Interactions of Hydroquinone Molecules in Crystal Structures: A Combined Cambridge Structural Database and DFT Study

Abstract

The geometries for all hydroquinone–hydroquinone interactions in crystal structures from the Cambridge Structural Database (CSD) were analyzed, and interaction energies of all hydroquinone–hydroquinone contacts were calculated at the B2PLYP-D3BJ/def2-TZVP level of theory. Four types of attractive hydroquinone–hydroquinone interactions were found in the CSD: classical hydrogen bonds, CH–O interactions, parallel displaced (stacking) interactions, and CH–π interactions. The analysis of all crystal structures in the CSD shows a large number of hydroquinone–hydroquinone contacts, 380 contacts in 148 crystal structures. The hydrogen bonds occur in 70 structures (101 contacts), CH–O interactions in 51 structures (69 contacts), and stacking interactions in 126 structures (178 contacts), while CH–π interactions occur in 59 structures (83 contacts). A detailed inspection revealed that some hydroquinone–hydroquinone contacts can have more than one interaction simultaneously. The calculated interaction energies show that the hydrogen bonds are the strongest interactions between two hydroquinone molecules. Most of the hydrogen bond contacts have interaction energies in the range of −6.7 kcal/mol to −7.3 kcal/mol. Most of the CH–O contacts have interaction energies in the range of −1.9 kcal/mol to −3.4 kcal/mol. Most of the CH–π contacts have interaction energies between −3.0 kcal/mol and −3.5 kcal/mol. Most of the interaction energies for stacking contacts are between −0.8 kcal/mol and −1.5 kcal/mol. The presence of two –OH groups for hydrogen bonding and the ability to form CH–O and CH–π interactions as well as stacking interactions and formation at small and large horizontal displacements make hydroquinone a promising agent for cocrystallization.