Journal of the American Chemical Society, Vol.139, No.8, 3095-3105, 2017
Fingerprints of Through -Bond and Through -Space Exciton and Charge pi -Electron Delocalization in Linearly Extended [2.2]Paracyclophanes
New stilbenoid and thiophenic compounds terminally functionalized with donor donor, acceptor acceptor, or donor acceptor moieties and possessing a central [2.2]paracyclophane unit have been prepared, and their properties interpreted in terms of through-bond and through space pi-electron delocalization (i.e., pi-conjugations). Based on photophysical data, their excited-state properties have been described with a focus on the participation of the central [2.2]paracyclophane in competition with through-bond conjugation in the side arms. To this end, two-photon and one-photonabsorption and emission spectroscopy, as a function of temperature, solvent polarity, and pressure in the solid state have been recorded. Furthermore, charge delocalization through the [2.2]paracyclophane in the neutral state and in the oxidized species (radical cations, dications and radical trications) has been investigated, allowing the elucidation of the vibrational Raman fingerprint of through-space charge delocalization. Thus, a complementary approach to both "intermolecular'' excitation and charge delocalizations in [2.2]paracyclophane molecules is shown which can serve as models of charge and exciton migration in organic semiconductors.