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Abstract: The study of a series of cis-[APtCl2] complexes (A=ethylenediamine, en, methylated at different positions) was carried out to evaluate the effect of different methyl substitutions on the cytotoxic properties of the resulting derivatives. As expected, differentially methylated complexes were found to differ widely in their cytotoxic effects on human cultured ovarian carcinoma cells (A2780). Molecular mechanics (MM) calculations have been performed to assess the relationship between differential diamine methylation and the repulsive energy of the corresponding complexes when interacting with DNA. Compounds that bind DNA at high energetic cost relative to cisplatin, due to the steric hindrance of additional methyl groups, have shown high values for IC50 (concentration inhibiting tumour cell growth by 50%). Semi-quantitative analyses with a DNA electrochemical biosensor confirm that the interaction between cis-[APtCl2] complexes and ds-DNA deposed onto the electrode is stronger for the non-methylated derivative with respect to the fully methylated congener. In addition, MM calculations were used to investigate the interactions between DNA and cis-[(P-L-A)PtCl2] complexes [A=en group linked to an antiestrogen-like pharmacophore, P, via a –(CH2)n– spacer (n =2, 4, 6, 8 and 10), L]. [Copyright &y& Elsevier]

The reaction of amine ligands with the unsaturated 46 e− cluster Os3(μ-H2)(CO)10 yields a series of complexes of formula Os3H(μ-H)(CO)10(amine). In these derivatives the presence of an unconventional hydrogen-bond M&z.sbnd;H⋯H&z.sbnd;N is detected by the evaluation of proton spin-lattice relaxation times. In order to elucidate the relationship between pKb and H⋯H length, the M&z.sbnd;H⋯H&z.sbnd;N distances were quantified for amines of known pKb. In practice, this was achieved by comparing the T1 values of the terminal hydride resonances of the protonated isotopomer with the T1 values of the corresponding derivative containing selectively deuterated amine. A nice correlation between the M&z.sbnd;H⋯H&z.sbnd;N distances and the pKb of the amine ligands was found. DFT calculations were carried out for the cluster on Os3H(μ-H)(CO)10(Benzylamine) to gain a fuller understanding of the possible coordination geometries of an amine ligand on the surface of a tri-osmium cluster. [Copyright &y& Elsevier]