Novel achiral indole-substituted titanocenes: Synthesis and preliminary cytotoxicity studies

A series of eight new titanocene dichloride derivatives has been synthesised and characterized. Four compounds from the series are lypophilic indole-functionalised titanocenes and four are hydrochloride salts of their dimethylaminomethyl-functionalised counterparts, which are water soluble. The compounds were tested for their in vitro cytotoxicities against the human kidney cancer cell line CAKI-1 and their results are compared with previously synthesised structural analogues. Surprisingly, two of the compounds showed no activity against the CAKI-1 cell line; however six compounds exhibited medium to high potency with IC50 values as low as 7.0 μM. These six complexes were tested further on this cell line using the co-solvent Soluphor P, which has been shown to improve both solubility and cytotoxicity of similar complexes. One of the compounds carrying a N-methylindole-substituent was obtained in the form of single crystals and allowed for the characterisation by X-ray crystallography; the compound crystallised in the space group P21/n (#14) with four molecules present in the monoclinic unit cell.