He-Dong Bian

Coordination assemblies of the CdII–BDC/bpt mixed-ligand system: positional isomeric effect, structural diversification and luminescent properties

To further systematically investigate the influence of the positional isomeric ligands on the structures and properties of transition metal complexes, we synthesized six Cd(II) complexes with three positional isomeric dipyridyl ligands (4,4′-bpt, 3,4′-bpt and 3,3′-bpt) and three positional isomeric phenyl dicarboxylate anions (p-BDC, m-BDC and o-BDC), namely, [Cd3(p-BDC)3(4,4′-bpt)2(H2O)5]·H2O (1), [Cd(p-HBDC)(p-BDC)0.5(3,4′-bpt)] (2), [Cd4(p-BDC)4(3,3′-bpt)4]·9H2O (3), [Cd(m-BDC)(3,3′-bpt)(H2O)]·2H2O (4), [Cd(o-BDC)(3,3′-bpt)(H2O)]·(3,3′-bpt)·4H2O (5), [Cd(o-BDC)(3,4′-bpt)(H2O)]·H2O (6). Structural analysis reveals that 1 is composed of a three dimensional (3D) 4-connected net giving an interesting 3-fold interpenetrating architecture. 2 and 3 possess a similar two dimensional (2D) layer structures. 4 presents an infinite one dimensional (1D) tubular-like chain. 5 displays a 2D honeycomb structure consisting of a 1D metal–organic helical chain. 6 exhibits a 2D wave-like layer structure with a (44)-sql network. Structural diversities indicate that the nature of isomeric benzene–dicarboxylates and bpt ligands plays crucial roles in modulating structures of these complexes. Intermolecular forces have important effects on the formation and strengthening of the supra-molecular architecture in these complexes. Moreover, the luminescent properties of them have been briefly investigated.

Synthesis, structures, and characterization of cadmium(II), cobalt(II), and copper(II) metal polymers with tetrazole-1-acetate

Three new coordination polymers {[Cd(tza)(2,2′-bpy)(H2O)](ClO4)} n 1, {[Co(tza)(2,2′-bpy)(H2O)](ClO4)} n 2, and {[Cu(tza)(phen)](ClO4)} n 3 (Htza = tetrazole-1-acetic acid, 2,2′-bpy = 2,2′-bipyridyl, phen = 1,10-phenanthroline) were synthesized and characterized by X-ray single-crystal diffraction, elemental analysis, and IR spectra. Complexes 1 and 2 exhibit 3-D architectures formed by π–π interaction of 2,2′-bpy ligands interlinking to the adjacent 2-D layers. Complex 3 is a 1-D zigzag double chain and the 3-D structure is formed by π–π stacking interaction of phen and nonclassical hydrogen bonding.

Co(II)/Ni(II) coordination polymers incorporated with a bent connector: crystal structures and magnetic properties

The hydrothermal reactions of a bent ligand, 1H-3,5-bis(4-pyridyl)-1,2,4-triazole (bpt), with Co/Ni(II) ions as well as a series of polycarboxylate co-ligands yielded five new coordination polymers, namely, {[Co2(fum)2(bpt)2(H2O)]·3H2O}n (1), {[Co(mal)(bpt)0.5(H2O)]·1.5H2O}n (2), {[Co2(bptc)(bpt)2(EtOH)(H2O)2]·2H2O}n (3), [Ni2(btc)(bpt)2(H2O)2]·6H2O (4), [Ni2(Hbidc)2(bpt)2]·7H2O (5) (here, H2fum = fumaric acid, H2mal = malonic acid, H4bptc = 3,3′,4,4′-benzophenone-tetracarboxylate acid, H4btc = 1,2,4,5-benzenetetracarboxylate acid, H3bidc = 1H-benzimidazole-5,6-dicarboxylic acid). These complexes exhibit different architectures and magnetic behaviors: 1 has a 3D (3,5)-connected (42·6)(42·65·83) topology, showing field-induced spin-flop transition; 2 and 3 both have a (3,4)-connected topology, exhibiting normal antiferromagnetism, with a 3D (63)(63·83) symbol for 2and a 2D (62·8)2(64·82) symbol for 3, respectively. In 4 and 5, the topological analysis results reveal that 4 can be simplified to a 3D 4-connected NbO net, while 5 is a 3D trinodal (3,4,6)-connected (63)(65·8)(612·8·102) net. Both 4 and 5 exhibit spin-canted antiferromagnetism.

