Luminescent Anionic Cyclometalated Organoplatinum (II) Complexes with Terminal and Bridging Cyanide Ligand: Structural and Photophysical Properties

We present the synthesis and characterization of two series of mononuclear heteroleptic anionic cycloplatinated(II) complexes featuring terminal cyanide ligand Q(+)[Pt(C<^>N)(p-MeC6H4)(CN)]- [C<^>N = benzoquinolate (bzq), Q(+) = K+ 1 and NBu4+ 4; 2-phenylpyridinate (ppy), Q(+) = K+ 2 and NBu4+ 5 and 2- (2,4-difluorophenyl)pyridinate (dfppy), Q(+) = K+ 3 and NBu4+ 6] and a series of symmetrical binuclear complexes (NBu4)-[Pt-2(C<^>N)(2)(p-MeC6H4)(2)(mu-CN)] (C<^>N = bzq 7, ppy 8, dfppy 9). Compounds 5, 6, and 7-9 were further determined by single-crystal X-ray diffraction. There are no apparent intermolecular Ptmiddotmiddotmiddot Pt interactions owing to the presence of bulky NBu4+ counterion. Slow crystallization of K[Pt(ppy)(p-MeC6H4)(CN)] 2 in acetone/ hexane evolves with formation of yellow crystals, which were identified by single-crystal X-ray diffraction methods as the salt complex {[Pt(ppy)(p-MeC6H4)(CN)](2)K-3(OCMe2)(4)(mu- OCMe2)(2)}[Pt(ppy)(p-MeC6H4)(mu-CN)Pt(ppy)(p-MeC6H4)]middot2acetone (10), featuring the binuclear anionic unit 8- neutralized by an hybrid inorganic-organometallic coordination polymer {[Pt(ppy)(p-MeC6H4)(CN)](2)K-3(OCMe2)(4)(mu-OCMe2)(2)}(+). The photophysical properties of all compounds were recorded in powder, polystyrene film, and solution states with a quantum yield up to 21% for 9 in the solid state. All complexes displayed bright emission in rigid media, and for the interpretation of their absorption and emission properties, density functional theory (DFT) and time-dependent DFT calculations were applied.