We introduce a quantum mechanics/molecular mechanics
semiclassical
method for studying the solvation process of molecules in water at
the nuclear quantum mechanical level with atomistic detail. We employ
it in vibrational spectroscopy calculations because this is a tool
that is very sensitive to the molecular environment. Specifically,
we look at the vibrational spectroscopy of thymidine in liquid water.
We find that the CO frequency red shift and the CC
frequency blue shift, experienced by thymidyne upon solvation, are
mainly due to reciprocal polarization effects, that the molecule and
the water solvent exert on each other, and nuclear zero-point energy
effects. In general, this work provides an accurate and practical
tool to study quantum vibrational spectroscopy in solution and condensed
phase, incorporating high-level and computationally affordable descriptions
of both electronic and nuclear problems.