Bismuth(iii) Thiophosphinates: Understanding How a Small Atomic Change Influences Antibacterial Activity and Mammalian Cell Viability

Diphenylphosphinothioic acid (HSP(=O)Ph-2) and diphenylphosphinodithioic acid (HSP(=S)Ph-2) have been used to synthesise four BiIII complexes: 1 [Bi(SP(=O)Ph-2)(3)], 2 [BiPh(SP(=O)Ph-2)(2)], 3 [BiPh2(SP(=O)Ph-2)], and 4 [Bi(SP(=S)-Ph-2)(3)], using BiPh3 and [Bi(OtBu)(3)] as bismuth sources. The complexes have been characterised by NMR spectroscopy, mass spectrometry, infrared spectroscopy, powder X-ray diffraction, and singe crystal X-ray crystallography (2-4). Biological studies indicated that despite complexes 2 and 3 reducing mammalian cell viability, their antibacterial activity provides a good degree of selectivity towards both Gram positive and Gram negative bacterial strains. The minimum inhibitory concentrations for complexes 2 and 3 are in the range of 0.52-5.5 mM towards the bacteria tested. Homoleptic complexes 1 and 4 were generally less active towards both bacterial and mammalian cells.