This review is concerned with three types of physical phenomena which
are affected by the environment of the species under study. They are t
he vibrational spectrum, nonlinear optical properties, and nuclear mag
netic shielding of the molecule (or atom) of interest. The two types o
f environment discussed are liquid solvents and zeolite cages. The emp
hasis is on the theoretical-calculational aspects but experimental stu
dies will also be referred to wherever appropriate. The primary object
ive is to bring under one wing these different phenomena and environme
nts. To give two examples: the methods used to evaluate the vibrationa
l spectrum of a molecule trapped in a zeolite cage should bear some re
lation to the chemical shift of an atom trapped in the zeolite; the ef
fects of a solvent on a species' nonlinear optical properties (e.g. se
cond harmonic generation) should be understandable in the same way as
the effects on the species' vibrational spectrum and magnetic shieldin
g constants. Both perturbation-theoretic and ab initio variational met
hods are employed in describing what has been accomplished and a gener
al, but brief, discussion of how electric fields behave in solutions i
s given. Most of the calculations reviewed are far from the accuracy o
f their gas phase counterparts and it is realized that, in the subject
of this article, many questions remain unanswered and that there is o
ften little consensus about the best approach to take for the problem
at hand. A bringing-together of the topics reviewed may shed some ligh
t. The references selected are not exhaustive but it is hoped that the
y are sufficient to illuminate the author's primary goal.