Polar layered coordination polymers incorporating triazacyclononane-triphosphonate metalloligands

Reactions of metalloligands M^III(notpH₃) (M = Fe, Co and notpH₆ = 1,4,7-triazacyclononane-1,4,7-triyl-tris(methylenephosphonic acid)) with Zn(OAc)₂ under hydrothermal conditions resulted in new metal phosphonates Zn₂Fe(notp)Cl(H₂O) (1) and ZnCo(notpH)(H₂O)·2H₂O (2). They crystallize in polar space groups P6₃ (for 1) and Pca2₁ (for 2), respectively, and exhibit layer structures in which the inorganic layers are separated by the organic groups of the notp ligands. However, the layer topologies of the two compounds are quite different. In 1, the layer contains 6-membered rings composed of one {FeN₃O₃} octahedron, one {Zn1O₃Cl}, one {Zn2O₄} and three {PO₃C} tetrahedra via corner-sharing connections, while in 2, the layer contains 10-membered rings composed of two {CoO₃N₃} octahedra, three {ZnO₄} and five {PO₃C} tetrahedra via vertex-sharing connections. Dielectric measurements on single crystals of 2 confirmed the presence of high dielectric anisotropy. Proton conductivity measurements revealed that the proton conduction is more favourable in 2 due to the presence of a continuous hydrogen bond network in this compound.

Application of temperature-controlled chiral hybrid structures constructed from copper(ii)-monosubstituted Keggin polyoxoanions and copper(ii)-organoamine complexes in enantioselective sensing of tartaric acid

Temperature usually occupies a crucial position in the construction of chiral compounds. By controlling the temperature of the reaction system, chiral and non-chiral compounds can be designed and synthesized. Given the above, three new chiral and non-chiral compounds based on copper(ii) monosubstituted polyoxoanions and Cu(en) complexes (en = ethylenediamine), d/l-[Cu(H₂O)(en)₂]₂{[Cu(H₂O)₂(en)][SiCuW₁₁O₃₉]}·5H₂O (1, d-1 and l-1) and [Cu(H₂O)(en)₂]{[Cu(en)₂]₂[SiCuW₁₁O₃₉]}·2.5H₂O (2), were successfully synthesized under hydrothermal conditions. The main synthesis conditions of compound 1 (d-1 and l-1) and compound 2 are the same, however, the only difference is that the reaction temperatures are 80 °C and 140 °C, respectively. What's more, compounds 1 and 2 can form a 1D chiral chain by Cu–O and W/Cu–O–W/Cu bonds, respectively, and further obtain a 3D-supramolecular framework through hydrogen bonding interaction. Meanwhile, due to the asymmetry of chiral compound 1, optical second-harmonic generation (SHG) was used to investigate the second-order nonlinear optical effect and it was found that the observed SHG efficiency of compound 1 is 0.3 times that of urea. To further investigate the chiral properties, d-1 and l-1 were used in the electrochemical enantioselective sensing of d-/l-tartaric acid (d-/l-tart) molecules, respectively, which demonstrates that d-1 and l-1 have a good application prospect in sensing chiral substances.

A pair of temperature-controlled chiral compounds, d- and l-[Cu(en)₂(H₂O)]₂{[Cu(en)(H₂O)₂][SiCuW₁₁O₃₉]}·5H₂O (en = ethanediamine) are isolated by hydrothermal method, having a good application prospect in sensing d-/l-tartaric acid.

Chiral induction in a pcu-derived network from achiral precursors

The first chiral network derived from a classic pcu net has been rationally prepared from achiral precursors.

Temperature controlled formation of polar copper phosphonates showing large dielectric anisotropy and a dehydration-induced switch from ferromagnetic to antiferromagnetic interactions

The reaction of copper(ii) chloride with 2-carboxyphenylphosphonic acid (2-cppH3) under hydrothermal conditions at 100 °C results in the formation of a polar compound, Cu3(2-cpp)2(H2O)5 (1), which shows large dielectric anisotropy. A similar reaction at 140 °C results in a centrosymmetric phase, Cu3(2-cpp)2(H2O)2 (2). Compound 1 can convert into 2 upon increasing the reaction temperature under hydrothermal conditions, and further to Cu3(2-cpp)2 (3) upon thermal treatment at 240 °C. This process is accompanied by a switch from ferromagnetic in 1 to antiferromagnetic interactions in 2 and 3.

