Time‐Dependent Differential and Integral Quantum Yields for Wavelength‐Dependent [4+4] Photocycloadditions

Abstract

The [4+4] photocycloaddition of anthracene is one of most relevant photoreactions and is widely applied in materials science, as it allows to remote‐control soft matter material properties by irradiation. However, highly energetic UV irradiation is commonly applied, which limits its application. Herein, the wavelength dependence of the photodimerization of anthracene is assessed for the first time, revealing that the reaction is induced just as effectively with mild visible light (410 nm). To fully establish [4+4] cycloadditions within defined chemical environments, a conceptual framework for the solution kinetics of the photo‐dimerization up to long reaction times is established by developing a novel photoreaction rate law that is dependent on individual rate coefficients of the key reaction steps. These coefficients can be determined based on low conversion photochemical experiments. Both differential and integral quantum yields can subsequently be predicted that are strongly time‐dependent, highlighting the need for a detailed reaction pathway analysis. The presented approach simplifies a complex photochemical scenario, making the photochemical anthracene dimerization, or potentially any other photochemical dimerization, amenable to a time‐dependent understanding at the elementary reaction level.

New Phosphine Oxides as High Performance Near- UV Type I Photoinitiators of Radical Polymerization

“…Photopolymerization is an important process of synthesis of polymers as it is mostly a green technology (low energy consumption, no use of solvent, reaction at low temperature). Therefore, it has applications in many industrial fields such as coatings, inks, adhesive optoelectronics, nanotechnologies, and 3D-printing [1][2][3][4][5][6][7][8][9][10]. Another unique property of photopolymerization is its safety, i.e., when the irradiation is turned off, radicals are no longer generated, in contrast to thermal initiators that keep decomposing.…”

Flow Photochemistry for Single‐Chain Polymer Nanoparticle Synthesis

“…Herein, SCNPs are prepared by the photodimerization of pendant anthracene units, [36–41] originally demonstrated by Berda and co‐workers [42] . In batch production, the process was carried out by irradiating a dilute solution of the linear polymer at 0.1 mg mL −1 in a quartz cuvette.…”

“…Numerous photochemical processes have been developed for the preparation of SCNPs such as the photodimerization of styrylpyrene units and radical-mediated thiol-yne coupling. [26,34,35] Herein, SCNPs are prepared by the photodimerization of pendant anthracene units, [36][37][38][39][40][41] originally demonstrated by Berda and co-workers. [42] In batch production, the process was carried out by irradiating a dilute solution of the linear polymer at 0.1 mg mL À1 in a quartz cuvette.…”

Predicting wavelength-dependent photochemical reactivity and selectivity

“…Addressing such challenges requires an in-depth understanding of photokinetic behavior, i.e., the rationalization of how fast lightinduced reactions proceed under defined conditions and their associated dependence on experimental parameters. Attempts to predict photochemical kinetics have been reported, yet the resulting methods have not been widely utilized 15,16 . While there are-occasionally-reports of reaction quantum yields, even with their knowledge, the prediction of photochemical conversion is seldomly performed.…”