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 d10 fragments {M­(PPh3)n}. The tetranuclear complexes of general
composition [Pt­(C^N)­(CN)2M­(PPh3)2]2 [C^N = ppy, M = Cu (1), Ag (2); C^N = tolpy (Htolpy = 2-(4-tolyl)-pyridine), M = Cu (4), Ag (5); C^N = F2ppy (HF2ppy
= 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)2Ag­(PPh3)]2 (C^N = ppy, 3; C^N = tolpy, 6); for the latter one an alternative
cluster topology, stabilized by the Pt–Ag metallophilic and
η1-Cipso(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 (Φem = 16–34%, λem = 470–511 nm). The luminescence studies and time-dependent
density functional theory computational analysis indicate that the
photophysical behavior is dominated by the 3π–π*
electronic transitions localized on the cyclometalated fragment and
mixed with MPtLCT contribution, while the d10-phosphine motifs have a negligible contribution into the frontier
orbitals and therefore show a little influence on the emission performance
of the described compounds.