Density Functional Theory Study on Subtriazaporphyrin Derivatives: Dipolar/Octupolar Contribution to the Second-Order Nonlinear Optical Activity

Density functional theory calculations have been carried out on the subtriazaporphyrin skeletons, an excellent prototype for investigating the dipolar/octupolar contribution to the second-order nonlinear optical (second-order NLO) activity, revealing the size effect and clarifying the nature of the limit when expanding the conjugated system is employed to improve the hyper-Rayleigh scattering response coefficient (β(HRS)). The octupolar and dipolar contributions are theoretically separated, rendering it possible to control the dipolar/octupolar second-order NLO contribution ratio by changing the number and orientation of the peripheral fused benzene moieties. In addition, both the dispersion and solvent effect were also revealed to lead to the enhancement of β(HRS).