New Coordination Polymers of Lanthanide(III) with Tetrazole-1-acetic Acid: Synthesis, Crystal Structures, and Magnetic Properties

New coordination polymers {[Ln(tza)3(H2O)2]·mH2O}n (Ln = LaIII 1 and PrIII 2, m = 2; Ln = NdIII 3, m = 1.5) and {[Sm2(tza)6(H2O)5]·H2O}n 4 (Htza = tetrazole-1-acetic acid) have been synthesized and characterized by IR spectroscopy, elemental analysis, X-ray crystallography, and magnetic measurements. The Htza ligand coordinates to the lanthanide cations through the carboxylate group in a monodentate, bridging bidentate coordination mode or bridging tridentate to two metal centres. Complexes 1 and 2 are isostructural. Complex 3 has a similar structure to 1 and 2, but the arrangement of ligands has changed. Complex 4 consists of two types of metallic molecules. Magnetic measurements show weak antiferromagnetic coupling between the metal centres in complexes 2 and 3.

Synthesis and structural characterization of 2D Zn(II), Cd(II), and Co(II) coordination polymers containing 3-chloro-1,2-benzenedicarboxylate and positional isomers of triazole-bipyridine

Three compounds, [Zn2L2(4,4′-bpt)2] n (1), [Cd2L2(3,4′-bpt)(H2O)2] n (2) and {[CoL(3,3′-bpt)(H2O)]∙H2O} n (3) (L = 3-Cl-1,2-benzenedicarboxylate dianion, 4,4′-bpt = 1H-3,5-bs(4-pyridyl)-1,2,4-itriazole, 3,4′-bpt = 1H-3-(3-pyridyl)-5-(4-pyridyl)-1,2,4-triazole and 3,3′-bpt = 1H-3,5-bis(3-pyridyl)-1,2,4-triazole), based on three positionally isomeric triazole-bipyridine ligands, were synthesized. Structural analyses of 1–3 reveal diverse 2-D network structures, which are based on different [ML] n (M = Zn, Cd, Co) chains. In the [ZnL] n chains of 1, the carboxylic groups of L connect the adjacent Zn(II) centers with a monodentate bridging coordination mode (μ2-η1  /  η1 ). In 2, [CdL] n is a double chain connected by the carboxylic groups of L with μ3-η1  /  η2/η2 and μ3-η1  /  η1  /  η2 bridges. The [CoL] n chains of 3 are formed by the carboxylic groups of L with the μ2-η1  /  η2 coordination mode. The powder X-ray diffraction and the thermal stability of 1–3, the luminescent properties of 1 and 2, and the magnetic behavior of 3 have been briefly investigated.

Coordination assemblies of CoII/NiII/MnII/ZnII with 1,1′-biphenyl-2,2′-dicarboxylic acid and three positional isomeric ligands: structural diversity and properties

Hydrothermal reactions of 1,1′-biphenyl-2,2′-dicarboxylic acid (H2dpa) with Co(II), Ni(II) Mn(II) and Zn(II) salts, and systematically varied N-donor co-ligands (positional isomeric dipyridyl bridging ligands: 4,4′-bpt, 3,4′-bpt and 3,3′-bpt), lead to the formation of a series of supramolecular complexes, namely, [Co(dpa)(4,4′-bpt)(EtOH)(H2O)] (1), [Ni(dpa)(4,4′-bpt)(H2O)2]·2.5H2O (2), [Cu(dpa)(4,4′-bpt)(H2O)]·2H2O (3), [M(dpa)(3,4′-bpt)]·H2O (M = Co for 4, Ni for 5, Mn for 6, and Zn for 7, respectively), [Zn3(OH)2(dpa)2 (3,3′-bpt)2]·2H2O (8) (where 4,4′-bpt = 1H-3,5-bis(4-pyridyl)-1,2,4-triazole, 3,4′-bpt = 1H-3-(3-pyridyl)-5-(4-pyridyl)-1,2,4-triazole and 3,3′-bpt = 1H-3,5-bis(3-pyridyl)-1,2,4-triazole). Structural analysis reveals that dpa manages the M(II) (M = Co, Ni, Mn and Zn) ions to form 1-D chains, which are further extended via the isomeric bpt connectors in different directions, to give rise to a variety of coordination polymers of 1–8. Magnetic susceptibilities of complexes 1–6 reveal the weak antiferromagnetic or ferromagnetic exchange interactions between the adjacent metal centers. Moreover, the luminescent properties of 7–8 have been briefly investigated.

