Halogen bonding receptors and uses thereof

Abstract

Halogen bonding receptors are described, as well as their use in sensing dicarboxylates.

Description

HALOGEN BONDING RECEPTORS AND USES THEREOF INTRODUCTION

[0001] The present invention relates to halogen bonding receptors and uses thereof. More specifically, the present invention relates to halogen bonding, pillararene-based receptors for use in optical sensing applications, particularly in the sensing of dicarboxylates. BACKGROUND OF THE INVENTION

[0002] As significant intermediates in many biosynthetic pathways,[1]dicarboxylates (DCBs) (Figure 1a) are implicated in a variety of chronic illnesses, including kidney and liver disease.[2]In addition, DCBs are commonly used in the manufacturing of plastics and as linkers in the ever- increasing production of metal-organic frameworks,[3-4]and hence are emerging as environmental pollutants of concern.[3]As a result, the recognition and sensing of DCBs is of intense interest for applications in health monitoring, industrial material production and environmental protection.[5-7].

[0003] In spite of recent advances, there remains a need for new compounds having improved DCB sensing properties.

[0004] The present invention was devised with the foregoing in mind. SUMMARY OF THE INVENTION

[0005] According to a first aspect of the present invention there is provided a compound having a structure according to formula I defined herein.

[0006] According to a second aspect of the present invention there is provided a sensing assembly comprising a compound having a structure according to formula I defined herein.

[0007] According to a third aspect of the present invention there is provided a use of a compound of the first aspect or a sensing assembly of the second aspect for determining the presence or absence of a dicarboxylate in a sample.

[0008] According to a fourth aspect of the present invention there is provided a process for determining the presence or absence of a dicarboxylate in a sample, the process comprising the steps of: a) contacting a sample with a compound of the first aspect or a sensing assembly of the second aspect; andb) determining the presence or absence of a dicarboxylate in the sample.

[0009] Suitably, in the compounds of the first aspect, pillar[5-6]arene A denotes a plane of symmetry (i.e., all instances of X1, X2, Y and Z, as well as sub-groups associated therewith, have identical definitions). DETAILED DESCRIPTION OF THE INVENTION

[0010] Throughout the entirety of the description and claims of this specification, where subject matter is described herein using the term “comprise” (or “comprises” or “comprising”), the same subject matter instead described using the term “consist of” (or “consists of” or “consisting of”) or “consist essentially of” (or “consists essentially of” or “consisting essentially of”) is also contemplated.

[0011] Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[0012] Features described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and / or steps are mutually exclusive. The invention is not restricted to the details of any of the specific embodiments recited herein. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

[0013] The term "(m-nC)" or "(m-nC) group" used alone or as a prefix, refers to any group having m to n carbon atoms.

[0014] The term “alkyl” as used herein refers to straight or branched chain alkyl moieties, typically having 1, 2, 3, 4, 5 or 6 carbon atoms. This term includes reference to groups such as methyl, ethyl, propyl (n-propyl or isopropyl), butyl (n-butyl, sec-butyl or tert-butyl), pentyl, hexyl and the like. Most suitably, an alkyl may have 1, 2, 3 or 4 carbon atoms.

[0015] The term “alkylene” as used herein refers to a divalent equivalent of an alkyl group as described above (e.g., methylene, ethylene, propylene, etc.).

[0016] The term “alkenyl” as used herein refers to straight or branched chain alkenyl moieties, typically having 1, 2, 3, 4, 5 or 6 carbon atoms. The term includes reference to alkenyl moieties containing 1, 2 or 3 carbon-carbon double bonds (C=C). This term includes reference to groups such as ethenyl (vinyl), propenyl (allyl), butenyl, pentenyl and hexenyl, as well as both the cis and trans isomers thereof.

[0017] The term “alkenylene” as used herein refers to a divalent equivalent of an alkenyl group as described above (e.g., vinylene, propenylene, butenylene, etc.).

[0018] The term "aryl" or “aromatic” as used herein means an aromatic ring system comprising 6, 7, 8, 9 or 10 ring carbon atoms. Aryl is often phenyl but may be a polycyclic ring system, having two or more rings, at least one of which is aromatic. This term includes reference to groups such as phenyl, naphthyl and the like.

[0019] The term “arylene” as used herein refers to a divalent equivalent of an aryl group as described above (e.g., phenylene).

[0020] The term "heteroaryl" or “heteroaromatic” as used herein means an aromatic mono-, bi-, or polycyclic ring incorporating one or more (for example 1-4, particularly 1, 2 or 3) heteroatoms selected from nitrogen, oxygen or sulfur. Examples of heteroaryl groups are monocyclic and bicyclic groups containing from five to twelve ring members, and more usually from five to ten ring members. The heteroaryl group can be, for example, a 5- or 6-membered monocyclic ring or a 9- or 10-membered bicyclic ring, for example a bicyclic structure formed from fused five and six membered rings or two fused six membered rings. Each ring may contain up to about four heteroatoms typically selected from nitrogen, sulfur and oxygen. Typically, the heteroaryl ring will contain up to 3 heteroatoms, more usually up to 2, for example a single heteroatom.

[0021] The term “heteroarylene” as used herein refers to a divalent equivalent of an heteroaryl group as described above (e.g., pyridylene).

[0022] The term “substituted” as used herein in reference to a moiety means that one or more, especially up to 5. Preferably, “substituted” as used herein in reference to a moiety means that 1, 2 or 3, of the hydrogen atoms in said moiety are replaced independently of each other by the corresponding number of the described substituents. Even more preferred, “substituted” as used herein in reference to a moiety means that 1 or 2, of the hydrogen atoms in said moiety are replaced independently of each other by the corresponding number of the described substituents. The term “optionally substituted” as used herein means substituted or unsubstituted.

[0023] It will, of course, be understood that substituents are only at positions where they are chemically possible, the person skilled in the art being able to decide (either experimentally or theoretically) without inappropriate effort whether a particular substitution is possible.

[0024] In a first aspect, the invention provides a compound having a structure according to formula I:wherein A is a pillar[5-6]arene; each Z is independently an optical sensor; each Y is independently a group linking A to Z; each X1is independently H, I or Br; and each X2is independently absent, H, I, or Br with the proviso that at least one X1, or at least one X2, is I or Br.

[0025] Through rigorous investigation, the inventors have developed the compounds of the first aspect, which are surprisingly active in the sensing of dicarboxylates. Without wishing to be bound by theory, it is believed that the unprecedented combination of optical sensor-conjugated halogen bonding sites optimally located on a pillararene having an appropriately sized, hydrophobic cavity provides enhanced sensing properties relative to other receptors.

