Solvent Effects in Molecular Hyperpolarizability Calculations

Molecular geometries, dipole moments, polarizabilities and
first-order hyperpolarizabilities
for five classic donor−aromatic π system−acceptor NLO
chromophores were calculated, using
semiempirical methods (PM3), in both vacuum and solvent environments.
Solvent effects
on the computed molecular geometries were found to be minimal.
Dipole moments calculated
for the molecules in vacuo showed good agreement with experimental data
obtained in
nonpolar solvents, but a substantial solvent dependence was observed
for molecules modeled
in a polar solvent. This dependence was very pronounced in the
calculated first-order
hyperpolarizabilities, β, where an increase of a factor as great as 6
was observed upon
changing from a vacuum to solvent environment.
Hyperpolarizabilities calculated for
molecules in solvent were found to be in better agreement with
experimental EFISH data
than those calculated for molecules in vacuo.