Ruthenium(III) and iridium(III) complexes with nicotine

A new chloride-dimethylsulfoxide-ruthenium(III) complex with nicotine trans-[Ru(III)Cl(4)(DMSO)[H-(Nicotine)]] (1) and three related iridium(III) complexes; [H-(Nicotine)]trans-[Ir(III)Cl(4)(DMSO)(2)] (2), trans[Ir Cl(4)(DMSO)[H-(Nicotine)]] (3) and mer-[Ir(III)Cl(3)(DMSO)(Nicotine)(2)] (4) have been synthesized and characterized by spectroscopic techniques and by single crystal X-ray diffraction (1, 2, and 4). Protonated nicotine at pyrrolidine nitrogen is present in complexes 1 and 3 while two neutral nicotine ligands are observed in 4. In these three inner-sphere complexes coordination occurs through the pyridine nitrogen. Moreover, in the outer-sphere complex 2, an electrostatic interaction is observed between a cationic protonated nicotine at the pyrrolidine nitrogen and the anionic trans-[Ir(III) Cl(4)(DMSO)(2)] complex. Electrophoretic mobility and atomic force microscopy (AFM) studies of the interaction between 1 and 3 complexes and plasmidic DNA pBR322 have been performed. These results show that the Ru(III) complex 1 interacts significantly with plasmidic DNA while a weak interaction is observed with the corresponding Ir(III) complex 3. (C) 2009 Elsevier Ltd. All rights reserved.