Characterization of non-covalent contacts in mono- and di-halo substituted acetaldehydes: probing the substitution effects of electron donating and withdrawing groups

In the current work, a systematic evaluation of the different types of non-covalent interactions (NCIs) in acetaldehyde dimers, including dimers of mono-halo (XCH2CHO)(2), di-halo (X2CHCHO)(2) and tri-halo substituted (X3CCHO)(2) acetaldehydes via the associated stabilization energy of these dimers has been performed. Furthermore, a topological analysis of the electron density based on the quantum theory of atoms in molecules (QTAIM) and non-covalent interaction reduced density gradient (NCI-RDG) isosurfaces has also been performed to evaluate the nature of these NCIs. The geometrical and electronic characteristics have been evaluated via the presence of different electron-donating groups (EDGs) and electron-withdrawing groups (EWGs) or substituents in dimers of these molecules, namely, XCH(Y)CHO and X2C(Y)CHO (wherein X = -F, -Cl, and -Br and Y = -SO3H, -CN, -NO2, -NH2, -CH3, -OCH3, and -SMe3). The C-HMIDLINE HORIZONTAL ELLIPSISO, C-HMIDLINE HORIZONTAL ELLIPSISX, XMIDLINE HORIZONTAL ELLIPSISX, XMIDLINE HORIZONTAL ELLIPSISO and CMIDLINE HORIZONTAL ELLIPSISO tetrel bonded contacts have been recognized to play an important role in the stabilization of the formed dimers. This study also establishes the fact that the overall stability of the dimeric assemblies is governed by the contributions from the mutual and complex interplay of a variety of interactions in the investigated dimers. Hence considerations based on strong H-bond donor-acceptor characteristics hold relevance for simple systems only, but slight alteration in the electronic environment can affect the overall stabilization energies of the system being investigated and the nature of the interactions that contribute towards the same.

Automated summary

In this study, a comprehensive evaluation of different types of non-covalent interactions (NCIs) in acetaldehyde dimers was conducted through the associated stabilization energy. The nature of these NCIs was further analyzed using the quantum theory of atoms in molecules (QTAIM) and non-covalent interaction reduced density gradient (NCI-RDG) isosurfaces. The presence of electron-donating and electron-withdrawing groups in the dimers was considered, and specific tetrel bonded contacts were identified as important for stabilization. It was found that the overall stability of the dimeric assemblies is influenced by a variety of interactions, and a slight change in the electronic environment can affect the stabilization energies and the nature of the contributing interactions.