NH···S and SH···N intramolecular hydrogen bond in β‐thioaminoacrolein: A quantum chemical study

Abstract

ABSTRACT:The conformational study of b-thioaminoacrolein was performed at various theoretical levels, HF, B3LYP, and MP2 with 6-311þþG(d,p) basis set, and the equilibrium conformations were determined. To have more reliable energies, the total energies of all conformers were recomputed at high-level ab initio methods, G2MP2, G3, and CBS-QB3. According to these calculations, the intramolecular hydrogen bond is accepted as the origin of conformational preference in thialamine (TAA) and thiolimine groups. The hydrogen bond strength in various resonance-assisted hydrogen bond systems was evaluated by HB energy, geometrical parameters, topological parameters, and charge transfers corresponding to orbital interactions. Furthermore, our results reveal that the TAA tautomer has extra stability with respect to the other tautomers. The population analyses of the possible conformations by NBO predict that the origin of this preference is mainly due to the p-electron delocalization in framework of TAA forms, especially usual p C¼ ¼C ! p* C¼ ¼S and Lp (N) ! p* C¼ ¼C charge transfers.

Quantitative decomposition of resonance‐assisted hydrogen bond energy in β‐diketones into resonance and hydrogen bonding (π‐ and σ‐) components using molecular tailoring and function‐based approaches

“…[47,48] It is noteworthy that the estimation of the О─НÁ Á ÁО═С IMHB energy in the malonaldehyde 1b by the MTA method matches quantitatively with the energy difference between its open and closed rotamers (see Scheme 1). [20,[49][50][51] The reason for this coincidence is that both the σand π-components of the RAHB interaction appear only in the closed form of malonaldehyde 1b. [18] Therefore, the Following finding suggests that the π-component changes due to strengthening the RAHB interaction.…”

Can halogen bond energy be reliably estimated from electron density properties at bond critical point? The case of the (A)nZ—Y•••X−(X, Y = F, Cl, Br) interactions

“…Such situations include, for example, intramolecular hydrogen bonds (or other noncovalent interactions) and systems of two molecules which are bonded by two or more intermolecular noncovalent interactions (for instance, Watson‐Crick base pairs). There are several procedures which allow the bond energy estimates in these special cases, among them the group of methods based on the comparison of energies of rotamers with and without the hydrogen bond (“closed” and “open” rotamers, respectively) including the related rotamers method, the isodesmic reactions method, and the molecular tailoring approach . However, all these methods are not universal, and their application strongly depends on the type of the structure under investigation.…”

A comparative study of two-ring resonance-assisted hydrogen bond systems

“…According to the previous studies, some of the topological parameters of HB critical point and ring critical point, especially electron charge density, are well correlated with IMHB energy [34,35]. Hence, we first considered the charge density for the evaluation of the IMHB strength in all of the title compounds.…”