Experimental evidence for the blue-shifted hydrogen-bonded complexes of CHF3 with π-electron donors

Abstract

Blue-shifted hydrogen-bonded complexes of fluoroform (CHF3) with benzene (C6H6) and acetylene (C2H2) have been investigated using matrix isolation infrared spectroscopy and ab initio computations. For CHF3-C6H6 complex, calculations performed at the B3LYP and MP2 levels of theory using 6-311++G (d,p) and aug-cc-pVDZ basis sets discerned two minima corresponding to a 1:1 hydrogen-bonded complex. The global minimum correlated to a structure, where the interaction is between the hydrogen of CHF3 and the π-electrons of C6H6 and a weak local minimum was stabilized through H…F interaction. For the CHF3-C2H2 complex, computation performed at MP2/aug-cc-pVDZ level of theory yielded two minima, corresponding to the cyclic C-H…π complex A (global) and a linear C-H…F (n-σ) complex B (local). Experimentally a blue-shift of 32.3cm−1 and 7.7cm−1 was observed in the ν1 C-H stretching mode of CHF3 sub-molecule in Ar matrix for the 1:1 C-H…π complexes of CHF3 with C6H6 and C2H2 respectively. Natural bond orbital (NBO), Atoms-in-molecule (AIM) and energy decomposition (EDA) analyses were carried out to explain the blue-shifting and the nature of the interaction in these complexes.