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Updated: Mar 14, 2026

Determination of the Photoisomerization Quantum Yield of a Hydrazone Photoswitch
Published on: February 7, 2022
Photoisomerization of Self-Assembled Monolayers of Azobiphenyls: Simulations Highlight the Role of Packing and
Valentina Cantatore1, Giovanni Granucci1, Guillaume Rousseau2
1Dipartimento di Chimica e Chimica Industriale, Università di Pisa , v. G. Moruzzi 13, I-56124 Pisa, Italy.
Abstract:
We present surface hopping simulations of the photodynamics of self-assembled monolayers (SAMs) of 4'-(biphenyl-4-ylazo)-biphenyl-4-thiol (ABPT) on Au(111). We show that trans → cis photoisomerization is suppressed because of steric hindrance in a well-ordered SAM. Photoisomerization is instead viable in the presence of defects. Two particularly important defects are the boundaries between domains of trans-ABPT molecules leaning in different directions (a line defect) and single cis molecules embedded in a SAM of trans (a point defect). Our findings explain the cooperative behavior observed during the photoisomerization of a trans-ABPT SAM, leading to large domains of pure cis and trans isomers. The line and point defects are predicted to produce different patterns of cis-ABPT molecules during the early stages of the photoconversion.
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