Rapid Luminescent Detection of Phosphate Esters in Solution and the Gas Phase Using (dppe)Pt{S₂C₂(2-pyridyl)(CH₂CH₂OH)}

Abstract

Organophosphate inhibitors of acetylcholine esterase (including phosphinates and phosphonates) are used as pesticides and as chemical warfare agents. [1][2][3][4][5][6][7] As such, their detection over a range of concentrations and conditions is required and has attracted considerable attention. [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] Several detection methods rely on an immobilized acetylcholine esterase detector coupled to a transducer (i.e., pH electrodes, 5,9,[11][12][13]15,16,22 fiber optics, 10,21 and piezoelectric crystals 14 ). Although the immobilized enzymes are sensitive and detect a broad spectrum of acetylcholine esterase inhibitors, they lack selectivity and are prone to false positives when exposed to choline mimics. 15,23,24 The rapid detection of volatile fluoro and cyano phosphates is of particular interest since these are major constituents in the chemical warfare arsenal. Reported is a new selective method for the rapid detection of these esters. The method uses a new platinum 1,2-enedithiolate complex with an appended alcohol that upon exposure to selected phosphate esters is converted to a roomtemperature lumiphore. 25 Complex, 1, was prepared by the literature procedure (eq 1). 26a,dThe chemical conversion of 1 to [(dppe)Pt{S 2 C 2 (CH 2 CH 2 -N-2-pyridinium)}] + , 2, by activated phosphate esters (eq 2) can be monitored by the emissions from 2 which have been assigned to a thiolate to heterocycle π* intraligand charger-transfer singlet, 1 ILCT*, and triplet, 3 ILCT*. While 1, and 1H + , are nonemissive (φ < 0.00001), 2 is emissive in room-temperature solution ( 1 φ ) 0.002, 3 φ ) 0.01, DMSO) and when immobilized in cellulose acetate/triethylcitrate films ( 1 φ ≈ 0.01, 3 φ ≈ 0.2). 26 Neutral pyridine-substituted complexes such as (dppe)Pt{S 2 C 2 -(2-pyridyl)(R)} R ) H, and CH 2 CH 2 OH, are not emissive due to a lowest lying d to d transition which leads to rapid nonradiative decay of emissive excited states. 26 However, the emissive properties of 2 are similar to those of [(dppe)Pt{S 2 C 2 (2-pyridinium)(H)}] + suggesting that either the steric bulk or solution dynamics of the [(dppe)Pt{S 2 C 2 (2-pyridinium)(CH 2 CH 2 OH)}] + side-chain increases the nonradiative decay rate. The gross differences in the photophysical properties of 2 and [(dppe)Pt-{S 2 C 2 (2-pyridinium)(H)}] + from those of 1H + could arise from the necessity for the 1,2-enedithiolate and heterocycle to be coplanar for emission from the ILCT excited states. 26d Whereas in 2 the 1,2-enedithiolate and heterocycle are held coplanar in the ground state, 26d the ability of the 1,2-enedithiolate and heterocycle to be coplanar in the [(dppe)Pt{S 2 C 2 (2-pyridinium)(R)}] + complexes depends on the bulk of the R group, and this could account for the emission from R ) H and not R ) CH 2 CH 2 OH.Given the chemical reactivity of 1 and combined photophysical properties of 1 and 2, activated phosphate esters serve to turn on the emission in this family of complexes. The reaction of 1 with phosphate, thiophosphate...

Fabrication of an optically driven pH gradient generator based on self-assembled proton pumps

“…9 The change in pH over time of the two reservoirs separated by the bR-PAA transducer when exposed to an 18 mW light source (line with circle for R1, line with square for R2) Fig. 10 Comparison between the experimental observations (line with circle) and theoretical model (line with triangle) used to predict the temporal change in pH for the R1 solution when exposed to a constant light source of phosphate esters using (dppe)Pt{S2C2(2-pyridyl) (CH2CH2OH)} luminophores has been an active area of research because organophosphates are often used to manufacture insecticides, herbicides, and chemical warfare agents (van Houten et al 1998). Accurately detecting the presence of phosphate esters is essential for monitoring pollution, chemical spills in industrial facilities, and the release of deadly chemical agents in public spaces.…”

Fluorescent Sensors for the Detection of Chemical Warfare Agents

“…The first fluorescent reactive chemosensors for the detection of organophosphates were reported by Pilato et al [20] A non-emissive platinum 1,2-enedithiolate complex with an appended primary alcohol was used as the chemosensor (Scheme 4). Upon exposure to an electrophilic OP analyte and an activating agent (triazole) in dichloromethane, the alcohol is converted into the phosphate ester.…”

“…Mechanism of the chemically reactive sensor developed by Pilato and co-workers. [20] Scheme 5. The chemically reactive sensor developed by Swager and coworkers.…”

Chromogenic and fluorogenic reagents for chemical warfare nerve agents' detection

“…The first example of a reactand based on this approach was developed by Pilato and co-workers 16 using a platinum 1,2-enedithiolate complex with an appended alcohol (molecule 1 in Fig. 4). )…”