Yukiyasu Kashiwagi

Organic molecular crystals exhibit diverse packing motifs and polymorphic forms governed by weak intermolecular interactions. We have previously reported transient intermediates appearing during solvent‐evaporative crystallization by visualizing fluorescence spectral changes. In the present study, we investigate the crystallization process of heterocyclic β‐diketonate–boron difluoride (hetero–BF ₂ ) complexes incorporating thiophene and furan rings by monitoring the evolution of fluorescence during solvent evaporation. Spectral analysis reveals that crystallization proceeds via dense liquid‐like cluster (LLC) intermediates. Unlike phenyl‐substituted BF ₂ complexes that display a transient redshifted fluorescence band, the heteroaromatic derivatives exhibit broadened emission. Structural analysis and DFT calculations indicate that larger dipole moments in the heteroaromatic systems promote competitive formation of H‐ and J‐type aggregation motifs within the LLC states. This competitive formation broadened the emission profile and suppressed the formation of only a redshifted band. These findings demonstrate that heteroaromatic substitution in the present BF ₂ systems reshapes the intermolecular interaction landscape of prenucleation clusters, thereby modulating aggregation pathways and crystallization behavior.

The title compound, hydronium 3,5-dicarboxybenzenesulfonate trihydrate, H ₃ O ⁺ ·C ₈ H ₅ O ₇ S ⁻ ·3H ₂ O, crystallizes in the triclinic space group P \overline 1 with one molecule in the asymmetric unit. The structure is the pseudopolymorph with an additional three water molecules to known hydronium 3,5-dicarboxybenzenesulfonate. The 3,5-dicarboxybenzenesulfonate (SIP ⁻ ) moiety is surrounded by nine molecules, i.e. three SIP ⁻ anions, five water molecules and one oxonium ion. The structure, containing a hydrogen-bonded water cluster with eight molecules, forms an R ₈ ⁶ (16) ring motif through intermolecular hydrogen bonding.

We report a π-extended N-phenylphenothiazine dye bearing thiophene substituents, designed to address the practical compromise between long-wavelength near-infrared (NIR) absorption and the isolability of a stable radical cation state. The target compound was synthesized via Suzuki–Miyaura cross-coupling and exhibited good solubility in common organic solvents. Cyclic voltammetry in dichloromethane showed a reversible one-electron oxidation at E⁰ = 0.19 V vs. Fc/Fc⁺. Chemical oxidation afforded the corresponding radical cation, which showed an intense NIR absorption maximum at 910 nm. DFT calculations support thiophene-induced narrowing of the HOMO–SOMO gap and predict a pronounced bathochromic shift of the main absorption band. The radical cation was isolated as a stable PF₆⁻ salt and readily processed into spin-coated films, which retained strong NIR absorption and remained stable for months under ambient conditions.

Systematic modulation of the volume fractions between the boron dipyrrin (BODIPY) unit and the tethered 3,4,5-tri(alkoxy)phenyl group was explored to establish a rational crystal-engineering strategy toward thin-film J-aggregate formation. We propose that the branched alkyl chains play two distinct roles: (i) inducing steric hindrance that enforces a large offset in the cofacial arrangement of chromophore units and (ii) imparting substantial conformational entropy that increases nucleation probability and relieves packing strain, thus promoting the tessellation of BODIPYs within crystalline thin films. In this proof-of-concept study, 3,4,5-tri(isopentyloxy)phenyl and 3,4,5-tris((S)-dihydrocitronellyloxy)phenyl groups were introduced as the branched alkyl chains to the BODIPY skeleton. The BODIPY core was further fine-tuned by introducing iodine and nitrile substituents. Eventually, the formation of a J-aggregate exhibiting exceptionally sharp absorption and fluorescence bands was achieved in a spin-coated film.

In the title compound tris[4-(3,4-dimethoxythiophen-2-yl)phenyl]amine (DMOT-TPA), C ₃₆ H ₃₃ NO ₆ S ₃ , the central nitrogen atom shows no pyramidalization, with the three para -phenylene rings arranged in a propeller-like geometry. Each thiophene ring is twisted by about 25–29° relative to the adjacent phenylene ring, giving a distorted π-conjugated framework. In the crystal, molecules are linked through multiple C—H...π interactions into two-dimensional sheets, which extend into a three-dimensional network. A Cambridge Structural Database survey revealed no prior examples of triphenylamines bearing 3,4-dimethoxythiophen units at the para positions. This unique structure provides new insights into the design of redox-active organic materials.

