl and C2- C13polyalkylether, each optionally substituted with one or more groups independently selected from -SO3H, -PO3H, - COOH; -X, -OR22, -NR23R24, -NHCOR25, -COOR26, -COR27, - CONR28R29, and oxo (=O); each Q2is independently selected from saturated or unsaturated 3- to 6-membered carbocyclyl optionally substituted with one or more groups independently selected from -NR23R24; and each Q3is independently selected from saturated or unsaturated 3- to 6-membered heterocyclyl having one or more heteroatoms selected from N, O and S. In embodiments of the compound of formula IV, each Q24is independently selected from C1 alkyl substituted with one or more groups independently selected from -SO3H, -PO3H, -COOH; -X, -OR22, -NR23R24, -NHCOR25, -COOR26, -COR27, and -CONR28R29; and each Q25is independently selected from C2-C6 alkyl and C2- C13polyalkylether, wherein the alkyl is optionally substituted with one or more groups independently selected from -SO3H, -PO3H, -COOH; -X, -OR22, -NR23R24, -NHCOR25, - COOR26, -COR27, and -CONR28R29. In embodiments of the compound of formula IV, each R13’is independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, -COH, C2-C6alkyl, saturated or unsaturated 3- to 6-membered carbocyclyl, and saturated or unsaturated 3- to 6-membered heterocyclyl having one or more heteroatoms selected from N, O and S, wherein the alkyl is optionally substituted with one or more groups independently selected from -SO3H, -PO3H, -COOH, -X, - NR23R24, oxo (=O), and -OH. In embodiments of the compound of formula IV, each R13’is independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, -COH, C2-C4 alkyl, wherein the alkyl is optionally substituted with one or more groups independently selected from -OH. In embodiments of the compound of formula IV, each R13’is -COH. In embodiments of the compound of formula IV, each R18’is independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, C1-C6 alkyl, saturated or unsaturated 3- to 6-membered carbocyclyl, and saturated or unsaturated 3- to 6-membered heterocyclyl having one or more heteroatoms selected from N, O and S, wherein the alkyl is optionally substituted with one or more groups independently selected from -SO3H, -PO3H, -COOH, -X, - NR30R31, and -OH. In embodiments of the compound of formula IV, each R18’is independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, C1-C6 alkyl, saturated or unsaturated 3- to 6-membered carbocyclyl, and saturated or unsaturated 3- to 6-membered heterocyclyl having one or more heteroatoms selected from N, O and S, wherein the alkyl is optionally substituted with one or more groups independently selected from -NR30R31, and -OH. In embodiments of the compound of formula IV, each R18’is independently selected from C1-C6 alkyl and saturated or unsaturated 3- to 6-membered heterocyclyl having one or more heteroatoms selected from N, O and S, wherein the alkyl is optionally substituted with one or more groups independently selected from -NR30R31. In embodiments, the compound of formula I, II, III or IV is a salt, optionally wherein the salt is a lithium salt, a sodium salt, a potassium, an ammonium salt, a tetraalkylammonium salt, a hydrochloride salt or a sulfuric acid salt. In embodiments, the compound is selected from: 2- 5 (pyrazin-2-yl)acetaldehyde, N- (pyrazinylmethyl)ethylenediamine, N-(pyrazin-2- ylmethyl)formamide, 3-fluoro-3-(pyrazin-2-yl)propan-1- amine, 2-pyrazineacetic acid, N-(pyridazin-3- ylmethyl)formamide, 1-(pyridazin-3-yl)cyclopropanamine, 2-10 amino-1-pyridazin-3-ylethanone, morpholin-4-yl(pyridazine- 4-yl)methanone, 3-pyridazinesulfonic acid, 1H-imidazole-4- carboxylic acid, pyrazine formate, 3-(trifluoromethyl)-2- pyrazinecarboxylic acid, 3-pyridazinecarboxylic acid; and salts thereof (for example the compound is selected from:15 N-(pyrazin-2-ylmethyl)formamide; N- (pyrazinylmethyl)ethylenediamine; 3-pyridazinesulfonic acid; 1H-imidazole-4-carboxylic acid; and salts thereof). In embodiments, the compound is selected from: 2-(pyrazin- 2-yl)acetaldehyde; N-(pyrazinylmethyl)ethylenediamine; N-20 (pyrazin-2-ylmethyl)formamide; 3-fluoro-3-(pyrazin-2- yl)propan-1-amine; 2-pyrazineacetic acid; N-(pyridazin-3- ylmethyl)formamide; 1-(pyridazin-3-yl)cyclopropanamine; 2- amino-1-pyridazin-3-ylethanone; morpholin-4-yl(pyridazine- 4-yl)methanone; sodium 3-pyridazinesulfonate; N-25 (pyrazinylmethyl)ethylenediamine dihydrochloride; 1H- imidazole-4-carboxylic acid; pyrazine formate; 3- (trifluoromethyl)-2-pyrazinecarboxylic acid; and 3- pyridazinecarboxylic acid (for example the compound is selected from: N-(pyrazin-2-ylmethyl)formamide; N-30 (pyrazinylmethyl)ethylenediamine; N- (pyrazinylmethyl)ethylenediamine dihydrochloride; sodium 3-pyridazinesulfonate; 1H-imidazole-4-carboxylic acid; and salts thereof). In another embodiment, the compound is a compound represented by any one of structures shown in Table 1: Table 1 Structure 1: Structure 2: Structure 3: Structure 4: Structure 5: Structure 6: Structure 7: Structure 8: Structure 9: Structure 10: Structure 11: Structure 12: Structure 13: Structure 14: Structure 15: 5 The compounds of the present disclosure may contain asymmetric carbon atoms (sometimes as the result of a deuterium atom) and thereby can exist as either individual stereoisomers or mixtures of enantiomers or mixtures of diastereomers. Accordingly, a compound of the present disclosure may exist as either a racemic mixture, a mixture of diastereomers, or as individual stereoisomers that are substantially free of other stereoisomers. 