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2024 | Book

Design of Crystal Structures Using Hydrogen Bonds on Molecular-Layered Cocrystals and Proton–Electron Mixed Conductor

Author: Masaki Donoshita

Publisher: Springer Nature Singapore

Book Series : Springer Theses

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About this book

This thesis addresses the design of crystal structures using hydrogen bonds. In particular, it focuses on the design of functionalities and the control over the packing of molecular assemblies, based on molecular designs.
Firstly, the synthesis and evaluation of a proton–electron mixed conducting charge transfer salt is reported. Focusing on the difference in the strength of hydrogen bonds and weaker intermolecular interactions, a system was rationally designed and constructed where electron-conducting molecular wires were encapsulated within a proton-conducting matrix. Next, the investigation of structural phase transitions in a cocrystal consisting of hydrogen-bonded two-dimensional molecular assemblies is reported. Drastic rearrangements of hydrogen-bonded molecular assemblies in the cocrystal led to single-crystal-to-single-crystal phase transitions, resulting in anisotropic changes in the crystal shape. Furthermore, chemical modification of a component molecule in the cocrystal is reported. The modification afforded control over the stacking patterns of the two-dimensional molecular assemblies, i.e., sheets, and the mechanism was discussed considering the intersheet intermolecular interactions and molecular motion.
It is suggested that hydrogen bonds are beneficial to construct molecular assemblies in molecular crystals because of their strength and well-defined directionality, and the consideration of coexisting weaker intermolecular interactions can lead to the design of whole crystal structures and, hence, functionalities. This thesis benefits students and researchers working on solid-state chemistry by presenting various methods for characterizing and evaluating the properties of molecular solids.

Table of Contents

Frontmatter
Chapter 1. General Introduction
Abstract
Molecular packing in crystal structures can significantly influence the physical and chemical properties of molecular materials. Hydrogen bonds are promising intermolecular interactions that control molecular packings owing to their sufficient strength and directionality. This thesis addresses the rational design of functionalities and higher-order control of molecular packing, with a focus on intermolecular hydrogen bonds.
Masaki Donoshita
Chapter 2. Rational Construction of Molecular Electron-Conducting Nanowires Encapsulated in Proton-Conducting Matrix in a Charge-Transfer Salt
Abstract
Insulated molecular wires have gained significant attention owing to their potential contribution to the fields of nanoelectronics and low-dimensional chemistry/physics. This study demonstrates, for the first time, the rational construction of molecular electron-conducting wires encapsulated in a proton-conducting matrix via the use of a molecular charge-transfer salt, which may pave the way for iono-electronics. As expected from the molecular structure of the newly designed complex anion (a propeller-shaped structure with hydrogen-bonding sites at four edges), a three-dimensional hydrogen-bonded framework was constructed within the crystal, which contained one-dimensional arrays of the electron donor, tetrathiafulvalene (TTF). Single-crystal crystallographic and spectroscopic studies clarified that non-stoichiometric deprotonation of anions and partial oxidation of TTF molecules occurred, whereas the anion was electronically inert. The moderate conductivities of electrons and protons were confirmed by DC- and AC-conductivity measurements. In addition, electronic isolation of the TTF wires was confirmed using magnetic susceptibility data.
Masaki Donoshita
Chapter 3. Drastic Rearrangement of Self-Assembled Hydrogen-Bonded Tapes in a Molecular Crystal
Abstract
For the first time, a two-step single-crystal-to-single-crystal (SCSC) transformation at varying temperatures is reported for a 2:1 hydrogen-bonded (H-bonded) crystal of 2-pyrrolidone (Py) and chloranilic acid (CA). Crystallographic studies revealed that sheets composed of H-bonded tapes exhibited a drastic translation of approximately 7 Å in the first SCSC transition, which was triggered by the freezing of the out-of-plane thermal motion of Py. The second SCSC transition was primarily caused by competing intersheet interactions between CA···CA and Py···Py, which resulted in a sheet translation of approximately 2 Å. Anisotropic and collective translations, which were accompanied by morphological changes in the crystal, were attributed to the selective and directional characteristics of H-bonds.
Masaki Donoshita
Chapter 4. Various Stacking Patterns of Two-Dimensional Molecular Assemblies in Hydrogen-Bonded Cocrystals: Insight into Competitive Intermolecular Interactions and Control of Stacking Patterns
Abstract
Control over stacking patterns in two-dimensional (2D) molecular assemblies is demonstrated by chemical modification. A target system is a hydrogen-bonded cocrystal (2:1) composed of 2-pyrrolidone (Py) and chloranilic acid (CA) (PyCA). X-ray crystallography revealed that weak intersheet interactions result in a variety of metastable overlapping patterns comprising 2D assemblies, mainly formed via hydrogen bonds, allowing reversible and irreversible structural phase transitions. Cocrystals of Py and anilic acids bearing different halogens were prepared, in which the 2D assemblies, isostructural to those observed in PyCA, exhibited various overlapping patterns. The order of stability for each overlapping pattern estimated using calculations of the intermolecular interactions did not completely coincide with those indicated by our experimental results. This can be explained by considering the entropic effect, that is, the molecular motion of Py, as detected using nuclear quadrupole resonance spectroscopy.
Masaki Donoshita
Chapter 5. General Conclusion
Abstract
The findings reported and described in each chapter are summarized in this chapter.
Masaki Donoshita
Backmatter
Metadata
Title
Design of Crystal Structures Using Hydrogen Bonds on Molecular-Layered Cocrystals and Proton–Electron Mixed Conductor
Author
Masaki Donoshita
Copyright Year
2024
Publisher
Springer Nature Singapore
Electronic ISBN
978-981-9970-62-9
Print ISBN
978-981-9970-61-2
DOI
https://doi.org/10.1007/978-981-99-7062-9

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