Synthesis, crystal structure and antimicrobial activities of two isomeric gold(I) complexes with nitrogen-containing heterocycle and triphenylphosphine ligands, [Au(L)(PPh 3)] (HL=pyrazole and imidazole)

Abstract

Two isomeric gold(I)–triphenylphosphine complexes with nitrogen-containing heterocycles, [Au(L)(PPh 3)] (HL=pyrazole ( 1), imidazole ( 2)), were isolated as colorless cubic crystals for 1 and colorless plate crystals for 2, respectively. The crystal structures of 1 and 2 were determined by single-crystal X-ray diffraction. These complexes were also fully characterized by complete elemental analyses, thermogravimetric/differential thermal analyses (TG/DTA) and FT-IR in the solid state and by solution NMR ( 31P, 1H and 13C) spectroscopy and molecular weight measurements in acetone solution. These complexes consisted of a monomeric 2-coordinate AuNP core both in the solid state and in solution. The molecular structures of 1 and 2 were compared with those of related gold(I) complexes, [Au(1,2,3-triz)(PPh 3)] ( 3, Htriz=triazole), [Au(1,2,4-triz)(PPh 3)] 2 ( 4) as a dimer through a gold(I)–gold(I) bond in the solid state, and [Au(tetz)(PPh 3)] ( 5, Htetz=tetrazole). Selective and effective antimicrobial activities against two Gram-positive bacteria ( B. subtilis, S. aureus) and modest activities against one yeast ( C. albicans) found in these gold(I) complexes 1– 4 are noteworthy, in contrast to poor activities observed in the corresponding silver(I) complexes.