5 Synthetic, separation, or purification methods to be used to obtain an enantiomer of a given compound are known in the art and are applicable for obtaining the compounds identified herein. Unless otherwise indicated, when a disclosed 10 compound is named or depicted by a structure without specifying the stereochemistry and has one or more chiral centres, it is understood to represent all possible stereoisomers of the compound. In other words, chiral centres that lack solid wedged or hashed wedged bonds 15 indicate a mixture of stereoisomers. The present disclosure also provides compounds of formula I, II, III, IV and their acceptable salts wherein one or more hydrogen is substituted with a deuterium atom. A first aspect of the present invention provides the 20 use of the compounds of formula I, II, or III as described herein, or a salt thereof as a redox-active component in a redox flow battery. A second aspect of the present invention provides the use of the compounds of formula II, III, or IV as 25 described herein, or a salt thereof as a redox-active component in a redox flow battery. A further aspect of the present invention provides electrolytic compositions which comprise at least one compound of formula I, II, III, or IV as described herein, 30 or a salt thereof. In embodiments, the electrolytic composition is for use in an energy storage device, for example as an anolyte in a redox flow battery. Accordingly, the present invention also provides the use of an electrolytic composition comprising at least one compound of formula I, II, III, or IV as described herein, or a salt thereof in an energy storage device, for example as an anolyte in a redox flow battery. 5 In embodiments, the electrolytic compositions of the invention comprise a solvent, for example where the composition comprises a redox-active compound (e.g. a compound of formula I, II, III or IV or a salt thereof) which is a solid at the operating temperature of the10 device. The solvent may be an aqueous solvent or a non- aqueous solvent. In embodiments, the electrolytic compositions does not comprise a solvent, for example where the composition comprises a redox-active compound (e.g. a compound of formula I, II, III or IV or a salt 15 thereof) which is a liquid at the operating temperature of the device. The compound of formula I, II, III or IV (or salt thereof) may be present in any suitable concentration for the required use. For example, when the compound of 20 formula I, II, III or IV (or salt thereof) is dissolved in a solvent, it may be present at a concentration of at least 0.001 M, or at least 0.01 M, or at least 0.02 M, or at least 0.03 M, or at least 0.04 M, or at least 0.05 M, or at least 0.1 M, or at least 0.2 M, or at least 0.3 M, 25 or at least 0.4 M, or at least 0.5 M, or at least one M, or at least 2 M, or at least 3 M, or at least 4 M, or at least 5 M; and at most 10 M, or at most 15 M, or at most 20 M, or at most 30 M, or at most 40 M, or at most 50 M. Suitably, the compound may be present at a concentration 30 of between 1 M and 6 M or 0.05 M and 4 M or 3.5 M and 6 M. The solvent may be any suitable solvent. For example the solvent may be water, or acetonitrile, or a dialkylcarbonate, such as dimethylcarbonate or diethylcarbonate or methylethylcarbonate or a cyclic carbonate such as ethylene carbonate or propylene carbonate, or a lactone, such as butyrolactone, or an acetamide, such as dimethylacetamide. Preferably, the solvent is non-toxic, non-flammable and has a broad 5 working redox potential window. In embodiments of the electrolytic compositions, the solvent is water. In embodiments, the electrolytic compositions of the invention further comprise at least one supporting electrolyte, for example a basic supporting electrolyte, 10 an acidic supporting electrolyte, or a neutral salt supporting electrolyte. The supporting electrolyte may be any suitable supporting electrolyte. The supporting electrolyte may be a base, or an acid, or a salt. The supporting electrolyte 15 may be a Bronsted base, or a Bronsted acid, or an alkali salt. The supporting electrolyte may be an alkali base. The supporting electrolyte may be a mineral acid. The supporting electrolyte may comprise a lithium cation, a sodium cation or a potassium cation. The supporting 20 electrolyte may comprise a chloride