Coordination Geometry Of Metal Center Research Articles

Eight new coordination polymers containing rigid 4-(4-carboxy-phenyl)-pyridine-2-carboxylic acid: Synthesis, structural diversity, fluorescence and magnetic properties

Eight new coordination polymers (CPs) were successfully synthesized through the solvo-thermal reactions of H2cppc ligand and a series of transition metal salts, [M(cppc)(H2O)2]n [M = Co, (1); Ni, (2); Zn, (3); Cd, (4)], [M(Hcppc)2]n [M = Cd, (5); Mn, (6); Cu, (7)], [Pb(cppc)(H2O)]n (8), [H2cppc = 4-(4-carboxy-phenyl)-pyridine-2-carboxylic acid]. These compounds were all characterized by elemental analysis, IR spectra, single-crystal X-ray diffraction, powder X-ray diffraction and thermal analysis. Compounds 1–4 have similar molecular formula except for different metal centers, notably, compounds 1–3 with isomorphic frameworks display two-dimensional layer structure, in which contain left- and right-handed chiral chains constructed from M2(H2O)2 dimers and cppc2− anions. However, compound 4 exhibits a three-dimensional network with Cd-O-Cd inorganic chains, different from that of compounds 1–3. Compounds 5–7 also have similar molecular formula except for different metal centers, the isomorphic compounds 5 and 6 exhibit two-dimensional undulating layers, while compound 7 displays one-dimensional chain. Compound 8 is a 2D layer structure with Pb2O2 secondary building units. In general, coordination geometries of metal centers and coordination modes of the ligands have an important effect on the structures of targeted compounds. Fluorescent experiments indicate that compounds 3–5 and 8 display apparently blue light emission in the solid state. Magnetic properties of compounds 1, 2, 6 and 7 are also investigated.

Metal-controlled structural diversity in Co(II) and Zn(II) complexes with mixed N- and O-donors: Synthesis, characterization and property

Abstract Co(II) and Zn(II) complexes based on 1-(5-tetrazolyl)-4-(1-imidazolyl)benzene (HL) and 1,4-benzenedicarboxylic acid (H 2 pbda): [Co 2 (L) 2 (pbda)(H 2 O) 3 ] ( 1 ) and [Zn(L)(pbda) 0.5 ] ( 2 ) have been prepared under hydrothermal conditions and characterized by single crystal and powder X-ray diffractions, IR, and thermogravimetric analysis. Complex 1 exhibits binodal (3,5)-connected 2D net structure with (3.5 2 )(3 2 .5 3 .6 4 .7) topology; while 2 is a binodal (3,4)-connected 2-fold interpenetrating 3D framework with dmc (4.8 2 )(4.8 5 ) topology. The influence of coordination geometries of metal centers on the structures of resultant complexes is discussed. Moreover, magnetic property of 1 and luminescence of 2 were investigated.

Conformational isomerism and hydrogen-bonded motifs of anion assisted supramolecular self-assemblies using Cu II/Co II salts and pyridine-4-acetamide

Six novel metal–organic complex assemblies constructed from a conformation-flexible ligand – pyridine-4-acetamide (PAT) and inorganic Cu II and Co II salts have been synthesized and structurally characterized by single crystal X-ray diffraction analysis. Crystal structure analysis reveals five types of architectures by variation of metal salts. In {[Cu(PAT) 2Cl 2]} n ( 1) and {[Co(PAT) 2Cl 2]} n ( 3), PAT ligands bridge metal centers to form one-dimensional chains. The chains are extended to three dimensions with the aid of two types of hydrogen bonded motifs ( R 4 2 ( 8 ) ) and R 2 2 (12)). {[Cu(PAT) 2(NO 3)](NO 3)(THF)} n ( 5) which exhibits two-dimensional coordinating layers forms open channels filled with solvent molecules. In [Cu(PAT) 2Cl 2] ( 2), [Co(PAT) 2Cl 2] ( 4) and [Co(PAT) 4(H 2O) 2](NO 3) 2(THF) 2 ( 6), PAT is observed as a monofunctional ligand. Complex 2 forms one-dimensional hydrogen bonded chains. Crystal structure of complex 4 has a two-dimensional infinite hydrogen-bonded network with R 4 2 ( 8 ) and R 2 2 ( 8 ) motifs formed by complementary amide–amide hydrogen bonds. [Co(PAT) 4(H 2O) 2](NO 3) 2(THF) 2 ( 6) crystallizes in centrosymmetric I4 1/ a space group. Complex 6 forms chiral channels which are filled with twisted solvent helices and anion helices. Within each channel the solvent helix and the anion helix have the same handedness; and adjacent channels have opposite handedness. Complexes 1, 2 and complexes 3, 4 illustrate examples of conformational supramolecular isomerism in {[Cu(PAT) 2Cl 2]} ∞ and {[Co(PAT) 2Cl 2]} ∞ , respectively. In these complexes, changes of PAT conformations and coordination geometry of metal center induced the structural versatility.

Folding of Coordination Polymers into Double-Stranded Helical Organization

Self-assembling coordination polymers based on Pd II and Cu II metal ions were prepared from complexation of a bent-shaped bispyridine ligand and a corresponding transition metal. These coordination polymers were observed to self-assemble into supramolecular structures that differ significantly depending on the coordination geometry of the metal center. The polymer based on Pd II self-assembles into a layer structure formed by bridging bispyridine ligands connected in a trans-position of the square-planar coordination geometry of metal center. In contrast, the polymer based on Cu II adopts a double-helical conformation with regular grooves, driven by interstranded, copper-chloride dimeric interaction. The double-stranded helical organization is further confirmed by structure optimization from density functional theory with aromatic framework, showing that the optimized double-helical structure is energetically favorable and consistent with the experimental results. These results demonstrate that weak metal-ligand bridging interactions can provide a useful strategy to construct stable double-stranded helical nanotubes.

