Search

The face-capping triphosphine, 1,1,1-tris(diphenylphosphino)methane (tppm), together with bridging alkynyl ligands and the counterions, facilitates the formation of a family of silver complexes, which adopt cluster frameworks of variable nuclearity. The hexanuclear compounds [Ag6(C2C6H4-4-X)3(tppm)2(An–)3] (X = H (1), CF3 (2), OMe (3), An– = CF3SO3–; X = OMe (4), An– = CF3COO–) are produced for the electron-accepting to moderately electron-donating alkynes and the appropriate stoichiometry of the reagents. 1 and 3 undergo an expansion of the metal core when treated with 1 equiv of Ag+ to give the species [Ag7(C2C6H4-4-X)3(tppm)2(CF3SO3)3](CF3SO3) (X = H (5), OMe (6)). The electron-donating substituent (X = NMe2) particularly favors this Ag7 arrangement (7) that undergoes geometry changes upon alkynylation, resulting in the capped prismatic cluster [Ag7(C2C6H4-4-NMe2)4(tppm)2(CF3SO3)](CF3SO3)2 (8). Alternatively, for the aliphatic tBu-alkyne, only the octanuclear complex [Ag8(C2But)4{(PPh2)3CH}2(CF3SO3)2](...

New tetrazole derivatives of chitosan with low, moderate, and high degrees of substitution were obtained using a novel approach, i.e. metal-catalyzed 1,3-dipolar cycloaddition of azide ion to cyanoethyl chitosan in water – the most straightforward, selective and preparatively convenient route to tetrazole chitosan derivatives. Ionic gelation of these tetrazole derivatives with sodium tripolyphosphate resulted in nanoparticles with an apparent hydrodynamic diameter of 100–800 nm and ζ-potential of 22–57 mV. The tetrazole derivatives of chitosan and their nanoparticles were tested as catalysts of the aldol reaction between p-chlorobenzaldehyde and acetone. The tetrazole derivatives have been found to possess better catalytic properties than the corresponding nanoparticles. The obtained data indicate that the tetrazole-chitosan polymers exhibit high catalytic activity in aldol reaction, and these catalysts are among the best studied so far. Tetrazole derivatives and their nanoparticles were also tested as antibacterial agents. The in vitro antibacterial activity against S. aureus and E. coli of the tetrazole-chitosan-based nanoparticles is much more than the activity of the corresponding tetrazole-chitosan polymers, and their activity is comparable with that of antibiotics ampicillin and gentamicin.

The reaction of [Cu(NCMe)4][PF6] with aromatic acetylenes HC2R and triphosphine 1,1,1-tris(diphenylphosphino)methane in the presence of NEt3 results in the formation of hexanuclear Cu(I) clusters with the general formula [Cu6(C2R)4{(PPh2)3CH}2][PF6]2 (R = 4-X-C6H4 (1-5) and C5H4N (6); X = NMe2 (1), OMe (2), H (3), Ph (4), CF3 (5)). The structural motif of the complexes studied consists of a Cu6 metal core supported by two phosphine ligands and stabilized by σ- and π-coordination of the alkynyl fragments (together with coordination of pyridine nitrogen atoms in cluster 6). The solid state structures of complexes 2-6 were determined by single crystal XRD analysis. The structures of the complexes in solution were elucidated by (1)H, (31)P, (1)H-(1)H COSY NMR spectroscopy, and ESI mass spectrometry. Clusters 1-6 exhibit moderately strong phosphorescence in the solid state with quantum yields up to 17%. Complexes 1-5 were found to form solvates (acetone, acetonitrile) in the solid state. The coordination of loosely bound solvent molecules strongly affects emission characteristics and leads to solvato- and vapochromic behavior of the clusters. Thus, solvent-free and acetonitrile solvated forms of 3 demonstrate contrasting emission in orange (615 nm) and blue (475 nm) regions, respectively. The computational studies show that alkynyl-centered IL transitions mixed with those of MLCT between the Cu6 metal core and the ligand environment play a dominant role in the formation of excited states and can be considerably modulated by weakly coordinating solvent molecules leading to luminescence vapochromism.

Polynuclear mixed-metal gold(I)–copper(I) complexes 1–3 based on the [{Au3Cu2(C2C6H4NHR)6}Au3{PPh2C6H4PPh2}3]2+ cluster core with acyl (1) and N-protected amino acid groups [R = BocGly (2), BocAla (3)] in alkynyl ligands were synthesized and characterized. The solid-state structures of 1 was determined by XRD, the other complexes were characterized by NMR spectroscopy and ESI-MS measurements. The luminescence behavior of these compounds were studied in dichloromethane solution at room temperature, moderate to strong orange emission at ca. 610 nm with maximum quantum yield of 0.46 for compound 3 was found.

