Guang-Juan Xu

Construction and property investigation of transition-metal complexes modified octamolybdate hybrid materials based on V-shaped organic ligands

Six new transition-metal complexes modified octamolybdate compounds have been successfully synthesized with two kinds of V-shaped flexible organic ligands under hydrothermal conditions, namely, [CuII(HL1)2(H2O)2(Mo8O26)] (1), [CuII(L1)2(Mo8O26)0.5] (2), [CuII(HL2)2(Mo8O26)]·2H2O (3), [CuII2(L2)4(Mo8O26)]·3H2O (4), [CuI3(L2)2(Mo8O26)0.5Cl] (5), [CuI4(L2)4(Mo8O26)] (6) where L1 = 3-((1H-imidazol-1-yl)methyl)pyridine, L2 = 3-((1H-1,2,4-triazol-1-yl)methyl)pyridine. Their crystal structures have been determined by X-ray single-crystal diffraction, elemental analyses, IR spectra, and thermogravimetric analyses (TGA). With L1 ligand, two compounds were obtained: compound 1 is a 1D β-octamolybdate based chain and compound 2 is a 2D 4-connected network most strikingly, whose octamolybdate anion shows a θ-isomer. With L2 ligand, compounds 3, 4, 5 and 6 were obtained, respectively. In compound 3, 1D β-octamolybdate-based metal–organic chains are further extended by hydrogen bonds to build a 3D supramolecular structure, while in compound 4, every two adjacent double-helical metal–organic chains are bridged by β-octamolybdate anions to generate a 2D 3-connected network. When CuSO4·5H2O was substituted by CuCl, two CuI compounds were attained. Interestingly, in compound 5 the octamolybdate anion threads through the metal–organic loop presenting a fascinating 2D polythreading topology, and in compound 6 the octamolybdate anions pillar the railroad-like metal–organic strands to generate a 2D 3-connected network. The structural differences among compounds 1–6 indicate the importance of the different coordination mode of organic ligands and various polyoxoanions, and of the pH values of the systems for the framework formation. Furthermore, the semiconducting properties of compounds 1–5 were investigated, and photoluminescence as well as photoconductivity for compound 5 were also studied. Compound 5 has a comparatively lower band gap and is photoconductive in the UV-vis range, so it can be potentially applied as a semiconductor of photoelectronic detectors.

pH-dependent self-assembly of divalent metals with a new ligand containing polycarboxylate: syntheses, crystal structures, luminescent and magnetic properties

Six new coordination polymers, namely, [Cd(HL)(4,4′-bpy)(H2O)]·H2O (1), [Cd3(L)2(4,4′-bpy)3(H2O)]·2.5H2O (2), [Co(HL)(4,4′-bpy)]·H2O (3), [Co2(L)(4,4′-bpy)0.5(μ3-OH)(H2O)2]·H2O (4), [Zn(HL)(BIMB)]·2H2O (5), [Zn3(L)2(BIMB)2]·3H2O (6), where H3L = 5-(4-carboxybenzyloxy)isophthalic acid, 4,4′-bpy = 4,4′-bipyridine, BIMB = 1,4-di(1H-imidazol-1-yl)benzene, have been synthesized under hydrothermal conditions and characterized by single crystal X-ray diffraction. In complexes 1, 3 and 5, H3L ligand is partially deprotonated in the form of HL2−; while in 2, 4 and 6, it is completely deprotonated due to the influence of different pH values. Complexes 1 and 5 are 2D layer structures, the hydrogen bonds between lattice-water molecules and carboxylate groups of HL2− ligands extend the 2D layer into a 3D framework; while complex 3 is a 3D framework with α-Po topology. Complex 2 is a 3D fourfold interpenetrating (3,4,4)-connected net with (63)(62·84)(64·82) topology. Complex 4 is a twofold interpenetrating (3,8)-connected net with (43)2(46·618·84) topology. And complex 6 is a twofold interpenetrating (3,4,6)-connected net with (4·62)(64·72)(42·66·74·8·92) topology. In addition, powder X-ray diffraction and thermogravimetric analyses for 1–6, photoluminescent properties for 1, 2, 5, 6 and magnetic properties for 3, 4 are investigated in detail.

