As part of an effort to develop new lumaphors involving late transition metal ions, this report describes the synthesis and characterization of the first platinum(II) derivatives containing 2,2':6',2 ''-terpyridine (trpy) and cyanide as co-ligands. According to existing models, including cyanide in the coordination sphere should raise the energies and minimize the influence of short-lived d-d excited states that otherwise compromise the excited-state lifetime. Both [Pt(trpy)(CN)](+) and the 4'-cyano-2,2':6',2 ''-terpyridine analogue [Pt(CN-T)(CN)](+) are emissive in dichloromethane solution, but the signals are weak. Part of the problem is that the d-pi* charge-transfer excited states also rise in energy, so that the emission actually originates from a (3)pi-pi* state with a relatively low radiative rate constant. However, another member of the series, the 4'-dimethylamino-2,2':6',2 ''-terpyridine (dma-T) derivative [Pt(dma-T)(CN)](+), proves to be a very promising platform with an emission quantum yield of phi=0.26 and an excited-state lifetime of tau=22 mu s in room-temperature, deoxygenated dichloromethane solution. In the dma-T complex the electron-rich dimethylamino substituent provides the basis for an emissive, but largely ligand-based, charge-transfer excited state. The orbital parentage is such that the photoluminescence persists in donating solvents like dimethylformamide, which ordinarily quenches d-pi* excited states in complexes of this type.
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