Crystal Multi‐Conformational Control Through Deformable Carbon‐Sulfur Bond for Singlet‐Triplet Emissive Tuning

Crystal‐state luminophores have been of great interest in optoelectronics for years, whereas the excited state regulation at the crystal level is still restricted by the lack of control ways. We report that the singlet‐triplet emissive property can be profoundly regulated by crystal conformational distortions. Employing fluoro‐substituted tetrakis(arylthio)benzene luminophores as prototype, we found that couples of molecular conformations formed during different crystallizations. The deformable carbon‐sulphur bond essentially drove the distortion of the molecular conformation and varied the stacking mode, together with diverse non‐covalent interactions, leading to the proportional adjustment of the fluorescence and phosphorescence bands. This intrinsic strategy was further applied for solid‐state multicolor emissive conversion and mechanoluminescence, probably offering new insights for design of smart crystal luminescent materials.     

Impact of nanoconfinement on the diisopropylammonium chloride (C6H16ClN) organic ferroelectric

The dielectric studies of diisopropylammonium chloride (DIPAC) nanoparticles embedded into opal and MCM-41 silica matrices are presented. It is shown that the ferroelectric phase transition shifts to low temperatures and broadens for DIPAC within the opal pores compared to bulk. The thermal hysteresis of the transition increases under opal nanoconfinement. No anomalies of the permittivity relevant to the ferroelectric transition are observed for DIPAC within the MCM-41 molecular sieves likely due to formation of the amorphous phase.     

Dielectric Properties of Nanoporous Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Films Filled with Ferroelectric SC(NH<Subscript>2</Subscript>)<Subscript>2</Subscript>

Temperature dependences of permittivity ε′ and third harmonic amplitude γ_3ω of nanocomposites obtained by embedding ferroelectric SC(NH₂)₂ in porous alumina films with pore sizes of 60 and 100 nm are studied. A substantial increase in the temperatures of ferroelectric phase transition T_c1 and T_c2 and that of phase transition T_i from incommensurate phase to paraphase are also observed. The temperatures of all phase transitions are found to rise as pore diameters shrink.     

Dielectric properties of mixed NaNO2-KNO3 ferroelectrics in nanoporous silicate matrices

Physics of the Solid State - Results of dielectric studies of MCM-41 molecular sieves with mesoporous channels (37.0 and 24.3 Å in size) loaded with the ferroelectric (NaNO2)1 ? x (KNO3)...     

Comparative study of the structural and spectral properties of tetraaza- and tetraoxaannelated tetracirculenes

The IR spectrum of a recently synthesized tetraaza[8]circulene (4N) molecule has been investigated and completely interpreted based on the calculation of the molecular structure and force field within the density functional theory (DFT) using the B3LYP/6-311G(d,p) method. The calculation has also successfully explained the X-ray diffraction data. The same method has been used to calculate the tetraoxa[8]circulene (4О) molecule and perform a comparative analysis of the IR spectra of both molecules. In contrast to 4О, the 4N molecule exhibits strong fluorescence, which hinders measurement of its Raman spectrum; hence, it is only predicted based on the DFT calculation in this study. A comparison of the IR and Raman spectra of the 4N molecule with the experimental and theoretical analogs for the 4О molecule has made it possible to assign all the observed vibrational transitions and explain the nature of normal vibrations in these complex molecules.     

Dielectric and Thermal Properties of KNO3 Encapsulated in Carbon Nanotubes

Physics of the Solid State - The results of the study of phase transitions of KNO3 encapsulated in carbon nanotubes are presented. It is shown that the temperature range of existence of KNO3...     

