An ionic gold(III)–zinc(II) pseudo-polymeric compound of [H3O][Au{S2CN(CH2)5}2]3[ZnCl4]2: Synthesis, supramolecular architecture and anti-tuberculosis activity

Abstract

An ionic Au(III)-Zn(II) dithiocarbamato-chlorido compound of [H3O][Au{S2CN(CH2)5}2]3[ZnCl4]2 (1) has been synthesised by the reaction of binuclear zinc(II) pentamethylenedithiocarbamate with a H[AuCl4]/2.0 M HCl solution. The obtained complex was successfully characterised by FT-IR spectroscopy, elemental analysis and single-crystal X-ray diffraction. There are six ionic moieties in the unit cell of 1: (i) three dithiocarbamato-gold(III) cations, one of which is structurally inequivalent to the other two; (ii) two symmetrically related tetrachloridozincate(II) anions and (iii) one hydronium cation that is disordered over four positions with equal occupancies of 0.25. The compound exhibits a rather complicated supramolecular structure, including pseudo-binuclear gold-rich [Au2(S2CNPm)4]2+ cations and {[ZnCl4]2}4– counter anions, which are stabilised by secondary Au···S and Cl···Cl interactions, respectively. In turn, the former pseudo-binuclear formations involving centrosymmetric mononuclear cations of [Au(S2CNPm)2]+ give the pseudo-polymeric cationic chains of (···[Au2(S2CNPm)4]2+···[Au(S2CNPm)2]+···)n; while the latter, pseudo-binuclear zinc(II) anions, {[ZnCl4]2}4–, as the double linkers combine the neighbouring cationic chains yielding a two-dimensional pseudo-polymeric network. The results on the biological activity of 1in vitro against the non-pathogenic strain Mycolicibacterium smegmatis (MIC 0.05 µg/disc) and virulent strains Mycobacterium tuberculosis H37Rv (0.14–0.19 µg/mL) and CN-40 (0.11–0.14 µg/mL) indicate a high efficiency of the studied Au(III)–Zn(II) compound against mycobacteria.