STM Investigation of the Photoisomerization and Photodimerization of Stilbene Derivatives on HOPG Surface

Abstract

The photochemical reactions of stilbene and its derivatives have been extensively investigated in the gas and liquid phases but less on surfaces. In this work, scanning tunneling microscopy (STM) has been employed to investigate the photoisomerization and photodimerization of two stilbene derivatives on HOPG surface. After UV-light irradiation, one stilbene derivative performs photoinduced trans to cis isomerization and a well-ordered Kagoménetwork with two types of cavities forms at the 1-phenyloctane/HOPG interface, which is totally different from the lamella structures (before irradiation). Another stilbene derivative can also perform trans to cis photoreaction and the assembly structures have two conformations. With the increase of the irradiation time, one of the two conformations according to the topochemical postulates can further perform [2 + 2] photodimerization reaction. The difference in alkoxy substitution is reflected in the self-assembled monolayer and consequently also in the photoreactivity.

Photochemical Reactions in Self‐Assembled Organic Monolayers Characterized by using Scanning Tunneling Microscopy

“…Besides, the photopolymerization and photoisomerization reactions that occur, particularly, in supramolecular networks provide us with crucial information that the controlled dimerized or isomerized products should mainly contribute to the restriction of the two‐dimensional nanopores from the molecular template. This reflects the unique template effect on obtaining highly efficient photoinduced chemical reactions of photosensitive molecules . In addition, the template also helps us to observe certain conformational isomers of the illuminated molecules, which is, however, hard to control in solution.…”

“…Stilbene and its derivations, which are structurally similar to azobenene derivatives, have widely been investigated as typical models of photochemical reactions. Liao et al . reported the reaction of stilbene derivatives on HOPG and the results are shown in Figure .…”

Photoresponsive supramolecular self-assemblies at the liquid/solid interface

“…The reorganization induced by an external stimulus can lead to dramatic changes in the adsorbed monolayer. the photodecomposition of diazoanthrone [84] or the photoisomerization of thioindigo [85], anthracene dimer [86], azobenzene [87][88][89][90][91][92][93][94][95], stilbene [94,96], diarylethene [97][98][99][100][101][102][103][104], or terthiophene [105] ( Fig. 4).…”

“…The same behavior is observed for stilbene derivatives. However, stilbene can also undergo a [2+2] photodimerization that leads to the formation of a substituted cyclobutane[96]. The isomerization from the trans to the cis form can be induced by UV light irradiation.…”

The impact of trans/cis photoisomerization on photoinduced electron transport between 4,4′-stilbenedicarboxylic acid and columnar perylenediimide aggregates in water

“…To better understand these results, the following experiments were designed. Firstly, we had a hypothesis that the addition of trans-or cis-SDBA to the aqueous solution of PDI-I may affect the aggregation of PDI due to the strong ionic interactions [41] so that the charge-separated states cannot be stabilized significantly by the charge diffusion along the one-dimensional aggregates of PDI-I [42], which [43,44]. Therefore, the similar fluorescence quenching experiments were carried out in methanol because PDI-I can be dissolved freely in methanol and no aggregates of PDI-I formed in methanol solution ( †Figure S3).…”