Coordination Polymers from an Amino-Functionalized Terphenyl-Tetracarboxylate Linker: Structural Multiplicity and Catalytic Properties.

An amino-functionalized terphenyl-tetracarboxylic acid, 2'-amino-[1,1':4',1″-terphenyl]-3,3″,5,5″-tetracarboxylic acid (H4tpta), was used as an adaptable linker to synthesize, under hydrothermal conditions, eight coordination polymers (CPs). The obtained products were formulated as [Co(µ6-H2tpta)]n (1), [Co(µ3-H2tpta)(2,2'-bipy)]n (2), [M3(µ6-Htpta)2(2,2'-bipy)2]n (M = Mn (3), Cd (4)), [Ni2(µ4-tpta)(phen)2(H2O)4]n (5), [Zn2(µ6-tpta)(phen)2]n (6), {[Zn2(µ6-tpta)(µ-4,4'-bipy)]·H2O}n (7), and [Zn2(µ6-tpta)(µ-H2biim)(H2O)2]n (8), wherein 2,2'-bipyridine (2,2'-bipy), 4,4'-bipyridine (4,4'-bipy), 1,10-phenanthroline (phen), or 2,2'-biimidazole (H2biim) are present as additional stabilizing ligands. The structural types of 1-8 vary from one-dimensional (1D) (2, 5) and two-dimensional (2D) (3, 4, 6) CPs to three-dimensional (3D) metal-organic frameworks (MOFs) (1, 7, and 8) with a diversity of topologies. The products 1-8 were investigated as catalysts in the Knoevenagel condensation involving aldehydes and active methylene derivatives (malononitrile, ethyl cyanoacetate, or tert-butyl cyanoacetate), leading to high condensation product yields (up to 99%) under optimized conditions. Various reaction conditions, substrate scope, and catalyst recycling were investigated. This work broadens the application of H4tpta as a versatile tetracarboxylate linker for the generation of diverse CPs/MOFs.

A new series of Co, Ni, Zn, and Cd metal-organic architectures driven by an unsymmetrical biphenyl-tricarboxylic acid: hydrothermal assembly, structural features and properties.

This study reports the hydrothermal synthesis of a novel series of twelve coordination compounds, namely, {[Cd(µ-Hnbtc)(H2O)4]·H2O}n (1), [Zn2(µ-Hnbtc)2(phen)2]·2H2O (2), [Zn(Hnbtc)(phen)2(H2O)]·4.5H2O (3), [Ni(Hnbtc)(phen)2(H2O)]·6H2O (4), [Zn2(µ-Hnbtc)2(2,2'-bipy)2]·2H2O (5), [Cd3(µ5-nbtc)(µ6-nbtc)(2,2'-bipy)2(H2O)]n (6), {[Zn3(µ3-nbtc)2(phen)3(H2O)2]·4H2O} (7), [Co(H2O)6][Co2(nbtc)2(µ-4,4'-bipy)(4,4'-bipy)2(H2O)6]·8H2O (8), {[Ni3(µ4-nbtc)2(µ-4,4'-bipy)2.5(µ-H2O)(H2O)3]·4H2O}n (9), {[Cd2(µ4-nbtc)(µ-OH)(2,2'-bipy)2]·H2O}n (10), [Cd2(µ4-nbtc)(µ-OH)(phen)2(H2O)]n (11), and {[Zn2(µ5-nbtc)(µ3-OH)(µ-4,4'-bipy)]·4,4'-bipy·H2O}n (12), which are derived from 3'-nitro-biphenyl-2,4,4'-tricarboxylic acid (H3nbtc) as a virtually unexplored building block. These compounds were generated in aqueous medium from the corresponding metal(ii) chlorides as a metal source, H3nbtc as a principal building block, NaOH as a base, and simple N,N-donor aromatic ligands as crystallization mediators (i.e., 1,10-phenanthroline, phen; 2,2'-bipyridine, 2,2'-bipy; or 4,4'-bipyridine, 4,4'-bipy). All products 1-12 were completely characterized in the solid state by IR spectroscopy, elemental and thermogravimetric (TGA) analyses, powder (PXRD) and single-crystal X-ray diffraction. Structures of 1-12 range from discrete 0D dimers (2 and 5) or monomers (3, 4, and 8) to 1D coordination polymers (CPs, 1, 6, 7, 10, and 11) and 3D metal-organic frameworks (MOFs, 9 and 12). A broad structural diversity of 1-12 is guided by the type of the metal(ii) node, the molar ratio between H3nbtc and sodium hydroxide, and the kind of crystallization mediator. Topological analysis and classification of metal-organic underlying nets was made, disclosing the following topological types: 2C1 (in 1 and 7), 1M2-1 (in 2 and 5), SP1-periodic net (in 10 and 11), tfz-d (in 12), and some topologically unique nets (in 6 and 9). Luminescence behavior of 1-3, 5-7, and 10-12 was studied in the solid state. Magnetic properties of a Ni(ii) MOF 9 were also investigated and modeled. All obtained products 1-12 represent the first structurally characterized examples of coordination compounds derived from H3nbtc, thus opening up its application in coordination chemistry as a novel tricarboxylate building block.