[0026] The structure of pillararenes will be familiar to one of ordinary skill in the art. In some instances, A may be a pillar[5]arene. In other instances, A may be a pillar[6]arene. Suitably, A is a pillar[5]arene. Pillararenes are understood to comprise an upper rim, a hydrophobic cavity and a lower rim.

[0027] It will be understood that one Y group is attached to one rim of pillar[5-6]arene A, whilst the other Y group is attached to the other rim of pillar[5-6]arene A. Suitably, both Y groups are attached to the same repeating unit of pillar[5-6]arene A.

[0028] Pillar[5-6]arene A may have a structure according to formula II:wherein 1 denotes a point of attachment to one of the two Y groups and2denotes a point of attachment to the other of the two Y groups; each R1is independently H or (1-2C)alkyl; and m is 4 or 5.

[0029] Both R1groups are suitably identical. More suitably, R1is methyl.

[0030] m is suitably 4 (i.e., A is a pillar[5]arene).

[0031] In many instances, R1is methyl and m is 4.

[0032] As discussed hereinbefore, in many instances, pillar[5-6]arene A denotes a plane of symmetry (i.e., all instances of X1, X2, Y and Z, as well as sub-groups associated therewith, have identical definitions).

[0033] Each Y may independently be a group providing a conjugated linkage between Z and X1and / or X2. Those of ordinary skill in the art will be readily familiar with the concept of conjugation. It will be understood that in those examples of Y outlined hereinbelow, X1and X2(when present) may be conjugatively linked to Z.

[0034] Each Y may be independently such that: (i) A is separated from Z by 5-15 bond lengths, suitably by 8-12 bond lengths; and / or (ii) X1is separated from A by 3-6 bond lengths, suitably by 4-5 bond lengths; and / or (iii) X2, when present, is separated from A by 9-12 bond lengths, suitably by 10-11 bond lengths.

[0035] For illustrative purposes, a non-limiting example of Y is depicted below, which has been annotated to show the relevant number of bond lengths separating A from Z:As will be clear from the above, references herein to separation by a certain number of bond lengths refers to the minimum distance separating the groups in question (i.e., the shortest route from one group to the other).

[0036] Each Y may independently have a structure according to formula III:wherein 3 denotes a point of attachment to A; 4 denotes a point of attachment to Z; L1is absent (in which case A is linked directly to Q1) or is a group separating A from Q1by 2-3 bond lengths; Q1is a triazole substituted with X1, or a charge-balanced triazolium group substituted with X1; L2is absent (in which case Q1is linked directly to L3) or is a group separating Q1from Q2by 4-5 bond lengths; Q2is absent (in which case Q1is linked directly to L3) or is a triazole substituted with X2, or a charge-balanced triazolium group substituted with X2; and L3is absent (in which case Q2is linked directly to Z) or is a group separating Q2from Z (or separating Q1from Z when L2and Q2are both absent) by 2-3 bond lengths; with the proviso that when Q2is absent, L2is also absent.

[0037] L1, L2and L3, when present, may be formed exclusively from carbon and hydrogen.

[0038] L1is suitably a -CH2- group.

[0039] L2, when present, may be a (2-3C)alkylene group, (2-3C)alkenylene group, an arylene group or a heteroarylene group. Suitably, when present, L2is a phenylene group. Most suitably, when present, L2is a 1,3-phenylene group.

[0040] L3is suitably absent, a -CH2- group or a -CH- group.

[0041] Q1may have a structure according to formula IIIa or IIIb:wherein 5 denotes a point of attachment to L2(or to L3when L2and Q2are absent); 6 denotes a point of attachment to L1; R2is absent or (1-3C)alkyl; with the proviso that when R2is not absent, the nitrogen atom to which it is attached carries a positive charge, which is balanced by a negatively charged counter ion.

[0042] R2is suitably absent or methyl.

[0043] In many instances, Q1has a structure according to formula IIIa.

[0044] Q2, when present, may have a structure according to formula IIIa or IIIb:wherein 7 denotes a point of attachment to L2; 8 denotes a point of attachment to L3; R3is absent or (1-3C)alkyl; with the proviso that when R3is not absent, the nitrogen atom to which it is attached carries a positive charge, which is balanced by a negatively charged counter ion.

[0045] R3is suitably absent or methyl.

[0046] In many instances, Q2, when present, has a structure according to formula IVa.

[0047] In many instances, each Y independently has a structure according to formula Va:wherein R2, R3, L1, L2, L3,3and4have any of the definitions outlined hereinbefore.

[0048] Suitably, each Y independently has a structure according to formula Va-i:(Va-i) wherein Ph denotes a phenylene group (e.g., a 1,3-phenylene group); and 3,4, R2, R3, X1and X2have any of the definitions outlined hereinbefore.

[0049] In many instances, each Y independently has a structure according to formula Vb:(Vb) wherein R2, X1, L1, L3,3and4have any of the definitions outlined hereinbefore.

[0050] Suitably, each Y independently has a structure according to formula Vb-i:wherein R2, X1, L3,3and4have any of the definitions outlined hereinbefore.

[0051] Each Z may independently be a fluorophore. Suitably, the fluorophore is selected from bodipy and coumarin. The structures of bodipy and coumarin will be very familiar to those skilled in the art as comprising the following core structures respectively:Those skilled in the art will also understand that the core structures of bodipy and coumarin can be straightforwardly substituted at a variety of positions and / or fused to additional cyclic groups whilst still preserving the fluorescence properties.

[0052] In many instances, Z is bodipy, having a core structure:wherein bodipy is bound to Y through one of the carbons labelled 1-4. Most suitably, bodipy is bound to Y through the carbon labelled 1.

[0053] Most suitably, bodipy has the following structure:wherein bodipy is bound to Y through one of the carbons labelled 1-4. Most suitably, bodipy is bound to Y through the carbon labelled 1.

[0054] In many instances, when each Y has a structure according to formula III, the moiety –L3–Z may have a structure:wherein 9 denotes a point of attachment to Q2 (or Q1 when both Q2 and L2 are absent).

[0055] X1and X2are sites at which the host compound having a structure according to formula I can partake in halogen bonding or hydrogen bonding with a target guest molecule. The fact that at least one X1, or at least one X2, is I or Br means that the compound having a structure according to formula I must be able to partake in at least some halogen bonding, thus making any hydrogen bonding an optional additional interaction.