anion, or a fluoride anion or a bromide anion, or a perchlorate anion, or a tetrafluoroborate, or a hexafluorophosphate anion. The supporting electrolyte may be LiOH, or NaOH, or KOH. The supporting electrolyte may be LiCl, or NaCl, or KCl, or 25 LiBF4, or NaClO4, NH4PF6, or LiPF6. The supporting electrolyte may be HCl or H2SO4. In embodiments of the electrolytic composition, the at least one supporting electrolyte is selected from KOH, HCl, and KCl. The supporting electrolyte may be dissolved in the 30 neat compound or a solution comprising the compound and solvent, in any suitable concentration. The supporting electrolyte may be dissolved at a concentration of at least 0.001 M, or at least 0.01 M, or at least 0.02 M, or at least 0.03 M, or at least 0.04 M, or at least 0.05 M, or at least 0.1 M, or at least 0.2 M, or at least 0.3 M, or at least 0.4 M, or at least 0.5 M, or at least one M, or at least 2 M, or at least 3 M, or at least 4 M, or at least 5 M. 5 Embodiments of the electrolytic composition which do not comprise a solvent, for example where the redox-active compound of the invention is a liquid at the operating temperature of the energy storage device, have a distinct advantage in that their volumetric energy densities (Wh / L)10 are maximised with respect to concentration of the redox- active compound. Selection of the solvent and supporting electrolyte are within the understanding of the person skilled in the art to determine. Redox-active compounds possessing acidic 15 protons may be deprotonated by a basic supporting electrolyte altering the solubility, polarizability and redox potential of the redox-active compound, when compared to use with an acidic supporting electrolyte. Similarly, redox-active compounds comprising basic 20 electron lone pairs may be protonated in the presence of acidic supporting electrolytes also impacting the solubility, polarizability and redox potential of the redox-active compound, in comparison to use with a basic supporting electrolyte. Solution complexation of the 25 redox-active compounds with ions of a neutral salt supporting electrolyte may also impact solubilities and redox potentials the of the redox-active compounds. In another aspect, the present invention provides a redox flow battery comprising an electrolytic composition 30 of the invention as defined herein. In embodiments of the redox flow battery, the electrolytic composition of the invention as defined herein is an anolyte. In another aspect, the invention provides a method for making a redox flow battery. In embodiments, the method for making a redox flow battery comprises at least selecting a redox-active compound of formula I, II, III or IV as a constituent of an anolyte, and a suitable supporting electrolyte. A suitable solvent may be chosen 5 in conjunction with the redox-active compound and supporting electrolyte, for example if the redox-active compound is a solid at the operating temperature of the redox flow battery. In embodiments, the method for making a redox flow battery comprises selecting a suitable 10 conjugate electrolyte (i.e. a catholyte) such that a stable redox couple is generated by matching the redox- active compounds of the anolyte and catholyte. A redox- flow battery may then be constructed using standard procedures and protocols. 15 Specific and general embodiments of the disclosure will now be described by way of the following non-limiting examples. EXAMPLES The examples and preparations provided below further 20 illustrate and exemplify the compounds of the present invention and methods of preparing such compounds. It is to be understood that the scope of the present invention is not limited in any way by the scope of the following examples and preparations. 25 Example 1: Electrochemical testing of electrochemical stability window of aqueous electrolyte Blank electrolytic solutions comprising water and one of three supporting electrolytes, HCl, KCl and KOH, dissolved at 1 M, were tested for their electrochemical 30 stability using cyclic voltammetry. Potentials were measured relative to either a Ag / AgCl reference electrode (HCl and KCl) or Hg / HgO reference electrode (KOH) at a scan rate of 20 mV / s. The cyclic voltammograms demonstrate that with progressive scans the baseline currents shift to more negative values. Example 2: Electrochemical stability testing The electrolytic compositions shown in Table 2 were 5 prepared. Table 2 Electrolytic Redox active compound Supporting composition electrolyte 1 N-(pyrazin-2- KOH (1 M) ylmethyl)formamide (1 mM) 2 N-(pyrazin-2- KCl (1 M) ylmethyl)formamide (1 mM) 3 N-(pyrazinylmethyl) KOH (1 M), ethylenediamine (1 mM) KCl (0.002 M)* 4 N-(pyrazinylmethyl) KCl (1 mM) ethylenediamine (1 mM) 5 1H-imidazole-4-carboxylic HCl (1 M) acid * In order to prepare electrolytic composition 3, N- (pyrazinylmethyl)ethylenediamine dihydrochloride was added to 1M KOH solution, along with 2 additional