Ab initio study of the hydrogen bonding between pyrrole and hydrogen fluoride: A comparison of NH center dot center dot center dot F and FH center dot center dot center dot pi interactions

The structures, vibrational frequencies, and association energies of the NH ... F and FH ...pi hydrogen-bonding complexes between pyrrole and hydrogen fluoride have been examined using the Hartree-Fock, Moller-Plesset (second order), and density functional theory. Full geometry optimization and energetics of these complexes are calculated using the 6-31G*, 6-31G**, 6-31+G*, 6-31+G**, 6-311G*, and 6-311++G** basis sets. The DFT calculations are carried out using the BLYP and B3LYP nonlocal exchange-correlation functionals. After BSSE (basis set superposition error) by the counterpoise (CP) method and ZPVE corrections, the association energies of the pi-type and NH ... F hydrogen-bonding complexes are calculated to be about 3.054 and 1.518 kcal/mol, respectively, at the MP4(SDTQ)/6-311++G**//MP2/6-31+G* level. The intermolecular interaction potential of the ct-type hydrogen-bonding complex is also discussed.