Han-Zhong Zhang

Construction of two interpenetrating coordination networks based on 4,4′-bis(1H-imidazol-1-yl-methyl)biphenyl and effect of carboxylic acids

To investigate the construction of interpenetrating coordination networks and the effect of ligands, [Zn(bimb)(bdc)]·H2O (1) and [Zn(bimb)(Hbtc)]·H2O (2) [bimb = 4,4′-bis(1H-imidazol-1-yl-methyl)biphenyl; H2bdc = 1,2-benzenedicarboxylic acid; H3btc = 1,3,5-benzenetricarboxylic acid] were hydrothermally synthesized and characterized by elemental analysis, IR spectra, Powder X-ray diffraction, and thermogravimetric analysis. Complex 1 shows a 3-D uoc type topology with twofold interpenetration. However, 2 exhibits a different 2-D self-penetrating network owing to hydrogen bonds of Hbtc between the two interpenetrating sql sheets, indicating that different carboxylic ligands could affect the interpenetration structures. Photoluminescence of bimb and the two complexes are also studied. Graphical Abstract Effect of H2bdc and H3btc as different mixed ligand on the structures of zinc coordination polymers based on bimb.

Ligand-induced isomerization: from 3D to 2D→3D POMOFs constructed from silicotungstate anions, Cu(I) and 1,n-di(4H-1,2,4-triazol-4-yl)benzene (n = 3, 4) ligands

Two novel POMOFs, [Cu4(1,3-dtzb)4(SiW12O40)]n (1) and [Cu4(1,4-dtzb)4(SiW12O40)]n (2), based on Keggin-type polyoxometalates have been hydrothermally synthesized by altering organic ligands {1,n-di(4H-1,2,4-triazol-4-yl)benzene: n = 3 (1,3-dtzb) and 4 (1,4-dtzb)}. In POMOF 1 constructed from the V-shaped 1,3-dtzb meta-ligand, the ligands link the Cu(I) ions to form a 20-member metallomacrocycle with [Cu2(1,3-dtzb)2] as the SBU, four of which assemble into a cage-like [Cu2(1,3-dtzb)2]4 motif to embed the POM anion, resulting in a 3D POMOF showing a new type of topological structure with a point symbol of {4·53·72}{52·8}. However, when the ligand is changed to the 1,4-dtzb straight para-ligand, POMOF 2 with a different structure is achieved. The ligands link the Cu(I) ions into a basic 3,3-connected net, and then the POM anions insert into the space between two adjacent nets to form a POM-pillared double-layer framework. The large cavities of the POM-pillared double layers allow the occurrence of an interpenetrated 2D→3D framework. The cyclic voltammetric behavior and photocatalytic properties of POMOFs 1 and 2 were also investigated.

A pair of novel Zn(II) enantiomeric coordination polymers based on a chiral multicarboxylate ligand: synthesis, crystal structures and molecular recognition properties

A pair of Zn(II) enantiomeric coordination polymers, 1-R and 1-S, namely, [Zn4((R)-H3L)2(OH)2(H2O)2]·3H2O {H3L= (R)- or (S)-5-(1-carboxyethoxymethyl)-isophthalic acid}, were synthesized via solvothermal reactions. Their structures were determined by single-crystal X-ray diffraction analysis and further characterized by IR spectra, elemental analyses, thermogravimetric analysis (TGA), solid-state circular dichroism (CD) and powder X-ray diffraction (PXRD). The pair of enantiomers crystallized in the same chiral space group, featuring a 3,6-c net and kgd topological type structure with a point symbol of (43)2(46·66·83). Their CD spectra exhibit obvious positive or negative Cotton effects, indicating their homochirality. 1-R and 1-S also proved to be second-harmonic generation (SHG) active. Moreover, their fluorescent selective recognition towards nitro aromatic compounds and metal cations were also investigated.

Five Co(II) coordination polymers with different counter anions based on [3,5-di(4H-1,2,4-triazol-4-yl)benzoato]− ligand: directed synthesis, structures and magnetic properties

As a continuing challenge to obtain the desired coordination polymers in the synthesis stage, the counter ions, the metal–ligand ratio and the involvement of template have great impact on their structure construction and crystal growth. In this paper, three different crystals of coordination polymers 1–3 {{[CoL(μ2-OH)]}n (1), {[CoL2(H2O)]·H2O}n (2), {[Co3L3(H2O)]·3NO3·4H2O}n (3)} {L = [3,5-di(4H-1,2,4-triazol-4-yl)benzoate]−} were obtained in one pot with HL and Co(NO3)2. By tuning the reactants ratio and employing different templates, each complex could also be synthesized separately. Single-crystal X-ray analyses show that complex 1 exhibited a two-dimensional (2D) layered gek2 net structure. Complex 2 with deprotonated [L]− has two dimensional (2D) nets structure with 3,5L66 topology. Complex 3 displays a new 5,5,6,6-connected three-dimensional (3D) topological network with a point symbol of (410·65)(45·65)2(47·63)2(48·67). When the reactant Co(NO3)2 was changed to CoCl2 or CoSO4, 4 and 5 {{[CoL(Cl)]·H2O}n (4) and {[Co2L2(SO4)(H2O)]·2H2O}n (5)} was formed with a similar structure to that of 1. Complexes 4 and 5 are two-dimensional (2D) frameworks with 4,6L26 topology. Five complexes have been characterized by elemental analysis, infrared spectroscopy, powder X-ray diffraction and thermogravimetry measurements. The magnetic properties of 1–5 are also investigated. The magnetic property investigation reveals that complex 1 exhibits frequency-dependent behavior.