Supramolecular Assembly and Ab Initio Quantum Chemical Calculations of 2‑Hydroxyethylammonium Salts of <i>para</i>-Substituted Benzoic Acids

Crystal structures of seven salts of 2-hydroxyethylamine with benzoic acid (<b>1</b>) and different substituted benzoic acids, such as <i>p</i>-methylbenzoic acid (<b>2</b>), <i>p</i>-methoxybenzoic acid (<b>3</b>), <i>p</i>-hydroxybenzoic acid (<b>4</b>), <i>p</i>-chlorobenzoic acid (<b>5</b>), <i>p</i>-bromobenzoic (<b>6</b>), and <i>p</i>-iodobenzoic (<b>7</b>) have been studied. The salts units of <b>1</b>–<b>7</b> serve as building blocks (BB) of the supramolecular architecture. In a crystal they are held together <i>via</i> proton-transferred N–H···O and normal O–H···O hydrogen bonds. The substituents on anions influence dipole–dipole interactions between anions and cations in molecular aggregates. As a result, they are organized in building blocks either <i>via</i> one charge-assisted (<b>1</b>, <b>2</b>) hydrogen bond or <i>via</i> two (<b>3</b>–<b>7</b>) hydrogen bonds. The dispersion interaction significantly contributes to intermolecular force fields driving the organization of hydrogen bonds in BB. In all studied compounds, building blocks are consolidated into 2-D layers through the N–H···O and O–H···O hydrogen bonds. For the crystal structures of <b>2</b>–<b>7</b>, with non-centrosymmetric space groups and the BB self-assembled by two hydrogen bonds, the macroscopic polarizations of a unit cell is practically perpendicular to the layers