Homoleptic and heteroleptic bismuth(III) thiazole-thiolates and the influence of ring substitution on their antibacterial and antileishmanial activity

Ahmad Luqman, Victoria L Blair, Rajini Brammananth, Paul K Crellin, Ross L Coppel, Lukasz Kedzierski, Philip C Andrews

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Two new homo- and heteroleptic bismuth thiazole-thiolato complexes derived from 4-phenylthiazole-2-thiol MBT(H) have been synthesised and structurally characterised, [BiPh(MBT)2]2 and [Bi(MBT)3]2. Syntheses were achieved using BiPh3 or Bi(OtBu)3 in protolysis reactions with MBT(H), or by salt metathesis with BiCl3 or BiPhCl2 and the sodium thiolate, [NaMBT]. The complexes were obtained under both standard solvent-free and solvent-mediated conditions, and by microwave irradiation. The solid-state structures of [BiPh(MBT)2]2 and [Bi(MBT)3]2, were determined using single-crystal X-ray diffraction, showing them to be dimeric. The bactericidal properties of the complexes against Mycobacterium smegmatis, Staphylococcus aureus, methicillin-resistant Staphylococcus aureus (MRSA), Enterococcus faecalis, vancomycin-resistant Enterococcus (VRE) and Escherichia coli revealed [BiPh(MBT)2]2 to be the most effective against all the bacteria with MIC values of 0.6 μg/mL (0.25 μM) against S. aureus and 0.9 μg/mL (0.27 μM) against E. faecalis. [Bi(MBT)3]2 was less active overall. However, comparisons with the analogous complex [Bi(4-BrMTD)3], revealed a significant hundred-fold enhanced activity against S. aureus, MRSA, VRE, and E. faecalis. Both complexes showed little or no toxicity towards mammalian COS-7 cells at 20 μg/mL. [BiPh(MBT)2]2 also was found to display good antileishmanial activity with an IC50 value of 0.11 μg/mL (0.17 μM), at which concentration the complex was non-toxic to human fibroblast cells.

Original languageEnglish
Pages (from-to)725-733
Number of pages9
JournalEuropean Journal of Inorganic Chemistry
Issue number4
Publication statusPublished - 2015


  • Antibiotics
  • Antiparasitic agents
  • Bismuth
  • Medicinal chemistry
  • S ligands

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