Ultrafast cis-to-trans photoisomerization of a bridged azobenzene through n pi excitation: Rotational pathway is not restricted

A bridged azobenzene was recently found by Siewertsen et al. to exhibit highly efficient photoisomerization through n absorption. In the work of the present Letter, cis-to-trans photoisomerization of this molecule in the gas phase was examined in detail via density-functional-based dynamical simulations. Our results indicate that rotation around the central NN bond is the dominant mechanism when this reaction proceeds via n excitation, and the bridging feature was found not to hinder the rotation. Nonadiabatic de-excitation occurred at an avoided crossing between the ground state and lowest singlet excited state near the midpoint of the rotational pathway. 2011 Elsevier B.V. All rights reserved.

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