Ligand-Mediated Regulation of the Chemical/Thermal Stability and Catalytic Performance of Isostructural Cobalt(II) Coordination Polymers.

Regulating the chemical/thermal stability and catalytic activity of coordination polymers (CPs) to achieve high catalytic performance is topical and challenging. The CPs are competent in promoting oxidative cross-coupling, yet they have not received substantial attention. Here, the ligand effect of the secondary ligand of CPs for oxidative cross-coupling reactions was investigated. Specifically, four new isostructural CPs [Co(Fbtx)1.5(4-R-1,2-BDC)]n (denoted as Co-CP-R, Fbtx = 1,4-bis(1,2,4-triazole-1-ylmethyl)-2,3,5,6-tetrafluorobenzene, 4-R-1,2-BDC = 4-R-1,2-benzenedicarboxylate, R = F, Cl, Br, CF3) were prepared. It was found that in the reactions of oxidative amination of benzoxazoles with secondary amines and the oxidative coupling of styrenes with benzaldehydes, both the chemical and thermal stabilities of the four Co-CPs with the R group followed the trend of -CF3 > -Br > -Cl > -F. Density functional theory (DFT) calculations suggested that the difference in reactivity may be ascribed to the effect of substituent groups on the electron transition energy of the cobalt(II) center of these Co-CPs. These findings highlight the secondary ligand effect in regulating the stability and catalytic performance of coordination networks.

The crucial roles of guest water in a biocompatible coordination network in the catalytic ring-opening polymerization of cyclic esters: a new mechanistic perspective.

The ring-opening polymerization (ROP) of cyclic esters/carbonates is a crucial approach for the synthesis of biocompatible and biodegradable polyesters. Even though numerous efficient ROP catalysts have been well established, their toxicity heavily limits the biomedical applications of polyester products. To solve the toxicity issues relating to ROP catalysts, we report herein a biocompatible coordination network, CZU-1, consisting of Zn4(µ4-O)(COO)6 secondary building units (SBUs), biomedicine-relevant organic linkers and guest water, which demonstrates high potential for use in the catalytic ROP synthesis of biomedicine-applicable polyesters. Both experimental and computational results reveal that the guest water in CZU-1 plays crucial roles in the activation of the Zn4(µ4-O)(COO)6 SBUs by generating µ4-OH Brønsted acid centers and Zn-OH Lewis acid centers, having a synergistic effect on the catalytic ROP of cyclic esters. Different to the mechanism reported in the literature, we propose a new reaction pathway for the catalytic ROP reaction, which has been confirmed using density functional theory (DFT) calculations, in situ diffuse reflectance IR Fourier transform spectroscopy (DRIFTS), and matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy (MALDI-TOF MS). Additionally, the hydroxyl end groups allow the polyester products to be easily post-modified with different functional moieties to tune their properties for practical applications. We particularly expect that the proposed catalytic ROP mechanism and the developed catalyst design principle will be generally applicable for the controlled synthesis of biomedicine-applicable polymeric materials.

Assembly of 1D, 2D and 3D lanthanum(iii) coordination polymers with perchlorinated benzenedicarboxylates: positional isomeric effect, structural transformation and ring-opening polymerisation of glycolide.

Utilizing a series of positional isomers of tetrachlorinated benzenedicarboxylic acid ligands, seven La(iii)-based coordination polymers were solvothermally synthesized and structurally characterized. Their structural dimensionalities varying from 1D double chains, to the 2D 3,4,5-connected network, to 3D 6-connected pcu topological nets are only governed by the positions of carboxyl groups on the tetrachlorinated benzene ring. A comprehensive analysis and comparison reveals that the size of the carbonyl solvent molecules (DMF, DEF, DMA, and NMP) can affect the coordination geometries around the La(iii) ions, the coordination modes of carboxylate groups, the packing arrangements, and the void volumes of the overall crystal lattices. One as-synthesized framework further shows an unprecedented structural transformation from a 3D 6-connected network to a 3D 4,5-connected net through the dissolution and reformation pathway in water, suggesting that these easily hydrolyzed lanthanide complexes may serve as precursors to produce new high-dimensional frameworks. The bulk solvent-free melt polymerisation of glycolide utilizing these La(iii) complexes as initiators has been reported herein for the first time. All complexes were found to promote the polymerization of glycolide over a temperature range of 200 to 220 °C, producing poly(glycolic acid) (PGA) with a molecular weight up to 93,280. Under the same experimental conditions, the different catalytic activities for these complexes may result from their structural discrepancy.

