Synthesis, structure and photophysical properties of binuclear methylplatinum complexes containing cyclometalating 2-phenylpyridine or benzo{h}quinoline ligands: a comparison of intramolecular Pt-Pt and π-π interactions.

The binuclear cyclometalated complexes [Pt(2)Me(2)(ppy)(2)(μ-dppm)], 1a, and [Pt(2)Me(2)(bhq)(2)(μ-dppm)], 1b, in which ppy = 2-phenylpyridyl, bhq = benzo{h}quinoline and dppm = bis(diphenylphosphino)methane, were synthesized by the reaction of [PtMe(SMe(2))(ppy)] or [PtMe(SMe(2))(bhq)] with 1/2 equiv of dppm at room temperature, respectively. Complexes 1a and 1b were fully characterized by multinuclear ((1)H, (31)P, (13)C, and (195)Pt) NMR spectroscopy and were further identified by single crystal X-ray structure determination. A comparison of the intramolecular Pt-Pt and π-π interactions in complexes 1a and 1b has been made on the basis of data on crystal structures and wave functions analysis. The binuclear complexes 1a and 1b are luminescent in the solid state, and showing relatively intense orange-red emissions stemming from (3)MMLCT excited states. The reaction of complex 1b with excess MeI gave the binuclear cyclometalated Pt(IV)-Pt(IV) complex [Pt(2)Me(4)(bhq)(2)(μ-I)(2)], 2. Crystal structure of complex 2 shows intermolecular C-H···I and C-H···π interactions in solid state.