Interaction of CHX₃(X = F, Cl, Br) with HNO induces remarkable blue shifts of both C–H and N–H bonds

Abstract

The hydrogen-bonded complexes formed from interaction of trihalomethanes CHX(3) (X = F, Cl, Br) with nitrosyl hydride HNO were studied using ab initio MO calculations at the second-order perturbation theory (MP2/6-311++G(d,p)). Each interaction contains at least five separate equilibrium structures. Calculated binding energies range from 4 to 8 kJ mol(-1) with both ZPE and BSSE corrections. While CHBr(3) leads to the most stable complexes with HNO, CHF(3) forms the least stable counterparts. The strength of complexes thus tends to increase from F to Cl to Br, which is consistent with a decrease of deprotonation enthalpy of the corresponding C-H bonds. It is remarkable that all the C-H and N-H bonds are shortened upon complexation, giving rise to an increase of their stretching frequencies. A blue shift is thus observed for the N-H bonds of the type N-HX (X = F, Cl, Br); such a contraction of the covalent N-H bond is extremely rare.

Existence of both blue-shifting hydrogen bond and Lewis acid–base interaction in the complexes of carbonyls and thiocarbonyls with carbon dioxide

“…The results point out that the C1-H2 bond contraction and its stretching frequency increase in all complexes considered here have a smaller magnitude as compared to those between XCHZ (with Z = O, S; X = CH 3 , H, F, Cl, Br) and HNO at the same MP2/aug-cc-pVTZ level. 50 Indeed, the C1-H2 bond lengths are shortened by 0.0004-0.0018 A ˚and the C1-H2 stretching frequencies are shifted to blue by 11-27 cm À1 (Table 3), whereas the C1-H2 bond length contractions amount to 0.0003-0.0040 A ˚and its corresponding stretching frequencies are shifted by 10-53 cm À1 for XCHZÁ Á ÁHNO. Following complexation, the largest increase of C1-H2 stretching frequency is found in CH 3 CHOÁ Á ÁCO 2 with a value of 27 cm À1 , as compared to that in all remaining XCHOÁ Á ÁCO 2 complexes.…”

“…Both trends discussed above are in line with that of the C-H bond polarization in the XCHO and XCHS isolated monomers, respectively. 49,50 Therefore, we would suggest that the bond contraction and the frequency blue shift of a C-H bond involved in hydrogen bond complexation are mainly determined by its polarization. In particular, the weaker the polarization of a C-H bond acting as proton donor is, the stronger its distance contraction and frequency blue shift as a result of complexation are, and vice versa.…”

“…45 While the characteristics of the conventional hydrogen bond are well understood, the origin of the blue-shifting hydrogen bond remains a matter of debate. [46][47][48][49][50] Several hypotheses and models have in fact been proposed to explain the differences between the blue shift and red shift of the stretching frequency of an A-H bond upon complexation. [46][47][48]51,52 However, no general explanation has been formulated on the origin of all H-bonded complexes that possess the blue-shifting phenomenon.…”

Remarkable shifts of Csp2‐H and O‐H stretching frequencies and stability of complexes of formic acid with formaldehydes and thioformaldehydes

“…We have pursued another approach to study the origin of the BSHB and, thereby, a classification of hydrogen bonds, which is rather based on inherent properties of isolated monomers. Implementing this approach, the stability and origin of hydrogen bond involving C‐H covalent bond have been explored . Our theoretical results obtained for the hydrogen‐bonded systems containing C‐H···O/N suggested that the origin of a BSHB in a A‐H···B complex can be probed on the basis of the deprotonation enthalpy (DPE) of the A‐H bond in the isolated proton donor and the proton affinity (PA) of the B atom in the isolated proton acceptor .…”

Effect of substituents on complex stability and characteristics of Csp2‐H∙∙∙O/S and O/S‐H∙∙∙S/Se hydrogen bonds in the systems of monosubstituted selenoformaldehyde with H2O and H2S

“…[6,9] A creative approach proposes that stability and the origin of blue-shifting H-bond can be explained on the basis of inherent characteristic of the A-H proton donor and the B proton acceptor. [10][11][12] This approach has expanded many studies on looking for the characteristics of both conventional and novel H-bonds. The A and B elements are extended more in the periodic table.…”