Coordination Polymers Constructed from an Adaptable Pyridine-Dicarboxylic Acid Linker: Assembly, Diversity of Structures, and Catalysis

4,4'-(Pyridine-3,5-diyl)dibenzoic acid (H₂pdba) was explored as an adaptable linker for assembling a diversity of new manganese(II), cobalt(II/III), nickel(II), and copper(II) coordination polymers (CPs): [Mn(μ₄-pdba)(H₂O)]_n (1), {[M(μ₃-pdba)(phen)]·2H₂O}_n (M = Co (2), Ni (3)), {[Cu₂(μ₃-pdba)₂(bipy)]·2H₂O}_n (4), {[Co(μ₃-pdba)(bipy)]·2H₂O}_n (5), [Co₂(μ₃-pdba)(μ-Hbiim)₂(Hbiim)]_n (6), and [M(μ₄-pdba)(py)]_n (M = Co (7), Ni (8)). The CPs were hydrothermally synthesized using metal(II) chloride precursors, H₂pdba, and different coligands functioning as crystallization mediators (phen: 1,10-phenanthroline; bipy: 2,2'-bipyridine, H₂biim: 2,2'-biimidazole; py: pyridine). Structural networks of 1-8 range from two-dimensional (2D) metal-organic layers (1-3, 5-8) to three-dimensional (3D) metal-organic framework (MOF) (4) and disclose several types of topologies: sql (in 1), hcb (in 2, 3, 5), tfk (in 4), 3,5L66 (in 6), and SP 2-periodic net (6,3)Ia (in 7, 8). Apart from the characterization by standard methods, catalytic potential of the obtained CPs was also screened in the Knoevenagel condensation of benzaldehyde with propanedinitrile to give 2-benzylidenemalononitrile (model reaction). Several reaction parameters were optimized, and the substrate scope was explored, revealing the best catalytic performance for a 3D MOF 4. This catalyst is recyclable and can lead to substituted dinitrile products in up to 99% product yields. The present study widens the use of H₂pdba as a still poorly studied linker toward designing novel functional coordination polymers.

Two-dimensional magnetic materials of cobalt(ii) triangular lattices constructed by a mixed benzimidazole–dicarboxylate strategy

Herein, three two-dimensional magnetic materials of cobalt(ii) coordination polymers with triangular lattices were synthesized using a mixed benzimidazole–dicarboxylate strategy.

Three novel polyoxometalate-based inorganic–organic hybrid materials based on 2,6-bis(1,2,4-triazol-1-yl)pyridine

Three novel inorganic–organic hybrid materials [Co(btp)₂(W₅O₁₆)(H₂O)]_n (1), [Cd₃(btp)₆(PW₁₂O₄₀)₂(H₂O)₆·6H₂O]_n (2), and [Ag₃(btp)₂(PMo₁₂O₄₀)·1.5H₂O]_n (3) (btp = 2,6-bis(1,2,4-triazol-1-yl)pyridine) have been hydrothermally synthesized and characterized by IR spectroscopy, single-crystal X-ray diffraction, powder X-ray diffraction (PXRD), elemental analysis and thermal gravimetric analysis (TGA). The most striking structure feature of compound 1 is a 3D polycatenation framework, interpenetrated by a 2D 4-connected sql topology layer and a 3D 6-connected rob topology framework. Compound 2 exhibits a rare meso-helices 3D network with different chiralities crossing coexistence. Compound 3 also holds a 3D framework formed by linking terminal oxygen atoms of [α-PMo₁₂O₄₀]³⁻ anions and silver ions in a 2D metal–organic layer. Compound 1 displays antiferromagnetic behavior. The luminescence, electrochemical and photocatalytic properties of compounds 1–3 have also been investigated. Compound 3 exhibits significant electrochemical activity for the reduction of H₂O₂ while compounds 1 and 2 show efficient photocatalytic activities for the degradation of Rhodamine B (RhB). Furthermore, the three compounds display luminescence behaviors in the solid state.

Three novel inorganic–organic hybrid materials based on 2,6-bis(1,2,4-triazol-1-yl)pyridine have been synthesized with different polyanions and transition metal ions.

Syntheses, structures, luminescence and magnetic properties of seven isomorphous metal–organic frameworks based on 2,7-bis(4-benzoic acid)-N-(4-benzoic acid)carbazole

Seven isomorphous lanthanide metal–organic frameworks with special luminescence and magnetic properties are synthesized and characterized.

Construction of two Zn(ii)/Cd(ii) multifunctional coordination polymers with mixed ligands for catalytic and sensing properties

Two Zn(ii)/Cd(ii) coordination polymers with different networks were constructed with mixed ligands. The former compound shows high catalytic activity for Knoevenagel condensation, and the latter compound can selectively recognize l-cysteine through the luminescence quenching effect.

Chiral spin density wave order on the frustrated honeycomb and bilayer triangle lattice hubbard model at half-filling

We study the Hubbard model on the frustrated honeycomb lattice with nearest-neighbor hopping t_{1} and second nearest-neighbor hopping t_{2}, which is isomorphic to the bilayer triangle lattice, using the SU(2)-invariant slave boson theory. We show that the Coulomb interaction U induces antiferromagnetic (AF) chiral spin density wave (χSDW) order in a wide range of κ=t_{2}/t_{1} where both the two-sublattice AF order at small κ and the decoupled three-sublattice 120° order at large κ are strongly frustrated, leading to three distinct phases with different anomalous Hall responses. We find a continuous transition from a χSDW semimetal with the anomalous Hall effect to a topological chiral Chern insulator exhibiting the quantum anomalous Hall effect, followed by a discontinuous transition to a χSDW insulator with a zero total Chern number but an anomalous ac Hall effect. The χSDW is likely a generic phase of strongly correlated and highly frustrated hexagonal lattice electrons.

A chiral coordination polymer with double coaxially nested helical chains exhibiting spin-canting antiferromagnetism

A chiral coordination polymer is reported, which contains rarely two types of double coaxially nested helical chains, exhibiting spin-canting antiferromagnetism.

Solvent-induced secondary building unit (SBU) variations in a series of Cu(ii) metal–organic frameworks derived from a bifunctional ligand

Three new three-dimensional (3D) Cu(ii) metal–organic frameworks (MOFs) with interesting SBU variations have been successfully constructed under solvothermal conditions by using a bifunctional ligand. The structural features of the three MOFs and CO₂ sorption performances were studied.

Self-assembly of two high-nuclearity manganese calixarene-phosphonate clusters: diamond-like Mn16 and drum-like Mn14

Variation of the phosphonic acid “converts” a tetradecanuclear drum-like MnII14 cluster (1) into a hexadecanuclear diamond-like MnII16 cluster (2).

Probing the magnetic and magnetothermal properties of M(ii)–Ln(iii) complexes (where M(ii) = Ni or Zn; Ln(iii) = La or Pr or Gd)

We report the crystal structures of Ni(ii)–Ln(iii) (where Ln = Gd or Pr) complexes and their suitably substituted diamagnetic analogues. Magnetic characterization revealed the nature of the magnetic exchange interactions and the magnetothermal properties.