NONLINEAR-OPTICAL PROPERTIES OF NITRO-ANILINE AND METHYL-ANILINE COMPOUNDS - AN EXACT CORRECTION VECTOR INDO-SDCI STUDY

We have applied the correction vector (CV) method coupled with the int ermediate neglect of differential overlap-single and double configurat ion interaction semiempirical approach to calculate the nonlinear opti cal coefficients of donor-acceptor conjugated compounds consisting in ortho-, meta-, and para-substituted benzene derivatives as well as the corresponding octupolar molecules. The CV method has been shown to be both exact and computationally effective. We find that for weak donor s such as a methyl group, the NLO response efficiency orders as: octu > para > meta > ortho; however, if the donor becomes stronger and cons ists in an amino group, then: para > ortho > meta > octu. The results are in agreement with experimental findings and can be rationalized in terms of a competition between the effects related to structural reso nance and charge separation length.