THE EFFECT OF VARYING GROUND-STATE AROMATICITY ON THE 1ST MOLECULAR ELECTRONIC HYPERPOLARIZABILITES OF ORGANIC DONOR-ACCEPTOR MOLECULES

A series of compounds of the form 4-dimethylaminophenyl-polyene-acceptor, where the polyene ranges from nothing to all-trans-1,3,5-hexatriene and the acceptor is 2-nitrovinyl, formyl, or 2,2-dicyanovinyl has been prepared and their beta values measured by solution electric-field-induced second-harmonic generation; these molecules, which lose only one aromatic resonance upon charge-transfer excitation, show enhanced beta compared to bi-aromatic molecules with the same substitution and total conjugation length, such as 4-dimethylamino-4'-nitrostilbene (DANS), a well-known benchmark for high beta organic molecules.