equivalents of 10 KOH The electrolytic compositions were then deoxygenated and tested using cyclic voltammetry using a Hg / HgO reference electrode (electrolytic compositions 1 and 3) or a Ag / AgCl reference electrode (electrolytic compositions 15 2, 4 and 5) at a scan rate of 20 mV / s. Cyclic voltammograms of the redox-active compounds were then performed and the second scan of each experiment recorded. Composition 1 was also tested using prolonged cycling (up to 1000 scans). The results of the tests are shown in 20 Figure 2 to Figure 4. The experiments demonstrate the redox-active compounds are capable of exhibiting good electrochemical redox stability, as in the case of N-(pyrazin-2- ylmethyl)formamide (1 mM) in KOH as supporting 5 electrolyte, where N-(pyrazin-2-ylmethyl)formamide is shown to be stable over 1000 scans as the position of the redox waves do not exhibit any appreciable shift in potential and no other redox waves / peaks appear in the tested range throughout the duration of the experiment. 10 The negative shifting of the scan currents may be attributed to electrode surface effects. Example 3: Solubility testing Solubility tests were performed on selected redox- active compounds. Firstly, calibration curves were 15 created. Fresh stock solutions (1 mM) of redox-active compounds were made. Using the stock solutions, five new solutions were made comprising: Stock solution (mL) Blank solution (mL) 0.1 3 0.2 3 0.3 3 0.4 3 0.5 3 The UV-vis absorption spectrum of each solution was 20 then measured and a graph of Maximum Absorbance (A.U.) versus Concentration (A = f(C)) was plotted. 2 mL of blank solution was then added to a UV-vis cuvette and an amount of the redox-active compound necessary to achieve saturation was added and left to stir 25 overnight, to ensure saturation. The saturated solution was then filtered through a 0.22 um filter, and 0.04 mL of the saturated solution was diluted at least 10,000 times. The UV-vis spectrum of the solution was then measured, ensuring that the dilution was sufficient to achieve a measured spectrum within the range of values of the calibration curve. The calibration curve and equation, C1V1 = C2V2, were then used to calculate the concentration of 5 the saturated solution. All experiments were conducted at 22.7 °C. Table 3: Saturation solution concentrations Redox active Blank Saturation R-Square of compound solution concentration calibration (Csat; M) curve N-(pyrazin-2- KOH (1 M) 11.2 ± 0.4 0.9906 ylmethyl)formamide N-(pyrazin-2- KCl (1 M) 10.4 ± 0.1 0.99784 ylmethyl)formamide sodium 3- KCl (1M) 4.8 ± 0.3 M 0.99662 pyridazinesulfonate 1H-imidazole-4- KCl (1 M) 0.14 ± 0.005 0.9988 carboxylic acid M 1H-imidazole-4- HCl (1 M) 1.3 ± 0.1 M 0.99883 carboxylic acid 10

Claims

SP3159 - 48 - C L A I M S 1. The use of a compound as a redox-active component in a redox flow battery, wherein the compound has the structural Formula I, II, or III, or a salt thereof:wherein R1, R2, R3, R4, R5, R6, R7, R8, R9, R10and R11are each independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, -NO2, -X, -OR13, -NR14R15, -NHCOR16, -COOR17, -COR18, -CONR19R20, - COONHR21, Q1, Q2, and Q3; R12is selected from the group consisting of H, -SO3H, -PO3H, -COOH, -OR13, -NR14R15, -NHCOR16, -COOR17, -COR18, -CONR19R20, -COONHR21, Q4, Q5, and Q6; each R13and R22is independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, -COH, Q7, Q8, and Q9; each R14, R15, R23and R24is independently selected from the group consisting of H, -OH, -SO3H, -PO3H, - COOH, -COH, Q10, Q11, and Q12; each R16and R25is independently selected from the group consisting of H, -NH2, Q13, Q14, and Q15; each R17and R26is independently selected from the group consisting of -NR30R31, Q16, Q17, and Q18; each R18and R27is independently selected from the group consisting of H, -NR30R31, -SO3H, -PO3H, -COOH, Q19, Q20, and Q21;each R19, R20, R28, and R29is independently selected from the group consisting of H, -OH, -SO3H, -PO3H, - COOH, and Q22; each R21is independently selected from the group consisting of H, -SO3H, -PO3H, -COOH; and Q23; each R30and R31is independently selected from the group consisting of H and C1-C6alkyl; each Q1and Q4is independently selected from C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, and C2-C13 polyalkylether, each optionally substituted with one or more groups independently selected from -SO3H, - PO3H, -NO2, -X, -OR22, -NR23R24, -NHCOR25, -COOR26, - COR27, -CONR28R29, oxo (=O), C1-C6alkoxyl, saturated or unsaturated 3- to 6-membered carbocyclyl and saturated or unsaturated 3- to 6-membered heterocyclyl, wherein the alkoxyl is optionally substituted with one or more groups independently selected from -SO3H, -PO3H, -COOH, -NO2, -X, -OR22, - NR23R24, -NHCOR25, -COOR26, -COR27, -CONR28R29, and oxo (=O), and the carbocyclyl and heterocyclyl are each optionally substituted with one or more groups independently selected from