Syntheses,Structures and Luminescent Properties of Zinc(II) and Cadmium(II) Complexes With the Ditopic Ligand 1,3-Bis(imidazol-1-ylmethyl)benzene

Abstract  

Three new complexes, namely [Zn(mbix)(SO₄)]·CH₃OH (1), Cd(mbix)₂(NO₃)₂ (2) and [Cd(mbix)₂(H₂O)₂]·(NO₃)₂ (3), have been obtained by reactions of flexible bidentate ligand 1,3-bis(imidazol-1-ylmethyl)benzene (mbix) with corresponding zinc(II) and cadmium(II) salts. The structures of these complexes have been determined by the X-ray single crystal diffraction analysis. Complex 1 features a 2D wavy network with (4,4) topology. Complex 2 has a 2D grid network with left- and right-handed helical chains, while complex 3 exhibits twofold parallel interpenetration structure. The differences of three complexes demonstrate that the coordination geometry of metal ions and the ratio of reactants have a great impact on the structure of the supramolecular architectures. The luminescent properties of three complexes are also investigated.     

Chiral magnetic soliton lattice on a chiral helimagnet

Using Lorenz microscopy and small-angle electron diffraction, we directly present that the chiral magnetic soliton lattice (CSL) continuously evolves from a chiral helimagnetic structure in small magnetic fields in Cr(1/3)NbS2. An incommensurate CSL undergoes a phase transition to a commensurate ferromagnetic state at the critical field strength. The period of a CSL, which exerts an effective potential for itinerant spins, is tuned by simply changing the field strength. Chiral magnetic orders observed do not exhibit any structural dislocation, indicating their high stability and robustness in Cr(1/3)NbS2.     

Stress measurement under high pressure using Kawai‐type multi‐anvil apparatus combined with synchrotron radiation

A system for stress measurement under high pressure has been developed at beamline BL04B1, SPring‐8, Japan. A Kawai‐type multi‐anvil apparatus, SPEED‐1500, was used to pressurize polycrystalline KCl to 9.9 GPa in a mechanically anisotropic cell assembly with the KCl sample sandwiched between dense Al₂O₃ pistons. The variation of deviatoric stress was determined from the lattice distortion measured using two‐dimensional X‐ray diffraction with monochromatic synchrotron X‐rays. The low‐pressure B1 phase transformed to the high‐pressure polymorph B2 during compression. The deviatoric stress increased with increasing pressure in both the B1 and B2 phases except for the two‐phase‐coexisting region at a pressure of 2–3 GPa. This new system provides one of the technical foundations for conducting precise rheological measurements at conditions of the Earth's lower mantle.     

Remarkable effect of hydrogen bonding between ring and axle components on deslipping reactions of rotaxanes

A series of rotaxanes 1·5, 2·5, 3·5, and 4·5 bearing a different substituent (X = NO₂, Br, H, and OMe, respectively) at para position on the phenol moiety of the ring component exhibit clear difference in deslipping behavior. The difference in the deslipping rates is consistent with the difference in intercomponent hydrogen bonding strength estimated from the O-H stretching vibration wavenumbers. The para substituent dictates the relative strength of the intra- and intermolecular hydrogen bonds. Thus the incorporation of an intramolecular hydrogen bond allows for tunability of the strength of the intercomponent interaction.     

Fabrication and characterization of magnetic nanoporous zeolite templated carbon

The effects of heat-treatment and guest adsorption on the structure and electronic/magnetic properties were investigated for zeolite templated carbon (ZTC) by using potassium, bromine, and helium as guest species. ZTC consists of a curved graphene network, which has regularly arranged nanopores with a periodicity of 1.4 nm. X-ray diffraction and Raman spectra reveal that the regular nanopore structure is preserved during vacuum heat-treatment (<380 °C) and potassium adsorption process. On the other hand, bromine adsorption is found to destroy the nanopore structure. Helium atoms adsorbed in the nanospace participate in the energy dissipation of the radical spins in ZTC through collisions with the spins.     

