Blue-Shifted Hydrogen-Bonded Complexes CF₃H−(HF)₁_≤<i>_n</i>_≤₃

The present work demonstrates the existence of cyclic structures in complexes of the CF3H molecule with hydrogen fluoride clusters, (HF)1≤n≤ 3, due to the formation of two types of hydrogen bonds, C−F···H−F and C−H···F. For the case of n = 3, a significant blue shift of the ν(C−H) stretching vibrational mode of fluoroform of about 60 cm-1 is predicted. This is indeed the largest theoretical estimate of a blue shift in a C−H···X system ever reported in the literature. The present analysis of the geometrical, energetical, and spectroscopic features of the cyclic CF3H−(HF)1≤n≤ 3 structures shows that the C−F···H−F bond is stronger than the C−H···F interaction. Therefore, they may be referred to as blue-shifted rather than blue-shifting complexes.