The excited state dynamics of the H-bonded 7-azaindole-phenol complex (7AI-PhOH) has been studied by combination of picosecond pump and probe experiments, LIF measurements on the nanosecond time scale and ab initio calculations. A very short excited state lifetime has been measured for the complex with a lack of specificity on the vibrational modes in the present system. In addition, no UV-visible fluorescence was observed by exciting the complex with nanosecond pulses. Two possible deactivation channels have been investigated by ab initio calculations: an excited state tautomerization assisted by a concerted double proton transfer (CDPT) and an excited state concerted proton electron transfer (CPET) that leads to the formation of a radical pair (hydrogenated 7AIH� radical and phenoxy PhO� radical). Both channels, CDPT and CPET, seem to be open according to ab initio calculations. The analysis of the ensemble of experimental and theoretical evidence favors the excited state concerted proton electron transfer mechanism. In this mechanism, the lengthening of the OH distance of the phenol molecule induces an electron transfer from PhOH to 7AI that is followed by a proton transfer in the same kinetic step. This process leads to the formation of the radical pair (7AIH����PhO�) in the electronically excited state through a very low barrier.

Excited state concerted proton electron transfer in the isolated 7-azaindole-phenol H-bonded complex

248th National Meeting (2014)

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