Probing Through-Bond and Through-Space Interactions in Singlet Fission-Based Pentacene Dimers

Abstract

Inter-chromophoric interactions such as coulombic coupling and exchange interactions are crucial to the functional properties of numerous π-conjugated systems. Here, we use magnetic circular dichroism (MCD) spectroscopy to investigate inter-chromophoric interactions in singlet fission relevant pentacene dimers. Using a simple analytical model, we outline a general relationship between the geometry of pentacene dimers and their calculated MCD response. We analyse experimental MCD spectra of different covalently bridged pentacene dimers to reveal how the molecular structure of the ‘bridge’ affects the magnitude of through-space coulombic and through-bond exchange interactions in the system. Our results show that through-bond interactions are significant in dimers with conjugated molecules as bridging units and these interactions promote the overall electronic coupling in the system. Our generalized approach paves the way for the application of MCD to investigate inter-chromophoric interactions across a range of π-conjugated systems.