Modeling Refuge Effect of Submerged Macrophytes in Lake System.

This paper considers a significant problem in biological control of algae issue in ecological environment. A four-dimensional dynamic model is carefully formulated to characterize the interactions among phytoplankton, submerged macrophyte, zooplankton, and general fish class in a lake ecosystem. The predation relationship is modeled by Beddington-DeAngelis functional responses derived from the classical Holling time budget arguments. Qualitative analyses of the global dynamics show that the system can generate very rich dynamics with potentially 10 different equilibria and several bistable scenarios. We perform analysis on the existence and local stability of equilibria and explore the refuge effect of macrophyte on the zooplankton with numerical simulations on aquatic ecosystems. We also discuss effective methods of biological control used to restrain the increase of phytoplankton. Our study shows the proposed model could have rich and complex dynamics including but not limited to bistable and chaotic phenomenon. Numerical simulation results demonstrate that both the refuge constant and the density of the macrophytes are two key factors where refuge effects take place. In addition, the intraspecific competition between the macrophyte and the phytoplankton can also affect the macrophyte's refuge effect. Our analytical and simulation results suggest that macrophytes provide structure and shelter against predation for zooplankton such that it could restore the zooplankton population, and that planting macrophyte properly might achieve the purpose of controlling algae growth.

Lanthanide coordination polymers based on 5-(2'-carboxylphenyl) nicotinate: syntheses, structure diversity, dehydration/hydration, luminescence and magnetic properties.

Twelve lanthanide coordination polymers associated with the organic ligand 5-(2'-carboxylphenyl) nicotinic acid (H2cpna): {[Ln(Hcpna)(cpna)(phen)]·H2O}n (Ln = Sm (1), Tb (2), Ho (3), phen = 1,10-phenanthroline), {[Sm(Hcpna)(cpna)(phen)]·2H2O}n (4), {[Ln2(cpna)3(H2O)3]·4H2O}n (Ln = Y (5), Tb(6), Dy (7), Ho (8)), [Lu2(cpna)3(H2O)2]n (9), {[Y2(cpna)3(phen)2(H2O)]·H2O}n (10), and [Ln(cpna)(phen)(NO3)]n (Ln = Tm (11), Lu (12)) have been prepared by hydrothermal methods and structurally characterized. The structure analyses reveal that complexes 1­3 are isostructural and possess unique three-dimensional (3D) frameworks based on the dodecanuclear Sm/Tb/Ho macrocycles. Complex 4 exhibits a one-dimensional (1D) wheel-chain structure, which further builds three-dimensional (3D) supramolecular architecture via O­HN hydrogen-bonding interactions. Complexes 5­8 are also isostructural and display three-dimensional (3D) open frameworks, which possess two types of channels along the a- and b-axis, respectively. Complexes 9 and 10 feature three-dimensional (3D) frameworks and are created from tetranuclear and dinuclear units, respectively. Complexes 11 and 12 are isostructural and demonstrate one-dimensional (1D) double chain structures, which further build three-dimensional (3D) supramolecular architecture via C­H···O hydrogen-bonding. The results show that the pH value of the reaction system, anion, auxiliary ligand and lanthanide contraction play a significant role in determining the structures of the complexes. In addition, the results of luminescent measurements for compounds 2 and 6 in the solid state at room temperature indicate that the different types of structures have a dissimilar influence on their characteristic luminescence. The magnetic properties of compounds 1, 3, 4, 7 and 11 have been investigated. Furthermore, thermal stabilities for 1­12 and the dehydration/hydration properties of compound 6 have also been studied.

