Quantum chemical design for enhanced second-order NLO response of terpyridine-substituted hexamolybdates

摘要

A dramatic increase in the second-order nonlinear optical (NLO) response of terpyridine-substituted hexamolybdates has been observed from 886.55× 10 ~(-30) esu (system 1) to 4622.92× 10 ~(-30) esu (system 7). The dipole polarizabilities and second-order nonlinear optical (NLO) properties of terpyridine derivatives of hexamolybdates have been investigated by using time-dependent density functional theory (TDDFT). The quantum mechanical design suggests that [Mo _6O _(18)(N _4C _(25)H _(14)(CF _3) _2 (CN) _2)] ~(2-) (system 7) is the best choice among all studied systems to improve nonlinearity. The electron-withdrawing ability of electron-acceptor groups (F, Cl, Br, I, CF _3, and CN) at the end of the terpyridine ligand directs the charge transfer (CT) from the POM cluster to the terpyridine segment along the z axis, which leads to an efficient second-order NLO molecular design. These small changes in molecular composition by substitution may have disproportionately huge effects on the NLO properties, which can be attributed to the so-called "butterfly effect".