Organic based fluorophores to selectively detect chemical warfare agents

Abstract

The present disclosure is directed to luminescent sensors able to detect low concentration levels of organophosphorus compounds (e.g., sarin) with high sensitivity and specificity. Sensor compounds disclosed herein can demonstrate an immediate change in color upon exposure to a drop or vapor of an organophosphorus compound. Detectors incorporating the sensor compounds and methods of their use are also disclosed herein.

Description

ORGANIC BASED FLUOROPHORES TO SELECTIVELY DETECTCHEMICAL WARFARE AGENTSCROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims a benefit of and priority to U.S. Provisional Application No. 63 / 549,061, filed February 2, 2024, which is hereby incorporated herein by reference.BACKGROUND

[0002] Sarin (O-isopropyl methyl phosphonofluoridate, also known as “GB”), is a synthetic chemical warfare agent (CWA), which disrupts the transmission of nerve impulses in the body. It specifically falls under the category of nerve agents, the most toxic and rapidly acting of the known CWA. Research and funds allocated to monitor, quantify, and eliminate the toxicity and the danger of CWAs to humans’ health has increased due to the threat of their possible use by terrorists in public areas. In specific, during the last two decades, a huge effort was made to investigate the feasibility of the development of low cost, portable, robust, highly selective and sensitive monitoring tools for such toxic materials. Semiconducting metal oxide (SMO) gas sensors are widely used in the gas detection market because of their low-cost, small size, and sensitivity. However, to fabricate a reliable sensor to detect sarin-like molecules, it is important to understand the mode of interaction between organophosphonate and the SMO surfaces. This area of chemistry is important to developing a rapid, non-volatile and non-corrosive catalytic agent for the destruction of chemical warfare agents but not well-identified because of the toxicity of these compounds. Simulant reagents including dimethyl methylphosphonate (DMMP) and methyldichlorophosphonate (MDCP) are the most commonly used compound for modeling the interactions of phosphonate esters (e.g., sarin) that occur in the spectrum of man-made chemicals such as pesticides and warfare agents.

[0003] The most common sensors are based on semiconducting metal oxide as base detection. The detection depends on changes occurred to the SMO band conductance associated to physical or chemical adsorption to the surface upon the exposure to a gas stream. Given all metal oxide surfaces are acidic in nature, they are very sensitive to compounds with various functionalities, thus show response to most gases without clear distinction between the type of these gases. Huge research fund is allocated to modify such sensors in such a way to improve selectivity. Several studies have been conducted to improve the selectivity by using filters, porous materials, even simulated / shape detection software; however, still selectivity remains an un-resolved issue to finalize a selective sensor prototype.

[0004] Although several studies have focused on providing sensitive and selective CWA detection, finding an optimal device that detects low concentrations of CWA with high selectivity is still a challenge. Methods including a combination of filtration, concentration, and array-based detection have been reported. Materials such as inorganic membranes, zeolites, and other adsorbents are used to selectively pre-concentrate and prefilter interfering molecules from the gas stream. Variables such as metal oxide composition and morphology, impregnation with metal catalysts and operational temperature are a few approaches that are under investigation to achieve distinguishable sensor array elements.

[0005] Since most chemical warfare nerve agents are not gases but polar organic liquids at ambient conditions with high vapor pressures, it is important to develop a new strategy to detect these nerve agents in solutions. Fluorescent chemosensors are powerful for exploring small organic and inorganic analytes in various systems due to their low detection limit, simplicity, and selectivity. The high sensitivity of the luminescent sensors is based on a variety of factors that affect their emissive properties. The most important feature to design a chemosensor is to provide a wide range of signal transductions when the analyte binds to the fluorophore that offer a possibility to monitor its concentration in real time and space via changes in emission intensities, wavelength, lifetime, and chirality.

[0006] Despite the fact that fluorescence based sensors have been extensively studied to detect various metal ions with high sensitivity, the available fluorescence sensors that selectively detect organic pollutants are limited. It has been reported thatporphyrin modified by quinoline shows a significant quenching property for the organic sensor due to the appearance of a new fluorophore which corresponds to the formation of a new complex between the sensor and the analyte. However, the sensor lacks selectivity and water solubility, so the work described herein aims at developing a new chemofluorescent sensor to selectively detect low concentration levels of sarin simulants in aqueous solutions.BRIEF SUMMARY OF THE INVENTION

[0007] The sensors disclosed herein may have an improved selectivity, may be designed to fit in suitable size and environment that is very selective to interact with the phosphorus central atom and kick off the attached halogen(s) substrate. The products of this reaction showed different electronic distribution resulting in a significant change in the compounds’ original light emission profile (e.g., observable color).

[0008] Given that sarin and the studied simulants are liquids in nature, Sensor Compounds 1 and 2, provide immediate response (within 30 seconds or less) for sarin simulants in solution using methanol as a solvent. The response was observed by gradual quenching of the sensor’s luminescence bands that is highly dependent on the simulants’ concentration.BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 shows a scheme of chemical reactions to prepare Sensor Compounds 1 and 2.

[0010] Figure 2 shows a chemical formula in which MDCP is bound to Sensor 1.

