2ND-HARMONIC GENERATION FROM NONDIPOLAR NONCENTROSYMMETRIC AROMATIC CHARGE-TRANSFER MOLECULES

Second-harmonic generation from powders of a series of three aromatic intramolecular charge-transfer moieties of D3h symmetry is reported. One compound is shown to be active while its symmetric structure precludes any molecular non-linear contribution of a vectorial nature such as usually prevails in polar paranitroaniline-like systems. Similar non-dipolar non-centrosymmetric molecular moieties could serve as building blocks in new types of optically non-linear materials where the packing is not influenced by dipole-dipole interactions and the statistical occurrence of non-centrosymmetry would consequently increase. © 1990.