Studies About the Effect of Halogenated Solvents on the Fluorescence Properties of 9-Aryl-Substituted Isoquinolinium Derivatives - A Case Study

It was demonstrated that 9-aryl-substituted isoquinolinium derivatives have significantly increased fluorescence quantum yields in halogenated solvents, mostly pronounced in chloroalkanes, which appears to be specific for this type of solvents. Further analysis with selected halogenated solvents revealed that the type and number of halogen substituents and the dielectric constant of the solvent have a distinct impact on the emission quantum yield. The solvent effect is explained by a solvation of the charge shift (CS) state by attractive halogen-π interactions (halogen bond), which impedes the torsional relaxation of the excited state.

Effects of Gamma Radiation on Single- and Multicomponent Organic Crystalline Materials

Exploration of highly ionizing radiation damage to organic materials has mainly been limited to polymers and single-component organic crystals due to their use in coatings and scintillation detection. Additional efforts are needed to create new tunable organic systems with stability in highly ionizing radiation to rationally design novel materials with controllable chemical and physical properties. Cocrystals are a promising class of compounds in this area because of the ability to rationally design bonding and molecular interactions that could lead to novel material properties. However, currently it is unclear if cocrystals exposed to radiation will maintain crystallinity, stability, and physical properties. Herein, we report the effects of γ radiation on both single-component- and multicrystalline organic materials. After irradiation with 11 kGy dose both single- (trans-stilbene, trans-1,2-bis(4-pyridyl)ethylene (4,4'-bpe), 1,n-diiodotetrafluorobenzene (1,n-C₆I₂F₄ ), 1,n-dibromotetrafluorobenzene (1,n-C₆Br₂F₄ ), 1,n-dihydroxybenzene (1,n-C₆H₆O₂ ) (where n = 1, 2, or 3)), and multicomponent materials (4,4'-bpe)·(1,n-C₆I₂F₄ ), (4,4'-bpe)·(1,n-C₆Br₂F₄ ), and (4,4'-bpe)·(1,n-C₆H₆O₂ ) were analyzed and compared to their preirradiated forms. Radiation damage was evaluated via single-crystal- and powder-X-ray diffraction, Raman spectroscopy, differential scanning calorimetry, and solid-state fluorimetry. Single-crystal X-ray diffraction analysis indicated minimal changes in the lattice postirradiation, but additional crystallinity changes for bulk materials were observed via powder X-ray diffraction. Overall, cocrystalline forms with 4,4'-bpe were more stable than the related single-component systems and were related to the relative stability of the individual conformers to γ radiation. Fluorescence signals were maintained for trans-stilbene and 4,4'-bpe, but quenching of the signal was observed for the cocrystalline forms to varying degrees. Three of the single components, 1,2-diiodotetrafluorobenzene (1,2-C₆I₂F₄ ), 1,4-diiodotetrafluorobenzene (1,4-C₆I₂F₄ ), and 1,4-dibromotetrafluorobenzene (1,4-C₆Br₂F₄ ), also underwent sublimation within an hour of exposure to air postirradiation. Further analysis using differential scanning calorimetry (DSC) and Raman spectroscopy attributed this phenomenon to removal of impurities adsorbed to the crystal surface during irradiation.

A Theoretical Study of the Halogen Bond between Heteronuclear Halogen and Benzene

Halogen bonds play an important role in many fields, such as biological systems, drug design and crystal engineering. In this work, the structural characteristics of the halogen bond between heteronuclear halogen XD (ClF, BrCl, IBr, ICl, BrF and IF) and benzene were studied using density functional theory. The structures of the complexes between heteronuclear halogen and benzene have Cs symmetry. The interaction energies of the complexes between heteronuclear halogen XD (ClF, BrCl, IBr, ICl, BrF and IF) and benzene range from -27.80 to -37.18 kJ/mol, increasing with the increases in the polarity between the atoms of X and D, and are proportional to the angles of a between the Z axis and the covalent bond of heteronuclear halogen. The electron density (ρ) and corresponding Laplacian (∇²ρ) values indicate that the interaction of the heteronuclear halogen and benzene is a typical long-range weak interaction similar to a hydrogen bond. Independent gradient model analysis suggests that the van der Waals is the main interaction between the complexes of heteronuclear halogen and benzene. Symmetry-adapted perturbation theory analysis suggests that the electrostatic interaction is the dominant part in the complexes of C₆H₆⋯ClF, C₆H₆⋯ICl, C₆H₆⋯BrF and C₆H₆⋯IF, and the dispersion interaction is the main part in the complexes of C₆H₆⋯BrCl, C₆H₆⋯IBr.

Exploring halogen⋯halogen interactions in supramolecular self-assemblies of BODIPY networks

In this study, the efficiency of halogen⋯halogen interactions to control supramolecular assemblies of boron dipyrromethene (BODIPY) (B1–B5) derivatives was explored.