[0011] Figure 3. The emission spectra of Sensor 1 after the addition of various concentrations of MDCP prepared in methanol as a solvent. Spectra were recorded at excitation wavelength of 235 nm.

[0012] Figure 4. Synchronous Scan Luminescence Spectra (SSLS) of Sensor 1 before and after adding various concentrations of MDCP recorded at AX of 60 nm.

[0013] Figure 5. UV-Visible spectra recorded for Sensor 1 before and after adding various concentrations of MDCP solution.

[0014] Figure 6. The emission spectra of Sensor 2 before and after the addition of various concentrations of MDCP. Spectra were recorded at excitation wavelength of 300 nm.

[0015] Figure 7. The Stern-Volmer plots of Sensor 1 binding to various MDCP concentrations. Insert is the plot at low MDCP concentrations.

[0016] Figure 8. Image of Sensor 2 before and after being exposed to MDCP vapor for 30 seconds.

[0017] Figure 9A shows a drawing of a badge detector in a first state where no organophosphorus compound is detected.

[0018] Figure 9B shows a drawing of a badge detector in a second state where the badge has been exposed to an organophosphorus compound.

[0019] Figure 10 shows a schematic representation of a spectrophotometer detector.DETAILED DESCRIPTION

[0020] In the present investigation, we developed luminescent sensors to detect very low concentration levels of sarin-like compounds using methyl dichlorophosphate (MDCP) as a simulant molecule. The sensors that were prepared by a condensation process provide high sensitivity and selectivity to sarin, even in the presence of methanol and other interfering reagents. This protocol is unique since the chemical warfare nerve agents are polar organic liquids at ambient conditions with high vapor pressures. In addition, a direct exposure of the sensor to MDCP vapor provide a sudden and clear color change from yellow to dark red. This finding is very important since all of the sensors available have poor selectivity and provide detection of vapors of simulant molecules at high temperature. For instance, methanol is one of the many and most common interfering compounds in the detection of sarin simulants is currently mixed with water in the testing protocol. Given the fact that the modified sensors tend to interact immediately with MDCP at room temperature, the materials can be used to encapsulate the CWA and reduce its toxic effect.SENSOR COMPOUNDS

[0021] Disclosed herein are sensor compounds useful for the detection of chemical warfare agents. Generally, sensor compounds disclosed herein can be reacted with chemical warfare agents to illicit a change in easily assayable characteristics of the sensor compound. For instance, in certain aspects, sensor compounds may react to form a covalent bond with a chemical warfare agent to induce a color change in the sensor compound. Alternatively, sensor compounds can form an ionic bond with the chemical warfare agent. In still further aspects, the sensor compounds can react through coordination of an electron-rich donor to an acceptor group of the chemical warfare agent.

[0022] In certain aspects, the compound can comprise a series of aromatic rings and heteroatom-containing linking groups. Generally, sensor compounds can be a conjugated diimine capable of coordinating to a phosphorus atom, particularly as present within an organophosphorus compound. In certain aspects, sensor compounds contemplated herein can have a Formula (I) as presented below:

[0023] As shown in Formula (I), sensor compounds disclosed herein can comprise three aromatic systems each interconnected by a pair of imines to form a single conjugated system. As will be understood by those of skill in the art, the color of the sensor compounds can depend, at least in part, on the size of this conjugated system. On the periphery of the conjugated system, sensor compounds can have heteroatomic substituents able to form coordination bonds with a phosphorus atom, such as those present in certain organophosphorus chemical warfare agents, e.g., including sarin gas and its derivatives. In this manner, the availability of the donor electrons of the heteroatomic substituents can be made more available for coordination with the organophosphorus atoms, and the size of the conjugated system can be extended by the coordination with phosphorus, thereby resulting in a color change.

[0024] Rings A and B each are part of conjugated systems connected by the diamine of sensor compounds. In certain aspects, each A and B independently can be any combination of aromatic moieties or functional groups that lead the compound to have a suitable amount of conjugation. In certain aspects, each of A and B independently can be substituted or unsubstituted aromatic hydrocarbon (e.g., phenyl); alternatively, a substituted or unsubstituted aromatic heterocycle comprising a number of heteroatoms independently selected from the group consisting of N, S and O.

[0025] Examples of suitable aromatic hydrocarbons notably include substituted or unsubstituted phenyl. In certain aspects, each of A and B can be a substituted or unsubstituted phenyl group. Where substituted, the ring can be substituted with 1, 2, 3, or 4 substituents (in addition to Yi and Y2 as shown in Formula (I) above), each substituent being independently selected from the group consisting of fluorine, chlorine, NO2, substituted or unsubstituted Ci to Cs alkoxy, aryloxy, alkylamino, dialkylamino, trihydrocarbylsilyl, or hydrocarbylaminosilyl. In other aspects, each of A and B can independently be selected from a multi-ring aromatic hydrocarbon, substituted or unsubstituted naphthyl, substituted or unsubstituted anthracenyl, substituted or unsubstituted phenanthryl, substituted or unsubstituted fluoranthyl, and substituted or unsubstituted pyrenyl.