[0056] Each X1may independently be I or H. Most suitably, each X1is I.

[0057] Each X2may independently be absent, I or H. Most suitably, each X2is absent or I.

[0058] In some instances, A has a structure according to formula II; and each Y has a structure according to formula Va or Vb, or a sub-formula thereof.

[0059] In some instances, each Y has a structure according to formula Va or Vb, or a sub-formula thereof; and each Z is bodipy.

[0060] In some instances, each Y has a structure according to formula Va or Vb, or a sub-formula thereof; X1is I; and X2, when present, is I.

[0061] In some instances, A has a structure according to formula II; X1is I; and X2, when present, is I.

[0062] In some instances, each Z is bodipy; X1is I; and X2, when present, is I.

[0063] In some instances, A has a structure according to formula II; each Y has a structure according to formula Va or Vb, or a sub-formula thereof; X1is I; and X2, when present, is I.

[0064] In some instances, A has a structure according to formula II; each Z is bodipy; each Y has a structure according to formula Va or Vb, or a sub-formula thereof; X1is I; and X2, when present, is I.

[0065] In particular instances, the compound has a structure according to any one of the following:where XAdenotes one or more anions suitable for balancing the charge on the triazolium groups. Suitably, XAis one or more NO3- groups.

[0066] Most suitably, the compound has the following structure:

[0067] The compound having a structure according to formula I may be immobilized on a solid support. It will be understood that immobilization of the compound on a solid support may result in one or more structural modifications to the compound. Purely for the sake of illustration, the compound may be immobilized on a solid support via one or both Y groups. For example, the compound may be covalently attached to a solid support via one or both L2groups (e.g., L2may be a 1,3,5-phenylene group that is attached to Q1and Q2at the 1 and 3 positions respectively, whilst being attached to a solid support at the 5 position). Alternatively, the compound may be covalently attached to a solid support via A. In one instance, one rim of A is bound to a group –Y(X1)(X2)-Z as described herein, whilst on the other rim of A, the group –Y(X1)(X2)-Z is replaced by a point of attachment to a solid support.

[0068] In a second aspect, the invention provides a sensing assembly comprising a compound of the first aspect. Alongside the compound of the first aspect, the sensing assembly may further comprise any additional componentry required to translate the sensing properties of the compound into a readable and / or quantifiable output. Such componentry may include, for example, a transducer, a computer, and / or, in some instances, a fluorimeter.

[0069] In a third aspect, the invention provides a use of a compound of the first aspect or a sensing assembly of the second aspect for determining the presence or absence of a dicarboxylate in a sample.

[0070] In a fourth aspect, the invention provides a process for determining the presence or absence of a dicarboxylate in a sample, the process comprising the steps of: a) contacting a sample with a compound of the first aspect or a sensing assembly of the second aspect; and b) determining the presence or absence of a dicarboxylate in the sample.

[0071] The following paragraphs are applicable to both the third and fourth aspects of the invention.

[0072] The sample that is contacted with the compound of formula I is suitably a sample that is suspected of containing a dicarboxylate.

[0073] The compounds and sensors of the invention may exhibit switch-on or switch-off properties in the presence of a dicarboxylate. Switch-on will be understood to denote an enhanced optical signal (e.g., increased fluorescence) relative to a rest state, whereas switch-off will be understood to denote a diminished optical signal (e.g., decreased fluorescence) relative to a rest state. Whether or not a given compound or receptor exhibits switch-on or switch-off properties in the presence of a given dicarboxylate may depend on the solvent in which the dicarboxylate is provided.

[0074] Determining the presence or absence of a dicarboxylate in the sample may be achieved by measuring the optical properties (e.g., fluorescence) of the compound of formula I upon contacting it with the sample.

[0075] The two –C(O)O- groups of the dicarboxylate may be separated from one another by 5 to 22 bond lengths. Suitably, the two –C(O)O- groups of the dicarboxylate are separated from one another by 7 to 20 bond lengths. More suitably, the two –C(O)O- groups of the dicarboxylate are separated from one another by 8 to 19 bond lengths,

[0076] The sample may be an organic solution, an aqueous solution or an aqueous-organic solution. Aqueous-organic solutions may contain any ratio of water to organic solvent. In some instances, the aqueous-organic solution may contain up to 50% v / v of water in organic solvent.

[0077] In some instances, the sample is a biological sample, in which case the third or fourth aspect of the invention may be conducted in vitro (i.e., ex vivo). Also described herein is compound having a structure according to formula I for use in diagnosing a condition or disease implicated by the presence of excess dicarboxylate in the liver or kidney.

