A series of ten cyclometallates and two μ2-peroxo bridged tris-aryl Sb(V) complexes derived from R/S-mandelic acid (= R/S-ManH2) were synthesised and characterised. As confirmed by X-ray crystallography the complexes 1Sr/s, [Sb(o-tol)3(man)], 2Sr/s, [Sb(m-tol)3(man)], 4Sr/s, [Sb(o-PhOMe)3(man)], 5Sr/s, [Sb(Mes)3(man)] and 6Sr/s, [Sb(p-tert-BuPh)3(man)] are all cyclometallates. Complexes 3Sr/s, [(Sb(p-tol)3(manH)2O2], contain a bridging O2 2 – anion in the solid-state but convert to the cyclometallates in DMSO solution with concomitant release of H2O2 and formation of complexes [Sb(p-tol)3(man)], 3Sr’/s'. All complexes underwent initial testing against both human fibroblasts and L. major V121 promastigotes. IC50 values were found to range from 2.07 (6Sr) to >100 (4Sr) μM and 0.21 (5Ss) to >100 (4Ss) μM for fibroblasts and parasites respectively. Two of the complexes were found to be ineffective, displaying no toxicity (4S/r). Despite the degree of mammalian toxicity, the selectivity of most complexes exceeded an SI of three and so were assessed for their anti-amastigote activity. Excellent anti-amastigote activity was observed for complexes at both 10 μM and 5 μM, with percentage infection value ranging from 0.15–3.00% for those tested at 10 μM and 0.25–2.50% for those at 5 μM.
- Mandelic acid