No abstract

The complexes (dppe)M{S2C2(2-pyridine)(CH2CH2OC(O)CH3)} (dppe = 1,2-bis(diphenylphosphino)ethane; M = Pd, Pt) were prepared from 1-(2-pyridyl)-4-acetoxy-2-bromobutan-1-one and the corresponding (dppe)M(SH)2 complexes. The acetyl group was removed from the metal complexes to yield the corresponding alcohols, (dppe)M{S2C2(2-pyridine)(CH2CH2OH)}. The lauroyl derivatives (dppe)M{S2C2(2-pyridine)(CH2CH2OC(O)(CH2)10CH3)} were prepared by esterifying the alcohols with lauroyl chloride. The alkylated pyridinium complexes [(dppe)M{S2C2(CH2CH2-N-2-pyridinium)}]+ were generated by the addition of either p-toluenesulfonyl chloride or bis(triazole) o-chloroaryl phosphate to (dppe)M{S2C2(2-pyridine)(CH2CH2OH)}. [(dppe)Pd{S2C2(CH2CH2-N-2-pyridinium)}][BPh4] crystallizes in the P1̄ space group with a = 9.1924(2) Å, b = 16.0191(2) Å, c = 17.4368(3) Å, α = 106.292(2)°, β = 96.235°, and γ = 95.183(2)°. The molecule is best described as a square planar palladium complex with a planar metallo-1,2-enedithiolate which is coplanar with the alkylated pyridinium. The pyridinium-substituted platinum 1,2-enedithiolate complexes have a 1,2-enedithiolate to heterocycle π* charge-transfer transition (ILCT) that is the lowest lying band. Like [(dppe)Pt{S2C2(2-pyridinium)(H)}]+, [(dppe)Pt{S2C2(CH2CH2-N-2-pyridinium)}]+ is luminescent in room-temperature solution with two emissive states assigned to the ILCT* singlet and triplet. The lifetime of the 1ILCT* is 0.2 ns, 1φ = 0.002, while the lifetime of the 3ILCT is 8.3 μs, 3φ = 0.01 (DMSO). While [(dppe)Pt{S2C2(CH2CH2-N-2-pyridinium)}]+ is emissive, the [(dppe)Pt{S2C2(2-pyridinium)(CH2CH2OR‘‘)}]+ complexes are weak emitters at best in solution with triplet quantum yields of <0.0001 (DMSO). These photophysical studies suggest that the heterocycle and the 1,2-enedithiolate must be coplanar in the ILCT excited states for the complexes to be emissive in room-temperature solution.

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...

Soluble molecularly imprinted polymers (MIPs) were prepared by reversible addition fragmentation chain transfer (RAFT) polymerization followed by ring-closing metathesis (RCM). The polymerization was done in the presence of a template to generate a processable star MIP. The core of the star polymer was a dithiobenzoate-substituted tris(β-diketonate)europium(III) complex. The tris(β-diketonate)europium(III) complex served as a polymerization substrate for the three-armed RAFT-mediated star polymer and as a luminescent binding site for dicrotophos, an organophosphonate pesticide. The star arms were AB block copolymers. Block A was either 1-but-3-enyl-4-vinylbenzene or a mixture of 1-but-3-enyl-4-vinylbenzene and styrene. Block B was styrene or methyl methacrylate. The but-3-enyls of block A were reacted by RCM with a second generation Grubbs catalyst to give an intramolecularly cross-linked core. The intramolecularly cross-linked MIP was soluble in common organic solvents. The 30% cross-linked soluble and processable star MIP was applied to the determination of dicrotophos with sub-ppb level detection limits.