C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, C2-C13 polyalkylether, C1-C6 alkoxyl, -SO3H, -PO3H, -COOH, -NO2, -X, -OR22, - NR23R24, -NHCOR25, -COOR26, -COR27, -CONR28R29, and oxo (=O); each Q2and Q5is independently selected from saturated or unsaturated 3- to 6-membered carbocyclyl, optionally substituted with one or more groups independently selected from C1-C6alkyl, C2-C6alkenyl, C2-C6alkynyl, C2-C13polyalkylether, C1-C6alkoxyl, -SO3H, -PO3H, -COOH, -NO2, -X, -OR22, - NR23R24, -NHCOR25, -COOR26, -COR27, -CONR28R29, and oxo (=O); andeach Q3and Q6is independently selected from saturated or unsaturated 3- to 6-membered heterocyclyl having one or more heteroatoms selected from N, O and S, optionally substituted with one or more groups independently selected from C1-C6 alkyl, C2-C6alkenyl, C2-C6alkynyl, C2-C13polyalkylether, C1-C6alkoxyl, -SO3H, -PO3H, -COOH, -NO2, -X, -OR22, - NR23R24, -NHCOR25, -COOR26, -COR27, -CONR28R29, and oxo (=O); each Q7is independently selected from C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, and C2-C13 polyalkylether, all optionally substituted with one or more groups independently selected from -SO3H, - PO3H, -COOH, -NO2, -X, -NR23R24, -NHCOR25, -COOR26, - COR27, -CONR28R29, oxo (=O), -OH, C1-C6 alkoxyl, saturated or unsaturated 3- to 6-membered carbocyclyl, and saturated or unsaturated 3- to 6- membered heterocyclyl, wherein the carbocyclyl and the heterocyclyl are each optionally substituted with one or more groups independently selected from C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, or C2-C13 polyalkylether, C1-C6 alkoxyl, -SO3H, -PO3H, -COOH, and -OH; each Q8, Q10, Q13, Q16and Q19is independently selected from saturated or unsaturated 3- to 6- membered carbocyclyl, optionally substituted with one or more groups independently selected from C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, C2-C13 polyalkylether, C1-C6 alkoxyl, -SO3H, -PO3H, -COOH, and -OH; each Q9, Q11, Q14, Q17and Q20is independently selected from saturated or unsaturated 3- to 6- membered heterocyclyl having one or more heteroatoms selected from N, O and S, optionally substitutedwith one or more groups independently selected from C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, C2-C13 polyalkylether, C1-C6 alkoxyl, -SO3H, -PO3H, -COOH, and -OH; each Q12is independently selected from C1-C6 alkyl, C2-C6alkenyl, C2-C6alkynyl, and C2-C13polyalkylether, each optionally substituted with one or more groups independently selected from -SO3H, - PO3H, -COOH, -NO2, -X, -NR30R31, -NHCOR25, -COOR26, - COR27, -CONR28R29, oxo (=O), -OH, C1-C6 alkoxyl, saturated or unsaturated 3- to 6-membered carbocyclyl, and saturated or unsaturated 3- to 6- membered heterocyclyl, wherein the carbocyclyl and the heterocyclyl are each optionally substituted with one or more groups independently selected from C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, or C2-C13 polyalkylether, C1-C6 alkoxyl, -SO3H, -PO3H, -COOH, and -OH; each Q15is independently selected from C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, and C2-C13 polyalkylether, all optionally substituted with one or more groups independently selected from -SO3H, - PO3H, -COOH, -NO2, -X, -NR30R31, -COOR26, -COR27, - CONR28R29, oxo (=O), -OH, C1-C6alkoxyl, saturated or unsaturated 3- to 6-membered carbocyclyl, and saturated or unsaturated 3- to 6-membered heterocyclyl, wherein the carbocyclyl and heterocyclyl are each optionally substituted with one or more groups independently selected from C1-C6 alkyl, C2-C6alkenyl, C2-C6alkynyl, C2-C13polyalkylether, C1-C6alkoxyl, -SO3H, -PO3H, -COOH, and -OH; each Q18and Q21is independently selected from C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, or C2-C13polyalkylether, all optionally substituted with one or more groups independently selected from -SO3H, - PO3H, -COOH, -NO2, -X, -NR30R31, -CONR28R29, oxo (=O), - OH, C1-C6 alkoxyl, saturated or unsaturated 3- to 6- membered carbocyclyl, and saturated or unsaturated 3- to 6-membered heterocyclyl, wherein the carbocyclyl and heterocyclyl are each optionally substituted with one or more groups independently selected from C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, C2-C13 polyalkylether, C1-C6 alkoxyl, -SO3H, -PO3H, -COOH, and -OH; each Q22is independently selected from C1-C7 alkyl, C2-C6alkenyl, C2-C6alkynyl, and C2-C13polyalkylether, all optionally substituted with one or more groups independently selected from -SO3H, - PO3H, -COOH, -NO2, -X, -NR30R31, oxo (=O), -OH, C1-C6 alkoxyl, saturated or unsaturated 3- to 6-membered carbocyclyl, and saturated or unsaturated 3- to 6- membered heterocyclyl, wherein the carbocyclyl and heterocyclyl are each optionally substituted with one or more groups independently selected from C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, C2-C13 polyalkylether, C1-C6 alkoxyl, -SO3H, -PO3H, -COOH, and -OH; each Q23is independently selected