A quantum chemical study of the hydrogen bonding in the CO₂⋯HF and N₂O⋯HF complexes

Summary

Quantum chemical ab initio calculations have been performed for the complex CO₂⋯HF and N₂O⋯HF. The interaction energies were computed through fourth order MBPT and were corrected for basis set superposition errors. Extended polarized basis sets were used which are constructed to give accurate values for electric moments and polarizabilities. The complex NNO⋯HF was found to be bent, while OCO⋯HF is linear, in agreement with experiment. The MBPT calculations give evidence for a second linear isomeric structure FH⋯NNO, a possibility which has also been suggested by recent experimental data. The computed binding energies are: 2.5 kcal/mol for OCO⋯HF, 2.4 kcal/mol for NNO⋯HF, and 3.0 kcal/mol for FH⋯NNO. At the SCF level, the FH⋯NNO complex is less stable than NNO⋯HF, but correlation has a large effect on the geometry and energetics of the latter complex. The NNO⋯HF complex seems to be a system where the positive intramolecular correlation correction prevails over the negative intermolecular component.