The title compound, [Zn ₂ (C ₂₂ H ₁₈ ClN ₄ O) ₂ ](ClO ₄ ) ₂ ·CH ₃ CN, consists of one centrosymmetric cationic dinuclear zinc(II) complex with two pentadentate ligands containing quinolin-8-olato and bis(pyridin-2-ylmethyl)amine groups, two perchlorate counter-ions and one acetonitrile solvate molecule. The Zn ^II atom adopts a distorted octahedral geometry and coordinates the O atom and the N atom of the quinolin-8-olato group and three N atoms of the bis(pyridin-2-ylmethyl)amine group in a ligand, and the O atom in an adjacent ligand generated by an inversion operation. The phenolato oxygen atoms in the two ligands of the cationic dinuclear complex are bridging coordinated with the two Zn ^II atoms. In the crystal, the cationic dinuclear complex molecules and perchlorate ions are linked by C—H...Cl and C—H...O hydrogen bonds, forming a three-dimensional network.

The binary composites of liquid (1_Liq) and crystalline (1_Cry) difluoroboron β-diketonate (BF₂dbk) complexes exhibited a metastable nature arising from the intricate interplay between their liquid and crystalline components in bulk. Differential scanning calorimetry (DSC) measurements indicate nearly complete miscibility of 1_Cry and 1_Liq when the fractional volume of 1_Liq occupied a substantial portion, corresponding to below 47 mol % of the 1_Cry content. In contrast, polarized optical microscopic (POM) observations unveiled that the 1_Cry/1_Liq composites between two glass slides crystallized regardless of the 1_Cry content. This discrepancy indicated the occurrence of heterogeneous nucleation in the vicinity of the glass surface, highlighting the metastable nature of supercooled liquid and/or glassy phases of the 1_Cry/1_Liq composites. Moreover, the 1_Cry/1_Liq composites exhibited thermal hysteresis in the photophysical properties through thermally assisted excimer formation, which was observed on a scale distinct from DSC and POM observations.

The binary composites of liquid (1Liq) and crystalline (1Cry) boron β-diketonate complexes exhibited a metastable nature arising from intricate interplay between their liquid and crystalline components in bulk. Differential scanning calorimetry (DSC) measurements indicate nearly complete miscibility of 1Cry and 1Liq when the fractional volume of 1Liq occupied a substantial portion, corresponding to below 47 mol% of the 1Cry content. By contrast, polarized optical microscopic (POM) observations unveiled that the 1Cry/1Liq composites between two glass slides crystallized regardless the 1Cry content. This discrepancy indicated the occurrence of heterogeneous nucleation in the vicinity of glass surface, highlighting the metastable nature of supercooled liquid and/or glassy phases of the 1Cry/1Liq composites. Moreover, the 1Cry/1Liq composites exhibited thermal hysteresis in the photophysical properties through thermally assisted excimer formation, which was observed in a distinct scale from DSC and POM observations.

The asymmetric unit of the title compound is composed of one host molecule, anti-4-(1⁹ H,5⁹ H-3-aza-1,5(3,9)-dicarbazolacyclooctaphane-3-yl)benzonitrile and one dichloromethane solvate molecule, C₃₆H₂₈N₄·CH₂Cl₂. The host molecule possesses a planar chirality but crystallizes as a racemate in the space group P2₁/c. It adopts an anti-configuration, in which two carbazole rings are partially overlapped with a parallel orientation. The two carbazole ring systems are slightly bent, and the C atoms at the 3- and 1-positions show the largest deviations from the mean planes. The dihedral angle between two carbazole rings is 9.42 (3)°, forming an intramolecular parallel π–π interaction [Cg...Cg = 3.2755 (9) Å]. In the crystal, the molecules are linked via host–host and host–guest C—H...π interactions, forming chain structures along the a-axis direction. The molecules are linked into a ribbon structure along the c-axis direction by further C—H...π interactions. As a result, The molecules are cross-linked by C—H...π interactions into a three-dimensional network.