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.

Solid-State Fluorescence of A Quasi-Isostructural Polymorphic Biphenyl Based Michael Addition Product

Polymorphic materials have gained significant attention owing to their fascinating physicochemical properties. Herein, a biphenyl based Michael addition product (Compound A) with an active methylene group (dimedone) was synthesized. Compound...

Multi-fold Sonogashira coupling: a new and convenient approach to obtain tetraalkynyl anthracenes with tunable photophysical properties

For the first time, a direct single-step one-pot route to access nine new symmetric tetraalkynylated anthracenes via Pd(CH₃CN)₂Cl₂/cataCXium®A catalyzed tetra-fold Sonogashira coupling is reported. Five of these tetraalkynylated anthracenes have been crystallographically characterized, with two of them exhibiting multiple interactions that significantly shorten the inter-planar distances in the solid-state structure. The rich photophysical properties exhibited by these molecules hold immense promise for future applications in sensors and optoelectronic devices. Two of the considered tetraalkynylated anthracenes comprising a D-π-A-π-D motif demonstrate solvatochromism and halochromism, with one of them showing a low bandgap of 1.79 eV. The remaining compounds demonstrate bandgaps in the range of 1.79-2.04 eV.

Design, synthesis, and characterization of pyridine-containing organic crystals with different substitution positions using solvothermal method

Four TB-/PHZ-based crystals were prepared via solvothermal method in one step. The relationship between structures and photophysical properties has been discussed.

Tuning charge-assisted and weak hydrogen bonds in molecular complexes of the proton sponge DMAN by acid co-former substitution

Varying the electronic character of the acid co-former substituent group predictably alters weak and strong intermolecular interactions.

9-Vinylanthracene Based Fluorogens: Synthesis, Structure-Property Relationships and Applications

Fluorescent dyes with aggregation-induced emission (AIE) properties exhibit intensified emission upon aggregation. They are promising candidates to study biomolecules and cellular changes in aqueous environments when aggregation formation occurs. Here, we report a group of 9-position functionalized anthracene derivatives that were conveniently synthesized by the palladium-catalyzed Heck reaction. Using fluorometric analyses, these dyes were confirmed to show AIE behavior upon forming aggregates at high concentrations, in viscous solvents, and when poorly solubilized. Their photophysical properties were then further correlated with their structural features, using density functional theory (DFT) calculation. Finally, we demonstrated their potential applications in monitoring pH changes, quantifying globular proteins, as well as cell imaging with confocal microscopy.

The Strong Light-Emission Materials in the Aggregated State: What Happens from a Single Molecule to the Collective Group

The strong light emission of organic luminogens in the aggregated state is essential to their applications as optoelectronic materials with good performance. In this review, with respect to the aggregation-induced emission and room-temperature phosphorescence luminogens, the important role of molecular packing modes is highlighted. As demonstrated in the selected examples, the molecular packing status in the aggregate state is affected by many factors, including the molecular configurations, the inherent electronic properties, the special functional groups, and so on. With the consideration of all these parameters, the strong fluorescence and phosphorescence in the aggregated state could be achieved in the rationally designed organic luminogens, providing some guidance for the further development.

Hydrogen- and halogen-bond cooperativity in determining the crystal packing of dihalogen charge-transfer adducts: a study case from heterocyclic pentatomic chalcogenone donors

A synergic cooperation between HB and XB interactions determines the supramolecular architectures in dihalogen CT adducts of hydantoin-like chalcogen donors.