Competition between X···H···Y Intramolecular Hydrogen Bonds and X····Y (X = O, S, and Y = Se, Te) Chalcogen−Chalcogen Interactions

Abstract

High-level G2(MP2) ab initio and B3LYP/6-311+G(3df,2p) density functional calculations have been carried out for a series of β-chalcogenovinylaldehydes, HC(X)−CHCH−CYH (X = O, S; Y = Se, Te). Our results indicate that for X = O, S and Y = Se, the O−H···Se and the S−H···Se intramolecular hydrogen bonds compete in strength with the O···Se and the S···Se interaction, while the opposite is found for the corresponding tellurium-containing analogues. The different strength of O−H···Se and O···H−Se intramolecular hydrogen bonds explains why the chelated enolic and keto forms of selenovinylaldehyde are very close in energy, although enol-tautomers are estimated to be about 10 kcal mol-1 more stable than keto-tautomers. The situation is qualitatively similar for selenothiovinylaldehyde, although the S−H···Se and S···H−Se intramolecular hydrogen bonds (IHBs) are weaker and much closer in strength, and the energy gap between enethiol- and thione-tautomers also smaller. The relative strengths of the X−H···Te and X···H−Te (X = O, S) IHBs, are very similar to those of the corresponding selenium analogues. However, there are dramatic differences as far as the X···Y (X = O, S; Y = Se, Te) interactions are concerned, which for Se-derivatives are rather small, while for Te-compounds are very strong. An analysis of these chalcogen-chalcogen interactions indicates that both, the electrostatic and the dative contributions are smaller for Se- than for Te-derivatives. In the latter, the electrostatic component clearly dominates when X = O, while the opposite is found for sulfur-containing derivatives. We have also shown that these two components are entangled in some manner, in the sense that strong electrostatic interactions favor the nO−σ*YH (or nS−σ*YH) dative interaction. The proton-transfer processes in species with IHBs were also investigated.

Reaction of an ammonium eneselenolate derived from a selenothioacetic acid S‐ester with electron‐deficient alkenes and alkynes

“…Although a few ␤-oxo selenocarbonyl compounds have been isolated as stable compounds [13], their tautomerization has not been reported. On the other hand, theoretical studies on ␤-oxo selenoaldehydes have suggested that their enol forms and eneselenol forms are energetically close [14].…”

The Dominant Role of Chalcogen Bonding in the Crystal Packing of 2D/3D Aromatics

“…[1][2][3][4] It belongs to the family of s-hole bonding, where the halogen bond (X-bond) is by far the most known. Since chalcogen atoms are electronegative elements, they are usually negatively charged in organic compounds.…”

Acidity Trends in α,β‐Unsaturated Sulfur, Selenium, and Tellurium Derivatives: Comparison with C‐, Si‐, Ge‐, Sn‐, N‐, P‐, As‐, and Sb‐Containing Analogues

“…For Te-containing compounds, we used the SKBJ relativistic potential of Stevens et al, [42] which accounts for the most important relativistic effects in conjunction with the basis set proposed by Sanz et al [43] For geometry optimizations and harmonic frequency calculations the aforementioned effective core potential was used together with the [4,1] + d basis for Te, [43] whereas for the first-, second-, and third-row atoms, a 6-31G(d) basis set was adopted. Hereafter, for the sake of simplicity we will refer to this basis set as 6-31G(d).…”

“…Hereafter, for the sake of simplicity we will refer to this basis set as 6-31G(d). The corresponding final energies were evaluated by using the (6 s,6p,3d,1f) G2-type basis set [43] for Te and a 6-311 + G(3df,2p) basis set expansion for the remaining atoms of the system. Again for the sake of simplicity the (6 s,6p,3d,1f) basis for Te will be named hereafter as a 6-311 + G(3df,2p) basis.…”