92
M. Osawa et al. / Chemical Physics Letters 436 (2007) 89–93
4. Conclusion
The 4B complex was found to exhibit intense blue room
temperature phosphorescence (Up = 0.24 and sT = 117 ls)
originated from the locally excited triplet of the biphenyl
moiety (3LE) in degassed 2-methyltetrahydrofuran solu-
tion. On the assumption that UST = 1.0 for 4B, the radia-
tive rate constant (kr) in the triplet state is calculated to
be 2.06 · 103 sꢀ1. This value is five-orders of magnitude
larger than the radiative rate constant of the triplet biphe-
nyl (0.024 sꢀ1). Further, fluorescence from 4B is very weak
(Uf < 10ꢀ4). Thus, the coordinated Au(I) atom gives a
markedly large heavy-atom effect on the S1–T1 and T1–S0
processes of the biphenyl chromophore in 4B.
Fig. 5. Absorption and emission spectra of 4B in degassed CH2Cl2
solution upon irradiation at 266 nm (interval time: 1 min).
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