Photophysical and biological characterization of new cationic cyclometalated M(III) complexes of rhodium and iridium

Synthesis and characterization of new cyclometalated complex salts [M(ptpy)2(ddmp)]PF6 (M = Rh, 1; M = Ir, 2; ptpy = 2-(p-tolyl)pyridinato; ddmp = 4,7-dichloro-2,9-dimethyl-1,10-phenanthroline) is described. Compounds 1 and 2 were obtained by the reaction of ddmp with the complexes [{M(μ-Cl)(ptpy)2}2] (M = Rh, Ir) in a mixture of CH2Cl2/MeOH/H2O under reflux conditions. The compounds 1 and 2 crystallized from dichloromethane/chloroform/hexane in the triclinic space group P 1 ¯ and their molecular structures were confirmed by single-crystal X-ray diffraction. Compound 2 exhibits strong yellow phosphorescence in a polymer matrix and in solution at ambient temperature. Both compounds display significant cytotoxicity against human cancer cell lines with the IC50 values in the high nanomolar range.