[0026] In certain aspects wherein any of A and B are an aromatic heterocycle, the aromatic heterocycle can comprise 1, 2, 3, 4, or more heteroatoms independently selected from N, S, and O. In certain aspects, any of A or B can be an aromatic heterocycle selected from substituted or unsubstituted pyridinyl (e.g., pyridin-2-yl, pyri din-3 -yl or pyridin-4-yl), substituted or unsubstituted pyrimidinyl, substituted or unsubstituted pyrazinyl, substituted or unsubstituted thiazolyl, substituted or unsubstituted isothiazolyl, and substituted or unsubstituted furanyl (e.g., furan-2-yl).

[0027] Where substituted, aromatic heterocycles contemplated herein as suitable for A and B can be substituted with 1, 2 or 3 substituents, each substituent being independently selected from the group consisting of halogen, NO2, C1-8 alkyl, C1-8 alkyl substituted with 1, 2 or 3 halogens or groups, and substituted or unsubstituted OCi-8-alkyl.

[0028] Sensor compounds can comprise various combinations of aromatic heterocycles and aromatic hydrocarbons as rings A and B in Formula (I) above. In certainaspects, A can be an aromatic heterocycle and each B can be an aromatic hydrocarbon. For instance, in certain aspects, ring A can be 2-pyraninyl, whereas each ring B can be a phenyl substituted only by Y1and Y2. Alternately, ring A can be a substituted or unsubstituted thiophen-2-yl group.

[0029] Each of Y1and Y2independently can be any substituent capable of binding the phosphorus compound. In certain aspects, each of Y1and Y2independently can be an acidic or protonated heteroatomic substituent. In certain aspects, each of Y1and Y2independently can be an amine substituent; alternatively, each of Y1and Y2independently can be a hydroxyl group. In certain aspects, Y1and Y2independently can be selected from NEE and OH. In certain aspects, Y1and Y2each are NH2. In other aspects, Y1can be NH2 and Y2can be OH. In still further aspects, Y1can be NH2, and Y2can be OH; or alternatively Y1can be OH and Y2can be NH2. In other aspects, it is contemplated that either or both of Y1and Y2can be a thiol (e.g., SH).

[0030] In certain aspects, substituents Y1and Y2each may be in the meta position of ring B with respect to the bond of the imine nitrogen to ring B. Alternatively, substituents Y1and Y2may be found at any other position about ring B. Where additional substituents are present on ring B to interrupt the symmetry imparted by the imine bond, each Y1and Y2independently can be in any of the 2’, 3’, 4’, 5’, or 6’ positions of ring B.

[0031] Substituents X1and X2are not limited to any particular structure, and may be any that are suitable for the preferred conjugated system. In certain aspects, X1and X2can be the same; alternatively X1and X2can be different. Each X1and X2can be H or a substituted or unsubstituted Ci to Cis hydrocarbyl group; alternatively, a substituted or unsubstituted Ci to Cis halogenated hydrocarbyl group; alternatively, a Ci to Cis hydrocarboxy group; alternatively, a Ci to Cis hydrocarbylsilyl group; alternatively, a Ci to C12 hydrocarbyl group or a Ci to C12 hydrocarbylsilyl group; or alternatively, a Ci to Cs alkyl group or a C3 to Cs alkenyl group.

[0032] X1and X2each independently can be, in certain aspects, a linear, branched, or cyclic alkyl group or an alkenyl group. As a non-limiting example, each X1and X2independently can be CF3, a methyl group, an ethyl group, a propyl group, a butyl group (e.g., t-Bu), a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an ethenyl group, a propenyl group, a butenyl group, a pentenyl group, ahexenyl group, a heptenyl group, an octenyl group, a nonenyl group, a decenyl group, a phenyl group, a tolyl group (or other substituted aryl group), a benzyl group, a naphthyl group, a trimethylsilyl group, a triisopropylsilyl group, a triphenylsilyl group, an allyldimethylsilyl group, or a 1 -methylcyclohexyl group; alternatively, Cl; alternatively, CF3; alternatively, a methyl group; alternatively, an ethyl group; alternatively, a propyl group; alternatively, a butyl group; alternatively, a pentyl group; alternatively, a hexyl group; alternatively, a heptyl group; alternatively, an octyl group, a nonyl group; alternatively, a decyl group; alternatively, an ethenyl group; alternatively, a propenyl group; alternatively, a butenyl group; alternatively, a pentenyl group; alternatively, a hexenyl group; alternatively, a heptenyl group; alternatively, an octenyl group; alternatively, a nonenyl group; alternatively, a decenyl group; alternatively, a phenyl group; alternatively, a tolyl group; alternatively, a benzyl group; alternatively, a naphthyl group; alternatively, a trimethylsilyl group; alternatively, a triisopropylsilyl group; alternatively, a triphenylsilyl group; alternatively, an allyldimethylsilyl group; or alternatively, a 1 -methylcyclohexyl group.

[0033] Sensor compounds disclosed herein can be characterized by an amount of conjugation. For instance, sensor compounds can exhibit an amount of conjugation within a suitable range to produce a color in the visible spectrum. In certain aspects, the amount of conjugation can be characterized by its size, according to a number of atoms that participate within the conjugated system. In certain aspects, sensor compounds can comprise a conjugated system having from 15 to 30 atoms, from 18 to 24 atoms, 19 atoms, 20 atoms, 21 atoms, 22 atoms, or 23 atoms.

