Blue-shifting hydrogen bonds and secondary interactions in the C 3H6⋯HCF3, C2H 4O⋯HCF3 AND C2H4S⋯ HCF3 cyclic complexes

Abstract

In this article, a theoretical study of molecular properties of small cyclic systems is presented. Through the calculations performed at the B3LYP/6-311++G(d,p) level of theory, the optimized geometries of the C 3H6⋯HCF3, C2H 4O⋯HCF3 and C2H4S⋯ HCF3 hydrogen-bonded complexes were determined. By analyzing the structural parameters, it was observed a contraction of the C-H bond length of the fluoroform (HCF3). As such, the examination of the harmonic infrared spectrum accused the existence of a blue-shift effect in this bond, once its stretch frequency is displaced to upward values accompanied by a significant diminishing on the absorption intensity. In the purpose to comprehend this vibrational phenomenon, topological parameters computed at the light of the Quantum Theory of Atoms in Molecules (QTAIM) were also used. An interesting aspect is the non-linearity deviation on the hydrogen bonds (O⋯H) and (S⋯H) due to the formation of a secondary interaction (H a⋯Fφ) between the fluoride (Ff) of fluoroform and the axial hydrogen atoms (Ha) of the heterocyclic structures.