Ferroelectric Behavior of a Hexamethylenetetramine‐Based Molecular Perovskite Structure

We report the development of a molecular ferroelectric material inspired by the hexamethylenetetramine (hmta) non‐centrosymmetric molecular rotator. The bromide salt of diprotonated hmta (hmtaH₂) crystalized as (hmtaH₂)(NH₄)Br₃ in a metal‐free ABX₃ perovskite‐type structure, in which the A and B sites are occupied by hmtaH₂²⁺ and ammonium cations, respectively. The compound crystallized in the Pma2 polar space group. A distorted polar perovskite structure formed owing to the distortion of {(NH₄)Br₆} octahedrons that are stabilized through the formation of NH???Br hydrogen bonds and the orientational ordering of positive charges on the non‐centrosymmetric hmtaH₂ molecules. This spontaneous polarization exhibited ferroelectric behavior with a nominally high Curie temperature (>400 K), in which the electrical switching of polarization originates from the rotation of the hmtaH₂ unit.     

Evaluation of proton conductivity of sulfonated polyimide/dihydroxy naphthalene charge‐transfer complex hybrid membranes

Sulfonated polyimide (SPI)/dihydroxynaphthalene (DHN) charge‐transfer (CT) complex hybrid films were investigated as possible alternative for polymer electrolyte membranes in polymer electrolyte fuel cells. SPI/DHN CT complex hybrid films include CT complexes, which might work as electronic conductors, and sulfonic acid units, which could work as proton conductors. Therefore, the origin of the conductivity of SPI/DHN complex hybrid films was evaluated by four‐probe impedance measurements in the through‐plane direction of the films. The obtained conductivity of the CT complex hybrid films increased with the increase of ion exchange capacity of the CT films and the decrease of CT complex concentration in the films. These results indicated that proton transfer dominantly occurred in the CT complex hybrid films. Proton conductivity of the CT complex hybrid films consisting of 2,6‐ or 1,5‐DHN showed the similar values, although the molecular geometries of the CT complex were different. The activation energy values for proton conductivity in the CT films were approximately the same as that of Nafion 212. Water uptake (WU) results were also conducted and suggest that CT complex formation could control the degree of WU of the films and prevent dissolution of SPI. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2991–2997     

Mechanophores with a Reversible Radical System and Freezing‐Induced Mechanochemistry in Polymer Solutions and Gels

Visualization and quantitative evaluation of covalent bond scission in polymeric materials are highly important for understanding failure, fatigue, and deterioration mechanisms and improving the lifetime, durability, toughness, and reliability of the materials. The diarylbibenzofuranone‐based mechanophore radical system enabled, through electron paramagnetic resonance spectroscopy, in situ quantitative evaluation of scission of the mechanophores and estimation of mechanical energy induced along polymer chains by external forces. The coagulation of polymer solutions by freezing probably generated force but did not cleave the mechanophores. On the other hand, cross‐linking led to efficient propagation of the force of more than 80 kJ mol^?1 to some mechanophores, resulting their cleavage and generation of colored stable radicals. This mechanoprobe concept has the potential to elucidate other debated issues in the polymer field as well.     

Experimental and theoretical study of charge‐transfer complex hybrid polyimide membranes

The nanostructure of sulfonated polyimide (SPI)/dihydroxynaphthalene (DHN) derivative charge‐transfer (CT) complex hybrid films, which are noble alternative polymer electrolyte membranes (PEMs), is determined by a combined visible spectroscopy/quantum mechanical approach. From the visible spectra of SPI/2,6‐dihydroxynaphthalene (2,6‐DHN) and 1,5‐dihydroxynaphthalene (1,5‐DHN) CT complex hybrid films, it is confirmed that these films have different maximum wavelength, although difference of the molecular structure is small. From the calculation based on the experimental result, SPI and DHNs form multiple interactions consisting of not only CT interaction, but also hydrogen bonding in multilayered structures. CT interaction between SPI and DHN defines the DHN position in the SPI matrix, with DHN sitting in the cavity formed between SPIs. The molecular structure of the CT films derived from the multiple and complex interactions can recognize small differences in the structural isomers and bring changes of the optical property. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 293–298