Insights into Host–Guest Binding in Hydroquinone Clathrates: Single-Crystal X-ray and Neutron Diffraction, and Complementary Computational Studies on the Hydroquinone-CO₂ Clathrate

Abstract

High-resolution 100 K X-ray and neutron single-crystal diffraction data of the non-stoichiometric hydroquinone-CO2 (HQ-CO2) clathrate are combined, with the aim of providing further insight into host–guest binding in hydroquinone clathrates, measuring the electrostatic nature of the cavity formed by the HQ host and, for the first time, estimating the quadrupole moment of the CO2 guest molecule via diffraction techniques. The experimental electron density reveals the cavity in the β-HQ structure to be moderately electronegative and largely featureless, but this does not mean that guest molecules are merely trapped. Calculated binding energies for a series of HQ clathrates reveal strong interactions with the host system and, in the case of CO2, a thermodynamic stability comparable to, or exceeding, that of many molecular cocrystals. The remarkable flexibility of the β-HQ host structure is explored through an analysis of its available clathrate structures at 100 K as well as calculated elastic tensors for crystals of β-HQ and the HQ-CO2 clathrate. Establishing the CO2 quadrupole moment from this analysis of the experimental diffraction data proves challenging, but the sign and estimated range of its magnitude are in agreement with spectroscopic measurements in the gas phase.

Current developments and trends in quantum crystallography

“…9) (Turner et al, 2015); (iv) the computation of quite accurate lattice energies for molecular crystals . The techniques currently available in CE have already found many applications in many hot topics of solid-state chemistry and physics: (supra)molecular recognition (Shi, Sobolev et al, 2015;Shi, Thomas et al, 2015;Dey, Bhandary et al, 2016;Shi et al, 2016Shi et al, , 2017Shi et al, , 2019Grosjean et al, 2021), polymorphism Thomas, Grosjean et al, 2019), effects of temperature and pressure on crystal structures (Eikeland, Thomsen et al, 2016, 2017Sussardi et al, 2023), and structure-property relationships (Thomas, Shi et al, 2017;Karothu et al, 2022).…”

Crystal Engineering of Hydrogen Bonding for Direct Air Capture of CO2: A Quantum Crystallography Perspective

“…Due to the weak scattering power of hydrogen atoms in XRD experiments, their positions are typically inferred closer to their parent atoms, resulting in shorter X-H distances than those obtained from neutron experiments. Fortunately, this discrepancy can be corrected using QC, and computational modeling, to gain a comprehensive understanding of the structures and functionalities of materials for carbon capture, including those explored for DAC applications [23,[25][26][27][28].…”

Influence of Lennard–Jones Parameters in the Temperature Dependence of Real Gases Diffusion through Nanochannels

“…Among the most common uses are the capture of pollutants, and storage of substances of interest such as fuels, flammable fluids or reagents, that require safe transport [16][17][18]22,23], or absorption of greenhouse gases and solid-liquid separation processes, commonly known as "selective clathration". The latter is based on the preference of a host structure for a certain substance present in a liquid sample, which is then confined in the solid phase as guest particles [10,18,21,[24][25][26][27].…”