[0034] Those of skill in the art will understand that the size of the conjugated system can be increased by coordination of organophosphorus compounds at substituents Y1and Y2. Such an increase in the size of the conjugated system can result in a red shift to the visible color of the sensor compound, for instance (and as pictured in Fig. 8) a transition from a bright yellow compound to a deep red. In certain aspects, the resulting conjugated system can be increased by 2 atoms, 3 atoms, 4 atoms, 5 atoms, 6 atoms, 7 atoms, or 8 atoms, or any range within these values, by the conjugation of an organophosphorus compound, and depending on the structure of the organophosphorus compound.

[0035] In certain aspects, suitable sensor compounds therefore can include those shown in Formulas (II) and (III) below:(ill).

[0036] Consistent with the description of ring A above, Y3of Formula (II) can be a heteroatom selected from N, S, or O. X1, X2, Y1and Y2for each of Formulas (II) and (III) may be as described above for Formula (I). In certain aspects of Formulas (I), (II), and (III), X1and X2each can be independently selected from H, a substituted or unsubstituted Ci to Cs linear or branched hydrocarbon; Y1and Y2each are either NH2 or OH; and Y3(where present) is S or O.

[0037] Exemplary compounds of Formulas (II) and (III) are shown below, respectively.Sensor Compound 1 Sensor Compound 2

[0038] The stereochemistry of sensor compounds disclosed herein generally is not limited to a particular orientation. Structures and formulas of compounds presented herein are intended to include all stereoisomers unless otherwise noted.

[0039] In certain aspects, stereoisomeric centers may arise resulting from the aromaticity surrounding the imine moieties. In certain aspects, each of the diimine moieties can be oriented in either of an E- or Z-configuration with respect to the bond between ring A and the imine carbon. As shown by the exemplary compounds pictured above, and in Formulas (I)-(III), sensor compounds disclosed herein may have each of these stereoisomer in the Z-configuration (Z,Z); alternatively, each stereoisomer in the E-configuration (E,E). E,Z stereoisomers are also contemplated herein.ORGANOPHOSPHORUS COMPOUNDS FOR DETECTION

[0040] Sensor compounds described above can be useful for the detection of organophosphorus compounds, particularly compounds that pose a threat as a chemical warfare agent such as sarin gas. Detection of dangerous organophosphorus compounds also may be relevant to maintaining safety during the industrial and lab-scale production of organophosphorus compounds. Organophosphorus compounds to which the sensor compounds may be applied are not necessarily limited to a particular organophosphorus compound, and may include any that may become coordinated to the sensor compounds described above to induce a shift in the visible color of the sensor compound.

[0041] Organophosphorus compounds suitable for detection using sensor compounds therefore can includes phosphates (e.g., phosphate esters, and thiophosphates), phosphonates (comprising one P-C bond), phosphinates (comprising two P-C bonds), phosphine oxides, phosphine imides, and 1°, 2°, or 3° phosphines (comprising one, two, or three P-C bonds, respectively).

[0042] Organophosphorus compounds for detection therefore can include compounds such as sarin, a phosphonate ester consistent with Formula (IV):

[0043] In Formula (IV), R1and R2each independently can be H, or a substituted or unsubstituted Ci to Cis hydrocarbyl group; alternatively, a substituted or unsubstituted Ci to Cis halogenated hydrocarbyl group; alternatively, a Ci to Cis hydrocarboxy group; alternatively, a Ci to Cis hydrocarbylsilyl group; alternatively, a Ci to C12 hydrocarbyl group or a Ci to C12 hydrocarbylsilyl group; or alternatively, a Ci to Cs alkyl group or a C3 to Cs alkenyl group. In certain aspects, R1and R2can be the same. In other aspects R1can be a methyl group, and R2can be a t-butyl group. In still further aspects, R1 can be a halogen; alternatively Cl; alternatively F.

[0044] Each R1and R2independently can be, in certain aspects, a linear, branched, or cyclic alkyl group or an alkenyl group. As a non-limiting example, each R1and R2independently can be CF3, a methyl group, an ethyl group, a propyl group, a butyl group (e.g., t-Bu), a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an ethenyl group, a propenyl group, a butenyl group, a pentenyl group, ahexenyl group, a heptenyl group, an octenyl group, a nonenyl group, a decenyl group, a phenyl group, a tolyl group (or other substituted aryl group), a benzyl group, a naphthyl group, a trimethylsilyl group, a triisopropylsilyl group, a triphenylsilyl group, an allyldimethylsilyl group, or a 1 -methylcyclohexyl group; alternatively, Cl; alternatively, CF3; alternatively, a methyl group; alternatively, an ethyl group; alternatively, a propyl group; alternatively, a butyl group; alternatively, a pentyl group; alternatively, a hexyl group; alternatively, a heptyl group; alternatively, an octyl group, a nonyl group; alternatively, a decyl group; alternatively, an ethenyl group; alternatively, a propenyl group; alternatively, a butenyl group; alternatively, a pentenyl group; alternatively, a hexenyl group; alternatively, a heptenyl group; alternatively, an octenyl group; alternatively, a nonenyl group; alternatively, a decenyl group; alternatively, a phenyl group; alternatively, a tolyl group; alternatively, a benzyl group; alternatively, a naphthyl group; alternatively, a trimethylsilyl group; alternatively, a triisopropylsilyl group; alternatively, a triphenylsilyl group; alternatively, an allyldimethylsilyl group; or alternatively, a 1 -methylcyclohexyl group.

