Fingerprints of Through-Bond and Through-Space Exciton and Charge Conjugations in Linearly Extended [2,2]Paracyclophanes

Abstract

New stilbenoid and thiophenic compounds terminally functionalized with donor-donor, acceptor-acceptor and donoracceptor moieties and substituting a central [2,2]paracyclophane unit have been prepared and their properties interpreted in terms of through-bond and through space conjugations. A description of the excited state properties based on photophysical data and with focus on the participation of the central [2,2]paracyclophane, or “phane” state, in competition with through-bond conjugation in the arms has been conducted. To this end, one-photon absorption and emission spectroscopy, as a function of temperature, of solvent polarity in solution and of pressure in solid state have been carried out. Furthermore, the analysis of charge delocalization in the face-toface [2,2]paracyclophane part in the neutral state and in the oxidized species (dications and trications) has been assessed allowing to elucidate the vibrational Raman fingerprint of charge delocalization in these systems. Thus, a complementary approach to “intermolecular” excitation and charge delocalization has been presented in [2,2]paracyclophane model systems by means of the pertinent spectroscopic techniques.