Dinuclear (N∧C∧N) Pincer Pt(II) Complexes with Bridged Organometallic Linkers: Synthesis, Structures, Self-Aggregation, and Photophysical Properties

A new family of cationic dinuclear cyclometalated Pt­(II) complexes containing an organometallic assembling ligand has been reported. The general formulas for these compounds is as follow: [R-(N∧C∧N)­PtL-LPt­(N∧C∧N)-R]­[X]2, where L-L = [Cp*Ir-p-(η4-C6H4S2)], R = H, X = OTf (5); R= CF3–, X = OTf (6a), SbF6 (6b); L-L = [Cp*Ir-p-(η4-C6H4Se2)] R= CF3–, X = OTf (7a), SbF6 (7b). In these coordination assemblies two cyclometalated R-(N∧C∧N)Pt moieties are held by either η4-dithio-p-benzoquinone complex [Cp*Ir-p-(η4-C6H4S2)] (3) or η4-diseleno-p-benzoquinone complex [Cp*Ir-p-(η4-C6H4Se2)] (4). The molecular structures of the known complex [4-CF3-(N∧C∧N)­PtCl] as well as two compounds of the above family [(N∧C∧N)­Pt–Cp*Ir-p-(η4-C6H4S2)Pt­(N∧C∧N)]­[CF3SO3]2 (5) and [CF3-(N∧C∧N)­PtCp*Ir-p-(η4-C6H4S2)Pt­(N∧C∧N)-CF3]­[CF3SO3]2 (6a) were ascertained by single crystal X-ray diffraction study and confirmed the formation of the target molecules. The solid-state packing of 5 and 6a confirms the presence π–π and short Pt···Pt interactions among individual units providing 1D supramolecular chains. To our knowledge, these are the only known examples where two cyclometalated Pt­(N∧C∧N) units are assembled by a bridging ligand (vide infra). All compounds show phosphorescence in the bluish-green region (486–521 nm) in the solution at room temperature and exhibit higher luminescence quantum yields relative to the analogous compounds containing a Pt­(terpy) chromophore in thin film.