Comparison of ab initio HF/6-31G^**, HF/6-31 + + G^** and MP2/6-31G^** calculated infrared spectra of 4(3H)-pyrimidinone and 4-hydroxypyrimidine with matrix isolation spectra

The results of ab initio calculations of infrared (IR) spectra of 4-hydroxypyrimidine and 4(3H)-pyrimidinone are reported. The vibrational spectra computed at the HF/6-31G^**, HF/6-31 + + G^** and MP2/6-31G^** levels of theory were found to reproduce well the experimental IR spectra of the Ar matrix isolated species. However, neither the enlargement of the basis set, with respect to the 6-31G^** set, nor partial account for the electronic correlation effects at the MP2 level were found to provide any considerable improvement of the predictions of the IR spectra.