Photoisomerization of Self-Assembled Monolayers of Azobiphenyls: Simulations Highlight the Role of Packing and Defects.
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.
Dipartimento di Chimica e Chimica Industriale, Università di Pisa , v. G. Moruzzi 13, I-56124 Pisa, Italy.
Valentina
V
Cantatore
Dipartimento di Chimica e Chimica Industriale, Università di Pisa , v. G. Moruzzi 13, I-56124 Pisa, Italy.
Giovanni
G
Granucci
Magistère 2 de Physique Fondamentale, Université de Paris Sud 11 , Orsay 91400, France.
Guillaume
G
Rousseau
Dipartimento di Chimica e Chimica Industriale, Università di Pisa , v. G. Moruzzi 13, I-56124 Pisa, Italy.
Giancarlo
G
Padula
Dipartimento di Chimica e Chimica Industriale, Università di Pisa , v. G. Moruzzi 13, I-56124 Pisa, Italy.
Maurizio
M
Persico