Geometric isotope effect of deuteration in a hydrogen-bonded host–guest crystal

Abstract

Deuteration of a hydrogen bond by replacing protium (H) with deuterium (D) can cause geometric changes in the hydrogen bond, known as the geometric H/D isotope effect (GIE). Understanding the GIEs on global structures and bulk properties is of great importance to study structure–property relationships of hydrogen-bonded systems. Here, we report a hydrogen-bonded host–guest crystal, imidazolium hydrogen terephthalate, that exemplifies striking GIEs on its hydrogen bonds, phases, and bulk dielectric transition property. Upon deuteration, the donor–acceptor distance in the O–H···O hydrogen bonds in the host structure is found to increase, which results in a change in the global hydrogen-bonded supramolecular structure and the emergence of a new phase (i.e., isotopic polymorphism). Consequently, the dynamics of the confined guest, which depend on the internal pressure exerted by the host framework, are substantially altered, showing a downward shift of the dielectric switching temperature.

Relevance of Hydrogen Bonds for the Histamine H2 Receptor-Ligand Interactions: A Lesson from Deuteration

“…To evaluate the effects linked with the isotopic substitution, we considered the work by Bordalo and co-workers [41], who used a very precise neutron diffraction analysis on alanine zwitterion to show that deuteration reduces the electrostatic attraction in the acidic N-D bonds by 2.3% relative to the matching N-H bonds. This results in the shortening of the N-D distances, as already noticed in various papers [42][43][44][45][46]. Considering both of these aspects, we imposed the empirical quantization in the following way.…”

“…These were both modeled with the implicit CPCM solvation associated with the corresponding dielectric constants of ε = 4.0 for the receptor environment, and ε = 78.4 for the aqueous solution. The effect of the isotope substitution was introduced through an implicit quantization, by 2.3% shortening of all acidic N-H and O-H bonds [41][42][43][44][45][46].…”

Polarizability and isotope effects on dispersion interactions in water

“…Isotope effect on dispersion interaction. Although a lot of efforts have been made [39][40][41][42][43][44][45][46][47][48][49][50][51][52] , the H/D isotope effect on intermolecular interactions is still in debate. Under Born-Oppenheimer approximation, the potential energy surfaces of complexes with different isotope(s) are the same, so the difference in the thermodynamic stability between the two isotopomers arises from the vibrational frequency of C-H and C-D bonds.…”

Coexistence of normal and inverse deuterium isotope effects in a phase-transition sequence of organic ferroelectrics

“…3,4 Other intriguing issues pertaining to hydrogen-bonded compounds are related to the replacement of hydrogen by deuterium, because the distinct quantum-mechanical properties of deuterium oen change the potential-energy curves of hydrogen bonds and alter proton dynamics sufficiently to have marked effects on the relative stability of phases and on electric, elastic, and optical properties, as well as on hydrogen-bond geometries. [5][6][7][8][9][10][11] These effects have been observed in many inorganic and organic compounds, including the KH 2 PO 4 (KDP) family, squaric acid, and 9-hydroxyphenalen-1-one, in which proton dynamics play crucial roles in polarization-and phaseswitching, as evidenced by the huge isotope effects observed upon deuteration of the hydrogen bonds. [12][13][14][15][16][17] Over the last decade, similar microscopic principles have been increasingly applied in the design of high-performance ferroelectric organic solids for use in environmentally benign electronic devices.…”