Synthesis, Characterisation, and Preliminary In Vitro Studies of Vanadium(IV) Complexes with a Schiff Base and Thiosemicarbazones as Mixed Ligands

Abstract [VO(sal‐L‐tryp)(H2O)] (1, sal‐L‐tryp = N‐salicylidene‐L‐tryptophanate) was used as a precursor to produce the new complexes [VO(sal‐L‐tryp)(MeATSC)]·1.5C2H5OH [2, MeATSC = 9‐Anthraldehyde‐N(4)‐methylthiosemicarbazone], [VO(sal‐L‐tryp)(N‐ethhymethohcarbthio)]·H2O [3, N‐ethhymethohcarbthio = (E)‐N‐ethyl‐2‐(4‐hydroxy‐3‐methoxybenzylidene)hydrazinecarbothioamide] and [VO(sal‐L‐tryp)(acetylethTSC)]·C2H5OH {4, acetylethTSC = (E)‐N‐ethyl‐2‐[1‐(thiazol‐2‐yl)ethylidene]hydrazinecarbothioamide} by reaction with the respective thiosemicarbazone. The chemical and structural properties of these ligands and complexes were characterised by elemental analysis, ESI‐MS, FTIR, UV/Vis, ESR and 1H and 13C NMR spectroscopy and X‐ray crystallography. Dimethyl sulfoxide (DMSO) and [D6]DMSO solutions of 1–4 were oxidised in air to produce vanadium(V) species, which were verified by ESI‐MS and 51V NMR spectroscopy. The anticancer properties of 2–4 were examined with three colon cancer cell lines, HTC‐116, Caco‐2 and HT‐29, and noncancerous colonic myofibroblasts, CCD18‐Co. Compounds 2–3 exhibited less inhibitory effects in the CCD‐18Co cells, which indicates a possible cytotoxic selectivity towards colon cancer cells. In general, compounds that exhibit antiproliferative activity to cancer cells but do not affect noncancerous cells may have a potential in chemotherapy.