[0045] In Formula (IV), X3can be H, a halogen, or a substituted or unsubstituted Ci to Cis hydrocarbyl group. As a non-limiting example, X3can be H, bromide, chloride, fluoride, CF3, a methyl group, an ethyl group, a propyl group, a butyl group (e.g., t-Bu), a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an ethenyl group, a propenyl group, a butenyl group, a pentenyl group, a hexenyl group, a heptenyl group, an octenyl group, a nonenyl group, a decenyl group, a phenyl group, a tolyl group (or other substituted aryl group), a benzyl group, a naphthyl group.

[0046] Sarin provides an exemplary organophosphorus compound having Formula (IV), and suitable for detection using sensor compounds described herein, wherein R1is methyl, R2is isopropyl, and X3is F. Another example is Soman, an organophosphorus compound of Formula (IV) wherein R1is methyl, R2is 1,2,2,2-tetramethylethyl, and X3is F. Additional suitable organophosphorus compounds include warfare agent simulants such as methyl dichlorophosphate (MDCP), dimethyl chlorophosphate (DMCP), trimethyl phosphate (IMP), trimethyl phosphate, dimethyl, methylphosphonate, and diisopropyl methylphosphonate.DETECTORS AND METHODS OF DETECTING ORGANOPHOSPHORUS COMPOUNDS

[0047] Detectors and methods for detecting organophosphorus compounds are contemplated herein. Generally organophosphorus detectors can comprise an amount of the sensor compound positioned within the detector so as to (i) contact and react with any organophosphorus compound present in a given environment, and (ii) detect a color change in the sensor compound.

[0048] Broadly, detectors contemplated herein can further comprise an optical sensor to detect a change in color of the sensor compound composition. In these or other aspects, detectors can comprise a controller to process and monitor a signal produced by the optical sensor. Detectors can further comprise an alarm to alert the detection of organophosphorus compound above a given threshold.

[0049] Physical implementations of detectors contemplated herein are not limited to any particular form. In certain aspects, the detector can be simply the sensor compound itself, wherein a color change may be observed following exposure to an organophosphorus compound. In other aspects, the detector can be a backing strip of material with a sensor compound composition comprising (or constating essentially of, or consisting of) the sensor compound deposited thereupon, much in the same manner as for pH strips, as those of ordinary skill in the art would understand. In such aspects, the sensor compound may be formulated on a surface or incorporated into gel-like polymers, or in a compressed pellet form that possesses a color change upon the exposure to the target gas.

[0050] Similarly, the detectors contemplated herein can include wearable devices (e.g., badges) to indicate a presence or an exposure to organophosphorus compounds. Operation of such detectors may be similar in principle to the strips described above, indicating a color change allowing the user to confirm the presence of an organophosphorus agent in the environment, signaling a need to evacuate, employ a gas mask, and / or additional protective measures for themselves and others in the vicinity.

[0051] In still further aspects, the detector can be a handheld device, for instance as exemplified (without limitation) in Fig. 9. As stated above, the handheld device can comprise an amount of the sensor compound disposed in a portion of the device that is exposed to airflow of the surrounding environment, while also being protected fromphysical damage during use. The handheld device can further comprise a colorimetric sensor to monitor any change in color from the sensor compound composition after exposure. The handheld device may also comprise an onboard processor, or alternatively connect to an external processor for receiving and processing a signal received by the colorimetric sensor into an output signal related to the presence of an organophosphorus compound, e.g., the presence of an organophosphorus compound above a threshold amount.

[0052] In certain aspects, the detector can further comprise a monitor and / or alarm to convey the output signal to a local user; alternatively or additionally, to a remote user. Handheld detectors as described herein are not limited to use by hand, and may be mounted in vehicles, or areas of increased concern such as churches, markets, schools, and public centers.

[0053] Detectors employing sensor compounds as described herein can advantageously detect extraordinarily low levels of organophosphorus compounds. In certain aspects, detectors can have a limit of detection (e.g., for sarin or a sarin analog) of 50 ppb, 100 ppb, 250 ppb, or 500 ppb, 1 ppm, 10, ppm, or 100 ppm. In other aspects, the detector can exhibit a linearity of the detection between 50 ppb and 300 ppm. The response time also can be surprisingly fast even at low levels of detection, with the above sensitivity being achieved in less than 10 seconds, less than 30 seconds, less than 1 minute, less than 2 minutes, less than 5 minutes, or less than 15 minutes in certain aspects.

[0054] Surprisingly, the sensitivity of detectors disclosed herein also can be exemplary, being able to achieve any of the limits of detection disclosed above even in the presence of alcohols (e.g., methanol, ethanol, isopropanol) and other organic solvents that may produce a false positive or otherwise interfere with conventional warfare agent detectors. In certain aspects, the selectivity of the detector to organophosphorus compounds relative to methanol can be at least IxlO3, IxlO4, IxlO5, IxlO6, IxlO7, IxlO8, IxlO9, IxlO10, or IxlO11, or any range therebetween, e.g., from IxlO3to IxlO9, or from IxlO9to IxlO9.