[0078] The following numbered statements 1 to 58 are not claims, but instead describe particular aspects and embodiments of the invention: 1. A compound having a structure according to formula I:wherein A is a pillar[5-6]arene; each Z is independently an optical sensor; each Y is independently a group linking A to Z;each X1is independently H, I or Br; and each X2is independently absent, H, I, or Br with the proviso that at least one X1, or at least one X2, is I or Br. 2. The compound as defined in statement 1, wherein A has a structure according to formula II:wherein 1 denotes a point of attachment to one of the two Y groups and2denotes a point of attachment to the other of the two Y groups; each R1is independently H or (1-2C)alkyl; and m is 4 or 5 3. The compound as defined in statement 2, wherein R1is methyl. 4. The compound as defined in statement 2 or 3, wherein m is 4. 5. The compound as defined in any one of the preceding statements, wherein each Y is a group providing a conjugated linkage between Z and X1and / or X2. 6. The compound as defined in any one of the preceding statements, wherein each Y is independently such that A is separated from Z by 5-15 bond lengths. 7. The compound as defined in any one of the preceding statements, wherein each Y is independently such that X1is separated from A by 3-6 bond lengths. 8. The compound as defined in any one of the preceding statements, wherein each Y is independently such that X1is separated from A by 4-5 bond lengths.9. The compound as defined in any one of the preceding statements, wherein each Y is independently such that X2, when present, is separated from A by 9-12 bond lengths. 10. The compound as defined in any one of the preceding statements, wherein each Y is independently such that X2, when present, is separated from A by 10-11 bond lengths. 11. The compound as defined in any one of the preceding statements, wherein each Y independently has a structure according to formula III:wherein 3 denotes a point of attachment to A; 4 denotes a point of attachment to Z; L1is absent (in which case A is linked directly to Q1) or is a group separating A from Q1by 2-3 bond lengths; Q1is a triazole substituted with X1, or a charge-balanced triazolium group substituted with X1; L2is absent (in which case Q1is linked directly to L3) or is a group separating Q1from Q2by 4-5 bond lengths; Q2is absent (in which case Q1is linked directly to L3) or is a triazole substituted with X2, or a charge-balanced triazolium group substituted with X2; and L3is absent (in which case Q2is linked directly to Z) or is a group separating Q2from Z (or separating Q1from Z when L2and Q2are both absent) by 2-3 bond lengths; with the proviso that when Q2is absent, L2is also absent. 12. The compound as defined in statement 11, wherein L1, L2and L3, when present, are formed exclusively from carbon and hydrogen. 13. The compound as defined in statement 11, wherein L1is a -CH2- group. 14. The compound as defined in statement 11, 12 or 13, wherein L2, when present, is a (2- 3C)alkylene group, (2-3C)alkenylene group, an arylene group or a heteroarylene group. 15. The compound as defined in statement 14, wherein L2, when present, is a phenylene group.16. The compound as defined in statement 14, wherein L2, when present, is a 1,3-phenylene group. 17. The compound as defined in any one of statements 11 to 16, wherein L3is absent, a - CH2- group or a -CH- group. 18. The compound as defined in any one of statements 11 to 17, wherein Q1has a structure according to formula IIIa or IIIb:wherein 5 denotes a point of attachment to L2(or to L3when L2and Q2are absent); 6 denotes a point of attachment to L1; R2is absent or (1-3C)alkyl; with the proviso that when R2is not absent, the nitrogen atom to which it is attached carries a positive charge, which is balanced by a negatively charged counter ion. 19. The compound as defined in statement 18, wherein Q1has a structure according to formula IIIa. 20. The compound as defined in any one of statements 11 to 19, wherein Q2, when present, has a structure according to formula IVa or IVb:wherein 7 denotes a point of attachment to L2; 8 denotes a point of attachment to L3; R3is absent or (1-3C)alkyl; with the proviso that when R3is not absent, the nitrogen atom to which it is attached carries a positive charge, which is balanced by a negatively charged counter ion. 21. The compound as defined in statement 20, wherein Q2, when present, has a structure according to formula IVa. 22. The compound as defined in any one of the preceding statements, wherein each Y independently has a structure according to formula Va:wherein R2, R3, L1, L2, L3,3and4are as defined in any one of the preceding statements. 23. The compound as defined in any one of the preceding statements, wherein each Y independently has a structure according to formula Va-i:wherein Ph denotes a 1,3-phenylene group; andR2, R3, X1and X2are as defined in any one of the preceding statements. 24. The compound as defined in any one of the preceding statements, wherein each Y independently has a structure according to formula Vb:wherein R2, X1, L1, L3,3andare as defined in any one of the preceding statements. 25. The compound as defined in any one of the preceding statements, wherein each Y independently has a structure according to formula Vb-i:wherein R2, X1, L3,3and4are as defined in any one of the preceding statements. 26. The compound as defined in any one of the preceding statements, wherein each Z is independently a fluorophore. 27. The compound as defined in statement 26, wherein the fluorophore is selected from bodipy and coumarin. 28. The compound as defined in statement 26, wherein the fluorophore is bodipy having a core structure:wherein bodipy is bound to Y through one of the carbons labelled 1-4. 29. The compound as defined in statement 28, wherein bodipy has the following structure:wherein bodipy is bound to Y through one of the carbons labelled 1-4. 30. The compound as defined in statement 28 or 29, wherein bodipy is bound to Y through the carbon labelled 1. 31. The compound as defined in any one of statements 11 to 30, wherein when each Y has a structure according to formula III, the moiety –L3–Z has a structure:wherein 9 denotes a point of attachment to Q2 (or Q1 when both Q2 and L2 are absent).32. The compound as defined in any one of the preceding statements, wherein each X1is independently I or H. 33. The compound as defined in any one of the preceding statements, wherein X1is I. 34. The compound as defined in any one of the preceding statements, wherein each X2is independently absent, I or H. 35. The compound as defined in any one of the preceding statements, wherein X2is absent or I. 36. The compound as defined in any one of the preceding statements, wherein A denotes a plane of symmetry (i.e., all instances of X1, X2, Y and Z, as well as sub-groups associated therewith, have identical definitions). 37 The compound as defined in any one of the preceding statements, wherein: A has a structure according to formula II; and each Y has a structure according to formula Va or Vb, or a sub-formula thereof. 38. The compound as defined in any one of the preceding statements, wherein: each Y has a structure according to formula Va or Vb, or a sub-formula thereof; and each Z is bodipy. 39. The compound as defined in any one of the preceding statements, wherein: each Y has a structure according to formula Va or Vb, or a sub-formula thereof; X1is I; and X2, when present, is I. 40. The compound as defined in any one of the preceding statements, wherein: A has a structure according to formula II; X1is I; and X2, when present, is I. 41. The compound as defined in any one of the preceding statements, wherein: each Z is bodipy; X1is I; and X2, when present, is I.42. The compound as defined in any one of the preceding statements, wherein: A has a structure according to formula II; each Y has a structure according to formula Va or Vb, or a sub-formula thereof; X1is I; and X2, when present, is I. 43. The compound as defined in any one of the preceding statements, wherein: A has a structure according to formula II; each Z is bodipy; each Y has a structure according to formula Va or Vb, or a sub-formula thereof; X1is I; and X2, when present, is I. 44. The compound as defined in any one of the preceding statements, wherein the compound has a structure according to any one of the following:where XAdenotes one or more anions suitable for balancing the charge on the triazolium groups (e.g., XAmay be one or more NO3-).45. The compound as defined in any one of the preceding statements, wherein the compound is immobilized on a solid support. 46. A sensing assembly comprising a compound as defined in any one of the preceding statements. 47 Use of a compound as defined in any one of statements 1 to 45, or a sensing assembly as defined in statement 46, for determining the presence or absence of a dicarboxylate in a sample. 48. The use as defined in statement 47, wherein the sample is an aqueous solution, an organic solution or an aqueous-organic solution. 49. The use as defined in statement 47 or 48, wherein the sample is a biological sample. 50. The use as defined in statement 47, 48 or 49, wherein the two –C(O)O- groups of the dicarboxylate may be separated from one another by 5 to 22 bond lengths. 51. The use as defined in statement 47 to 50, wherein the two –C(O)O- groups of the dicarboxylate may be separated from one another by 7 to 20 bond lengths. 52 The use as defined in statement 47 to 50, wherein the two –C(O)O- groups of the dicarboxylate may be separated from one another by 8 to 19 bond lengths. 53. A process for determining the presence or absence of a dicarboxylate in a sample, the process comprising the steps of: a) contacting a sample with a compound as defined in any one of statements 1 to 45, or a sensing assembly as defined in statement 46; and b) determining the presence or absence of a dicarboxylate in the sample. 54. The process as defined in statement 53, wherein the sample is an aqueous solution, an organic solution or an aqueous-organic solution. 55. The use as defined in statement 53 or 54, wherein the sample is a biological sample. 56. The use as defined in statement 53, 54 or 55, wherein the two –C(O)O- groups of the dicarboxylate may be separated from one another by 5 to 22 bond lengths.57. The use as defined in statement 53 to 56, wherein the two –C(O)O- groups of the dicarboxylate may be separated from one another by 7 to 20 bond lengths. 58. The use as defined in statement 53 to 57, wherein the two –C(O)O- groups of the dicarboxylate may be separated from one another by 8 to 19 bond lengths. EXAMPLES