Synthesis, structures, and magnetic properties of metal-organic polyhedra based on unprecedented {V7} isopolyoxometalate clusters

Two isostructural vanadium-based metal-organic polyhedra (denoted as VMOP-16 and VMOP-17) were synthesized by a solvothermal method, which are built from unprecedented {V₇} isopolyoxometalate clusters and dicarboxylate ligands. To our knowledge, the {V₇} second building unit is reported for the first time and features the highest nuclearity of vanadium-oxygen clusters compared with reported vanadium-based MOPs.

Tuning of chain chirality by interchain stacking forces and the structure-property relationship in coordination systems constructed by meridional FeIII cyanide and MnIII Schiff bases

We synthesized six Fe(iii)-Mn(iii) bimetallic compounds by self-assembling the newly developed mer-Fe cyanide PPh₄[Fe(Clqpa)(CN)₃]·H₂O (1) and PPh₄[Fe(Brqpa)(CN)₃]·H₂O (2) with Mn Schiff base Mn(5-Xsalen)⁺ cations. These compounds include [Fe(Xqpa)(CN)₃][Mn(5-Ysalen)]·pMeOH·qH₂O [qpaH₂ = N-(quinolin-8-yl)picolinamide; salen = N,N'-ethylenebis(salicylideneiminato) dianion; X = Cl, Y = H (3); X = Cl, Y = Br (4); X = Br, Y = H (5); X = Br, Y = F (6); X = Br, Y = Cl (7); X = Br, Y = Br (8)]. When precursor 1 was used, compounds 3 and 4 were isolated to give a dinuclear entity and a linear chain structure, respectively. The reaction of precursor 2 with the Schiff bases afforded four linear Fe(iii)-Mn(iii) chain complexes. Chain chirality with P- and M-helicity emerges in 4, 7, and 8, while 5 exhibits chain helicity opposite to the previous chain complexes and 6 presents no chain helicity. Such a structural feature is heavily dependent on the interchain π-π contacts and the Fe precursor bridging unit. Chiral induction from a local ethylenediamine link of Y-salen is propagated over the chain via noncovalent π-π interactions. All the bimetallic compounds show antiferromagnetic interactions transmitted by the cyanide linkage. A field-induced metamagnetic transition is involved in 4, 7, and 8, while a field-induced two-step transition is evident in 6. From a magnetostructural viewpoint, the coupling constant is primarily governed by the Mn-N_ax-C_ax angle (ax = axial) in the bimetallic chain complexes composed of mer-Fe(iii) tricyanides, although the torsion angle plays a role.

Enantiopure phosphonic acids as chiral inducers: homochiral crystallization of cobalt coordination polymers showing field-induced slow magnetization relaxation

Homochiral crystallization of (M)- or (P)-Co(SO₄)(1,3-bbix)(H₂O)₃ (1M or 1P) from an achiral precursor is achieved in the presence of a catalytic amount of (S)- or (R)-3-phenyl-2-((phosphonomethyl)amino) propanoic acid.

Atypical temperature-dependence of symmetry transformation observed in a uranyl phosphonate

The first example of phase transformation from a centrosymmetric space group at LT to a chiral space group at HT is reported, which was clearly resolved in a single-crystal-to-single-crystal manner in a 3D uranyl(vi) phosphonate compound.

Spontaneous symmetry breaking of Co(ii) metal–organic frameworks from achiral precursors via asymmetrical crystallization

Enantioenriched 3D pseudo-enantiomorphs integrating porosity, chirality and magnetism together with different colour and morphology were obtained through spontaneous symmetry breaking.

The racemate-to-homochiral approach to crystal engineering via chiral symmetry breaking

Racemate-to-homochiral crystallization was highlighted for symmetry breaking phenomena by showing clear pictures of the mechanism and development history.

An organometallic complex revealing an unexpected, reversible, temperature induced SC–SC transformation

A reversible, temperature driven phase transformation that takes place at ca. 180 K, in a single-crystal to single-crystal manner, has been observed for a monometallic transition metal coordination complex based on a fac-Re(CO)₃ core, with a chelated 2,2′-bipyridine unit and a halogenated N-(4-iodophenyl)nicotinamide axial co-ligand.