Probe of the NH bond strength in 1L(a) and 1L(b) states of 7-azaindole with IR-dip spectroscopy: insights into the electronic-state dependence of the multiple proton/hydrogen transfers in hydrogen-bonded clusters.
The difference in the NH bond strengths in the (1)L(a) and (1)L(b) state of 7-azaindole is examined with the fluorescence-detected IR-dip spectroscopy. It has been found that the NH stretch fundamental (3456 cm(-1)) measured by probing the vibronic band at 280 cm(-1) above the zero-point level of (1)L(b) is remarkably red-shifted with respect to those (3483-3489 cm(-1)) obtained by probing the other six vibronic bands in the 0-717 cm(-1) region. The electronic state of the band at 280 cm(-1) was assigned to a S(1)(L(b))/S(2)(L(a)) mixing state [Kang et al. J. Chem. Phys. 2005, 123 , 094306.]; the prominent red shift of the NH stretch fundamental indicates that the (1)L(a) component significantly contributes to weaken the NH bond strength. This finding provides insight into electronic-state dependence of the proton/hydrogen-atom transfer reactions in the hydrogen-bonded 7-azaindole clusters.
Sakota
Kenji
K
Sekiya
Hiroshi
H