and
and
Received: November 12, 1996
A new series of nonlinear optical molecules are described where
the ground state polarization is
predominantly zwitterionic when the molecules are dissolved in
solution. The molecules, which are derived in
general from facile reactions between tertiary amines and
tetracyano-p-quinodimethane (TCNQ), are of a type
where
the stabilization of the charge-separated ground state is favored by an
increase in aromaticity over the neutral, quinoidal
forms of the molecules. The measured second-order optical
nonlinearity of one in the series has been measured by
hyper-Rayleigh scattering and a figure of merit value, *
Authors to whom correspondence should be addressed.
(0),
being the product of the dipole moment and static first
hyperpolarizability, is found to be 9500 ×
10-48 esu. This value, which is higher
than most other reported values,
is taken from studies in chlorinated solvents of relatively low
polarity, but the discussion emphasizes the evolution
of (0) with solvent polarity, showing that even higher
values could be expected with only modest increases in the
polarity of the surrounding medium. The analysis of experimental
data taken during dipole moment studies is
thoroughly examined, and it is concluded that full account must be
taken of the molecular shape to correlate the
results with theoretical calculations. An ellipsoidal reaction
field model is preferred for these highly one-dimensional
molecules having strongly anisotropic polarizabilities.
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Department of Physics, University of
Durham.
Department of Chemistry, University of
Durham.
Université de Mons Hainaut.
University of Antwerp-UIA.
California Institute of Technology.
Abstract published in Advance ACS
Abstracts, March 1, 1997.