Cytotoxic Activities of Bis‐cyclometalated Rhodium(III) and Iridium(III) Complexes Containing 2,2’‐Biphenyldiamine

The synthesis and characterization of new bis-cyclometalated complex salts [M(ptpy)(2)(2,2'-biphenyldiamine)]PF6 (M=Rh, 1; M=Ir, 2; ptpy=2-(p-tolyl)pyridinato) are described. Compounds 1 and 2 were obtained by bridge-splitting reactions of [{M(mu-Cl)(ptpy)(2)}(2)] (M=Rh or Ir) with 2,2'-biphenyldiamine in CH2Cl2/MeOH/H2O mixtures. The molecular structure of compound 2 in the crystal was confirmed by single-crystal X-ray diffraction. 2 crystallized from dichloromethane/methanol/n-heptane in the monoclinic space group P2(1)/(n). The cytotoxic activities of both new compounds were examined and evaluated. Compound 1 and 2 exhibit significant cytotoxicity against human cancer cell lines with the IC50 values in the low micromolar range.