The infrared (IR) spectra of pyridine molecule and three different pyridine-gold complexes (Py-Au 18 -S, Py-Au 18 -V, Py-Au 32 ) computed by QM and QM/DIM methods are displayed in Fig. . The top row shows the IR spectra of the gas-phase pyridine minimum-energy structure, while the other three rows show the spectra calculated using the optimized configurations (with the distances restrained at 3, 4, and 5Å). In these three rows, the green curves correspond to the spectra of the pyridine molecule at the geometry extracted from each of these complexes. Overall, the QM/DIM method (blue curves) reproduces similar trends in the harmonic frequency shifts and comparable IR intensities relative to the full QM profiles (red curves) for the tested systems.