Inter-molecular vibrational frequencies of doubly hydrogen-bonded complexes involving 2-pyridone: Reliability of few selected theoretical level of calculations

The ground state fundamental inter-molecular vibrational frequencies of seven different doubly hydrogen-bonded mixed dimers involving 2-pyridone (2PY) have been predicted by different quantum chemistry calculations. Calculations have been performed by different DFT functionals with several basis sets and by the ab initio MP2/6-31G∗∗ level. The reliability of these calculations to predict the inter-molecular vibrations has been tested by comparing the experimentally measured and theoretically predicted values. Such vibrations have been measured by dispersed fluorescence (DF) spectroscopy. The comparison shows that the B3LYP/6-31+G∗∗, B3LYP/6-311++G∗∗ and MPWB1K/6-31+G∗∗ calculation predicted frequency values are in excellent agreement with the observed values and also to those predicted at MP2/6-31G∗∗ level of calculation.