Unraveling the Mechanisms of On-Surface Photoinduced Reaction with Polarized Light Excitations

Abstract

On-surface reaction has been shown as a powerful strategy to achieve atomically precise nanostructures. Numerous reactions have been realized on surfaces with thermal annealing as the primary excitation. In contrast, far fewer reactions have been triggered by light on surfaces despite its advantages due to the nonthermal process. This is possibly ascribed to our limited understanding on the excitation mechanisms of on-surface photoinduced reactions. In this work, we have studied the photoinduced debrominated coupling by using a linearly polarized light. We successfully achieved the reaction with no annealing process and obtained oligomers as the primary reaction products, which is in contrast with the formation of polymers with traditional thermal treatments. By exploring the dependence of reaction yield on the angle of incidence, we demonstrate an experimental method that can provide fundamental insights. The comparison with the theoretical approximation suggests indirect hot carrier excitation as the leading excitation mechanism. Our results not only provide fundamental insight into the surface photochemical reactions but also set the basis for harnessing light to construct unconventional nanomaterials.

Light-Induced Increase of the Local Molecular Coverage on a Surface

“…Light-induced bond dissociation 30 − 32 and formation 33 , 34 have already been reported. The combined use of light and temperature was used to promote the growth of long poly p -phenylene polymers by mild heating.…”

Kinetics of On-Surface Dechlorinated Aryl–Aryl Coupling

“…In this context, on-surface Ullmann-type or dehalogenative C–C coupling stands as the predominant type of reaction in on-surface synthesis due to its high effectiveness, reliability, and controllability, making it a fundamental approach for predictable and precise on-surface construction of carbon nanostructures. − Additional design can be made through the choice of different halogen atoms (I, Br, Cl), allowing for a wide window of excitation conditions. From the relatively weak C–I bond over the moderate C–Br bond to the more rigid C–Cl bond, the required heating condition on Au(111) ranges from below room temperature to 573 K. , Functionalization of molecular backbones with two distinct types of halogens has effectively realized the intended hierarchical steps at different activation temperatures …”