Photocytotoxic Activity of Ruthenium(II) Complexes with Phenanthroline-Hydrazone Ligands

This paper reports on the synthesis and characterization of two new polypyridyl-hydrazone Schiff bases, (E)-N′-(6-oxo-1,10-phenanthrolin-5(6H)-ylidene)thiophene-2-carbohydrazide (L¹) and (E)-N′-(6-oxo-1,10-phenanthrolin-5(6H)-ylidene)furan-2-carbohydrazide (L²), and their two Ru(II) complexes of the general formula RuCl(DMSO)(phen)(Lⁿ)](PF6). Considering that hydrazides are a structural part of severa l drugs and metal complexes containing phenanthroline derivatives are known to interact with DNA and to exhibit antitumor activity, more potent anticancer agents can be obtained by covalently linking the thiophene acid hydrazide or the furoic acid hydrazide to a 1,10-phenanthroline moiety. These ligands and the Ru(II) complexes were characterized by elemental analyses, electronic, vibrational, ¹H NMR, and ESI-MS spectroscopies. Ru is bound to two different N-heterocyclic ligands. One chloride and one S-bonded DMSO in cis-configuration to each other complete the octahedral coordination sphere around the metal ion. The ligands are very effective in inhibiting cellular growth in a chronic myelogenous leukemia cell line, K562. Both complexes are able to interact with DNA and present moderate cytotoxic activity, but 5 min of UV-light exposure increases cytotoxicity by three times.