The diamides and disulfonamides m-C(6)H(4)(CONHAr)(2) (Ar = Ph, 1; p-n-BuC(6)H(4), 2, 2,4,6-Me(3)C(6)H(2), 3), m-C(6)H(4)(SO(2)NHPh)(2), 4, and 2,6-C(6)H(3)N(CONHPh)(2), 5, readily synthesized on a multigram scale, bind strongly to halides and acetate in organic solvents with K(a)'s as high as 6.1 x 10(4) (NMR spectroscopy). The binding stoichiometry is 1:1 in solution for all cases except for the 4.F(-) and 4.OAc(-) complexes, where both 1:1 and 1:2 binding stoichiometries were found. The association constants in CD(2)Cl(2) ((1)H NMR) follow the trend Cl(-) > Br(-) > I(-) for all the receptors. F(-) and OAc(-) binding may be stronger or weaker than Cl(-) depending on the nature of the receptor. The presence of the pyridine nitrogen in 5 and of the more rigid amide in 1-3 and 5 vs the less rigid sulfonamide structure in 4 increases selectivity for smaller anions. The enthalpy and entropy of formation for 2.Cl(-) were DeltaH = -31 kJ/mol; DeltaS = -23 J/(mol.K) (VT-NMR). The X-ray structure of [PPh(4)](2)[1.Br][Br].CH(2)Cl(2), shows 1:1 complexation of Br(-) via two N-H.Br(-) hydrogen bonds and a syn-syn nonplanar binding conformation for 1. Solution hydrogen bonding was confirmed by FT-IR and NMR spectroscopy. The receptor conformation changes on complexation. Trends in structure/binding relationships show receptor flexibility is an important factor in anion recognition.

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Human arsenic metabolism produces a number of species with varying toxicities; the presence of some has been identified while the existence of others has been postulated through indirect evidence. Speciation methods for the analysis of arsenite (AsIII), monomethylarsonous acid (MMAIII), dimethylarsinous acid (DMAIII), arsenate (AsV), monomethylarsonic acid (MMAV), dimethylarsinic acid (DMAV), arsino-glutathione (As(GS)3), monomethylarsino-glutathione (MMA(GS)2) and dimethylarsino-glutathione (DMA(GS)) were developed in this study through the use of cation exchange and reverse phase chromatography in a complementary manner. Electrospray ionization mass spectrometry (ESI-MS) was used for molecular identification of the arsenicals while inductively coupled plasma mass spectrometry (ICP-MS) was employed for quantitation purposes. Validation of the developed methods against each other for the quantitation of trivalent and pentavalent arsenicals was performed. The effect of reduced glutathione (GSH) concentration on the formation of arsenic-glutathione (As-GSH) complexes was studied. In the presence of glutathione, the occurrence of chromatographic artifacts on the cation exchange column was observed. The stability of trivalent arsenicals and As-GSH complexes was studied at various pH conditions. The results shed light on the importance of sample preparation, storage and proper choice of analytical column for the accurate identification of the As species. Reinvestigation of some of the previously reported As speciation studies of glutathione-rich biological samples needs to be performed for the verification of occurrence of As-GSH complexes and DMAIII.

Lead poisoning, which is especially prevalent in children, is still the most common environmentally caused disease nationally and worldwide. 1 Development of extractants and fluorescent chemosensors 2 for Pb(II) is of importance for monitoring EPA mandated levels and for a variety of applications related to lead toxicity, biodistribution, and removal. For such applications, it is essential to achieve high selectivity for Pb(II) against both alkaline earth and other common metal ions present in biological systems, such as Cu(II) and Zn(II). 3 Exploiting the unique coordination properties of Pb(II) 3,4 provides opportunities for the design of selective sensors 5 and extractants. 6 Successful fluorescent Pb(II) sensor designs are based on complexation by peptides, 7 ionizable chelates, 8 DNAzymes, 9 or macrocycles 10 with covalently linked fluorophores. Macrocycles can be tedious to synthesize and typically exhibit a wide variety of polydentate Pb(II) coordination patterns. On the other hand, ion exchange extraction from water to an organic solvent by simpler chelates can lead to improved selectivity by taking advantage of the unique preference of Pb(II) for low-coordinate hemidirected 3 geometries with a stereochemically expressed lone pair. Moreover, simpler chelates tend to be easier to synthesize, an advantage that could potentially be exploited for sensor discovery by using rapid screening methods. 11 As part of our effort to design low-coordinate Pb(II) extractants and sensors, we now wish to report efficient and selective ion-exchange extraction of Pb(II) from water into 1,2-dichloroethane (DCE) with concurrent fluorescence quenching using as an ion-exchanger, the sulfonamide fluorophore 1. This simple system does not require a secondary co-ligand in order to extract Pb and shows remarkable extraction selectivity against other metals with D Pb > 130 D Cu and D Pb > 1400 D Zn .Sulfonamide 1 is available in good yields from o-phenylenediamine and 1-(dimethylamino)-5-naphthalene sulfonyl chloride (dansyl chloride). 12 The dansyl group is a well-known E-mail: kavallie@fiu.edu. † Florida International University. ‡ University of Miami.Supporting Information Available: Synthesis, procedures, extraction plots, and X-ray crystallographic details of 1. This material is available free of charge via the Internet at http://pubs.acs.org. (Figure 1). Neither Ca(II) nor Na(I) were extracted to any appreciable extent. We ascribe the observed selectivity to the formation of the low-coordinate complex 3, which is apparently disfavored for other competing metals. The crystal structure of the binary Pb complex of the analogous bis-(phenylsulfonyl) derivative of phenylenediamine, which is insoluble in DCE, has showed the formation of a coordination polymer via S=O-Pb axial coordination and a stereochemically active lone pair. 15 The fact that the dansyl complex 3 is soluble in DCE indicates that the S=O-Pb axial coordination is no longer significant and is most likely replaced by weak coordination from solvent molecules or wate...