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 activityElectronic supplementary information (ESI) available. CCDC 1041500-1041502. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c5ra05604g

Binuclear phosphanegold( i ) complexes of a bipodal thiocarbamate dianion, (R 3 PAu) 2 L, R = Et ( 1 ), Ph ( 2 ) and Cy ( 3 ), where LH 2 is {1,4-[MeOC(&z.dbd;S)N(H)] 2 C 6 H 4 }, 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. Compact molecular structures of antimicrobial (R 3 PAu) 2 L (R = Et ( 1 ), Ph (( 2 ) and Cy (( 3 ); LH 2 = {1,4-[MeOC(&z.dbd;S)-N(H)] 2 C 6 H 4 }), arise from intramolecular Au π(aryl) interactions, proven by theory to be attractive and 12 kcal mol -1 more stable than anticipated Au O interactions.