Journal of the American Chemical Society, Vol.119, No.28, 6575-6582, 1997
Large Molecular Hyperpolarizabilities - Quantitative-Analysis of Aromaticity and Auxiliary Donor-Acceptor Effects
The linear and nonlinear optical properties of donor-acceptor ct-electron chromophores having conjugated bridges varying in aromaticity and electron excessivity are investigated using the INDO/1 semiempirical Hamiltonian. NLO response properties of such chromophores are more sensitive to the electron excessivity of the bridges than to bridge aromaticity. Electron-excessive/deficient heterocyclic bridges have lesser/greater tendency to deplete the electron density from the donor/acceptor groups and thus increase their donor/acceptor ability. Thus, electron-excessive heterocyclic bridges act as auxiliary donors while electron-deficient heterocyclic bridges act as auxiliary acceptors, significantly enhancing NLO response. Interposing charged five-membered auxiliary donor and acceptor fragments between strong donor or acceptor groups results in large computed second-order NLO response.
Keywords:NONLINEAR-OPTICAL-PROPERTIES;BOND-LENGTH ALTERNATION;PUSH-PULL POLYENES;CONJUGATED MOLECULES;ORGANIC-MOLECULES;SEMIEMPIRICAL METHODS;STILBENE DERIVATIVES;SUBSTITUTED POLYENES;POLARIZABILITIES;SYSTEMS