Photophysical properties of functionalized terphenyls and implications to photoredox catalysis

Developing efficient organic photoredox catalysts is essential for advancing sustainable CO 2 conversion technologies. This paper investigates the photophysical properties of oligo- p -phenylenes (OPP- n ), with a focus on p -terphenyl (OPP-3), and its functionalized derivatives to identify structural features that may enhance their photocatalytic potential. We examine how symmetric and asymmetric terminal substitutions affect excitation energies, oscillator strengths, exciton characteristics, and fluorescence. Our results show that push–pull derivatives have significantly lower excitation energies and larger oscillator strengths, promoting efficient radical anion generation. These derivatives also exhibit longer fluorescence lifetimes, which may improve the probability of productive interactions with sacrificial electron donors. Exciton analysis reveals that asymmetric substitutions introduce charge-transfer character, whereas higher oligomers maintain tightly bound excitons with limited delocalization. Overall, functionalized OPP- n chromophores, especially push–pull derivatives of OPP-3, demonstrate favorable optical and excitonic properties for photoredox catalysis, making them promising candidates for CO 2 reduction and hydrogen evolution applications.