[0079] One or more examples of the invention will now be described, for the purpose of illustration only, with reference to the accompanying figures: Fig. 1.1H NMR spectrum of 3·XB. Asterisks indicate signals arising from permethylated P5A impurity. Fig. 2.13C NMR spectrum of 3·XB. Asterisks indicate signals arising from permethylated P5A impurity. Fig.3. Experimental and theoretical mass spectra of 3·XB. Fig.4.1H NMR spectrum of 4·XB. Fig.5.13C NMR spectrum of 4·XB. Fig.6. Experimental and theoretical mass spectra of 4·XB. Fig.7.1H NMR spectrum of 4·HB. Fig.8.13C NMR spectrum of 4·HB. Fig.9. Experimental and theoretical mass spectra of 4·HB. Fig.10. Absorption and emission spectra of 4·XB. (10 μM, CHCl3, 298K) Fig.11. Absorption and emission spectra of 4·HB. (10 μM, CHCl3, 298K) Fig. 12. Stacked emission spectra of 4·XB with increasing concentrations of−OAc (up to a maximum of 71 mM) (1 μM, CHCl3, 298K) Fig.13. Stacked emission spectra of 4·HB with increasing concentrations of−OOC(CH2)10COO−(up to a maximum of 142 μM), showing the lack of a directional fluorescence response. (1 μM, CHCl3, 298K) Fig.14. Fluorescence response of receptor 4·XB upon addition of−OOC(CH2)10COO−. ([4·XB] = 1 μM, [DCB]max = 142 μM, CHCl3, 298K)Fig.15. Stacked emission spectra of 4·XB with increasing concentrations of−OOC(CH2)10COO−(up to a maximum of 142 μM). (1 μM, 50% ACN : H2O (buffered to pH = 8.0 with 50 mM HEPES), 298K) Fig.16. Stacked emission spectra of 4·HB with increasing concentrations of−OOC(CH2)10COO−(up to a maximum of 142 μM). (1 μM, 50% ACN : H2O (buffered to pH = 8.0 with 50 mM HEPES), 298K) Fig. 17. Stacked1H NMR spectra of 4·HB upon addition of increasing concentrations of−OOC(CH2)10COO−. (1 mM, CDCl3, 298K) Fig. 18. Stacked1H NMR spectra of 4·XB upon addition of increasing concentrations of−OOC(CH2)10COO−. (1 mM, CDCl3, 298K) Fig.19. Relative fluorescence response of receptor 4·HB to addition of DCB (C12) measured in 50% ACN : H2O (buffered to pH = 8.0 with 50 mM HEPES), ([4·HB] = 1 μM, 298K) 1. Instrumental and General Experimental Details General Information

[0080] Solvents and reagents were purchased from commercial suppliers and used as received. Dry solvents were obtained by purging with nitrogen and passing through a MBraun MPSP-800 column. H2O was de-ionised and micro-filtered using a Milli-Q® Millipore machine.

[0081] Experiments were conducted at room temperature unless otherwise stated. Merck silica gel 60 was used for flash column chromatography. TBA salts were stored in vacuum desiccators prior to use. NMR spectra were either recorded on a Bruker Avance III HD Nanobay NMR spectrometer equipped with a 9.4 T magnet or a Bruker NEO 600 with broadband helium cryoprobe.1H NMR titrations were recorded on a Bruker Avance III NMR equipped with a 11.75 T magnet.

[0082] Chemical shifts are quoted in parts per million relative to the residual solvent peak.

[0083] UV-vis and fluorescence measurements were carried out on a Duetta (Horiba) using quartz cuvettes with a path length of 10 mm. Unless otherwise noted, all fluorescence spectra were acquired with a wavelength of excitation of 490 nm, 5 nm excitation and emission slits and were recorded in, at least, triplicate repeat measurements to ensure signal stability. Anion titration studies were carried out by titrating a 1 µM solution of the receptor with aliquots of a concentrated solution of TBA-anion in the same receptor solution to ensure a constant receptor concentration.

[0084] (TBA)2DCB salts,

[0050] were prepared in line with literature procedures.

[0085] 50 mM HEPES buffer was prepared by dissolving HEPES (N-(2-Hydroxyethyl)piperazine- N’-(2-ethanesulfonic acid)) in distilled water and then adjusting the pH to 8.0 by addition of small volumes of a highly concentrated (3M) NaOH solution.

[0086] Tris[(1-benzyl-1H-1,2,3-triazol-4-yl)methyl]amine is abbreviated as TBTA.

[0087] All data analysis and fitting were carried out with OriginPro 2023.

[0051] 2. Synthesis and Characterisation of Compounds Synthesis of hydrogen bonding (HB) analoguesScheme 1a – Synthesis of 2-HB

[0088] Having regard to Scheme 1a, 8-Ethynyl-BODIPY

[0052] was subjected to typical CuAAC (‘click’) conditions with a large excess 1,3-diazidobenzene,[53-54]producing the mono-click product 2·HB in 91% yield (Scheme S1). The bis alkyne-functionalised P5A 3·HB was obtained in moderate yield (12%) by statistical condensation of 1,4-bis(prop-2-yn-1-yloxy)benzene and 1,4- dimethoxybenzene with paraformaldehyde under conventional P5A synthesis conditions.

[0055] 2·HB was then re-subjected to CuAAC conditions with 3·HB to afford title compound 4·HB in 46% yield (Scheme 1b).Scheme 1b. Synthesis of 3·HB and 4·HB.

