Synthesis, Structure and Bactericide Activity of (Aminophosphane)gold(I) Thiolate Complexes

Abstract

Reaction of the aminophosphane ligands 2-(diphenylphosphanylamino)pyridine (Ph2PNHpy, 1) and 3-(diphenylphosphanylamino)-1,2,4-triazole [Ph2PNH(Htrz), 2] with the gold(I) compound [AuCl(tht)] (tht = tetrahydrothiophene) gave the complexes [AuCl(Ph2PNHpy)] (3) and [AuCl{Ph2PNH(Htrz)}] (4), respectively. A series of new gold(I) thiolate derivatives were synthesized from the reactions of complex 3 or 4 with 1 equiv. of a deprotonated thiol ligand. Complexes [Au(SR)(PPh2NHpy)] (5–8) were prepared by reaction of complex 3 with the corresponding thiol HSR [HSR = 2-mercaptopyridine (2-HSpy), 2-mercaptonicotinic acid (2-H2-mna), 2-thiouracil (2-HTU) or 2-thiocytosine (2-HTC)] in the presence of sodium carbonate or triethylamine. Complexes [Au(SR){PPh2NH(Htrz)}] (9–11) were prepared by the treatment of complex 4 with triethylamine and the respective thiol HSR [HSR = 2-mercaptopyridine (2-HSpy), 2-thiocytosine (2-HTC) or 6-thioguanine (6-HTG)]. The susceptibility of Enterococcus faecalis ATCC25923, Staphylococcus aureus ATCC29213 and Escherichia coli TG1 towards the synthesized gold(I) complexes was evaluated. Some of them exhibit powerful anti-bacterial activity, being more efficient against Gram-positive microorganisms. Complexes 7–9 and 11 present excellent activity against E. faecalis, whereas the highest sensitivity of S. aureus was against complexes 7 and 8. The structures of complexes 4, 5, 8 and 9 were determined by X-ray structural analysis. None of the four compounds shows aurophilic interactions between the gold(I) centres in the crystals. The four complexes possess intermolecular hydrogen bonds that lead to supramolecular arrangements.