Assessing One- and Two-Photon Optical Properties of Boron Containing Arenes

Linear and nonlinear optical properties of a series of bis( E -dimesitylborylethenyl)-substituted arenes have been modeled by high-level computational protocols. The former compounds show a remarkable interest as infrared two-photon absorbers and hence may be used in the field of optical active and smart materials or for energy storage purposes. Excited state topologies, absorption and emission spectra, excited state metrics, natural transition orbitals and two-photon absorption cross-section of a series of chromophores have been computed by means of density functional theory (DFT) and time-dependent DFT (TD-DFT). An extended benchmark test on the performance of different functionals had been performed. Dynamic and vibronic effects on absorption and emission spectra have been taken into account by sampling the conformational space by means of Wigner distribution and the former have been evidenced as rather important in order to recover absorption maxima and spectral band shape. Important infrared two photon absorption cross sections involving transitions to the second excited state have been observed. In particular, thiophene bridges have been evidenced as the most beneficial to increase TPA efficiency leading to cross-section exceeding 1000 GM.