This
study investigates the interactions of both purine (adenine
and guanine) and pyrimidine (cytosine, thymine, and uracil) nucleobases
with a pair of silver atoms (Ag
2
). Full geometry optimizations
were performed on several structures of each nucleobase/Ag
2
complex and the corresponding isolated monomers using the M06-2X
density functional with a correlation consistent triple-ζ basis
set augmented with diffuse functions on all atoms and a relativistic
pseudopotential on Ag (aug-cc-pVTZ for H, C, N, and O and aug-cc-pVTZ-PP
for Ag; denoted aVTZ). Harmonic vibrational frequency computations
indicate that each optimized structure corresponds to a minimum on
the M06-2X/aVTZ potential energy surface. Relative electronic energies
for interactions between Ag
2
and each nucleobase were compared
to elucidate energetic differences between isomers. Further analysis
of the changes in vibrational frequencies, infrared intensities, and
Raman scattering activities reveals how different Ag
2
binding
sites might be differentiated spectroscopically. These results provide
molecular-level insight into the interactions between nucleobases
and silver, which may lead to better understanding and interpretation
of surface-enhanced Raman spectroscopy experiments on nucleobases
and related systems.