Trapping an Unexpected/Unprecedented Hexanuclear Ce(III) Hydrolysis Product with Neutral 4-Amino-1,2,4-triazole

Using Ce(III) as both a representative lanthanide and actinide analog, the ability of mixtures of acidic and basic azoles to allow direct access to homoleptic N-donor f-element complexes in one pot reactions from hydrated salts as starting materials was examined by reacting mixtures of 4-amino-1,2,4-triazole (4-NH₂-1,2,4-Triaz), 5-amino-tetrazole (5-NH₂-HTetaz), and 1,2,3-triazole (1,2,3-HTriaz) in 1 : 1 and 1 : 3 ratios with CeCl₃ ⋅ 7H₂O, [C₂mim]₃[CeCl₆] ([C₂mim]⁺=1-ethyl-2-methylimidazolium), and Ce(NO₃)₃ ⋅ 6H₂O. Although unsuccessful in our goal, structural analysis revealed that neutral 4-NH₂-1,2,4-Triaz is structure directing via η²μ₂κ² bridging, with the formation of the dinuclear complexes [Ce₂Cl₂(μ₂-4-NH₂-1,2,4-Triaz)₄(H₂O)₈]Cl₄ ⋅ 4H₂O, [Ce₂(μ₂-4-NH₂-1,2,4-Triaz)₄(4-NH₂-1,2,4-Triaz)₂(Cl)₆], and [4-NH₂-1,2,4-HTriaz][Ce₂(μ₂-4-NH₂-1,2,4-Triaz)₂(μ₂-NO₃)(NO₃)₆(H₂O)₂]. When the synthetic conditions favored hydrolysis, the hexanuclear Ce(III) complex [Ce₆(μ₃-O)₄(μ₃-OH)₂(μ₃-Cl)₂(Cl)₆(μ₂-4-NH₂-1,2,4-Triaz)₁₂] ⋅ 7H₂O was isolated. This unexpected hydrolysis product represents the first example of a high nuclearity lanthanide complex where all Ln atoms are pairwise connected through 12 N-donor ligands or 12 neutral bridging ligands of any type, a rare example of incorporation of non-oxo coordinating anions in the M₆X₈ core, and the first reported Ce(III) hexanuclear complex of this type.     

Antiaromatic Sapphyrin Isomer: Transformation into Contracted Porphyrinoids with Variable Aromaticity

Sapphyrin is a pentapyrrolic expanded porphyrin with a 22π aromatic character. Herein, we report the synthesis of a 20π antiaromatic sapphyrin isomer 1 by oxidative cyclization of a pentapyrrane precursor P₅ with a terminal β-linked pyrrole. The resulting isomer 1 , containing a mis-linked bipyrrole unit in the skeleton, exhibits a reactivity for further oxidation due to the distinct antiaromatic electronic structure, affording a fused macrocycle 2 , possessing a spiro-carbon-containing [5.6.5.6]-tetracyclic structure. Subsequent treatment with an acid afforded a weakly aromatic pyrrolone-appended N-confused corrole 3 , and thermal fusion gave a [5.6.5.7]-tetracyclic-ring-embedded 14π aromatic triphyrin(2.1.1) analog 4 . The cyclization at the mis-linked pyrrole moiety of P₅ played a crucial role in synthesizing the antiaromatic porphyrinoid susceptible to facile transformation to novel porphyrinoids with variable aromaticity.     

Quantum-chemical study of the structure and magnetic properties of mono- and binuclear Cu(II) complexes with 1,3-bis(3-(pyrimidin-2-yl)-1<Emphasis Type="Italic">H</Emphasis>-1,2,4-triazol-5-yl)propane

On the basis of X-ray crystallographic data on molecular copper complexes with 1,3-bis(3-(pyrimidin-2-yl)-1H-1,2,4-triazol-5-yl)propane, quantum-chemical optimization of their equilibrium structure has been performed by the density functional theory method with subsequent analysis of the electron density distribution by Bader’s atoms in molecules method and g-factor anisotropy calculation. The topological parameters of electron density at the Cu–N bond critical points have been considered, and the bond energies have been estimated using the Espinosa equation. A phenomenon of variable coordination of nitrate ions with Cu(II) ions in the inner coordination sphere of the mononuclear copper complex with 1,3-bis(3-(pyrimidin-2-yl)-1H-1,2,4-triazol-5-yl)propane has been revealed. The contributions of different components to the gfactor anisotropy have been analyzed in the framework of the gauge-independent atomic orbital method. The largest contribution to the g-factor is made by the orbital (Zeeman) and spin–orbit components accounting for very high averaged g-factor values of 2.1413 and 2.5636 for the doublet state of the mononuclear complex and the triplet state of the binuclear complex, respectively.