Poly[[triaqua-(µ(3)-4-oxidopyridine-2,6-dicarboxyl-ato)thulium(III)] monohydrate].

In the title coordination polymer, {[Tm(C(7)H(2)NO(5))(H(2)O)(3)]·H(2)O}(n), the Tm(III) atom is eight-coordinated by a tridentate 4-oxidopyridine-2,6-dicarboxyl-ate trianion, two monodentate anions and three water mol-ecules, forming a distorted bicapped trigonal-prismatic TmNO(7) coordination geometry. The anions bridge adjacent Tm(III) ions into double chains. Adjacent chains are further connected into sheets. O-H⋯O hydrogen bonds involving both coordinated and uncoordinated water mol-ecules generate a three-dimensional supra-molecular framework.

Poly[[triaqua-(µ(3)-4-oxidopyridine-2,6-dicarboxyl-ato)holmium(III)] mono-hydrate].

In the title coordination polymer, {[Ho(C(7)H(2)NO(5))(H(2)O)(3)]·H(2)O}(n), the Ho(III) atom is eight-coordinated by a tridentate 4-oxidopyridine-2,6-dicarboxyl-ate trianion, two monodentate anions and three water mol-ecules, forming a distorted bicapped trigonal-prismatic HoNO(7) coordination geometry. The anions bridge adjacent Ho(III) ions into double chains. Adjacent chains are further connected into sheets. O-H⋯O hydrogen bonds involving both coordinated and uncoordinated water mol-ecules generate a three-dimensional supra-molecular framework.

Poly[[triaqua-(µ(3)-4-oxidopyridine-2,6-dicarboxyl-ato)terbium(III)] monohydrate].

In the title coordination polymer, {[Tb(C(7)H(2)NO(5))(H(2)O)(3)]·H(2)O}(n), the Tb(III) atom is eight-coordinated by a tridentate 4-oxidopyridine-2,6-dicarboxyl-ate trianion, two adjacent monodentate anions and three water mol-ecules, forming a distorted bicapped trigonal-prismatic TbNO(7) coordination environment. The anions bridge adjacent Tb(III) ions into double chains. Adjacent chains are further connected into sheets parallel to (10). O-H⋯O hydrogen bonds involving both coordinated and uncoordinated water mol-ecules generate a three-dimensional network.

Poly[diaqua-tris-(µ(4)-1,3-phenyl-enediacetato)-dineodymium(III)].

In the title coordination polymer, [Nd(2)(C(10)H(8)O(4))(3)(H(2)O)(2)](n), each of the two Nd(III) ions is nine-coordinated by eight O atoms from six different 2,2'-(m-phenyl-ene)diacetate (pda) bivalent anions and by one O atom from a water mol-ecule, forming a distorted tricapped trigonal-prismatic coordination geometry. Eight Nd(III) ions and 12 pda ligands form a large [Nd(8)(pda)(12)] ring, and four Nd(III) ions and six pda ligands form a small [Nd(4)(pda)(6)] ring. These rings are further connected by the coordination inter-actions of pda ligands and Nd(III), generating a three-dimensional supra-molecular framework.

Poly[[triaqua-(µ(3)-4-oxidopyridine-2,6-dicarboxyl-ato)europium(III)] monohydrate].

