Synthesis and Luminescence Properties of [Pt{4-(o-MeC6H4)- pzbipy}Cl]SbF6 [pzbipy = 6-2''-pyrazinyl)-2,22'-bipyridine]

The synthesis and characterisation of the 4-(o-R-C )pzbipy [R = H, CH or CF ; pzbipy = 6-(2″- pyrazinyl)-2,2′-bipyridyl] ligands are described. Reaction of the 4-(o-MeC )pzbipy ligand with [Pt(PhCN) Cl ] in the presence of AgSbF affords [Pt{4-(o-MeC )pzbipy}Cl]SbF as a marooncoloured microcrystalline solid. The [Pt{4-(o-MeC )pzbipy}Cl] cation exhibits low intensity photoluminescence in dichloromethane that maximises at 543 nm and which is assigned to a MLCT excited state (τ = 20 ns). The emission spectrum of the cation was also recorded in a frozen DME {1 : 5:5 (v/v) DMF / MeOH / EtOH} glass; a highly structured band is observed with vibrational spacings of ca. 1400 cm , indicating emission from an intraligand 3π-π state (τ = 11 μs). Variable temperature solid emission spectra show maxima that occur at significantly lower energies than is observed in fluid solution and that shift to the red when the temperature is lowered; specifically, λ (em) is 674 nm at 280 K (τ = 80 ns) and 723 nm at 80 K (τ = 1.3 μs). Emission behaviour of this type is typical of emission from a metal-metal-ligand charge transfer (MMLCT) excited state that has its origins in d (Pt)-d (Pt) orbital interactions in the crystal.