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 Ga^tBu₃ 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 Ga^tBu₂(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.