Cyclometalated Platinum(II) Cyanometallates: Luminescent Blocks for Coordination Self-Assembly.

A family of cyanide-bridged heterometallic aggregates has been constructed of the chromophoric cycloplatinated metalloligands and coordinatively unsaturated d fragments {M(PPh)}. The tetranuclear complexes of general composition [Pt(C^N)(CN)M(PPh)] [C^N = ppy, M = Cu (1), Ag (2); C^N = tolpy (Htolpy = 2-(4-tolyl)-pyridine), M = Cu (4), Ag (5); C^N = Fppy (HFppy = 2-(4, 6-difluorophenyl)-pyridine), M = Cu (7), Ag (8)] demonstrate a squarelike arrangement of the molecular frameworks, which is achieved due to favorable coordination geometries of the bridging ligands and the metal ions. Variation of the amount of the ancillary phosphine (for M = Ag) afforded compounds [Pt(C^N)(CN)Ag(PPh)] (C^N = ppy, 3; C^N = tolpy, 6); for the latter one an alternative cluster topology, stabilized by the Pt-Ag metallophilic and η-C(C^N)-Ag bonding, was observed. The solid-state structures of all of the title species 1-8 were determined crystallographically. The complexes exhibit moderately strong room-temperature phosphorescence as crystalline powders (Φ = 16-34%, λ = 470-511 nm). The luminescence studies and time-dependent density functional theory computational analysis indicate that the photophysical behavior is dominated by the π-π* electronic transitions localized on the cyclometalated fragment and mixed with MLCT contribution, while the d-phosphine motifs have a negligible contribution into the frontier orbitals and therefore show a little influence on the emission performance of the described compounds.