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Updated: Aug 18, 2026

Determination of the Photoisomerization Quantum Yield of a Hydrazone Photoswitch
Published on: February 7, 2022
Photoisomerization of azobenzene from first-principles constrained density-functional calculations
Murilo L Tiago1, Sohrab Ismail-Beigi, Steven G Louie
1Department of Physics, University of California at Berkeley, Berkeley, California 94720-7300, USA.
Abstract:
Despite considerable work in the field, the precise mechanism for the photoisomerization of azobenzene, C(12)H(10)N(2), is still an open issue. Early theoretical studies of the problem indicated that isomerization occurs through an in-plane inversion path, and this has been used to explain recent time-resolved UV-visible spectroscopy measurements. On the other hand, a number of recent theoretical studies have concluded that a torsion of the N-N bond ("rotation path") is probably the most favorable mechanism for photoisomerization involving the first excited state. We have performed first-principles calculations using constrained density-functional theory (DFT) and time-dependent DFT in the local-density approximation, with results that also favor the rotation path mechanism. Our results are compared with other analyses, primarily based on configuration interaction.
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