Solvent-triggered single-crystal-to-single-crystal transformation from a monomeric to polymeric copper(II) complex based on an aza macrocyclic ligand

Reversible solvent-triggered single-crystal-to-single-crystal (SCSC) transformations are observed between two copper(II) azamacrocyclic complexes: [Cu(C₁₆H₃₈N₆)(H₂O)₂](C₁₂H₆O₄) (1) and [Cu(C₁₆H₃₈N₆)(C₁₂H₆O₄)] (2). Complex (1) was prepared via self-assembly of a copper(II) azamacrocyclic complex containing butyl pendant groups, [Cu(C₁₆H₃₈N₆)(ClO₄)₂], with 2,7-naphthalenedicarboxylic acid. When monomeric compound (1) was immersed in CH₃OH, coordination polymer (2) was obtained, indicating a solvent-triggered SCSC transformation. Furthermore, when (2) was immersed in water, an reverse SCSC transformation from (2) to (1) occurred. Complex (1) presents a 3D supramolecular structure formed via intermolecular hydrogen-bonding interactions, whereas complex (2) features a 1D zigzag coordination polymer. The reversible SCSC transformation of (1) and (2) was characterized using single-crystal X-ray diffraction and in situ powder X-ray diffraction techniques. Despite its poor porosity, complex (2) displayed interesting CO₂ adsorption behaviour under CO₂ gas.

Synthesis, crystal structure, and thermal properties of poly[aqua-(μ5-2,5-di-carb-oxy-benzene-1,4-di-carboxyl-ato)strontium]

In the title polymer, the eightfold-coordinated Sr^II atoms are linked by bridging (H₂BTEC)^2– anions to generate a two-dimensional network Thermal analysis (TG–SDTA–MS) has been undertaken.

A coordination polymer formulated as [Sr(H₂BTEC)(H₂O)]_n (H₄BTEC = benzene-1,2,4,5-tetra­carb­oxy­lic acid, C₁₀H₆O₈), was synthesized hydro­thermally and characterized by single-crystal and powder X-ray diffraction, scanning electron microscopy and thermal analysis. Its crystal structure is made up of a zigzag inorganic chain formed by edge-sharing of [SrO₈] polyhedra running along [001]. Adjacent chains are connected to each other via the carboxyl­ate groups of the ligand, resulting in a double-layered network extending parallel to (100). O—H⋯O hydrogen bonds of medium-to-weak strength between the layers consolidate the three-dimensional structure. One of the carb­oxy­lic OH functions was found to be disordered over two sets of sites with half-occupancy.

Recent progress in the synthesis of metal-organic frameworks

Metal-organic frameworks (MOFs) have attracted considerable attention for various applications due to their tunable structure, porosity and functionality. In general, MOFs have been synthesized from isolated metal ions and organic linkers under hydrothermal or solvothermal conditions via one-spot reactions. The emerging precursor approach and kinetically tuned dimensional augmentation strategy add more diversity to this field. In addition, to speed up the crystallization process and create uniform crystals with reduced size, many alternative synthesis routes have been explored. Recent advances in microwave-assisted synthesis and electrochemical synthesis are presented in this review. In recent years, post-synthetic approaches have been shown to be powerful tools to synthesize MOFs with modified functionality, which cannot be attained via de novo synthesis. In this review, some current accomplishments of post-synthetic modification (PSM) based on covalent transformations and coordinative interactions as well as post-synthetic exchange (PSE) in robust MOFs are provided.

Control of pore distribution of porous carbons derived from Mg2+ porous coordination polymers

Control of pore distribution of porous carbons from porous coordination polymers.

Evaluation of structural transformation in 2D metal–organic frameworks based on a 4,4′-sulfonyldibenzoate linker: microwave-assisted solvothermal synthesis, characterization and applications

Structural transformation has been observed in 2D MOFs.

Poly[tetra-aqua-(μ(8)-butane-1,2,3,4-tetra-carboxyl-ato)distrontium]

In the title compound, [Sr(2)(C(8)H(6)O(8))(H(2)O)(4))](n), the Sr(II) ion is coordinated by six O atoms of four symmetry-related ligands and two water mol-ecules in a distorted bicapped trigonal-prismatic environment. The butane-1,2,3,4-tetra-carboxyl-ate ligands lie on inversion centers and bridge Sr(II) ions, forming a three-dimensional network. Within the three-dimensional structure, there are O-H⋯O hydrogen bonds involving the water mol-ecules and carboxyl-ate O atoms.

Poly[[aqua-(μ(5)-3,4,5,6-tetra-carb-oxy-cyclo-hexane-1,2-dicarboxyl-ato)strontium] monohydrate]

In the title compound, {[Sr(C₁₂H₁₀O₁₂)(H₂O)]·H₂O}_n, the Sr^II ion is coordinated by six O atoms of five symmetry-related 3,4,5,6-tetra­carb­oxy­cyclo­hexane-1,2-dicarboxyl­ate ligands and one water mol­ecule in a slightly distorted monocapped trigonal–prismatic environment. The ligands bridge the Sr^II ions, forming a two-dimensional structure. In the crystal, O—H⋯O hydrogen bonds further connect the structure into a three-dimensional network. The H atoms of two of the carboxyl groups were refined as half-occupancy.

Poly[hexaaquabis(μ3-heptanedioato-κ3O:O′:O′′)dimagnesium]

In the title compound, [Mg₂(C₇H₁₀O₄)₂(H₂O)₆]_n, the Mg^II ion is coordinated by three aqua ligands and three O atoms from three heptanedioato ligands in a distorted octa­hedral geometry. Each heptanedioato ligand bridges three Mg atoms, generating polymeric layers parallel to the bc plane. The polymeric layers related by translation along the a axis inter­act further via O—H⋯O hydrogen bonds, which consolidate the crystal packing.

Poly[(μ(6)-benzene-1,3,5-tricarboxyl-ato-κO:O:O:O:O:O)tris-(N,N-dimethyl-formamide-κO)tris-(μ(3)-formato-κO:O')trimagnesium(II)]

The title complex, [Mg(3)(CHO(2))(3)(C(9)H(3)O(6))(C(3)H(7)NO)(3)](n), exhib-its a two-dimensional structure parallel to (001), which is built up from the Mg(II) atoms and bridging carboxyl-ate ligands (3 symmetry). The Mg(II) atom is six-coordinated by one O atom from a dimethyl-formamide mol-ecule, two O atoms from two μ(6)-benzene-1,3,5-tricarboxyl-ate ligands and three O atoms from three μ(3)-formate ligands in a distorted octa-hedral geometry.