Electron-​flux infrared response to varying π-​bond topology in charged aromatic monomers

The interaction of delocalized π-​electrons with mol. vibrations is key to charge transport processes in π-​conjugated org. materials based on arom. monomers. Yet the role that specific arom. motifs play on charge transfer is poorly understood. Here we show that the mol. edge topol. in charged catacondensed arom. hydrocarbons influences the Herzberg-​Teller coupling of π-​electrons with mol. vibrations. To this end, we probe the radical cations of picene and pentacene with benchmark armchair- and zigzag-​edges using IR multiple-​photon dissocn. action spectroscopy and interpret the recorded spectra via quantum-​chem. calcns. We demonstrate that IR bands preserve information on the dipolar π-​electron-​flux mode enhancement, which is governed by the dynamical evolution of vibronically mixed and correlated one-​electron configuration states. Our results reveal that in picene a stronger charge π-​flux is generated than in pentacene, which could justify the differences of electronic properties of armchair- vs. zigzag-​type families of technol. relevant org. mols.