[0055] Without being bound by theory, it is believed that the surprising sensitivity of detectors disclosed herein may be attributed at least in part to the nature of the coordination complex formed by the sensor compound and the organophosphorus compound within the detector, and its attributes relative to the sensor compound. As will be understood by those of skill in the art given the disclosure above, the coordinationcomplex formed within the detector can have the following general formula (V), wherein each of R1, R2, X1, X2, X3, Y1, Y2, A and B are defined as above.

[0056] In the case of detecting a sarin compound (e.g., sarin and its simulants, including MDCP), the coordination complex thus formed can be synonymous to a “sarin derivative.”

[0057] In certain aspects, R1 can be halogen, alternatively F. In other aspects, R2can be methyl; alternatively tert-butyl. In still further aspects, A can be thiophen-2-yl; alternatively furan-2-yl; alternatively pyridin-2-yl. In other aspects, X1and X2each can be H. Detectors comprising coordination complexes of Formula V are contemplated herein. Such aspects can have the coordination complexes arranged within the detector as for the sensor compounds described above.

[0058] It is further contemplated, without limitation, that the sensitivity and specificity achieved in the presently disclosed detectors may be at least in part due to the size of the red shift in visible color observed by the reaction of the sensor compound having a first color with the organophosphorus compound to form a coordination complex having a second color. In certain aspects, the difference in visible color can be characterized qualitatively, e.g., with the first color being yellow, and the second color being red. Alternatively, the difference may be characterized quantitatively, by describing the associated wavelength of light in each of the colors. For instance a yellow sensor compound may be characterized by associated visible light wavelength of approximately 600 nm, and a deep red coordination complex with the organophosphorus compound may be defined by a wavelength of approximately 725 nm. In such aspects, the difference in the associated wavelength of light for each of the first and second colors can be 125 nm.

[0059] Thus, in certain aspects, it is contemplated that a difference between the first color and the second color can be at least 10 nm, at least 25 nm, at least 50 nm, at least 100 nm, at least 125 nm, at least 150 nm, or at least 200 nm. Alternatively, the differencebetween the first color and the second color can be in a range from 25 nm to 250 nm, from 50 nm to 200 nm, or from 100 nm to 150 nm.

[0060] Detectors disclosed herein also may have an exemplary shelf life, demonstrating a stability of the sensor compound in an uncoordinated state under typical use conditions and across a wide range of temperature and humidity. In certain aspects, the detector can maintain any sensitivity to organophosphorus described above at 25 °C, 95% relative humidity, for at least 7 days, at least 14 days, at least 1 month, at least 3 months, at least 6 months, at least 12 months, or at least 24 months.

[0061] Methods for detecting an airborne chemical warfare agent using detectors also are contemplated herein. Generally, methods are not limited to a particular implementation, and can encompass any procedure comprising (i) deploying a detector comprising an amount of a sensor compound into a detection area; (ii) monitoring a color of the sensor compound; (iii) generating an output signal indicating the color change (or lack of color change) of the sensor compound; and optionally, (iv) correlating the color of the sensor compound to the presence (or absence) of an organophosphorus compound in the detection area.EXAMPLES

[0062] The invention is further illustrated by the following examples, which are not to be construed in any way as imposing limitations to the scope of this invention. Various other aspects, modifications, and equivalents thereof which, after reading the description herein, can suggest themselves to one of ordinary skill in the art without departing from the spirit of the present invention or the scope of the appended claims.PREPARATION OF SENSOR COMPOUNDS

[0063] Sensor Compound 1 was prepared by a one-step reaction of 1,2- phenylenediamine (2 moles) with 2,6-pyridinedicarboxaldehyde (1 mole) in ethanol at 70 °C for 4 hours. After cooling to room temperature, a yellow precipitate formed from the reaction mixture, the precipitate was filtered to yield (N,N-(2,6- pyridinediyldimethylidyne)bis-l,2-benzenediamine as a yellow solid.

[0064] Sensor Compound 2 was prepared in a similar process by reacting 2- aminophenol (2 moles) with 2,5-thiophenedicarboxaldehyde (1 mole) in ethanol at 70 °C. As above, the reaction mixture was cooled to room temperature to precipitate Sensor Compound 2 as a yellow solid.

[0065] Sensor Compound 1 and Sensor 2 were identified as yellow precipitates that were characterized using FTIR, andNMR spectroscopic techniques.REACTION OF SENSOR COMPOUNDS WITH MDCP

[0066] Sensor compounds prepared as above were evaluated for their reactivity with a sarin analog, MDCP. Generally, 60 ppm solution of the sensor compound was prepared in methanol under continuous stirring at ambient temperature for 30 minutes prior testing. The sensor compound was exposed to a series of 7 different concentrations of MDCP, ranging from 5 ppm to 1000 ppm. After the exposure, the resulting reaction product was evaluated by emission spectra, SSLS, and UV-Vis (see Figs. 3-5). Fig. 6 shows an emission spectra collected using an excitation wavelength of 235 nm. As shown in Figs. 3-4, each of the sensor compounds demonstrated a proportional decrease in the initial peak and rise of alternative peaks in the emission spectra, signifying the presence of a color change associated with reaction of even minor amounts of MDCP.

