Metathesis in Single Crystal: Complete and Reversible Exchange of Metal Ions Constituting the Frameworks of Metal−Organic Frameworks

Metathesis in Single Crystal: Complete and Reversible Exchange of Metal Ions Constituting the Frameworks of Metal−Organic Framework

Metathesis in Single Crystal: Complete and Reversible Exchange of Metal Ions Constituting the Frameworks of Metal−Organic Frameworks

Metathesis in Single Crystal: Complete and Reversible Exchange of Metal Ions Constituting the Frameworks of Metal−Organic Framework

Solvated Square-Planar Ternary Copper(II) Complexes: Solvent-Dependent Zipper and Columnar Structures

Two ternary copper(II) complexes having the general formula [Cu(pyp)X] with the tridentate Schiff base 2-N-(picolinylidene)phenol (Hpyp) and halide (X- = Cl-, Br-) as the ancillary ligand have been synthesized and characterized. Both complexes exhibit solvatomorphism due to cocrystallization with different solvent molecules. Two cases have been investigated:  (i) the dihydrated species [Cu(pyp)Cl]·2H2O (1) and [Cu(pyp)Br]·2H2O (2), isolated by slow evaporation of aqueous methanol solution of the complexes, and (ii) the corresponding monomethanolic forms [Cu(pyp)Cl]·CH3OH (3) and [Cu(pyp)Br]·CH3OH (4), obtained by crystallization of 1 and 2 from dry methanol. To investigate the crystal compositions and packing features, single-crystal X-ray diffraction measurements as well as thermogravimetric and differential scanning calorimetric measurements have been carried out. In the context of structural features, the hydrated forms and also the monomethanolic forms are isomorphic. The dihydrated form shows a zipperlike infinite chain structure through hydrogen bonding with the water molecules and π···π interactions. The parallel zippers are again connected to each other through hydrogen bonding between the water molecules to give a two-dimensional sheet structure. In contrast, the methanol-containing species form cyclic hydrogen-bonded dimeric host−guest units which are π-stacked to one-dimensional columnar structures

Unique Asymmetric (Cu^II₄) Double-Stranded Helicate from a Hexadentate Piperazine-Based Ligand: Ligand Conformation Isomerism upon Coordination

In methanol, the reaction of Cu(ClO4)2·6H2O and a sterically constrained piperazine imine phenol ligand (H2L), in the presence of NEt3, affords a novel tetranuclear copper(II) complex of formula [CuII4(μ3-L)2(μ-OH)2(H2O)2](ClO4)2·H2O (1). The X-ray structure of this complex shows an elongated Cu4 quasi-tetrahedron coordinated to two hexadentate chair-(e,a)-μ3-piperazine bridging ligands. Variable-temperature magnetic studies show an St = 0 spin ground state resulting from antiferromagnetic interactions between CuII ions within the complex

Unique Asymmetric (Cu^II₄) Double-Stranded Helicate from a Hexadentate Piperazine-Based Ligand: Ligand Conformation Isomerism upon Coordination

In methanol, the reaction of Cu(ClO4)2·6H2O and a sterically constrained piperazine imine phenol ligand (H2L), in the presence of NEt3, affords a novel tetranuclear copper(II) complex of formula [CuII4(μ3-L)2(μ-OH)2(H2O)2](ClO4)2·H2O (1). The X-ray structure of this complex shows an elongated Cu4 quasi-tetrahedron coordinated to two hexadentate chair-(e,a)-μ3-piperazine bridging ligands. Variable-temperature magnetic studies show an St = 0 spin ground state resulting from antiferromagnetic interactions between CuII ions within the complex

Synthesis of Phase-Pure Interpenetrated MOF-5 and Its Gas Sorption Properties

For the first time, phase-pure interpenetrated MOF-5 (1) has been synthesized and its gas sorption properties have been investigated. The phase purity of the material was confirmed by both single-crystal and powder X-ray diffraction studies and TGA analysis. A systematic study revealed that controlling the pH of the reaction medium is critical to the synthesis of phase-pure 1, and the optimum apparent pH (pH*) for the formation of 1 is 4.0−4.5. At higher or lower pH*, [Zn2(BDC)2(DMF)2] (2) or [Zn5(OH)4(BDC)3] (3), respectively, was predominantly formed. The pore size distribution obtained from Ar sorption experiments at 87 K showed only one peak, at ∼6.7 Å, which is consistent with the average pore size of 1 revealed by single crystal X-ray crystallography. Compared to MOF-5, 1 exhibited higher stability toward heat and moisture. Although its surface area is much smaller than that of MOF-5 due to interpenetration, 1 showed a significantly higher hydrogen capacity (both gravimetric and volumetric) than MOF-5 at 77 K and 1 atm, presumably because of its higher enthalpy of adsorption, which may correlate with its higher volumetric hydrogen uptake compared to MOF-5 at room temperature, up to 100 bar. However, at high pressures and 77 K, where the saturated H2 uptake mostly depends on the surface area of a porous material, the total hydrogen uptake of 1 is notably lower than that of MOF-5

Synthesis of Phase-Pure Interpenetrated MOF-5 and Its Gas Sorption Properties

For the first time, phase-pure interpenetrated MOF-5 (1) has been synthesized and its gas sorption properties have been investigated. The phase purity of the material was confirmed by both single-crystal and powder X-ray diffraction studies and TGA analysis. A systematic study revealed that controlling the pH of the reaction medium is critical to the synthesis of phase-pure 1, and the optimum apparent pH (pH*) for the formation of 1 is 4.0−4.5. At higher or lower pH*, [Zn2(BDC)2(DMF)2] (2) or [Zn5(OH)4(BDC)3] (3), respectively, was predominantly formed. The pore size distribution obtained from Ar sorption experiments at 87 K showed only one peak, at ∼6.7 Å, which is consistent with the average pore size of 1 revealed by single crystal X-ray crystallography. Compared to MOF-5, 1 exhibited higher stability toward heat and moisture. Although its surface area is much smaller than that of MOF-5 due to interpenetration, 1 showed a significantly higher hydrogen capacity (both gravimetric and volumetric) than MOF-5 at 77 K and 1 atm, presumably because of its higher enthalpy of adsorption, which may correlate with its higher volumetric hydrogen uptake compared to MOF-5 at room temperature, up to 100 bar. However, at high pressures and 77 K, where the saturated H2 uptake mostly depends on the surface area of a porous material, the total hydrogen uptake of 1 is notably lower than that of MOF-5

Postsynthetic Modification Switches an Achiral Framework to Catalytically Active Homochiral Metal−Organic Porous Materials

Postsynthetic Modification Switches an Achiral Framework to Catalytically Active Homochiral Metal−Organic Porous Material