Three novel 3D (3,8)-connected metal–organic frameworks constructed from flexible-rigid mixed ligands

Three novel 3D (3,8)-connected networks, namely [Cd2(L1)2(1,3-bdc)] 1, [Cd2(L2)2(1,4-bdc)]·3H2O 2 and [Cd3(L3)2(1,3-bdc)2] 3, where L1 = 3,5-bis(pyridin-4-ylmethoxy)benzoic acid, L2 = 3,4-bis(pyridin-4-ylmethoxy)benzoic acid, L3 = 3,5-bis(pyridin-3-ylmethoxy)benzoic acid, bdc = benzenedicarboxylate, have been synthesized hydrothermally and characterized. Complex 1 exhibits a twofold interpenetrating network constructed from Cd2-based secondary building units (SBUs) [Cd2(CO2)2O2N4] with (42·6)2(44·622·82) topology. Complex 2 is constructed from Cd2-based SBUs [Cd2(CO2)4N4] with (43)2(46·618·84) topology. The structure of 3 is based on linear Cd3-based SBUs [Cd3(CO2)6N2] with a Schlafli symbol (42·5)2(44·56·610·75·82·9). In addition, X-ray powder diffraction (XRPD) and luminescent properties of 1–3 were also investigated in detail.

Anion-directed genuine meso-helical supramolecular isomers of two 1D Ag(I) complexes based on arene-linked bis(pyrazolyl)methane ligands

Two genuine supramolecular isomers (Lp = p-[CH(pz)2]2C6H4), have been successfully obtained under similar solvothermal conditions by the reaction of arene-linked p-bis[bis(1-pyrazolyl)methyl]benzene ligand with AgNO3. Both of the compounds are made of unusual meso-helical chains and present a three-dimensional (3D) supramolecular structure. Compounds 1 and 2 were characterized by elemental analyses, IR spectra, single-crystal X-ray diffraction and thermogravimetric (TG) analyses. The fluorescence property of them has also been studied.

Two new metal-organic frameworks possessing binodal high-connected topologies based on Cd4-clusters and organic ligands

Two new compounds, [Cd2(bptc)(bpimb)(H2O)] · 2H2O (1) and [Cd2(bptc)(bpib)] · 4H2O (2) (where H4bptc = biphenyl-3,3′,4,4′-tetracarboxylic acid, bpimb = 1,3-bis((2-(pyridin-2-yl)-1H-imidazol-1-yl)methyl)benzene, bpib = 1,4-bis(2-(pyridin-2-yl)-1H-imidazol-1-yl)butane), were synthesized by reactions of the corresponding metal salts with H4bptc and N-containing auxiliary ligands and their structures have been determined by single-crystal X-ray diffraction. Compound 1 is built by Cd4-clusters which further construct a 3-D (3,8)-connected framework with tfz-d notation; 2, also built by Cd4-clusters, is a 3-D (4,8)-connected framework with (32 · 42 · 52)(34 · 48 · 512 · 64) topology. In addition, the elemental analyses, infrared spectra, fluorescence, and thermogravimetric analyses for 1 and 2 are discussed.

A new luminescent 3-D metal-organic framework of diamond-like network possessing 8-fold interpenetration

A new 3-D coordination polymer [Zn(L)2] (1) (HL = 4-(pyridin-4-ylmethoxy)benzolic acid) was synthesized under hydrothermal conditions with Zn(OAc)2 · 2H2O and HL and characterized by single crystal X-ray diffraction (XRD). Compound 1 displays a 3-D 8-fold interpenetrating structure with diamondoid framework containing large adamantanoid cages. Meanwhile, it exhibits intense fluorescence at 402 nm in the solid state. In addition, powder XRD and thermogravimetric (TG) analysis for 1 are also reported.