Cu(II)-Based Molecular Hexagons Forming Honeycomb-like Networks Exhibit High Electrical Conductivity

Four new Cu(II)-based hexagonal complexes with the metallomacrocycle formulae [Cu₆(5-nip)₆(3-py)₆(H₂O)₁₂] (1), [Cu₆(5-nip)₆(3-Clpy)₆(H₂O)₁₂] (2), [Cu₆(5-nip)₆(3-Brpy)₆(H₂O)₁₂] (3), and [Cu₆(5-nip)₆(3-Ipy)₆(H₂O)₁₂] (4) have been synthesized using 5-nitroisophthalic acid (H₂5-nip) and pyridine (py)/3-halopyridine (3-Xpy; X = Cl, Br, and I) ligands. The structural features and supramolecular interactions of compounds 1-4 have been investigated using the single-crystal X-ray diffraction (SCXRD) technique. Interestingly, the hexagonal complexes undergo hydrogen bonding and π···π stacking interactions to form fascinating two-dimensional (2D) honeycomb-like structures. The synthesized complexes exhibit high electrical conductivity, arising from charge transport through space via π···π contacts. However, complexes containing 3-Brpy (3) and 3-Ipy (4) exhibit photosensitivity due to the presence of halogens with a larger size and lower ionization energy. The conductivity results are also in accordance with the theoretical prediction calculated by density functional theory (DFT) study.

A novel three-dimensional copper aspartate coordination compound with efficient photoluminescence

Solvothermal reaction of a copper salt, racemic aspartic acid (AspH3), and 1,2,4-triazole (TaH) leads to a nanoporous copper aspartate, Cu4(Asp)2(Ta)2(H2O)2 · 2H2O (1). The compound was characterized by FT-IR spectroscopy and elemental analysis, and the structure was determined by single-crystal X-ray diffraction. Pairs of l-Asp3− and d-Asp3− ligands in unprecedented μ 4-1,2κO:3,4κOκN coordination modes chelate pairs of adjacent copper cations to form a centrosymmetric 8n-membered rectangular pipe, and these pipes are further bridged by copper cations in four directions of the bc plane to form a 3D porous structure with approximately rectangular channels of  ~ 5 × 10 Å2 along the crystallographic a-axis. Along the corners of the rectangular channels, each Ta− ligand connects three adjacent copper cations in a μ 3 coordination mode to form the final 3D porous framework with relatively large rectangular channels of  ~ 2 × 8 Å2 along the a-axis. Water molecules reside in these large channels. The thermal stability and solid-state photoluminescence properties of the title compound are also investigated.

Kinetic Study on the Preparation of Fumaric Acid from Maleic Acid by Batch Noncatalytic Isomerization

In recent years, the increase in demand for fumaric acid from industry has resulted in an increased need for a high-selectivity process for the conversion of maleic acid to fumaric acid. A highly selective conversion of fumaric acid was achieved without a catalyst by a simple one-step hydrothermal reaction. In addition, the competitive conversion of maleic acid, fumaric acid, and malic acid was first systematically investigated in detail without using a catalyst. The products were characterized by X-ray diffraction and Fourier transform infrared, which demonstrated that the product was fumaric acid. The highly selective conversion of fumaric acid was achieved, and the yield of fumaric acid could reach 92%. Furthermore, a reaction kinetic model was put forward to study the competitive transformation process. The kinetic model predictions were found to agree well with the experimental data. The kinetic parameters were used to explain the changes in the content of every substance at different reaction temperatures and reaction times. In addition, the initial maleic acid concentration in the reaction was also considered as an influencing factor. These results can facilitate the conditional control and product control of industrial processes for the production of fumaric acid or malic acid using latter without a catalyst.

Assembly of a series of coordination polymers built from rigid a tetracarboxylate ligand and flexible bis(imidazole) linker: syntheses, structural diversities, luminescence sensing, and photocatalytic properties

Hydrothermal reactions of aromatic terphenyl-4,2'',5'',4'-tetracarboxylic acid (H₄tta) and transitional metal cations in the presence of two flexible N-donor ancillary ligands afforded four novel coordination polymers, namely, {[Zn(tta)_0.5(m-bimb)]·H₂O}_n (1), [Ni₂(tta)(m-bimb)₂(H₂O)]_n (2), [Ni(H₂tta)(o-bimb)·H₂O]_n (3), and [Cd(tta)_0.5(o-bimb)]_n (4), from solvothermal reactions in the presence of bis(imidazole) bridging linkers (m-bimb = 1,3-bis(imidazol-1-ylmethyl)benzene, and o-bimb = 1,2-bis(imidazol-1-ylmethyl)benzene). Their structures were determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses (EA), powder X-ray diffraction (PXRD), and thermogravimetric (TG) analyses. Compound 1 displayed a 2-fold 3D → 3D parallel entangled (4,4)-connected bbf net with the point symbol of (6⁴·8²)(6⁶)₂. Compound 2 featured a predocumented 3D (4,8)-connected (3²·5³·6)(3⁴·4⁴·5⁹·6¹¹) net. Compound 3 exhibited a 2D 4-connected sql sheet with the point symbol of (4⁴·6²), and compound 4 showed a 2D 4-connected (3²·6²·7²) kgm sheet. To our delight, fluorescence measurements showed that compound 1 could selectively and sensitively detect Cr³⁺ cations and nitrobenzene derivatives (nitrobenzene (NB), p-nitrotoluene (PNT), and p-nitroaniline (PNA)), which suggested that CPs of 1 was a promising bifunctional luminescence sensor material that could sense metal ions and small organic molecules. Moreover, 1 showed excellent photocatalytic activity.

Coordination frameworks containing compounds as catalysts

This article describes a collection of MOF containing compounds as catalysts in a diverse range of organic transformation reactions.

The influence of different coordination environments on one-dimensional Cu(ii) coordination polymers for the photo-degradation of organic dyes

The role of coordination environment in 1D Cu(ii) coordination polymers for photo-catalytic activity has been investigated. Pyridine-2,6-dicarbohydrazide based polymeric complex 3 has the highest photo-catalytic rate constant (k = 0.72 h⁻¹) for rhodamine B degradation.

Self-assembly of two supramolecular indium(iii) metal–organic frameworks for reversible iodine capture and large band gap change semiconductor behavior

Conjunction of benzimidazole and metal In(iii) to construct supramolecular MOFs opens up an ingenious direction for synthesizing materials with multi-functionality.

A series of phenyl sulfonate metal coordination polymers as catalysts for one-pot Biginelli reactions under solvent-free conditions

A series of phenyl sulfonate metal coordination polymers have been obtained under hydrothermal conditions, which show high catalytic performances for one-pot Biginelli condensation reactions under solvent-free conditions.