Synthesis, crystal structure and antimicrobial activities of two isomeric gold(I) complexes with nitrogen-containing heterocycle and triphenylphosphine ligands, [Au(L) (PPh3)] (HL = pyrazole and imidazole)

Two isomeric gold(I)-triphenylphosphine complexes with nitrogen-containing heterocycles, [Au(L)(PPh3)] (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 (P-31, H-1 and C-13) 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) (PPh3)] (3, Htriz = triazole), [Au(1,2,4-triz) (PPh3)](2) (4) as a dimer through a gold(I)-gold(I) bond in the solid state, and [Au(tetz) (PPh3)] (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. (C) 2000 Elsevier Science Inc. All rights reserved.