[0089] Having regard to Scheme 1b, [Cu(MeCN)4]PF6(5.0 mg, 0.013 mmol) and TBTA (7.1 mg, 0.013 mmol) were placed in a 5 mL microwave vial and degassed for 10 minutes. The solids were dissolved in the minimum amount of degassed dry DCM (3 mL) and stirred at room temperature for 15 min. HB BODIPY precursor 2·HB (25.0 mg, 0.058 mmol) and P5A bis-alkyne 3·HB (12.0 mg, 0.015 mmol) were dissolved in the minimum amount of degassed dry DCM (2 mL) and the resulting solution added to the pre-complexed CuI / TBTA solution. The resulting solution was stirred at room temperature for 12 h, after which the reaction mixture was diluted with DCM (15 mL) and washed with NH4OH / EDTA (aq.) (2 x 20 mL) and H2O (20 mL). All aqueous layers were back-extracted with DCM (10 mL) and the combined organic layers were dried over MgSO4and the volatiles removed in vacuo. 4·HB was obtained by columnchromatography of the resulting crude solid in acetone:DCM mixtures graded from v / v 0:100 to 3:97, as a purple solid. Yield 24.2 mg (46%).1H NMR (400 MHz, Acetone-d6) δ: 9.088.96 (2s, 2H each, Hd,i), 8.64 (t, J = 2.1 Hz, 2H, He), 8.17 (m, 4H, Hf,h), 7.94 (t, J = 8.2 Hz, Hg), 7.13 (s, 2H, Hk), 6.87-6.84 (m, 8H, Hn), 6.18 (broad s, 4H, Hb), 5.20 (m, 4H, Hj), 3.76-3.59 (m, 34H, Hl,o), 2.53 (s, 12H, Hc),1.62 (s, 12H, Ha) ppm.13C{1H} NMR (151 MHz, Acetone-d6) δ: 156.6, 150.5, 150.5, 150.5,149.8,145.7, 143.1, 140.6, 138.4, 138.1, 132.2, 131.7, 129.2, 128.9, 128.8, 128.2, 128.2, 128.1, 128.1, 128.1, 128.0, 127.9, 127.7, 123.4, 122.0, 120.1, 115.1, 113.7, 113.5, 113.4, 112.2, 75.4, 62.2, 55.1, 55.1, 55.1, 55.0, 13.6, 12.9 ppm. HR-ESI-MS: m / z calculated for [C91H89B2F4N16O10]+, [M+H]+: 1663.7064, found: 1663.7053. Synthesis of halogen bonding (XB) analoguesScheme 2a – Synthesis of 2·XB.

[0090] Having regard to Scheme 2a, BODIPY iodo-alkyne, 1·XB, was prepared in accordance with literature procedures.[35, 37]Mono-functionalised intermediate 2·XB was prepared via a CuAAC reaction.

[0037] Scheme 2b – Synthesis of 3·XB

[0091] Having regard to Scheme 2b, 3·HB (170.0 mg, 0.313 mmol) and catalytic CuI (5.9 mg, 0.031 mmol) were dissolved in dry THF (2 mL). N-iodomorpholine hydriodide (420 mg, 1.235 mmol) was added, and the mixture stirred at room temperature, under exclusion of light, for 3 h, after which only one spot was visible by TLC (10% EtOAc v / v in hexanes). The reaction mixture was diluted with DCM (50 mL), and poured onto a saturated DCM pad of neutral alumina. The pad was eluted with DCM until the solution ran clear and the organic layer decolourised with saturated Na2S2O3 (aq.) (25 mL), and washed with H2O (3 x 100 mL). The organic layer was dried over MgSO4 and the volatiles removed in vacuo. The crude product was dry-loaded onto SiO2and eluted with 10% EtOAc v / v in hexanes to afford 3·XB as an off-white solid. The product was estimated by1H NMR to be 66% pure, with the contaminant identified as non-functionalised per-methoxypillar[5]arene, residual from the synthesis of 3·HB. As the side product would not react in the subsequent step, 3·XB was used without further purification. Yield: 329.1 mg (66%).1H NMR (400 MHz, CDCl3) δ: 6.896.886.856.806.76 (5 s, 2H each, HAr), 4.79 (s, 4 H, Ha), 3.72 (m, 10H, HCH2), 3.69-3.61 (m, 24H, HMe) ppm.13C{1H} NMR (151 MHz, CDCl3) δ: 150.6, 150.4, 150.3, 148.7, 129.4, 128.7, 128.0, 127.7, 127.6, 116.2, 114.3, 113.8, 113.7, 113.4, 89.5, 57.7, 55.8, 55.7, 55.6, 55.5, 29.8, 29.7, 29.6, 29.0 ppm. Iodoalkyne environment is not observed, and is likely coincident with the CDCl3solvent resonance. HR-ESI-MS: m / z calculated for [C49H48I2O10Na]+, [M+Na]+: 1073.1229, found: 1073.1272.Scheme 2c – Synthesis of 4·XB

[0092] Having regard to Scheme 2c, [Cu(MeCN)4]PF6(5.6 mg, 0.015 mmol) and TBTA (8.0 mg, 0.015 mmol) were placed in a 5 mL microwave vial and degassed for 10 minutes. The solids were dissolved in the minimum amount of degassed dry DCM (3 mL) and stirred at room temperature for 15 min. XB BODIPY precursor 2·XB (40 mg, 0.072 mmol) and P5A bis-alkyne 3·XB (18.9 mg, 0.018 mmol) were dissolved in the minimum amount of degassed dry DCM (2 mL) and the resulting solution added to the pre-complexed CuI / TBTA solution. The resulting solution was stirred at room temperature, under exclusion of light, for 12 h, after which the reaction mixture was diluted with DCM (15 mL) and washed with NH4OH / EDTA (aq.) (2 x 20 mL)and H2O (20 mL). All aqueous layers were back-extracted with DCM (10 mL) and the combined organic layers were dried over MgSO4and the volatiles removed in vacuo.4·XB was obtained by column chromatography of the resulting crude solid in acetone:DCM mixtures graded from v / v 0:100 to 3:97, as a purple solid. Yield 28.0 mg (72%).1H NMR (400 MHz, Acetone-d6) δ: 8.17 (broad s, 2H, Hf), 8.08 (app. s, 6H, Hd,e,g), 7.23 (s, 2H, Hi), 6.91-6.86 (m, 8H, Hl), 6.23 (s, 4H, Hb), 5.16 (app. t, 4H, Hh), 3.81-3.64 (m, 34H, Hj,k,m), 2.55 (s, 12H, Hc), 1.64 (s, 12H, Ha) ppm.13C{1H} NMR (151 MHz, Acetone-d6) δ: 157.2, 150.5, 150.5, 150.4, 150.4, 150.0, 148.8, 146.4, 142.7, 138.1, 137.5, 132.1, 131.1, 129.4, 128.4, 128.3, 128.2, 128.2, 128.1, 128.0, 127.8, 124.3, 121.8, 121.8, 115.9, 113.7, 113.5, 113.4, 85.2, 83.5, 62.7, 55.3, 55.1, 55.1, 55.0, 13.9, 13.2 ppm. HR-ESI-MS: m / z calculated for [C91H85B2F4I4N16O10]+, [M+H]+: 2167.2930, found: 2167.2886. 3. Optical characterisation of 4·XB and 4·HB