In the title coordination polymer, {[Eu(C(7)H(2)NO(5))(H(2)O)(3)]·H(2)O}(n), the Eu(III) atom is eight-coordinated by a tridentate 4-oxidopyridine-2,6-dicarboxyl-ate (hpc) trianion, two monodentate hpc anions and three water mol-ecules, forming a distorted bicapped trigonal-prismatic coordination geometry. The hpc ligands bridge adjacent Eu(III) ions, forming infinite double chains. Adjacent chains are further connected by hpc ligands into sheets. O-H⋯O hydrogen bonds then generate a three-dimensional supra-molecular framework.

Kinetic determination of tryptophan by using the B-Z oscillating chemical system.

A simple and rapid method was devised for determination of tryptophan, based on the Belousov-Zhabotinskii (B-Z) oscillating chemical system. Changes in oscillating period and amplitude were linearly proportional to the negative logarithm of L-tryptophan concentration over the range of 6.44 x 10(-7)-2.55 x 10(-4) M, with the regression coefficients of near unity and a lower detection limit of 6.5 x 10(-8) M. D-tryptophan was also examined although it is rarely found in most biological fluids, and perhaps not at all in natural proteins. The change of period against to negative logarithm of D-tryptophan concentration over the range of 4.9 x 10(-5)-8.24 x 10(-4) M is linear. Because the optimum conditions for determination of L- and D-tryptophan are not the same, a little amount of D-tryptophan does not affect the determination of L-tryptophan. Various influences were studied and a possible mechanism of perturbation to the B-Z oscillator by tryptophan was also discussed. Spectrophotometry and fluorescence spectrophotofluorimetry were used for comparison and confirmation of the results.

Determination of 1-naphthylamine by using oscillating chemical reaction.

A simple and rapid analytical method for determining 1-naphthylamine was proposed by perturbation with different amounts of 1-naphthylamine on the classical Belousov-Zhabotinskii (B-Z) oscillating chemical system. The results show that the changes both in oscillating period and amplitude were linearly proportional to the logarithm of the concentration of 1-naphthylamine (logC) very well ranging from 7.08x10(-5) to 7.08x10(-6) molL(-1) and 7.08x10(-5) to 1.0x10(-6) molL(-1), with the corresponding regression coefficient are 0.9957 and 0.9922, respectively. For the later, a lower detection limit of 5.64x10(-9) molL(-1) was obtained. Influence of injection point, temperature and reactant variables on this oscillating system was also investigated in detailed. The results obtained were compared with other determination methods. A possible reaction mechanism was interpreted by using bromide ion selective electrode to inspect the concentration change of Br(-) ion in the oscillating process.

Determination of furfural in an oscillating chemical reaction using an analyte pulse perturbation technique.

A rapid and convenient method for the determination of furfural is presented that is based upon sequential perturbation of the Mn(II)-catalyzed B-Z oscillating system with different amounts of furfural using a continuous-flow stirred tank reactor (CSTR). When the sample was injected, the change in the amplitude and/or period was linearly proportional to the logarithm of the concentration of furfural over the range 3 x 10(-8) approximately 1 x 10(-5) mol L(-1). This method gave a detection limit of 3 x 10(-9) mol L(-1) under optimum conditions. Finally, the possible mechanism of furfural perturbation in the oscillating reaction is discussed. When the furfural was injected into the Mn(II)-catalyzed B-Z oscillating system, the change in the amplitude and/or period was linearly proportional to the logarithm of the concentration of furfural over the range 3 x 10(-8)~1 x 10(-5) mol L(-1), with a detection limit of 3 x 10(-9) mol L(-1) under optimum conditions.

Improved sensitivity for some [corrected] metal ions by use of sulfide in the Belousov-Zhabotinskii oscillating reaction.

A highly sensitive method for the determination of trace amounts of some [corrected] metal ions by use of sulfide in the Belousov-Zhabotinskii (B-Z) oscillating chemical reaction is proposed. The use of sulfide increased strongly the sensitivity of the B-Z reaction for some [corrected] metal ions, such as Ag+, Pb2+, Hg2+, Cd2+, Cu2+, and Bi3+. Results showed that the variational ratio of oscillating period (P(R)) is linearly proportional to the negative logarithm of concentration of metal ions. The detection limit is down to 10(-12) mol L(-1). Various influencing factors on the determination were also examined.