The importance of Au⋯π(aryl) interactions in the formation of spherical aggregates in binuclear phosphane gold(i) complexes of a bipodal thiocarbamate dianion: a combined crystallographic and computational study, and anti-microbial activity

• Main Authors: Yeo, C.I., Khoo, C.H., Chu, W.C., Chen, B.J., Chu, P.L., Sim, J.H., Cheah, Y.K., Ahmad, J., Halim, S.N.A., Seng, H.L., Ng, S., Otero-de-la-Roza, A., Tiekink, E.R.T.
• Format: Article
• Published: Royal Society of Chemistry 2015
• Subjects: Q Science (General); QD Chemistry; QH Natural history; R Medicine
• Online Access: http://eprints.um.edu.my/19375/; http://dx.doi.org/10.1039/C5RA05604G

Binuclear phosphanegold(i) complexes of a bipodal thiocarbamate dianion, (R3PAu)2L, R = Et (1), Ph (2) and Cy (3), where LH2 is {1,4-[MeOC(S)N(H)]2C6H4}, have been synthesised, and characterised spectroscopically (NMR and IR) and by X-ray crystallography. The gold atoms are linearly coordinated within a P-,S-donor set, and are oriented toward the central ring to form intramolecular Au ⋯π(aryl) interactions, rather than the intramolecular Au ⋯O interactions normally observed in mononuclear analogues. This phenomenon has been investigated by theory (LC-ωPBE-XDM) for 1 which revealed that the geometry optimised species with two Au ⋯π(aryl) interactions is more stable by at least 12 kcal mol-1 compared to conformations having one or more Au ⋯O interactions instead. The disk diffusion, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) methods were used to observe the inhibitory effect of complexes 1-3. The disk diffusion results demonstrated that 1 exhibited a broad spectrum of anti-bacterial activity toward 24 strains of Gram-positive and Gram-negative bacteria. By contrast, the anti-bacterial activity of 2 and 3 was limited to Gram-positive bacteria. Further evaluation showed that 1 exhibited marked bactericidal activity against B. cereus, B. subtilis, E. faecalis, L. monocytogenes, S. aureus, S. saprophyticus and methicillin resistant S. aureus cf. standard antibiotics tetracycline and chloramphenicol.