Fluorinated metal-organic frameworks of 1,4-bis(1,2,4-triazol-1-ylmethyl)-2,3,5,6-tetrafluorobenzene: synergistic interactions of ligand isomerism and counteranions.

A fluorinated bis(triazole) ligand, 1,4-bis(1,2,4-triazol-1-ylmethyl)-2,3,5,6-tetrafluorobenzene (Fbtz), was applied to coordinate with a series of Mn(II), Co(II), Fe(II), and Cu(II) ions, respectively. In comparison with its nonfluorinated analogue 1,4-bis(1,2,4-triazol-1-ylmethyl)benzene (btx), Fbtz is able to build six novel metal-organic frameworks by acting as a versatile bridge combining with the terminal chlorides (1-5) or acetates (6) ligands. The solid-state crystal structures of 1-6 are studied by single-crystal X-ray crystallography to form the following structures: 3D polymers [M(Fbtz)2Cl2]n (1: M = Mn, 2: M = Co), 1D double chain polymers {[M(Fbtz)2Cl2]·CH2Cl2·xH2O}n (3: M = Co, x = 1; 4: M = Fe, x = 2), {[Cu(Fbtz)2Cl2]·4H2O}n (5), and a 1D double-stranded helical polymer {[Cu2(Fbtz)(OAc)2]·2H2O}n (6). Conformations of Fbtz in 1-6 can be tuned as a result of varying the anions or solvent system, which ultimately form a series of novel coordination frameworks with different supramolecular architectures. The antibacterial activities of all complexes are investigated. Complexes 4 and 5 show a wide range of bactericidal activities to Gram positive (B. subtilis and S. aureus) and negative (E. coli and P. fluorescence) bacterial strains. The synergistic interactions of ligand isomerism and counteranions have profound effects on the supramolecular networks and properties.

An efficient strategy to achieve hydrophilic polymeric silver(I) materials with exceptional antibacterial activity.

Three isomeric water-soluble and light-stable silver(I) coordination polymers with a fluorinated carboxylate ligand were prepared by template-controlled method, which show different 2D polymeric coordination structures with a novel layered inorganic connectivity in the solid state. In water solution, they dissociate into several stable polynuclear silver(I) oligomers and exhibit extraordinary antimicrobial activities against selected bacteria.

Redetermination of 2,4'-methyl-ene-diphenol.

In the previous determination [Finn & Musti (1950 ▶). J. Soc. Chem. Ind. (London), 69, S849] of the title compound, C(13)H(12)O(2), the three-dimensional coordinates and displacement parameters were not reported. This redetermination at room temperature reveals that the dihedral angle between the benzene rings is 79.73 (6)°. In the crystal, inter-molecular O-H⋯O hydrogen bonds between adjacent mol-ecules result in two-dimensional wave-like supra-molecular motifs parallel to the ab plane.

Unique Zn(II) coordination entanglement networks with a flexible fluorinated bis-pyridinecarboxamide tecton and benzenedicarboxylates.

Entangled nets in coordination compounds with both self-penetrating and interpenetrating structural features have been first constructed by using a flexible bis-pyridinecarboxamide and isophthalate or 5-methylisophthalate. Distinct entangled systems showing both 3-fold interpenetration and polyrotaxane can also be obtained by altering the 5-substituents of isophthalate.

4,4'-Methylenediphenol-4,4'-bipyridine (2/3): decarboxylation of 5,5'-methylenedisalicylic acid under hydrothermal conditions.

Reaction of 5,5'-methylenedisalicylic acid (5,5'-H(4)mdsa) with 4,4'-bipyridine (4,4'-bipy) and manganese(II) acetate under hydrothermal conditions led to the unexpected 2:3 binary cocrystal 4,4'-methylenediphenol-4,4'-bipyridine (2/3), C(13)H(12)O(2).1.5C(10)H(8)N(2) or (4,4'-H(2)dhdp)(4,4'-bipy)(1.5), which is formed with a concomitant decarboxylation. The asymmetric unit contains one and a half 4,4'-bipy molecules, one of which straddles a centre of inversion, and one 4,4'-H(2)dhdp molecule. O-H...N interactions between the hydroxy and pyridyl groups lead to a discrete ribbon motif with an unusual 2:3 stoichiometric ratio of strong hydrogen-bonding donors and acceptors. One of the pyridyl N-atom donors is not involved in hydrogen-bond formation. Additional weak C-H...O interactions between 4,4'-bipy and 4,4'-H(2)dhdp molecules complete a two-dimensional bilayer supramolecular structure.