Red-emitting cyclometalated platinum(II) complexes with imidazolyl phenanthrolines: Synthesis and photophysical properties

Three cyclometalated platinum(II) complexes with substituted imidazolyl phenanthrolines L1-L3 have been synthesized and characterized using spectral and electrochemical techniques. The effect of substituent (in the appended aromatic ring to the imidazolyl moiety) on the electronic feature and redox potential of the cyclometalated platinum(II) complexes of general formula [Pt(ppy)(L1-L3)]Cl (1-3) are discussed. Complexes 1-3 are luminescent in the solution and solid state. Complex 1, with two trifluoromethyl moieties present in the ligand shows a higher degree of Pt-II...Pt-II interaction than the ligand incorporated with N,N-dimethyl moiety. The excimer formation through pi - pi and d - pi (Pt...Pt) interactions is evident and the degree of excimer formation is in the order 1 > 2 > 3. Excited-state properties are corroborated by static and time-dependent density functional theory.