from C1-C6alkyl, C2-C6 alkenyl, C2-C6 alkynyl, and C2-C13 polyalkylether, each optionally substituted with one or more groups independently selected from -SO3H, - PO3H, -COOH, -NO2, -X, -NR30R31, oxo (=O), -OH, C1-C6 alkoxyl, saturated or unsaturated 3- to 6-membered carbocyclyl, and saturated or unsaturated 3- to 6- membered heterocyclyl, wherein the carbocyclyl and heterocyclyl are each optionally substituted with one or more groups independently selected from C1-C6alkyl, C2-C6alkenyl, C2-C6alkynyl, C2-C13polyalkylether, C1-C6 alkoxyl, -SO3H, -PO3H, -COOH, and -OH; each -X is a halide; wherein at least one of R1, R2, R3and R4is not H; wherein if one of R1, R2, R3or R4is -COOH, then at least one of the remaining R1, R2, R3and R4groups is not H or -COOH; wherein if one of R1, R2, R3or R4is C1 alkyl, then at least one of the remaining R1, R2, R3or R4groups is not H or C1 alkyl; wherein if one of R1, R2, R3or R4is Cl, then at least one of the remaining R1, R2, R3or R4groups is not H; wherein if one of R1, R2, R3or R4is -OMe, then at least one of the remaining R1, R2, R3or R4groups is not H; wherein if one of R1, R2, R3or R4is -CONH2, then at least one of the remaining R1, R2, R3or R4groups is not H; and wherein if one of R1, R2, R3or R4is C2 alkenyl, then at least one of the remaining R1, R2, R3or R4groups is not H.

2. The use of claim 1, wherein R1, R2, R3, R4, R5, R6, R7, R8, R9, R10and R11are each independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, -NO2, -X, -OR13, -NR14R15, - NHCOR16, -COOR17, -COR18, -CONR19R20, -COONHR21, Q1, Q2, and Q3; each Q1is independently selected from C1-C6alkyl and C2-C13 polyalkylether, each optionally substituted with one or more groups independentlyselected from -SO3H, -PO3H, -COOH; -X, -OR22, -NR23R24, -NHCOR25, -COOR26, -COR27, -CONR28R29, and oxo (=O); each Q2is independently selected from saturated or unsaturated 3- to 6-membered carbocyclyl optionally substituted with one or more groups independently selected from -NR23R24; each Q3is independently selected from saturated or unsaturated 3- to 6-membered heterocyclyl having one or more heteroatoms selected from N, O and S; each R12is independently selected from H and C1-C3 alkyl; each R13is independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, -COH, C1-C4alkyl, wherein the alkyl is optionally substituted with one or more -OH; each R14is H; each R15is each independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, -COH, - OH, and C1-C4 alkyl, wherein the alkyl is optionally substituted with one or more groups selected from - SO3H, -PO3H, -COOH, -X, -NH2, oxo (=O), and -OH; each R16is independently selected from the group consisting of H, -NH2 and C1-C4 alkyl optionally substituted with one or more groups independently selected from -OH; each R17is independently selected from the group consisting of -NH2 and C1-C4 alkyl optionally substituted with one or more groups independently selected from -NH2, and -OH; each R18is independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, -NR30R31, C1-C6alkyl, saturated or unsaturated 3- to 6-membered carbocyclyl, and saturated or unsaturated 3- to 6- membered heterocyclyl having one or more heteroatomsselected from N, O and S, wherein the alkyl is optionally substituted with one or more groups independently selected from -SO3H, -PO3H, -COOH, -X, -NR30R31, and -OH; each R19is H; each R20is independently selected from the group consisting of H, -OH, -SO3H, -PO3H, -COOH, and C1-C7alkyl, wherein the alkyl is optionally substituted with one or more groups independently selected from -NH2 and -OH; each R21is independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, and C1-C6 alkyl, wherein the alkyl is optionally substituted with one or more groups independently selected from -SO3H, - PO3H, -COOH, -NR30R31, oxo (=O), and -OH; each R22is independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, -COH, and C1-C4 alkyl, wherein the alkyl is optionally substituted with one or more groups independently selected from the group consisting of -NR23R24, and -OH; each R23is H; each R24is independently selected from the group consisting of H, -OH, -SO3H, -PO3H, -COOH, -COH, and C1-C6alkyl, wherein the alkyl is optionally substituted with one or more groups independently selected from -SO3H, -PO3H, -COOH, -NR30R31, -X, oxo (=O), and -OH; each R25is independently selected from the group consisting of H, -OH, -NH2, and C1-C4 alkyl, wherein the alkyl is optionally substituted with one or more groups independently selected from -NH2, and -OH; each R26is independently selected from C1-C4 alkyl optionally substituted with one or more groups independently selected from -OH;each R27is independently selected from the group consisting of H, -OH, -NH2, and C1-C4 alkyl, wherein the alkyl is optionally substituted with one or more groups independently selected from -OH, and -NH2; each R28and R29is H; and each R30and R31is H.

