Exploring the twisted molecular configurations for tuning their optical and nonlinear optical response properties: A quantum chemical approach

Unlike the previous several investigations on planar donor-pi-acceptor chromophores, the present investigation highlights the importance of twisted molecular configurations to effectively tune the optical and nonlinear optical (NLO) response properties. A variety of substitutions are made to design several twisted molecular compounds (1-7). These compounds are designed using pyrenyl and naphthalimide moieties, which are twisted with each other in their molecular configurations. The calculated versus experimental highest intensity absorption energy peaks (3.482 V. 3.444 eV) and experimental ionization potentials (6.07 V. 5.93 eV) of parent compound 1 reproduced reasonably well at M06/6-311G** methodology. The twisted chromophores show significantly larger amplitudes of third-order NLO polarizabilities (), which are found to be as large as 778.31 x 10(-36) esu for compound 7 at the M06/6-311G** methodology. The amplitudes were also compared with planar donor-pi-acceptor prototype para-nitroaniline (p-NA) molecule to provide the semi-quantitative assessment. For instance, the amplitudes of all compounds are about similar to 7-similar to 39 times bigger from the amplitude of p-NA at the same computational level. The origin of larger amplitudes has been traced though three-level model using the TD-DFT results. The larger oscillator strengths, lower transitions energies and larger change between the electronic dipole moment between the ground and the excited states. We believe the present study will not only put these compounds under the spotlight of material science but also provide structure-property relationships in designed compounds. (c) 2020 Elsevier Inc. All rights reserved.

Automated summary

Unlike previous investigations on planar donor-pi-acceptor chromophores, this study highlights the importance of twisted molecular configurations in tuning optical and nonlinear optical response properties. Twisted molecular compounds designed in this study exhibit significantly larger amplitudes of third-order NLO polarizabilities compared to planar compounds, showcasing higher absorption energy peaks and larger nonlinearity.