[0067] Both sensor compounds show strong luminescent features that were found to be reactive towards various concentrations of MDCP prepared in methanol.

[0068] Each sensor compound provides two active chelating sites that quickly attack the central P-atom of the sarin analog, providing an immediate response (30 seconds) towards MDCP even for a very low detection limit up to 50 ppb (part per billion) as depicted from Figures 4 and 6 with a wide linear range from 0.05-300 ppm (as depicted from Figure 7).ASPECTS

[0069] The invention is described herein with reference to numerous aspects and specific examples. Many variations will suggest themselves to those skilled in the art in light of the detailed description. All such obvious variations are within the full intended scope of the appended claims. All such obvious variations are within the full intended scopeof the appended claims. Other aspects of the invention can include, but are not limited to, the following (aspects are described as “comprising” but, alternatively, can “consist essentially of’ or “consist of’):

[0070] Aspect 1. A sensor compound having formula (II) or (III):wherein:X1and X2each are independently selected from H, a substituted or unsubstituted alkyl group, a halogen, a hydroxyl group, or an amino group;Y1and Y2each are independently selected from O, N, S; andY3is S or O.

[0071] Aspect 2. The sensor compound defined in aspect 1, wherein the sensor compound is selected from:

[0072] Aspect 3. A sensor for detecting a sarin compound, the sensor comprising: a sensor compound defined in aspects 1 or 2; and a detector configured to detect a color difference between a first color of the sensor compound and a second color of a sarin derivative formed by a reaction between the sensor compound and the sarin compound.

[0073] Aspect 4. The chemofluorescent sensor defined in aspect 3, wherein the sarin compound is an organophosphonate.

[0074] Aspect 5. The chemofluorescent sensor defined in aspect 3, wherein the sarin compound is an organophosphonate selected from sarin and methyl dichloromethylphosphate.

[0075] Aspect 6. The chemofluorescent sensor defined in aspect 5, wherein the sarin derivative has a formula selected from:wherein:R1is a substituted or unsubstituted alkyl group;X1and X2each are independently selected from H, a substituted or unsubstituted alkyl group, a halogen, a hydroxyl group, or an amino group;Y1and Y2each are independently selected from O, N, S; andY3is S or O.

[0076] Aspect 7. The chemofluorescent sensor defined in aspect 3, wherein the first color of the sensor compound is red.

[0077] Aspect 8. The chemofluorescent sensor defined in aspect 3, wherein the sensor has a limit of detection of at least about 0.050 ppm, and a linear detection response toward the sarin compound throughout the range of 0.05 - 300 ppm.

[0078] Aspect 9. The chemofluorescent sensor defined in aspect 3, wherein the sensor has a selectivity in a range from about 1,000 to about 10,000 relative to an interfering reagent.

[0079] Aspect 10. The chemofluorescent sensor defined in aspect 9, wherein the interfering reagent is methanol.

[0080] Aspect 11. The chemofluorescent sensor defined in aspect 3, the reaction between the sensor and the sarin compound occurs within 30 seconds.

[0081] Aspect 12. The chemofluorescent sensor defined in aspect 3, the sensor compound has complete solubility in a 10:90 V% solution of methanol: water.

[0082] Aspect 13. The chemofluorescent sensor defined in aspect 3, wherein the detector is a colorimetric sensor.

[0083] Aspect 14. The chemofluorescent sensor defined in aspect 3, wherein the detector is configured to detect a color change one or both of: a change in emission intensity of the sensor compound; and a change in emission wavelength of the sensor compound.

[0084] Aspect 15. The chemofluorescent sensor defined in aspect 14, further comprising a processor configured to calculate an amount of the sarin compound present based on one or both of the change in emission intensity of the sensor compound and the change in emission wavelength of the sensor compound.

[0085] Aspect 16. The chemofluorescent sensor defined in aspect 15, further comprising a controller configured to generate an alarm signal when the amount of the sarin compound exceeds a threshold amount.

[0086] Aspect 17. A method of detecting the presence of a sarin compound, comprising positioning in a detection area, a sensor comprising any sensor compound defined herein; reacting the sensor compound with the sarin compound to form a sarin derivative; and detecting a color change in the sensor compound.

[0087] Aspect 18. The method defined in aspect 17, wherein the method for detecting the presence of a sarin compound in a range from 0.05 -300 ppm.

[0088] Aspect 19. The method defined in aspect 17, wherein the detection area is a place of worship, shopping center, airport, or sporting arena.

[0089] Aspect 20. A sarin derivative selected from:

[0090] Aspect 21. A chemical warfare agent sensor for detecting a sarin compound, the sensor comprising: a sensor compound having Formula (II) or (III):a detector configured to detect a color difference between the sensor compound and a sarin derivative formed by a reaction between the sensor compound and the sarin compound; wherein: the sensor has a low detection limit of 50 part per billion (ppb) of the sarin compound; the sensor has a selectivity for the sarin compound relative to an interfering reagent such as methanol in a range from 1,000 to 10,000; the sensor has a linear detection range at room temperature in a range from 0.05 to 300 ppm; the reaction between the sensor compound and the sarin compound occurs within 30 seconds; the sensor compound has complete solubility in a solution of 10:90 V% methanol: water; and the sensor derivative has a formula selected from:wherein:R1is a substituted or unsubstituted alkyl group;X1and X2each are independently selected from H, a substituted or unsubstituted alkyl group, a halogen, a hydroxyl group, or an amino group;Y1and Y2each are independently selected from O, N, S; andY3is S or O.