D10-Metal coordination polymers based on analogue di(pyridyl)imidazole derivatives and 4,4′-oxydibenzoic acid: influence of flexible and angular characters of neutral ligands on structural diversity

A series of mixed-ligand coordination complexes, namely [Zn(L(1))(oba)] (), [Cd(L(1))(oba)] (), [Zn(2)(L(2))(oba)(2)].8H(2)O (), [Cd(2)(L(2))(oba)(2)].2H(2)O (), [Zn(3)(L(3))(oba)(3)] (), [Cd(2)(L(3))(oba)(2)].(L(3)) (), [Cd(L(4))(oba)].H(2)O () and [Cd(L(5))(oba)].3H(2)O (), where L(1) = 2-(2-pyridyl)imidazole, L(2) = 1,4-bis[2-(2-pyridyl)imidazol-1-yl]butane, L(3) = 1,4-bis[2-(2-pyridyl)imidazol-1-ylmethyl]benzene, L(4) = 1,3-bis[2-(2-pyridyl)imidazol-1-ylmethyl]benzene, L(5) = 1,2-bis[2-(2-pyridyl)imidazol-1-ylmethyl]benzene and H(2)oba = 4,4'-oxydibenzoic acid, have been synthesized under hydrothermal conditions. Their structures have been determined by single crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectra, and thermogravimetric (TG) analyses. In compounds and , oba(2-), L(1) ligand and Zn(II) or Cd(II) ions assemble to form the parallel chains or parallel sheets which are linked by the weak hydrogen bonding and pipi stacking interactions to give the 2D supramolecular sheet or 3D supramolecular net, respectively. For , L(2) ligands connect [Zn(oba)] chains to generate a unusual (10,3)-b topological structure which is the first example for eight-fold interpenetrating framework based on the (10,3)-b net. In , L(2) ligands link [Cd(oba)] double-chains to give a 2D sheet which is assembled by pipi stacking interactions to obtain a 3D supramolecular net. In , L(3) ligands link Zn(II) ions from alpha-Po net formed by Zn(II) ions and oba(2-) anions to show a novel 3D 8-connected self-penetrating framework with the unreported (4(16).6(11).8) topological structure. In , the double-chains constructed by Cd(II) and oba(2-) anions are linked by one kind of L(3) ligand to form a layer-like structure which is assembled by pipi stacking interactions to show a 3D supramolecular structure. In , oba(2-) anions coordinate to Cd(II) cations to form chains which are connected by L(4) to form a four-fold interpenetrating diamond network. In , the weak hydrogen bonding and pipi stacking interactions connect the [Cd(L(5))(oba)] chains to give a 2D supramolecular sheet. By careful inspections of the structures of , we believe that the different flexible and angular neutral ligands, coordination geometries of metal centers and weak interactions (hydrogen bonds and pipi stacking interactions) are crucial factors for the formation of the different structures. The photoluminescent properties of have been studied in the solid state at room temperature.

Syntheses and Characterizations of Coordination Polymers Constructed from 4-Pyridylacetic Acid

Assembly of 4-pyridylacetic acid hydrochloride (Hpya·HCl) and Zn(CH3COO)2·2H2O, 3CdSO4·8H2O, or MnCl2·4H2O gave rise to five polymeric complexes {[Zn(C7H6NO2)2]·7H2O}n (1), [trans-M(C7H6NO2)2(H2O)2]n (M = Zn, 2; Cd, 3; Mn, 5), and [cis-Cd(C7H6NO2)2(H2O)2]n (4), respectively. X-ray diffraction analyses reveal that complex 1 has a two-dimensional (2D) framework comprising rhombic grids of cavity dimensions 13.965 × 12.475 Å, and the structure is extended into a three-dimensional network with large unique quasi-aperture by hydrogen bond and π−π stacking interactions. Complexes 2, 3, and 5 possess a 2D structure consisting of alternate left and right helical chains with rhombic grids of dimensions 15.933 × 5.692, 16.445 × 5.834, and 16.179 × 5.706 Å, respectively. Complex 4 has a 2D network constructed by right helical chains. Different crystallization conditions result in different coordination geometries of metal centers in zinc (1 and 2) and cadmium complexes (3 and 4). Thermogravimetric analyses of the complexes were performed.

Functional Micropore Chemistry of Crystalline Metal Complex-Assembled Compounds

Abstract Syntheses of new porous frameworks with specific pore size and type are of considerable interest for the appearance of zeolite-like functionalities. It is useful to take advantage of metal complex-assembled compounds because of designable frameworks, high microporosity, and flexible frameworks based on a variety of coordination geometries of metal centers and multifunctionality of bridging organic parts. Many recent reports show that the synthesis procedures are developing from serendipitious to rational level. Therefore, the micropore chemistry of metal complex-based assemblages is directed toward not only new frameworks but also functionalities such as gas and small molecule adsorption, ion exchange, heterogeneous catalysis, photo-chemical and -physical properties. For chemical and physical functionalities robustness of a framework is required even in the absence of guest molecules in the cavity. The stability is largely dependent on the structural dimensionality of the assemblages. A wide variety of structures of metal complex-based assemblages are listed and recent findings in this functional chemistry are described.