Theoretical study of the nonlinear polarizabilities in H<SUB>2</SUB>N and NO<SUB>2</SUB> substituted chromophores containing two hetero aromatic rings

The static first- and second-hyperpolarizabilities of a number of amino- and nitro-substituted chromophores containing two hetero aromatic rings have been calculated by ab initio time dependent Hartree-Fock (TDHF) method. The computed nonlinear polarizabilities correlate well with frontier orbital energies and hardness parameter (η). Furan and thiophene rings at the donor site and the thiazole and pyridine at the acceptor site are predicted to enhance the first hyperpolarizability (β) - but not γ values. The nature of the dependence of β and γ on the twist angle between the bridging rings have been explored