Claims

CLAIMSWhat is claimed is:

1. A sensor compound having Formula (II) or (III):wherein:X1and X2each are independently selected from H, a substituted or unsubstituted alkyl group, a halogen, a hydroxyl group, or an amino group;Y1and Y2each are independently selected from OH, NH2, SH; andY3is S or O.

2. The sensor compound of claim 1, selected from:

3. A chemofluorescent sensor for detecting an organophosphorus compound, the chemofluorescent detector comprising: a sensor compound having Formula (I):wherein:A and B each independently are a substituted or unsubstituted aromatic hydrocarbon, or a substituted or unsubstituted aromatic heterocycle;X1and X2each independently is H or a substituted or unsubstituted Ci to Cis hydrocarbyl group; andY1and Y2each independently is NH2, OH, or SH.

4. The chemofluorescent sensor of claim 3, wherein A is fluoren-2-yl, thiophen-2-yl, or pyridine-2-yl.

5. The chemofluorescent sensor of claim 4, wherein B is phenyl.

6. The chemofluorescent sensor of claim 3, wherein the organophosphorus compound is an organophosphonate having Formula (IV):wherein:R1is H, Cl, F, or a substituted or unsubstituted Ci to Cis hydrocarbyl group;R2is H, or a substituted or unsubstituted Ci to Cis hydrocarbyl group; and X3is H, Cl, F, or a substituted or unsubstituted Ci to Cis hydrocarbyl group.

7. The chemofluorescent sensor of claim 3, wherein the organophosphorus compound is an organophosphonate selected from sarin, methyl dichlorophosphate (MDCP), dimethyl chlorophosphate (DMCP), trimethyl phosphate (TMP), trimethyl phosphate, dimethyl, methylphosphonate, and diisopropyl methylphosphonate.

8. The chemofluorescent sensor of claim 3, wherein the detector is a colorimetric sensor comprising: a light source; an excitation monochromator; an emission monochromator; and a detector.

9. The chemofluorescent sensor of claim 3, wherein the detector is configured to detect a color difference between a color of the sensor compound and a color of a sarin derivative formed by a reaction between the sensor compound and an organophosphorus compound.

10. The chemofluorescent sensor of claim 9, wherein: the color of the sensor compound is yellow; and the color of the sarin derivative is red.

11. The chemofluorescent sensor of claim 9, wherein the sarin derivative has Formula (V):wherein:A is pyridine-2-yl, thiophen-2-yl, or furan-2-yl;B is a substituted or unsubstituted aromatic hydrocarbon, or a substituted or unsubstituted aromatic heterocycle;X1is H or a substituted or unsubstituted Ci to Cis hydrocarbyl group; andR2is a Ci to Cis hydrocarbyl group, a Ci to Cis halogenated hydrocarbyl group, a Ci to Cis hydrocarboxy group, or a Ci to Cis hydrocarbylsilyl group.

12. The chemofluorescent sensor of claim 9, wherein:A is fluoren-2-yl, thiophen-2-yl, or pyridine-2-yl;B is phenyl; andX1and X2each is H.

13. The chemofluorescent sensor of claim 3, having a limit of detection of less than 500 ppb.

14. The chemofluorescent sensor of claim 3, having a selectivity in a range from about 1,000 to about 10,000 relative to methanol.

15. The chemofluorescent sensor of claim 3, further comprising a processor configured to calculate an amount of the organophosphorus compound present based on one or both of the change in emission intensity of the sensor compound and the change in emission wavelength of the sensor compound.

16. The chemofluorescent sensor of claim 3, further comprising a controller configured to generate an alarm signal when the amount of the organophosphorus compound exceeds a threshold amount.

17. The chemofluorescent sensor of claim 3, wherein the chemofluorescent sensor is a wearable badge, a handheld device, a desktop detector, or a vehicle-mounted detector.

18. A method of detecting the presence of an organophosphorus compound, comprising: positioning in a detection area, a sensor comprising the sensor compound of claim 1; reacting the sensor compound with an organophosphorus compound to form a sarin derivative; and detecting a color change in the sensor compound.

19. The chemofluorescent detector of claim 18, wherein detecting a color change in the sensor compound comprises one or both of: detecting a change in an emission intensity of the sensor compound; and detecting a change in an emission wavelength of the sensor compound.

20. The method of claim 18, wherein the detection area is a place of worship, shopping center, airport, or sporting arena.

21. A sarin derivative compound having Formula (V):wherein:A is pyridine-2-yl, thiophen-2-yl, or furan-2-yl;B is a substituted or unsubstituted aromatic hydrocarbon, or a substituted or unsubstituted aromatic heterocycle;X1is H or a substituted or unsubstituted Ci to Cis hydrocarbyl group; andR2is a Ci to Cis hydrocarbyl group, a Ci to Cis halogenated hydrocarbyl group, a Ci to Cis hydrocarboxy group, or a Ci to Cis hydrocarbylsilyl group.

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