Preparation, Structure, and Redox Behavior of Bis(diarylmethylene)dihydrothiophene and Its π‑Extended Analogues

The preparation, X-ray structure, and optoelectronic properties of bis­(diarylmethylene)­dihydrothiophene <b>1</b> and its π-extended analogues <b>2</b> are described. The development of a simple, short-step synthetic route allowed us to prepare derivatives with different aryl units. X-ray crystallographic analysis of <b>1b</b> and <b>2b</b> revealed their quinoidal structures, which exhibit strong electronic absorption in the visible region. Cyclic voltammetry measurements revealed their strong electron-donating properties. <b>1b</b> showed two-step electrochromic behavior between the corresponding radical cation and dication

Preparation, Structure, and Redox Behavior of Bis(diarylmethylene)dihydrothiophene and Its π‑Extended Analogues

The preparation, X-ray structure, and optoelectronic properties of bis­(diarylmethylene)­dihydrothiophene <b>1</b> and its π-extended analogues <b>2</b> are described. The development of a simple, short-step synthetic route allowed us to prepare derivatives with different aryl units. X-ray crystallographic analysis of <b>1b</b> and <b>2b</b> revealed their quinoidal structures, which exhibit strong electronic absorption in the visible region. Cyclic voltammetry measurements revealed their strong electron-donating properties. <b>1b</b> showed two-step electrochromic behavior between the corresponding radical cation and dication

Thermosalient Effect of 5‑Fluorobenzoyl-4-(4-methoxyphenyl)ethynyl-1-methylimidazole without Phase Transition

5‑Fluorobenzoyl-4-(4-methoxyphenyl)ethynyl-1-methylimidazole 1 exhibited a thermosalient effect without phase transition. The crystal of 1 was jumped by heating to about 80 °C using a hot plate. No phase transition peak was observed at this temperature range according to DSC measurement, unlike renowned thermosalient crystals. Variable-temperature X-ray crystal structure analyses revealed that anisotropical cell constant expansion resulting from the torsion angle change between the imidazole group and carbonyl moiety induced unit cell constant expansion and the thermosalient effect

Thermosalient Effect of 5‑Fluorobenzoyl-4-(4-methoxyphenyl)ethynyl-1-methylimidazole without Phase Transition

5‑Fluorobenzoyl-4-(4-methoxyphenyl)ethynyl-1-methylimidazole 1 exhibited a thermosalient effect without phase transition. The crystal of 1 was jumped by heating to about 80 °C using a hot plate. No phase transition peak was observed at this temperature range according to DSC measurement, unlike renowned thermosalient crystals. Variable-temperature X-ray crystal structure analyses revealed that anisotropical cell constant expansion resulting from the torsion angle change between the imidazole group and carbonyl moiety induced unit cell constant expansion and the thermosalient effect

Protonic Conductivity and Hydrogen Bonds in (Haloanilinium)(H₂PO₄) Crystals

Brønsted acid–base reactions between phosphoric acid (H₃PO₄) and haloanilines in alcohols formed 1:1 proton-transferred ionic salts of (X-anilinium⁺)­(H₂PO₄^–) and 2:1 ones of (X-anilinium⁺)₂(HPO₄^2–) (X = F, Cl, Br, and I at o, m, and p positions of anilinium). Only the former 1:1 single crystals showed proton conductivity under the N₂ condition, and the latter 2:1 crystals became protonic insulators. In crystals, diverse hydrogen-bonding structures from 1D to 2D networks were achieved by modification of the molecular structure of X-anilinium cations. The protonic conductivity was associated with the connectivity of H₂PO₄^– anions in the hydrogen-bonding networks. The hydrogen-bonding ladder chains in (<i>o</i>-cloroanilinim)­(H₂PO₄^–) and (<i>o</i>-bromoanilinim)­(H₂PO₄^–) resulted in the highest protonic conductivity of ∼10^–3 S cm^–1. The protonic conductivity of the ladder-chain (H₂PO₄^–) arrangements was higher than that of 2D sheets. The motional freedom of protons was analyzed by difference Fourier analysis of the single-crystal X-ray structure. The 2D layer, including (H₂PO₄^–)₂ dimers and (H₂PO₄^–)₄ tetramers, showed relatively low protonic conductivity, and the activation energy for proton conductivity was lowered by increasing the hydrogen-bonding connectivity and uniformity between H₂PO₄^– anions

Narrow-Band Green-Emitting Phosphor Ba₂LiSi₇AlN₁₂:Eu²⁺ with High Thermal Stability Discovered by a Single Particle Diagnosis Approach

