Photophysics and photochemistry of biphenylyl triphenylphosphine gold(I) complexes

Biphenylyl triphenylphosphine gold(I) complexes (4-biphenylyl, 4B; 2-biphenylyl, 2B) having the Au-C bond are synthesized. The gold(I) complex (4B) was found to exhibit intense blue room temperature phosphorescence (Φp = 0.24 and τT = 117 μs) originated from the locally excited triplet of the biphenyl moiety (3LE) in degassed 2-methyltetrahydrofuran solution. 2B, however, is nonluminescent. On the assumption that ΦST = 1.0 for 4B, the radiative rate constant (kr) in the triplet state is calculated to be 2.06 × 103 s−1. This value is five-orders of magnitude larger than the radiative rate constant of the triplet biphenyl (0.024 s−1).