Theoretical study of nonlinear optical properties of some azoic dyes

Abstract

In this paper we presented semi-empirical PM3, ab-initio (HF, MP2) and DFT (B3LYP, B3PW91) calculation of the dipole moment, polarizability, and first hyperpolarizability of some azoics dyes derivatives which have electron donor and electron acceptor groups on either sides. The first hyperpolarizability of these molecules was calculated with PM3 method, HF/6-31G**, HF/6-31+G**, HF/6-31++G**, DFT with B3LYP and B3PW91 functional, and MP2/6-31++G** based on finite field approach using GAUSSIAN03 program. The effects of the intramolecular charge transfer (ICT) from the donor to the acceptor groups on the molecular geometry and atomic charge distribution of these NLO chromophores are derived from its HF, MP2 and DFT calculations. The variation of this property has also been correlated to E (HOMO-LUMO) gap and to the nature of the highest occupied molecular orbital HOMO and the lowest unoccupied molecular orbital HOMO. The study reveals that the azoics dyes derivatives have large hyperpolarizability values; hence they may be used in the development of nonlinear optical materials.