Reactions of the {AuC2R}n polymer (R = –C6H4NO2, –C6H5, –C6H4Ph, –C6H4OMe, –C6H4NMe2, –C(OH)Me2, –C6H10(OH)) with stoichiometric amount of 1,4-bis(diphenylphosphino)butane and Cu(I) ions afford the dicationic complexes of general formula [Au6Cu2(C2–R)6(PPh2(CH2)4PPh2)3](PF6)2. The compounds obtained (1–7) display common “rods-in-belt” structural motif with the “Cu2{Au(C2R)2}3” central cluster core wrapped about by the {Au3(Ph2P(CH2)4PPh2)3} belt. This structural pattern was revealed in solid state by X-ray crystallography and confirmed in solution using the NMR spectroscopy. The complexes 6 and 7 containing hydroxyl substituents in the alkynyl ligands demonstrate structural distortions due to hydrogen bonding inside the cluster core. All complexes studied exhibit intense phosphorescence in dichloromethane solution, the characteristics of which depend on donor ability of the alkynyl ligand substituents. Comparison of the emission wavelengths in 1–7 with those observed in the congeners based on the aromatic diphosphine (PPh2C6H4PPh2) showed considerable blue shift of the emission band maxima in the complexes under study. The theoretical DFT calculations indicated that the triplet emission in 1–7 is mainly determined by electron transitions inside the cluster core with some admixture of MLCT character, the contribution of which plays more important role compared to the analogs with aromatic diphosphine and causes the observed hypsochromic shift of emission.

The reaction of [Cu(NCMe)4][PF6] with aromatic acetylenes HC2R and triphosphine 1,1,1-tris(diphenylphosphino)methane in the presence of NEt3 results in the formation of hexanuclear Cu(I) clusters with the general formula [Cu6(C2R)4{(PPh2)3CH}2][PF6]2 (R = 4-X-C6H4 (1–5) and C5H4N (6); X = NMe2 (1), OMe (2), H (3), Ph (4), CF3 (5)). The structural motif of the complexes studied consists of a Cu6 metal core supported by two phosphine ligands and stabilized by σ- and π-coordination of the alkynyl fragments (together with coordination of pyridine nitrogen atoms in cluster 6). The solid state structures of complexes 2–6 were determined by single crystal XRD analysis. The structures of the complexes in solution were elucidated by 1H, 31P, 1H–1H COSY NMR spectroscopy, and ESI mass spectrometry. Clusters 1–6 exhibit moderately strong phosphorescence in the solid state with quantum yields up to 17%. Complexes 1–5 were found to form solvates (acetone, acetonitrile) in the solid state. The coordination of loosely bound solvent molecules strongly affects emission characteristics and leads to solvato- and vapochromic behavior of the clusters. Thus, solvent-free and acetonitrile solvated forms of 3 demonstrate contrasting emission in orange (615 nm) and blue (475 nm) regions, respectively. The computational studies show that alkynyl-centered IL transitions mixed with those of MLCT between the Cu6 metal core and the ligand environment play a dominant role in the formation of excited states and can be considerably modulated by weakly coordinating solvent molecules leading to luminescence vapochromism.

The reactions of gold acetylides (AuC2R)n with triphosphine ligands PPh2-(CH2)n-PPh-(CH2)2-PPh2 (n = 1, dpmp; 2, dpep) in the presence of M(+) ions (M = Cu, Ag) lead to an assembly of the heterometallic clusters, the composition of which is determined by the steric bulkiness of the alkynyl groups and the flexibility of the phosphine motifs. For R = Ph, an unprecedented hexanuclear complex [Au5Cu(C2R)4(dpmp)2](2+) (1) was isolated, while for the aliphatic alkynes (R = 1-cyclohexanolyl, 2-borneolyl, 2,6-dimethyl-4-heptanolyl) a family of compounds based on a tetrametallic framework was prepared, [Au3Cu(C2R)3(dpmp)](+) (2, R = 1-cyclohexanolyl), [Au3M(C2R)3(dpep)]2(+2) (3, M = Cu, R = 1-cyclohexanolyl; 4, M = Cu, R = 2-borneolyl; 5, M = Ag, R = 2-borneolyl), and [Au3Ag(C2R)3(dpep)](+) (6, R = 2,6-dimethyl-4-heptanolyl). Clusters 1, 2, and 4-6 were studied by X-ray crystallography. The NMR spectroscopic investigations showed that 1 and 3-5 are stereochemically non-rigid in solution and reversibly undergo possible dissociation (3) or isomerization (4, 5) processes. All the title complexes exhibit room temperature luminescence in the solid state in the spectral region from 414 to 566 nm, showing a dependence of emission energy on the structure and composition of the metal core. Computational studies with density functional methods were carried out to rationalize the dynamic and photophysical behavior of these compounds.