Record-high thermal stability achieved in a novel single-component all-organic ferroelectric crystal exhibiting polymorphism

Keto-enol tautomerism of β-diketo molecules in the presence of graphitic materials through π-π stacking

The pseudo aromatic structures of the enol forms of β-diketo molecules are stabilized on the surface of graphitic materials through π-π interaction. This phenomenon has been studied through a relative binding energy calculation using density functional theory. The intermolecular interaction as well as the relative stability of the keto or enol tautomer is also influenced by the functional groups attached to the graphitic materials. The theoretical results are supported by spectroscopic evidence. Our study with three different graphitic materials, with a comparable extent of π-electrons and acid functionalities, reveals that π-π interaction is the main governing factor for the stability of the enol forms. Then comes the role of intermolecular H-bonding between the adsorbate and adsorbent. This can stabilize both the keto and enol tautomers, according to the arrangements of the functional groups and the geometry of the β-diketo molecules. Acid groups on the adsorbent can enhance enolization through H-bonding, but an excess of functional groups may decrease the possibility of π-π interaction by disrupting the π-clouds of the graphitic surface and pushing the adsorbate and adsorbent away from each other beyond a π-π stacking distance. In that situation, H-bonding becomes crucial for determining the relative stability. Our results indicate that graphitic materials with acid functionalities across their edges, and ample π-cloud, are the most suitable catalysts for enolization.

Polymorphs with Remarkably Distinct Physical and/or Chemical Properties

Polymorphism in crystals is known since 1822 and the credit goes to Mitscherlich who realized the existence of different crystal structures of the same compound while working with some arsenate and phosphate salts. Later on, this phenomenon was observed also in organic crystals. With the advent of different technologies, especially the easy availability of single crystal XRD instruments, polymorphism in crystals has become a common phenomenon. Almost 37 % of compounds (single component) are polymorphic to date. As the energies of the different polymorphic forms are very close to each other, small changes in crystallization conditions might lead to different polymorphic structures. As a result, sometimes it is difficult to control polymorphism. For this reason, it is considered to be a nuisance to crystal engineering. It has been realized that the property of a material depends not only on the molecular structure but also on its crystal structure. Therefore, it is not only of interest to academia but also has widespread applications in the materials science as well as pharmaceutical industries. In this review, we have discussed polymorphism which causes significant changes in materials properties in different fields of solid-state science, such as electrical, magnetic, SHG, thermal expansion, mechanical, luminescence, color, and pharmaceutical. Therefore, this review will interest researchers from supramolecular chemistry, materials science as well as medicinal chemistry.

Soft Ferroelectrics Enabling High-Performance Intelligent Photo Electronics

Soft ferroelectrics based on organic and organic-inorganic hybrid materials have gained much interest among researchers owing to their electrically programmable and remnant polarization. This allows for the development of numerous flexible, foldable, and stretchable nonvolatile memories, when combined with various crystal engineering approaches to optimize their performance. Soft ferroelectrics have been recently considered to have an important role in the emerging human-connected electronics that involve diverse photoelectronic elements, particularly those requiring precise programmable electric fields, such as tactile sensors, synaptic devices, displays, photodetectors, and solar cells for facile human-machine interaction, human safety, and sustainability. This paper provides a comprehensive review of the recent developments in soft ferroelectric materials with an emphasis on their ferroelectric switching principles and their potential application in human-connected intelligent electronics. Based on the origins of ferroelectric atomic and/or molecular switching, the soft ferroelectrics are categorized into seven subgroups. In this review, the efficiency of soft ferroelectrics with their distinct ferroelectric characteristics utilized in various human-connected electronic devices with programmable electric field is demonstrated. This review inspires further research to utilize the remarkable functionality of soft electronics.

Homochiral anionic modification toward the chemical design of organic enantiomeric ferroelectrics

The well-developed design strategy of molecular modification for assembling molecular ferroelectrics mainly focuses on the cations. Herein, by homochiral anionic modification of the non-ferroelectric (quinuclidinium)(HSO₄), we designed high-temperature multiaxial organic enantiomeric ferroelectrics, (quinuclidinium)(l- and d-camphorsulfonate). This work paves a new road for precisely constructing excellent molecular ferroelectrics.

Crystal structures and the ferroelectric properties of homochiral metal-organic frameworks constructed from a single chiral ligand

MOFs have proven to be promising candidates for designing ferroelectric materials. Herein, two new homochiral MOFs, Co-MOF-1 and Co-MOF-2, have been synthesized using the chiral ligand, HL (HL = phenyl-((pyridin-4-ylmethyl)-amino)-acetic acid), and Co(NO₃)₂·6H₂O. Co-MOF-1 was obtained via a two-step synthetic route involving a hydrogel to Zn-MOF conversion and a dissolution-recrystallization process. Co-MOF-2 was directly synthesized by a coordination reaction between chiral ligand, HL, and Co(NO₃)₂·6H₂O under hydrothermal conditions. We investigate the correlation between the ferroelectric properties of the samples and their crystal structures. The ferroelectric properties of Co-MOF-1 and Co-MOF-2 are drastically different. Indeed, Co-MOF-2 shows an obvious hysteretic behavior, while a clear electric hysteresis loop was not observed for Co-MOF-1. These significant disparities may be attributed to the different molecular dipole moments in Co-MOF-1 and Co-MOF-2. The different octahedral coordination units in the molecular structures of the Co-MOFs may alter the dipole moments of the molecules, resulting in the absence of a hysteresis loop for Co-MOF-1.