Experimental demonstration of the relationship between the second- and third-order polarizabilities of conjugated donor-acceptor molecules
The dependence of the second- and third-order polarizabilities ((beta) and (gamma) ) on ground-state polarization was measured for a series of donor-acceptor polyenes using electric field induced second harmonic generation and third harmonic generation, respectively. The changes in ground-state polarization, associated with the donor/acceptor strength or solvent polarity, were probed by x-ray crystallography, 1H-NMR, electronic absorption, and Raman spectroscopies. The observed behavior of (beta) and (gamma) as a function of ground- state polarization agrees well with theoretical predictions. In particular, positive and negative peaks, as well as sign changes, were observed for both (beta) and (gamma) . The dependences for (beta) and (gamma) are consistent with a derivative relationship between them. In addition, the third-order polarizability of a series of molecules possessing zero bond length alternation was found to be negative, in agreement with predictions based on the relationship between the polarizabilities and ground-state geometry.
© 1994 Society of Photo-Optical Instrumentation Engineers (SPIE). The research described in this paper was performed in part by the Jet Propulsion Laboratory (JPL), California Institute of Technology, as part of its Center for Space Microelectronics Technology and was supported by the Advanced Research Projects Agency (administered by the Air Force Office of Scientific Research (AFOSR)) and the Ballistic Missiles Defense Initiative Organization, Innovative Science and Technology Office, through a contract with the National Aeronautics and Space Administration (NASA). We thank the AFOSR for support through grant # F49620-92-J-0177 and AASERT for support through grant # F49620-92-J-0278. Support at the Beckman Institute from the National Science Foundation (grant # CHE-9106689) and the North Atlantic Treaty Organization is gratefully acknowledged. G. B. thanks the National Research Council and NASA for a Resident Research Associateship at JPL. CBG thanks the JPL dfrector's office for a postdoctoral fellowship. The authors would like to thank Professor Jean-Luc Brédas, Dr. Brian M. Pierce and Fabienne Meyers for helpful discussions and Howard D. Jones for expert technical assistance.
Published - 153_1.pdf