Synthesis, crystal structures and magnetic properties of two new nickel(II) complexes with α-amino acid Schiff base

Two nickel(II) complexes [Ni(napgly)(MeOH)] n (1) and [Ni(napphe)(H2O)2(MeOH)] · H2O (2), where the tridentate Schiff-base ligands H2napgly and H2napphe are condensed from 2-hydroxyl-1-naphthaldehyde with glycine and L-phenylalanine, respectively, were prepared and structurally characterized. In 1, two inversion-related Ni(II) ions were bridged by two O atoms from the phenolate groups of two napgly anions, forming a centrosymmetric dimeric unit which was further linked by carboxylate groups to give a two-dimensional network. Magnetic susceptibility studies performed on the complex revealed anti-ferromagnetic coupling between the metal centers. In 2, the crystal structures of the complex displayed a distorted octahedral coordination geometry in which the ONO-donor Schiff base was bonded to the metal. Intermolecular H-bonds linked the compound into a 2-D layer structure.

Synthesis, characterization, DNA/protein interaction and cytotoxicity studies of Cu(II) and Co(II) complexes derived from dipyridyl triazole ligands

Four different transition metal complexes containing dipyridyl triazole ligands, namely [Cu(abpt)2Cl2]·2H2O (1), [Cu(abpt)2(ClO4)2] (2), [Co2(abpt)2(H2O)2Cl2]·Cl2·4H2O (3) and [Co2(Hbpt)2(CH3OH)2(NO3)2] (4) have been designed, synthesized and further structurally characterized by X-ray crystallography, ESI-MS, elemental analysis, IR and Raman spectroscopy. In these complexes, the both ligands act as bidentate ligands with N, N donors. DNA binding interactions with calf thymus DNA (ct-DNA) of the ligand and its complexes 1~4 were investigated via electronic absorption, fluorescence quenching, circular dichroism and viscosity measurements as well as confocal Laser Raman spectroscopy. The results show these complexes are able to bind to DNA via the non-covalent mode i.e. intercalation and groove binding or electrostatic interactions. The interactions with bovine serum albumin (BSA) were also studied using UV-Vis and fluorescence spectroscopic methods which indicated that fluorescence quenching of BSA by these compounds was the presence of both static and dynamic quenching. Moreover, the in vitro cytotoxic effects of the complexes against four cell lines SK-OV-3, HL-7702, BEL7404 and NCI-H460 showed the necessity of the coordination action on the biological properties on the respective complex and that all four complexes exhibited substantial cytotoxic activity.

Study on the structural changes of bovine serum albumin with effects on polydatin binding by a multitechnique approach.

Polydatin is a traditional Chinese medicine which shows effective biological activity as antimicrobial and antiviral agent. The secondary structure changes of bovine serum albumin (BSA) were investigated by the methods of Fourier transform infrared spectroscopy (FT-IR), circular dichroism (CD) and Raman spectroscopy. The experimental results indicated that polydatin changed the secondary structure of BSA. The presence of polydatin decreased α-helix content of BSA. The conformations of disulfide bridges and the microenvironment of Tyr, Trp residues were also changed.

Three CoII/CoIII complexes with a 1-substituted tetrazole-5-thiol ligand

1-Methyl-5-mercapto-tetrazole (mmtz) reacts with Co(II) salts in the presence of N-containing ligands and three CoII/CoIII complexes, [CoII(mmtz)2(4,4′-bipy)(H2O)2] n (1), [CoIII(mmtz)2(1,10-phen)2]NO3 (2), and [ (mmtz)2(2,2′-bipy)2(μ-OH)2]Cl2 (3), have been characterized using single-crystal X-ray diffraction structure determination, IR, and elemental analysis. Complex 1 has a 1-D polymeric structure with neutral [Co(mmtz)2(4,4′-bipy)(H2O)2] as repeating unit. These 1-D infinite chains are further connected into a 3-D supramolecular framework through intermolecular hydrogen bonds. In 2, mmtz is an S-bonding ligand to form a mononuclear structure. In 3, mmtz as a μ 2 bridging ligand links Co(III) ions to form a dimeric structure. Thermostability of 2 and 3 and electrochemical properties of 1–3 are discussed.