Dipole Moment Additivity in Pseudodimeric Head-to-Tail Nonlinear Optical Chromophores: Dielectric and Solid State Characterization.

A phenyl and an azobenzenyl chromophore incorporating amino donors and cyanovinyl and nitro acceptors, with principal molecular moments held at 110C angles by propenoylpiperzine linkages, were synthesized. A model compound was prepared and analyzed by X-ray crystallography, revealing the extended conformation and sterochemistry of the linkage. The measured dipole moments of the two donor- acceptor compounds, when compared to appropriate monomeric reference compounds, reflect the vector additivity predicted from the crystal structure, and indicate enhanced electric field orientability of the dimers in solution compared to the monomers. Thus, extended oligomers such as those reported here may be useful in the preparation of highly oriented dye- polymer films for electro-optic applications by electric field poling.