Effects of cation-anion interactions on the structures and photophysical properties of anionic d0 tungsten-benzylidyne complexes

Abstract The structures and photophysical properties of anionic tungsten–benzylidyne complexes of the type [Na(L)][W(CPh)(OBu t ) 4 ] ([Na(L)] 1 ; L=blank, 15-crown-5, crypt-2,2,2) are strongly dependent on the nature of the [Na(L)] + ion. The structures of the 1 − ions are qualitatively similar, consisting of square-pyramidal tungsten centers with short WC bonds, but differ as a function of cation in the extent of their Na–OBu t interactions, the geometries of their OBu t ligands, and their WO bond distances. The 1 − ions exhibit long-lived luminescence ( τ >1 μs) in fluid solution and the solid state at room temperature. The emission lifetimes and energies are cation dependent even in polar solvents, indicating the presence of [Na(L)] + / 1 − ion pairs in solution for some L. The emissive state is a spin triplet of either [π(WCPh)] 1 [d xy ] 1 or [π(WCPh)] 1 [π*(WCPh)] 1 configuration.