Role of charge transfer on the nonlinear optical properties of donor-π-acceptor (D-π-a) conjugated schiffbases with DFT approach

Abstract

D-π-A conjugated systems of two Schiff bases have been investigated using density functional theory method. Experimental observations on charge transfer (CT) using ultraviolet-visible absorption study have been verified by time-dependent density functional theory calculations. The transition corresponding to CT absorption band is found to be HOMO 0 → LUMO 0 . The HOMO-LUMO picture along with the natural bond orbital analysis show the highly delocalized CT interaction in the ring system, and it could be attributed to the large value of first order hyperpolarizability (β) at molecular level. However, owing to the lack of effective CT in the D-π-A system at molecular level, there is no effective second harmonic generation observed at solid state. But in the case of third order nonlinear optical property, the presence of strongest donor in a molecule causes the large value of second order hyperpolarizability (γ).