3. The use of claim 1 or claim 2, wherein R1, R2, R3, R4, R5, R6, R7, R8, R9, R10and R11are each independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, -NO2, -X, -OR13, -NR14R15, - NHCOR16, -COOR17, -COR18, -CONR19R20, -COONHR21, Q1, and Q2; each Q1is independently selected from C1-C6 alkyl and C2-C13 polyalkylether, wherein the alkyl is optionally substituted with one or more groups independently selected from -SO3H, -PO3H, -COOH; -X, -OR22, -NR23R24, -NHCOR25, -COOR26, -COR27, -CONR28R29, and oxo (=O); each Q2is independently selected from saturated or unsaturated 3- to 6-membered carbocyclyl optionally substituted with one or more groups independently selected from -NR23R24; each R12is independently selected from H and C1-C3alkyl; each R13is independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, -COH, C1-C4 alkyl, wherein the alkyl is optionally substituted with one or more -OH; each R14is H; each R15is each independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, -COH, - OH, and C1-C4 alkyl, wherein the alkyl is optionallysubstituted with one or more groups selected from - COOH, -X, -NH2, oxo (=O), and -OH; each R16is independently selected from the group consisting of H, and C1-C4 alkyl optionally substituted with one or more groups independently selected from -OH; each R17is independently selected from the group consisting of -NH2 and C1-C4 alkyl optionally substituted with one or more groups independently selected from -NH2, and -OH; each R18is independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, -NR30R31, C1-C6 alkyl, saturated or unsaturated 3- to 6-membered carbocyclyl, and saturated or unsaturated 3- to 6- membered heterocyclyl having one or more heteroatoms selected from N, O and S, wherein the alkyl is optionally substituted with one or more groups independently selected from -NR30R31, and -OH; each R21is independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, and C1-C6 alkyl, wherein the alkyl is optionally substituted with one or more groups independently selected from -NR30R31and -OH; each R19is H; each R20is independently selected from the group consisting of H, -OH, -SO3H, -PO3H, -COOH, and C1-C7 alkyl, wherein the alkyl is optionally substituted with one or more groups independently selected from -NH2 and -OH; each R21is independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, and C1-C6alkyl, wherein the alkyl is optionally substituted with one or more groups independently selected from -SO3H, - PO3H, -COOH, -NR30R31, oxo (=O), and -OH;each R22is independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, -COH, and C1-C4 alkyl, wherein the alkyl is optionally substituted with one or more groups independently selected from the group consisting of -NR23R24, and -OH; each R23is H; each R24is independently selected from the group consisting of H, -OH, -SO3H, -PO3H, -COOH, -COH, and C1-C6 alkyl, wherein the alkyl is optionally substituted with one or more groups independently selected from -NR30R31, oxo (=O), and -OH; each R25is independently selected from -OH and C1-C4 alkyl; each R26is independently selected from C1-C4 alkyl; each R27is independently selected from the group consisting of H, -OH, -NH2, and C1-C4 alkyl; each R28and R29is H; and each R30and R31is H.

4. The use of any preceding claim, wherein R1, R2, R3, R4, R5, R6, R7, R8, R9, R10and R11are each independently selected from the group consisting of H, -SO3H, -COOH, -OR13, -COR18, Q1, and Q2; each Q1is independently selected from C1-C6alkyl substituted with one or more groups independently selected from -COOH, -X, -NR23R24, and oxo (=O); each Q2is independently selected from saturated or unsaturated 3- to 6-membered carbocyclyl substituted with one or more groups independently selected from -NR23R24; each R12is H; each R13is -COH; each R18is independently selected from C1-C6 alkyl and saturated or unsaturated 3- to 6-memberedheterocyclyl having one or more heteroatoms selected from N, O and S, wherein the alkyl is substituted with one or more groups independently selected from -NR30R31; each R23is H; each R24is independently selected from C1-C6alkyl substituted with one or more groups independently selected from -NR30R31and oxo (=O); each R30is H; and each R31is H.

