Controllable assembly of Cu(ii) coordination compounds based on a flexible zwitterionic benzimidazole–dicarboxylate ligand: synthesis, structural diversity, reversible SCSC transformation and magnetic properties

Abstract

The reversible SCSC transformation of a paddle-wheel cluster to a 1D linear polymer could be accomplished.

Metal–Organic Architectures Assembled from Multifunctional Polycarboxylates: Hydrothermal Self-Assembly, Structures, and Catalytic Activity in Alkane Oxidation

“…The five-coordinate Cu1 atom forms a well-distorted square-pyramidal {CuN 3 O 2 } environment (τ = 0.256) that is occupied by two oxygen and one nitrogen atoms from three μ 3 -Hcpic 2– ligands and two phen nitrogen atoms (Figure a). The Cu–O [1.911(4)–1.975(4) Å] and Cu–N [1.999(6)–2.559(5) Å] distances are well comparable to those of related copper derivatives. − In 3 , the Hcpic 2– spacers show a μ 3 -mode (Scheme , mode III), with the COO – groups being monodentate; the dihedral angle that separates the aromatic functionalities attains 58.86°. The neighboring Cu1 atoms are interconnected via the oxygen and nitrogen donors from the μ 3 -Hcpic 2– spacers, thus forming a CP with a 1D double-chain structure (Figure b).…”

“…The five-coordinate copper­(II) atom is surrounded by two carboxylate oxygen donors coming from two different μ 3 -cpna 2– moieties, an nitrogen donor from another μ 3 -cpna 2– ligand, and two phen nitrogen donors, thus forming a distorted square-pyramidal {CuN 3 O 2 } environment with the τ parameter of 0.0792 (τ = 0 or 1 for a regular square-pyramidal or trigonal-bipyramidal geometry, respectively) . The Cu–N and Cu–O bonds are in the 2.034(4)–2.382(4) and 1.934(3)–1.965(3) Å ranges, respectively (Figure a); these bond lengths are within the typical values for related copper­(II) compounds ,, and CPs of other metals derived from H 2 cpna . In 1 , cpna 2– acts as a μ 3 -N,O 2 spacer, with the carboxylate groups being monodentate (mode I, Scheme ).…”

A Comparative Study of Proton Conduction Between a 2D Zinc(II) MOF and Its Corresponding Organic Ligand

“…Zwitterionic-type ionic liquids are a class of attractive organic ligands in the assembly of MOFs with diverse structures and applications in catalysis, magnetism, optics, and so forth. − By contrast, it has been observed that studies on proton conductive MOFs based on zwitterionic-type ligands are extremely rare. ,, For example, by using an angular compound, 1,3-bis­(4-carboxyphenyl)­imidazolium (H 2 L1), Kitagawa et al successfully synthesized a 3D MOF, [{(Zn 0.25 ) 8 (O)}­Zn 6 (L1) 12 (H 2 O) 29 (DMF) 69 (NO 3 ) 2 ] n , in which protons from methylene groups of the imisdazolium units in each channel are transferred efficiently by H 2 O units in the cavity, resulting in a high σ value of 2.3 × 10 –3 S/cm at 95% RH and ambient temperature . Wang and co-workers described a cationic MOF, [Ce­(Cbp) 2 ]­Br 0.25 C l0.75 ·6H 2 O·2DMF, containing the zwitterionic-based ligand, 4-carboxy-1-(4-carboxybenzyl)­pyridinium bromide (H 2 Cbp), which can undergo rapid water-induced phase transformation into a new neutral MOF, [Ce­(Cbp) 3 (H 2 O) 3 ]·8H 2 O to attain an optimal σ value of 1.104 × 10 –4 S/cm under 90 °C and 95% RH .…”

Experimental and Theoretical Study of Dynamic Structural Transformations between Sensing Copper(II)-Uracil Antiferromagnetic and Metamagnetic Coordination Compounds

“…Small changes in the synthetic conditions (temperature, stoichiometry, or ratio between the solvents, among others) can be considered as stimuli, and the resulting structural changes are the answers to these stimuli. If the structural transformations are coupled with some concurrent detectable changes of their physical characteristics such as color, optical, electric, magnetic, and porous properties, they will be endowed with the potential as smart materials with sensing and switching functions …”