[0093] The absorption and emission spectra for compounds 4·XB and 4·HB are shown in Figures 10 and 11. Both receptors showed the expected absorption and emission features for BODIPY-containing compounds, with absorption maxima of 518 nm and 516 nm and emission maxima of 531 nm and 532 nm for 4·XB and 4·HB respectively. This corresponds to Stokes shifts of roughly 13-16 nm, which is in line with previous reports. 4. Fluorescence Titration Studies

[0094] Fluorescence titration studies of receptors 4·XB and 4·HB with DCB salts were conducted in both CHCl3 and in 50% ACN : H2O (buffered to pH = 8.0 with 50 mM HEPES); and with TBAOAc in CHCl3. Representative, stacked emission spectra, with arrows showing the direction of change upon addition of analyte (if any), are shown in Figures 12-16 for each class of titration. 5.1H NMR Threading Studies

[0095] To confirm that the DCB analytes thread inside the pillar[5]arene cavity, qualitative1H NMR studies were conducted in CDCl3, in which aliquots of (TBA)2(OOC(CH2)10COO) were added to solutions of the receptors. The stacked spectra for 4·HB and 4·XB are presented Figures 17 and 18 respectively. The triazole proton Hd and the P5A phenyl proton Hk both show shifts, indicating threading concurrent with binding to the HB donors.6. Results and Discussion

[0096] Exploiting the dichloroethane solvent-templated synthesis of P5As,

[0038] the bis alkyne- functionalised P5A 3·HB was obtained in moderate yield (12%) by statistical condensation of 1,4- bis(prop-2-yn-1-yloxy)benzene and 1,4-dimethoxybenzene with paraformaldehyde under conventional P5A synthesis conditions.

[0039] Iodination of 3·HB by N-iodomorpholine hydroiodide afforded the P5A bis-iodoalkyne 3·XB in quantitative yield (Scheme 2b). Subsequently, the host 4·XB was afforded in 72% yield by a further CuAAC reaction between 3·XB and two equivalents of 2·XB (Scheme 2c). The hydrogen bonding receptor analogue 4·HB was prepared in a similar manner (Schemes 1a-b). Both receptors were fully characterised by1H and13C NMR, optical spectroscopy, and high-resolution mass spectrometry (Figures 4-9).

[0097] The ability of the receptors to respond to DCBs in organic media (CHCl3) was first investigated by fluorescence host-guest binding studies with DCBs with a range of alkyl chain lengths, in which the intensity of the BODIPY emission was measured upon successive additions of a DCB tetrabutylammonium (TBA) salt, prepared by neutralisation of the corresponding DCA with TBA hydroxide.

[0033]

[0098] XB host 4·XB demonstrated a marked ‘switch-on’ fluorescence response in CHCl3 upon the addition of a range of aliphatic straight chain DCBs with the number of carbon atoms in the backbone, n, ranging from n = 8–16 (Figure 14). Such a response likely arises from an inhibition in the ability of the BODIPY chromophore to rotate about its meso position upon anion binding.

[0037] Qualitative1H NMR studies in CDCl3 showed a marked upfield shift in the P5A phenyl proton resonance, Hi, coupled with an upfield shift in the DCB methylene proton resonances upon addition of a DCB guest solution to the host, confirming the threading of the DCB through the P5A cavity (Figure 18).

[0040]

[0099] Calculation of the host-guest association constants K,

[0041] via global fitting of the fluorescence emission isotherms at a range of wavelengths, demonstrated binding affinity is dependent on the length of the carbon backbone, with the strongest binding for n = 12, likely due to size complementarity of the DCB guest with the separation of the XB host binding sites (Table 1).Table 1. Association constants K[a](M-1) of receptor 4·XB in CHCl3.8 6800 10 8400 12 9900 14[b]8600 16 6700 TBAOAc[c]240 [a] Determined in CHCl3 at 298 K by global fitting of fluorescence isotherms to a 1:1 binding model and errors <5% unless otherwise noted. [b] Error <7%. [c] Fitted to 1:2 host-guest binding model, K11 reported.

[0100] Interestingly, the first association of−OAc, fitted with a 1:2 host-guest binding stoichiometry, was 30 times lower than for any of the DCBs, highlighting the importance of the DCB-P5A threading interaction for the recognition event. In stark contrast, no fluorescence response was measured for 4·HB upon addition of DCB salts, despite a1H NMR experiment demonstrating threading of the TBA salt of dodecanedioic acid (Figures 13 and 17). This suggests that the interaction between the carboxylate functional group and the HB binding sites of 4·HB is insufficient to elicit a fluorescence response from the BODIPY reporter group, highlighting the superior signal transduction characteristics of XB in the context of fluorescent anion sensing.

[0101] Attention then turned to exploiting the hydrophobicity of the P5A cavity and XB donors for the enhanced recognition of DCBs in 50% ACN : H2O (buffered to pH = 8.0 with 50 mM HEPES). Fluorescence titration experiments were conducted with the TBA salt of dodecanedioic acid, as it had demonstrated the strongest binding in CHCl3. In contrast to the experiments in CHCl3, both 4·XB and 4·HB exhibited ‘switch-off’ fluorescence responses upon the addition of the DCB (Figures 15, 16 and 19) which may be a consequence of reduced meso rotation of the BODIPY in this more viscous solvent mixture,

[0043] leading to anion binding-induced quenching acting as the dominant quenching method, consistent with previous studies.

[0044] Impressively however, the dianionic carboxylate was bound with high affinity by both 4·XB and 4·HB, with K = 104,000 M-1and 28,500 M-1, respectively (Table 2). This represents a 10-fold enhancement in binding for the XB receptor upon changing to the aqueous organic mixture, notably illustrating the potency of the hydrophobic effect employed by this receptor.

