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

Abstract

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)[Pt2(C^N)2(p-MeC6H4)2(μ-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 Pt···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)]2K3(OCMe2)4(μ-OCMe2)2}[Pt(ppy)(p-MeC6H4)(μ-CN)Pt(ppy)(p-MeC6H4)]·2acetone (10), featuring the binuclear anionic unit 8- neutralized by an hybrid inorganic-organometallic coordination polymer {[Pt(ppy)(p-MeC6H4)(CN)]2K3(OCMe2)4(μ-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.