The narrow-band green-emitting phosphor Ba₂LiSi₇AlN₁₂:Eu²⁺ was discovered by analyzing a single particle in a powder mixture, which we call the single particle diagnosis approach. Single crystal X-ray diffraction analysis of the particle revealed that Ba₂LiSi₇AlN₁₂:Eu²⁺ crystallizes in the <i>Pnnm</i> space group (No. 58) with <i>a</i> = 14.0941 Å, <i>b</i> = 4.8924 Å, <i>c</i> = 8.0645 Å, and <i>Z</i> = 2. The crystal structure is composed of a corner-sharing (Si,Al)­N₄ corrugated layer and edge-sharing (Si,Al)­N₄ and LiN₄ tetrahedra. Ba­(Eu) occupies the one-dimensional channel in a zigzag manner. The luminescence properties were also measured using a single crystalline particle. Ba₂LiSi₇AlN₁₂:Eu²⁺ shows a green luminescence peak at approximately 515 nm with a narrow full-width at half-maximum of 61 nm. It shows high quantum efficiency of 79% with 405 nm excitation and a small decrease of luminescence intensity even at 300 °C

Discovery of New Nitridosilicate Phosphors for Solid State Lighting by the Single-Particle-Diagnosis Approach

Discovery of novel luminescent materials is of fundamental importance in the advancement of solid state lighting and flat panel display technologies. In this work, we report a single-particle-diagnosis method for the discovery of new phosphors by just characterizing a luminescent crystalline particle as small as 10 μm in diameter. We explored single-particle fluorescence imaging and spectroscopy techniques to evaluate the photoluminescence of a phosphor particle distinguished from a complex powder mixture and applied a high-resolution single-crystal X-ray diffractometer to determine its crystal structure. The approach enabled us to discover two new phosphors in the Ba₃N₂–Si₃N₄–AlN ternary system: Ba₅Si₁₁Al₇N₂₅:Eu²⁺ and BaSi₄Al₃N₉:Eu²⁺. Ba₅Si₁₁Al₇N₂₅:Eu²⁺ crystallizes in the space group of <i>Pnnm</i> (no. 58) with <i>a</i> = 9.5923(2), <i>b</i> = 21.3991(5), <i>c</i> = 5.8889 (2) Å and <i>Z</i> = 2, while BaSi₄Al₃N₉:Eu²⁺ in the space group of <i>P</i>21/<i>C</i> (no.14) with <i>a</i> = 5.8465(4), <i>b</i> = 26.7255(18), <i>c</i> = 5.8386(4) Å, β = 118.897° and <i>Z</i> = 4. The single-particle photoluminescence of Ba₅Si₁₁Al₇N₂₅:Eu²⁺ shows yellow emission (λ_em = 568 nm, fwhm = 98 nm) and a quantum efficiency of 36% under the 405 nm excitation. BaSi₄Al₃N₉:Eu²⁺ shows blue emission (λ_em = 500 nm, fwhm = 67 nm) upon the 365 nm excitation

Collective In-Plane Molecular Rotator Based on Dibromoiodomesitylene π‑Stacks

Interest in artificial solid-state molecular rotator systems is growing as they enable systems to be designed for achieving specific physical functions. The phase transition behavior of four halomesitylene crystals indicated dynamic in-plane molecular rotator characteristics in dibromoiodomesitylene, tribromomesitylene, and dibromomesitylene crystals. Such molecular rotation in diiodomesitylene crystals was suppressed by effective I···I intermolecular interactions. The in-plane molecular rotation accompanied by a change in dipole moment resulted in dielectric phase transitions in polar dibromoiodomesitylene and dibromomesitylene crystals. No dielectric anomaly was observed for the in-plane molecular rotation of tribromomesitylene in the absence of this dipole moment change. Typical antiferroelectric–paraelectric phase transitions were observed in the dibromomesitylene crystal, whereas the dielectric anomaly of dibromoiodomesitylene crystals was associated with the collective in-plane molecular rotation of polar π-molecules in the π-stack. We found that the single-rope-like collective in-plane molecular rotator was dominated by intermolecular I···I interactions along the π-stacking column of polar dibromoiodomesitylene

Dynamic Behavior, Electrochromism, and Two-Photon Absorption of Dicyanomethylenated Quinacridone

Molecular structures of dicyanomethylenated quinacridone (<b>1</b>) as a solid and in solution were examined on the basis of single-crystal X-ray structural analysis, temperature-dependent ¹H NMR in CD₂Cl₂, and theoretical calculations. Crystal <b>1</b> had a curved, butterfly-shaped molecular structure. Thermally activated flipping between the curved, butterfly-shaped structure and an armchair structure occurred in solution. Electrochemical reduction triggered a dynamic change from the curved, butterfly-shaped conformation in the neutral state to a planar conformation in the dianion state, which represented electrochromic behavior with electrochemical bistability. A large two-photon absorption cross section of compound <b>1</b> was observed in the resonance-enhancement region of 423 GM (1 GM = 1 × 10^–50 cm⁴ s photon^–1 molecule^–1) at 710 nm. Multiple donor–acceptor charge-transfer pathways of molecule <b>1</b> enhanced two-photon absorption