One ligand different metal complexes: Biological studies of titanium(IV), tin(IV) and gallium(III) derivatives with the 2,6-dimethoxypyridine-3-carboxylato ligand

The reaction of 2,6-dimethoxypyridine-3-carboxylic acid (DMPH) with different precursors [Ti(η5-C5H5)2Cl2], [Ti(η5-C5H4Me)2Cl2], [Ti(η5-C5H4SiMe3)(η5-C5H5)Cl2], [Ti(η5-C5Me5)Cl3], SnMe3Cl and GatBu3 yielded the complexes [Ti(η5-C5H5)2(DMP-κO)2] (1), [Ti(η5-C5H4Me)2(DMP-κO)2] (2), [Ti(η5-C5H4SiMe3)(η5-C5H5)(DMP-κO)2] (3), [Ti(η5-C5Me5)(DMP-κ2O,O′)3] (4), [SnMe3(μ-DMP-κO:κO′)]∞ (5), and [GatBu2(μ-DMP-κO:κO′)]2 (6). 1–6 have been characterized by spectroscopic methods and the molecular structure of the complexes 1, 2, 3, 5 and 6 have been determined by X-ray diffraction studies. The cytotoxic activity of 1–6 was tested against the tumour cell lines human adenocarcinoma HeLa, human myelogenous leukaemia K562, human malignant melanoma Fem-x and human breast carcinoma MDA-MB-361. The results of this study show a higher cytotoxicity of the tin(IV) and gallium(III) derivatives in comparison to their titanium(IV) counterparts. Furthermore, the different titanium compounds showed differences in their cytotoxicities with a higher activity of complex 4 (mono-(cyclopentadienyl) derivative) compared to that of 1–3 (bis-(cyclopentadienyl) complexes). A qualitative UV–vis study of the interactions of these complexes with DNA has also been carried out.