The first members of a promising new family of hybrid amino acid-polyoxometalates have emerged from a search for modular functional molecules. Incorporation of glycine (Gly) or norleucine (Nle) ligands into an yttrium-tungstoarsenate structural backbone, followed by crystallization with p-methylbenzylammonium (p-MeBzNH3(+)) cations, affords (p-MeBzNH3)6K2(GlyH)[As(III)4(Y(III)W(VI)3)W(VI)44Y(III)4O159(Gly)8(H2O)14]⋅47 H2O (1) and enantiomorphs (p-MeBzNH3)15(NleH)3[As(III)4(Mo(V)2Mo(VI)2)W(VI)44Y(III)4O160(Nle)9(H2O)11][As(III)4(Mo(VI)2W(VI)2)W(VI)44Y(III)4O160(Nle)9(H2O)11] (generically designated 2: L-Nle, 2 a; D-Nle, 2 b). An intensive structural, spectroscopic, electrochemical, magnetochemical and theoretical investigation has allowed the elucidation of site-selective metal substitution and photoreduction of the tetranuclear core of the hybrid polyanions. In the solid state, markedly different crystal packing is evident for the compounds, which indicates the role of noncovalent interactions involving the amino acid ligands. In solution, mass spectrometric and small-angle X-ray scattering studies confirm maintenance of the structure of the polyanions of 2, while circular dichroism demonstrates that the chirality is also maintained. The combination of all of these features in a single modular family emphasizes the potential of such hybrid polyoxometalates to provide nanoscale molecular materials with tunable properties.

Eight new members of a family of mixed-metal (Mo,W) polyoxometalates (POMs) with amino acid ligands have been synthesized and investigated in the solid state and solution using multiple physical techniques. While the peripheral POM structural framework is conserved, the different analogues vary in nuclearity of the central metal-oxo core, overall redox state, metal composition, and identity of the zwitterionic α-amino acid ligands. Structural investigations reveal site-selective substitution of Mo for W, with a strong preference for Mo to occupy the central metal-oxo core. This core structural unit is a closed tetrametallic loop in the blue reduced species and an open trimetallic loop in the colorless oxidized analogues. Density functional theory calculations suggest the core as the favored site of reduction and reveal that the corresponding molecular orbital is much lower in energy for a tetra- versus trimetallic core. The reduced species are diamagnetic, each with a pair of strongly antiferromagnetically coupled Mo centers in the tetrametallic core, while in the oxidized complexes all Mo is hexavalent. Solution small-angle X-ray scattering and circular dichroism (CD) studies indicate that the hybrid POM is stable in aqueous solution on a time scale of days within defined concentration and pH ranges, with the stability enhanced by the presence of excess amino acid. The CD experiments also reveal that the amino acid ligands readily exchange with other α-amino acids, and it is possible to isolate the products of amino acid exchange, confirming retention of the POM framework. Cyclic voltammograms of the reduced species exhibit an irreversible oxidation process at relatively low potential, but an equivalent reductive process is not evident for the oxidized analogues. Despite their overall structural similarity, the oxidized and 2e-reduced hybrid POMs are not interconvertible because of the respective open- versus closed-loop arrangement in the central metal-oxo cores.

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Reaction of sulfonium ylides (Me)(2)SCHC(O)C(6)H(4)R (R = H; m-NO(2); p-NO(2); p-OMe; p-Me and p-Br) with AgNO(3) in dichloromethane leads to various compounds. Single crystal X-ray diffraction analysis reveals that the adducts take 3 forms: (i) two-dimensional polymer, [AgNO(3)(Me(2)SCHC(O)C(6)H(5))](n) (1), with nitrate bridges in which each nitrate coordinates to three silver atoms through two oxygen atoms and two Me(2)SCHC(O)C(6)H(5) ligands coordinate to silver centers through carbon atoms; (ii) cationic binuclear, [Ag(Me(2)SCHC(O)C(6)H(4)-m-NO(2))(2)](2)(NO(3))(2)·2H(2)O (2), in which Me(2)SCHC(O)C(6)H(4)-m-NO(2) ligands simultaneously coordinate through both carbon and oxygen atoms with nitrate as a counter ion, and (iii) cationic mononuclear and anionic binuclear, [Ag(Me(2)SCHC(O)C(6)H(4)-p-NO(2))(2)](2)[{AgNO(3)(μ-NO(3)) (Me(2)SCHC(O)C(6)H(4)-p-NO(2))}(2)]·2CH(3)OH (3), in which nitrate groups act as bridging as well as terminal ligands, and Me(2)SCHC(O)C(6)H(4)-p-NO(2) ligands display C-coordination. Characterization of the obtained compounds was also performed by infrared, (1)H- and (13)C-NMR spectroscopy and analytical data indicated a 1 : 2 stoichiometry between the silver(I) nitrate and ylide p-OMe (4) and 1 : 1 for ylides p-Me (5) and p-Br (6). In addition, the antibacterial effects of DMSO-solutions of complexes 1-6 were evaluated by the agar disc diffusion method against three Gram positive and three Gram negative bacteria. All complexes displayed antibacterial activity against these bacteria, with high levels of inhibitory potency exhibited against the Gram negative species.

The reaction of sulfur ylides SMe2C(H)C(O)R (R = 4-nitrophenyl, phenyl, and 3-nitrophenyl) with [PdCl2(cod)] gives the new Pd(ii) complexes of type cis- and trans-[PdCl2(SMe2C(H)C(O)R)2] (R = phenyl (1), 3-nitrophenyl (2), and 4-nitrophenyl (3)).