Journal of Physical Chemistry p. 702 - 707 (1989)
Update date:2022-08-04
Topics:
Fujiwara, Yoshihisa
Sasaki, Mamoru
Tanimoto, Yoshifumi
Itoh, Michiya
Several para-substituted diphenylcarbenes were generated from the corresponding diphenyldiazomethanes at room temperature and 77 K.The transient absorption (Tn <- T1 and Tn <- T0) and fluorescence (T1 -> T0) spectra of the triplet states of a series of para-substituted diphenylcarbenes were obtained by laser flash photolysis and two-step laser-induced fluorescence (TS-LIF) spectroscopy at room temperature.A significant fluorescence spectral shift of these excited triplet states diphenylcarbenes between TS-LIF at room temperature and fluorescence at 77 K was observed.No spectral difference was detected in a structurally rigid carbene, 10,11-dihydrodibenzocycloheptenylidene.The facts are discussed in terms of a temperature dependence of the rotation of phenyl rings around a C-C<*> bond and/or of a bending motion of a C-C<*>-C bond in the fluorescent state of the diphenylcarbenes.Very small heavy-atom and deuterium isotope effects on the fluorescence (T1 -> T0) lifetimes of these diphenylcarbenes were observed.The data suggests that there is no Sn state of diphenylcarbene involved in the T1 relaxation process.
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