[0045] It is also important to note the 4-fold stronger anion affinity demonstrated by the XB receptor over its HB counterpart, showing its potency in aqueous-containing media.

[0045] Table 2. Association constants K[a](M-1) of 4·XB and 4·HB in aqueous-organic mixtures. −1Guest K (M ) 4·XB 4·HB −OOC(CH2)10COO−104,000[b]28,500[b][a] Determined at 298 K by global fitting of fluorescence isotherms to 1:1 binding model. [b] 50% ACN : 50% H2O pH = 8.0 (50 mM HEPES buffer) and errors <15%.

[0102] In summary, the synthesis of a novel XB, BODIPY-appended, P5A host molecule 4·XB is reported, as an optical molecular sensor for a range of anthropogenically generated molecules of environmental interest. Upon addition of DCBs to organic solutions of 4·XB, marked turn-ON emission of the BODIPY reporter groups was observed, while no such response was observed for HB analogue 4·HB, highlighting the superiority of XB-based systems as binding event signal transducers.1H NMR binding studies confirmed the DCBs thread through the P5A cavity. On account of the hydrophobic nature of the P5A cavity, a marked increase in host-guest binding affinity is observed in highly competitive 50% ACN : H2O aqueous-organic solvent mixtures. Such increased affinity demonstrates the combination of guest threading through a hydrophobic P5A cavity and the use of hydrophobic XB binding groups as a uniquely potent strategy for the sensing of pollutants in aqueous media.

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Claims

CLAIMS 1. A compound having a structure according to formula I:wherein A is a pillar[5-6]arene; each Z is independently an optical sensor; each Y is independently a group linking A to Z; each X1is independently H, I or Br; and each X2is independently absent, H, I, or Br with the proviso that at least one X1, or at least one X2, is I or Br.

2. The compound as claimed in claim 1, wherein A has a structure according to formula II:wherein 1 denotes a point of attachment to one of the two Y groups and2denotes a point of attachment to the other of the two Y groups; each R1is independently H or (1-2C)alkyl; and m is 4 or 5 3. The compound as claimed in claim 2, wherein R1is methyl; and / or m is 4.

4. The compound as claimed in any one of the preceding claims, wherein each Y is independently such that A is separated from Z by 5-15 bond lengths.

5. The compound as claimed in any one of the preceding claims, wherein each Y is independently such that: X1is separated from A by 3-6 bond lengths; and X2, when present, is separated from A by 9-12 bond lengths.

6. The compound as claimed in any one of the preceding claims, wherein each Y independently has a structure according to formula III:wherein 3 denotes a point of attachment to A; 4 denotes a point of attachment to Z; L1is absent (in which case A is linked directly to Q1) or is a group separating A from Q1by 2-3 bond lengths; Q1is a triazole substituted with X1, or a charge-balanced triazolium group substituted with X1; L2is absent (in which case Q1is linked directly to L3) or is a group separating Q1from Q2by 4-5 bond lengths; Q2is absent (in which case Q1is linked directly to L3) or is a triazole substituted with X2, or a charge-balanced triazolium group substituted with X2; and L3is absent (in which case Q2is linked directly to Z) or is a group separating Q2from Z (or separating Q1from Z when L2and Q2are both absent) by 2-3 bond lengths; with the proviso that when Q2is absent, L2is also absent.

7. The compound as claimed in claim 6, wherein L1, L2and L3, when present, are formed exclusively from carbon and hydrogen.

8. The compound as claimed in claim 6 or 7, wherein L1is a -CH2- group.

9. The compound as claimed in claim 6, 7 or 8, wherein L2, when present, is a (2-3C)alkylene group, (2-3C)alkenylene group, an arylene group or a heteroarylene group.

10. The compound as claimed in any one of claims 6 to 9, wherein L3is absent, a -CH2- group or a -CH- group.

11. The compound as claimed in any one of claims 6 to 10, wherein Q1has a structure according to formula IIIa or IIIb:wherein 5 denotes a point of attachment to L2(or to L3when L2and Q2are absent); 6 denotes a point of attachment to L1; R2is absent or (1-3C)alkyl; with the proviso that when R2is not absent, the nitrogen atom to which it is attached carries a positive charge, which is balanced by a negatively charged counter ion.

12. The compound as claimed in any one of claims 6 to 11, wherein Q2, when present, has a structure according to formula IVa or IVb:wherein 7 denotes a point of attachment to L2; 8 denotes a point of attachment to L3;R3is absent or (1-3C)alkyl; with the proviso that when R3is not absent, the nitrogen atom to which it is attached carries a positive charge, which is balanced by a negatively charged counter ion.

13. The compound as claimed in any one of the preceding claims, wherein each Y independently has a structure according to: (i) formula Va:wherein R2, R3, L1, L2, L3,3and4are as defined in any one of the preceding claims; or (ii) formula Vb:wherein R2, X1, L1, L3,3andare as defined in any one of the preceding claims.

14. The compound as claimed in any one of the preceding claims, wherein each Z is independently a fluorophore.

15. The compound as claimed in claim 14, wherein the fluorophore is selected from bodipy and coumarin.

16. The compound as claimed in claim 14, wherein the fluorophore is bodipy having the following structure:wherein bodipy is bound to Y through one of the carbons labelled 1-4.

17. The compound as claimed in claim 16, wherein bodipy is bound to Y through the carbon labelled 1.

18. The compound as claimed in any one of the preceding claims, wherein X1is I and X2is absent or I.

19. The compound as claimed in any one of the preceding claims, wherein A denotes a plane of symmetry (i.e., all instances of X1, X2, Y and Z, as well as sub-groups associated therewith, have identical definitions).

20. The compound as claimed in any one of the preceding claims, wherein the compound has a structure according to any one of the following:

21. The compound as claimed in any one of the preceding claims, wherein the compound is immobilized on a solid support.

22. A sensing assembly comprising a compound as claimed in any one of the preceding claims. 23 Use of a compound as claimed in any one of claims 1 to 21, or a sensing assembly as claimed in claim 22, for determining the presence or absence of a dicarboxylate in a sample.

24. The use as claimed in claim 23, wherein the two –C(O)O- groups of the dicarboxylate are separated from one another by 5 to 22 bond lengths.

25. The use as claimed in claim 23 or 24, wherein the sample is an aqueous solution, an organic solution or an aqueous-organic solution.

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