An Ab Initio Study on the First- and Third-Order Polarizabilities of the Octupolar Heteroaromatic-Substituted Triazines

Abstract

The first- and third-order polarizabilities of a series of octupolar heteroaromatic-substituted triazines have been investigated by using the ab initio coupled perturbed Hartree−Fock (CPHF) method. Effects of donor or acceptor substitution have also been considered. Finally, we have explored the impact of electron correlation on the molecular polarizabilities of these octupolar triazines at the Møller−Plesset second-order perturbation (MP2) theory level. The results show that octupolar triazines containing thiophene derivatives have larger first-order polarizabilities than the corresponding analogues containing furan and pyrrole derivatives, and yet octupolar triazines containing pyrrole derivatives exhibit larger third-order polarizabilities than other ones. Attaching acceptor groups (NO2) to these octupolar molecules results in an increase of the first- and third-order polarizability values of NO2-substituted octupolar molecules in comparison with the corresponding unsubstitution. Similar conclusions hold for the NH2-substituted situation. The effects of acceptor substitution on the first-order polarizabilities exceed these of donor substitution; nevertheless, for the third-order polarizabilities, the situation reverses. These observations are supported by the predictions based on the valence-bond three-charge-transfer model. With the introduction of the electron correlation correction, the first-order polarizabilities do not increase much, whereas the third-order polarizabilities significantly increase.