A Significant Two-Dimensional Structural Transformation in a Coordination Polymer that Changes Its Electronic and Protonic Behavior

A 2D-to-2D (2D: two-dimensional) structural transformation accompanying significant bond rearrangement and coordination environment change is demonstrated in a coordination polymer (CP) comprised of copper(II) ions and terephthalate (BDC²⁻) ligands for the first time. When immersed in water, a free-standing membrane of 2D Cu(BDC)(DMF) (Cu-1; DMF: N, N-dimethylformamide) transforms into 2D Cu(BDC)(H₂O)₂ (Cu-2) while maintaining its highly oriented layered structure. In the 2D sheet, paddlewheel-type Cu[II] dimers coordinated with four bidentate BDC ligands in a square-planar array in Cu-1 were released to form uniform aqua-bridged Cu[II] chains, which are cross-linked with each other by unidentate BDC ligands, in Cu-2. The present facile approach to implement the 2D-to-2D transformation accompanied by bond rearrangement, which is characteristic of CPs, leads to a marked increase in in-plane magnetic susceptibility and proton conductivity. In situ experiments in support of theoretical calculations unveiled the energy diagram that governs the unique structural transformation

Design of a Conducting Metal–Organic Framework: Orbital-Level Matching in MIL-140A Derivatives

On the basis of the results of first-principles band calculations, we report a strategy for the development of a conducting metal–organic framework (MOF). The charge carrier in a zirconium-based MOF, MIL-140A, is expected to be localized because of a mismatch of the energy levels of bridging ligands’ π* and Zr 4d orbitals. On the basis of the findings, we propose a candidate structure for a conducting MOF

Isomerization-Controlled Proton–Electron Coupling in a π-Planar Metal Complex

Proton-coupled electron transfer (PCET) is a ubiquitous and fundamental process in biochemistry and electrochemistry performed by transition-metal complexes. Most synthetic efforts have been devoted to selecting the components, that is, metal ions and ligands, to control the proton–electron coupling. Here, we show the first example of controlling the proton–electron coupling using the cis–trans metal–ligand isomerization in a π-planar platinum complex, Pt(itsq)₂ (itsq¹⁻: o-iminothiosemiquinonate). Both the isomers, which were obtained separately, were characterized by single-crystal X-ray diffraction, and the cis-to-trans isomerization was achieved by immersing in organic solvents. Theoretical calculations predicted that the proton–electron coupling evaluated from the energetic stabilization of the lowest unoccupied molecular orbital by protonation varies greatly depending on the geometrical configuration compared to the metal substitution

Unconventional Magnetic and Resistive Hysteresis in an Iodine-Bonded Molecular Conductor.

Article first published online: 14 JUL 2015Simultaneous manipulation of both spin and charge is a crucial issue in magnetic conductors. We report on a strong correlation between magnetism and conductivity in the iodine-bonded molecular conductor (DIETSe)2 FeBr2 Cl2 [DIETSe=diiodo(ethylenedithio)tetraselenafulvalene], which is the first molecular conductor showing a large hysteresis in both magnetic moment and magnetoresistance associated with a spin-flop transition. Utilizing a mixed-anion approach and iodine bonding interactions, we tailored a molecular conductor with random exchange interactions exhibiting unforeseen physical properties

Structural Insight into Order-Disorder Transition and Charge-Transfer Phase Transition in an Iron Mixed-Valence Complex (n-C3H7)4N[FeIIFeIII(dto)3] with a Two-Dimensional Honeycomb Network

International audienc

The Role of a Three Dimensionally Ordered Defect Sublattice on the Acidity of a Sulfonated Metal–Organic Framework

Understanding the role that crystal imperfections or defects play on the physical properties of a solid material is important for any application. In this report, the highly unique crystal structure of the metal–organic framework (MOF) zirconium 2-sulfoterephthalate is presented. This MOF contains a large number of partially occupied ligand and metal cluster sites which directly affect the physical properties of the material. The partially occupied ligand positions give rise to a continuum of pore sizes within this highly porous MOF, supported by N₂ gas sorption and micropore analysis. Furthermore, this MOF is lined with sulfonic acid groups, implying a high proton concentration in the pore, but defective zirconium clusters are found to be effective proton trapping sites, which was investigated by a combination of AC impedance analysis to measure the proton conductivity and DFT calculations to determine the solvation energies of the protons in the pore. Based on the calculations, methods to control the p<i>K</i>_a of the clusters and improve the conductivity by saturating the zirconium clusters with strong acids were utilized, and a 5-fold increase in proton conductivity was achieved using these methods. High proton conductivity of 5.62 × 10^–3 S cm^–1 at 95% relative humidity and 65 °C could be achieved, with little change down to 40% relative humidity at room temperature

The Role of a Three Dimensionally Ordered Defect Sublattice on the Acidity of a Sulfonated Metal–Organic Framework

Understanding the role that crystal imperfections or defects play on the physical properties of a solid material is important for any application. In this report, the highly unique crystal structure of the metal–organic framework (MOF) zirconium 2-sulfoterephthalate is presented. This MOF contains a large number of partially occupied ligand and metal cluster sites which directly affect the physical properties of the material. The partially occupied ligand positions give rise to a continuum of pore sizes within this highly porous MOF, supported by N₂ gas sorption and micropore analysis. Furthermore, this MOF is lined with sulfonic acid groups, implying a high proton concentration in the pore, but defective zirconium clusters are found to be effective proton trapping sites, which was investigated by a combination of AC impedance analysis to measure the proton conductivity and DFT calculations to determine the solvation energies of the protons in the pore. Based on the calculations, methods to control the p<i>K</i>_a of the clusters and improve the conductivity by saturating the zirconium clusters with strong acids were utilized, and a 5-fold increase in proton conductivity was achieved using these methods. High proton conductivity of 5.62 × 10^–3 S cm^–1 at 95% relative humidity and 65 °C could be achieved, with little change down to 40% relative humidity at room temperature

Electronic Structure Evolution with Composition Alteration of Rh_xCu_y Alloy Nanoparticles.

組成が違っても触媒活性が同等な新規Rh-Cuナノ粒子の電子状態の観測 : 合金の複合的な電子状態が寄与することを示唆. 京都大学プレスリリース. 2017-01-30.The change in electronic structure of extremely small Rh[x]Cu[y] alloy nanoparticles (NPs) with composition variation was investigated by core-level (CL) and valence-band (VB) hard X-ray photoelectron spectroscopy. A combination of CL and VB spectra analyses confirmed that intermetallic charge transfer occurs between Rh and Cu. This is an important compensation mechanism that helps to explain the relationship between the catalytic activity and composition of Rh[x]Cu[y] alloy NPs. For monometallic Rh and Rh-rich alloy (Rh[0.77]Cu[0.23]) NPs, the formation of Rh surface oxide with a non-integer oxidation state (Rh((3-δ)+)) resulted in high catalytic activity. Conversely, for alloy NPs with comparable Rh:Cu ratio (Rh[0.53]Cu[0.47] and Rh[0.50]Cu[0.50]), the decreased fraction of catalytically active Rh((3-δ)+) oxide is compensated by charge transfer from Cu to Rh. As a result, ensuring negligible change in the catalytic activities of the NPs with comparable Rh:Cu ratio to those of Rh-rich and monometallic Rh NPs