Photophysical and structural characterization of the bis-cyclometalated compound [Ir(ptpy)2(κ2N-tppz)]PF6 and evaluation of its cytotoxic activity

Abstract

The synthesis and structural characterization of the bis-cyclometalated compound [Ir(ptpy)2(κ2N-tppz)]PF62 (ptpy = 2-(p-tolyl)pyridinato, tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine) is described. Compound 2 was prepared by reaction of [{Ir(µ-Cl)(ptpy)}2] (1) with tppz in a refluxing solution of CH2Cl2/MeOH and H2O. The resulting complex 2 was purified by chromatography and crystallized from dichloromethane/methanol/isohexane and its molecular structure confirmed by a single-crystal X-ray diffraction study. The emission spectrum of 2 exhibited the new compound as red-emitting phosphorescent complex. The cytotoxic potential of 2 was characterized by determination of the substance’s IC50 value against two different human cancer cell lines (HT-29, MCF-7). In comparison to cisplatin, these values (1.4 μM, 4.2 μM) show a significant increase in cytotoxicity.