Theoretical study of the variation of first hyperpolarizability in a number of push-pull benzene,thiophene and trans butadiene molecules

摘要

The static linear (alpha) and quadratic hyperpolarizabilities (beta_(vec)) of a number of push-pull benzene,thiophene and trans 1,3-butadiene molecules have been calculated using the AM1 finite field method. The calculated beta-(vec) has been found to vary linearly with the static first hyperpolarizability (beta_0) obtained using two state model. The calculated first hyperpolarizability (beta_(vec)) shows satisfactory correlations with the ground state BLA parameter (deltar) of conduit,dipole moment,changes of conduil-donor/acceptor bond indices (deltaI_(C-D/A) and the amount of charge ransfer from donor/to acceptor (delta_q ~D_(ct) (deltaq~A_(ct).Among the chosen molecules the msot regular trend of beta can be found with the molecular hardness parameter (eta). It has been observed that push-pull thiophene and trans 1,3-butadiene molecules exhibit rather close similarity with regard to the ground state polarization and the pattern of variation of the first hyperpolarizability with deltar and deltaq~(D/A)_ct.