5. The use of a compound as a redox-active component in a redox flow battery, wherein the compound has the structural Formula II, III, or IV, or a salt thereof:are independently selected from the group consisting of H, -SO3H, - PO3H, -NO2, -F, -OR13’, -NR14R15, -NHCOR16, -COOR17, - COR18’, -COONHR21, Q2, Q3, Q24or Q25; each R13is independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, -COH, Q7, Q8, and Q9; each R18is independently selected from the group consisting of H, -SO3H, -PO3H, -COOH, Q19, Q20, and Q21; each Q7is independently selected from C2-C6 alkyl, C2-C6alkenyl, C2-C6alkynyl, and C2-C13polyalkylether, all optionally substituted with one or more groups independently selected from -SO3H, - PO3H, -COOH, -NO2, -X, -NR23R24, -NHCOR25, -COOR26, -COR27, -CONR28R29, oxo (=O), -OH, C1-C6alkoxyl, saturated or unsaturated 3- to 6-membered carbocyclyl, and saturated or unsaturated 3- to 6- membered heterocyclyl, wherein the carbocyclyl and the heterocyclyl are each optionally substituted with one or more groups independently selected from C1-C6alkyl, C2-C6alkenyl, C2-C6alkynyl, or C2-C13polyalkylether, C1-C6 alkoxyl, -SO3H, -PO3H, -COOH, and -OH; each Q24is independently selected from C1 alkyl substituted with one or more groups independently selected from -SO3H, -PO3H, -NO2, -X, -OR22, -NR23R24, -NHCOR25, -COOR26, -COR27, -CONR28R29, C1-C6alkoxyl, saturated or unsaturated 3- to 6-membered carbocyclyl and saturated or unsaturated 3- to 6- membered heterocyclyl, wherein the alkoxyl is optionally substituted with one or more groups independently selected from -SO3H, -PO3H, -COOH, - NO2, -X, -OR22, -NR23R24, -NHCOR25, -COOR26, -COR27, - CONR28R29, and oxo (=O), and the carbocyclyl and heterocyclyl are each optionally substituted with one or more groups independently selected from C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, C2-C13 polyalkylether, C1-C6alkoxyl, -SO3H, -PO3H, -COOH, - NO2, -X, -OR22, -NR23R24, -NHCOR25, -COOR26, -COR27, - CONR28R29, and oxo (=O); each Q25is independently selected from C2-C6 alkyl and C2-C13 polyalkylether, each optionally substituted with one or more groups independently selected from -SO3H, -PO3H, -NO2, -X, -OR22, -NR23R24, -NHCOR25, -COOR26, -COR27, -CONR28R29, oxo (=O), C1-C6alkoxyl, saturated or unsaturated 3- to 6-membered carbocyclyl and saturated or unsaturated 3- to 6- membered heterocyclyl, wherein the alkoxyl isoptionally substituted with one or more groups independently selected from -SO3H, -PO3H, -COOH, - NO2, -X, -OR22, -NR23R24, -NHCOR25, -COOR26, -COR27, - CONR28R29, and oxo (=O), and the carbocyclyl and heterocyclyl are each optionally substituted with one or more groups independently selected from C1-C6alkyl, C2-C6alkenyl, C2-C6alkynyl, C2-C13polyalkylether, C1-C6 alkoxyl, -SO3H, -PO3H, -COOH, - NO2, -X, -OR22, -NR23R24, -NHCOR25, -COOR26, -COR27, - CONR28R29, and oxo (=O); and each of R12, R14, R15, R16, R17, R21, R25, R26, R27, R28, R29, Q2, Q3, Q7, Q8, Q9, Q19, Q20, Q21and X are as defined in any preceding claim.

6. The use of a compound according to any preceding claim, wherein the compound is selected from: 2- (pyrazin-2-yl)acetaldehyde, N- (pyrazinylmethyl)ethylenediamine, N-(pyrazin-2- ylmethyl)formamide, 3-fluoro-3-(pyrazin-2-yl)propan- 1-amine, 2-pyrazineacetic acid, N-(pyridazin-3- ylmethyl)formamide, 1-(pyridazin-3- yl)cyclopropanamine, 2-amino-1-pyridazin-3- ylethanone, morpholin-4-yl(pyridazine-4- yl)methanone, 3-pyridazinesulfonic acid, 1H- imidazole-4-carboxylic acid, pyrazine formate, 3- (trifluoromethyl)-2-pyrazinecarboxylic acid, 3- pyridazinecarboxylic acid; and salts thereof.

7. An electrolytic composition comprising at least one compound as defined in any of claims 1 to 6.

8. The electrolytic composition of claim 7, wherein the electrolytic composition additionally comprises at least one supporting electrolyte, wherein thesupporting electrolyte may be a basic supporting electrolyte, an acidic supporting electrolyte, or a neutral salt supporting electrolyte, for example wherein the supporting electrolyte is selected from 5 the group consisting of: KOH, HCl, and KCl.

9. The electrolytic composition of claim 6 or claim 7, wherein the electrolytic composition additionally comprises solvent, wherein the solvent may be an 10 aqueous solvent or a non-aqueous solvent.

10. The electrolytic composition of claim 9, wherein the solvent is water. 15 11. The electrolytic composition of any of claims 7 to 9, wherein the electrolytic composition does not comprise a solvent.

12. A redox flow battery comprising an electrolytic 20 composition as defined in any one of claims 7 to 11, for example wherein the electrolytic composition as defined in any one of claims 7 to 11 is an anolyte.

13. A method for making a redox flow battery according 25 to claim 12.

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