Dong-Feng Li

A novel Cu(II)-W(V) bimetallic assembly magnet {[Cu(en)2]3[W(CN)8]2·H2O}∞ (en = ethylenediamine) with cube-like W8Cu12 units from a coordinated anion template self-assembly reactionElectronic supplementary information (ESI) available: selected hydrogen bonding parameters in 1 (Table S1) and perspective view showing the three linkages for the title compound (Fig. S1). See http://www.rsc.org/suppdata/nj/b1/b108791f/

A novel molecular-based magnet of three-dimensional (3-D) cyanide-bridged bimetallic assembly, {[Cu(en)2]3[W(CN)8]2·H2O}∞ (1), where en = ethylenediamine, was synthesized and structurally characterized. The assembly has a three-dimensional network structure extended by three kinds of CuII–NC–WV–CN–CuII linkages with very long axial Cu–Ncyanide interactions due to Jahn–Teller effects. The network is based on a W8Cu12 cube-like unit with eight [W(CN)8]3− anions at the corners of the distorted cube and twelve [Cu(en)2]2+ cations at the middle of the edges, in which a coordination anion [W(CN)8]3− acting as template/guest is capsulated in the cavity of the W8Cu12 cube. Magnetic studies reveal that the complex displays 3-D ferromagnetic ordering over the lattice below the Curie temperature at around 2 K.

Synthesis, crystal structure and magnetic properties of a CuII–WV/IV bimetallic complex with a novel open framework structure

Fabricated by cyano- and alkoxyl-bridged groups, a novel three-dimensional structural compound, {[Cu2(H2Tea)2]5[WV(CN)8]2[WIV(CN)8]·xH2O}∞ (H3Tea = triethanolamine), has been formed. In the structure, there exist two kinds of W atoms and three types of Cu2O2 pairs. The W(1) and W(2) atoms, with oxidation states +5 and +4 respectively, are each linked to the Cu2O2 units through two of its eight cyanide ligands, forming two kinds of 1D zigzag chain along the c-axis (nominally the W1-chain and the W2-chain). Each W2-chain is connected to four adjacent W1-chains through a third type of Cu2O2 unit, leading to the formation of a three-dimensional open framework with channels generated along the [001] direction. The structure may also be viewed as being constructed from W(1)Cu3 and W(2)Cu4 clusters, cross-linked by μ-O bridges. The magnetic properties show that the complex displays 3D antiferromagnetic ordering below 2.2 K, although ferromagnetic interactions are present within the W(1)Cu3 clusters. The dominant antiferromagnetic coupling at low temperature is attributed to the antiferromagnetic exchanges between the W(1)Cu3 clusters through the alkoxyl bridges.

Carboxyester hydrolysis promoted by dizinc(II) macrocyclic polyamine complexes with hydroxyethyl pendants: a model study for the role of the serine alkoxide nucleophile in zinc enzymes

A novel dinuclear Zn(II) complex with hexaaza macrocycle bearing two hydroxyethyl pendants (L1), 3,6,9,16,19,22-hexaaza-6,19-bis(2-hydroxyethyl)-tricyclo[22,2,2,211,13]triaconta-1,11,13,24,27,29-hexaene), was synthesized as a model for alkaline phosphatase. The Zn(II) complex [Zn2L1(CH3CO2)2](ClO4)2(H2O)2 was isolated as a colorless crystal, triclinic, space group P-1. Both Zn(II) ions adopt the geometry of a distorted trigonal bipyramid in a pentacoordinated environment with Zn⋯Zn distance of 8.74 A. The solution complexation study has revealed that the alcoholic hydroxyl group of the complex Zn2L1 exhibits a low pKa value at 25 °C. Zn(II)-bound alkoxides, which act as reactive nucleophiles toward the hydrolysis of 4-nitrophenyl acetate in 10% (v/v) CH3CN at 25 °C, with I = 0.10 M (NaNO3) and pH 9.0, have shown a second-order rate constant of 0.32 ± 0.01 M−1s−1, a value that is approximately 13 times greater than the value for the corresponding dinuclear Zn(II) complex formed by a hexaaza macrocycle without hydroxyethyl pendants (L2). The pH–rate profile for Zn2L1 gave a sigmoidal curve. A possible mechanism has been proposed: the Zn(II)–RO− function acts as a nucleophile in the first step of the hydrolytic mechanism, to give an acetyl intermediate, which is subsequently hydrolyzed to acetate by a Zn(II)–OH− group.

Synthesis, structure and properties of an imidazolate-bridged dicopper complex of a novel macrocycle with two alcohol-pendants as an active site model of Cu, Zn-SOD

Abstract The imidazolate-bridged dicopper complex of a macrocyclic ligand with two hydroxyethyl pendants L, L=3,6,9,17,20,23-hexaza-6,20-bis(2-hydroxyethyl)-tricyclo[23.3.1.1.11,15]triaconta-1(29),11(30),12,14,25,27-hexaene, has been synthesized as a possible model for Cu,Zn-SOD. Single-crystal X-ray analysis revealed the geometry of the imidazolate-bridged CuCu center, and the distance between the two Cu(II) ions is 5.8135(9) A. The two metals are each pentacoordinated with geometries between trigonal-bipyramid (TBP) and tetragonal-pyramid (TP). Magnetic measurement of the imidazolate-bridged dicopper complex exhibited the presence of an antiferromagnetic exchange interaction with a coupling constant of −2J=72.8 cm−1. Investigation on the pH-dependent ESR of the complex in frozen 50% aqueous DMSO solution at 110 K revealed the existence of the imidazolate-bridged dicopper structure in solution mainly in the range 5.5≤pH≤12. The SOD activity of the complex has been evaluated by the nitro blue tetrazolium assay and the complex catalyzed the dismutation of superoxide at pH 7.8 with an IC50 value of 0.36 μmol dm−3.

New Multifunctional Porous Materials Based on Inorganic–Organic Hybrid Single‐Walled Carbon Nanotubes: Gas Storage and High‐Sensitive Detection of Pesticides

Single-walled carbon nanotubes (SWNTs) that are covalently functionalized with benzoic acid (SWNT-PhCOOH) can be integrated with transition-metal ions to form 3D porous inorganic-organic hybrid frameworks (SWNT-Zn). In particular, N(2)-adsorption analysis shows that the BET surface area increases notably from 645.3 to 1209.9 m(2)  g(-1) for SWNTs and SWNT-Zn, respectively. This remarkable enhancement in the surface area of SWNT-Zn is presumably due to the microporous motifs from benzoates coordinated to intercalated zinc ions between the functionalized SWNTs; this assignment was also corroborated by NLDFT pore-size distributions. In addition, the excess-H(2)-uptake maximum of SWNT-Zn reaches about 3.1 wt. % (12 bar, 77 K), which is almost three times that of the original SWNTs (1.2 wt. % at 12 bar, 77 K). Owing to its inherent conductivity and pore structure, as well as good dispersibility, SWNT-Zn is an effective candidate as a sensitive electrochemical stripping voltammetric sensor for organophosphate pesticides (OPs): By using solid-phase extraction (SPE) with SWNT-Zn-modified glassy carbon electrode, the detection limit of methyl parathion (MP) is 2.3 ng mL(-1).

A three-dimensional CuII–WIV bimetallic porous assembly containing a zigzag ladder structure

The asymmetric unit of the three-dimensional Cu(II)-W(IV) polymeric assembly [Cu(en)(2)][Cu(en)][W(CN)(8)].4H(2)O](n) (en is ethylenediamine, C(2)H(8)N(2)) or [Cu(2)W(CN)(8)(C(2)H(8)N(2))(3)].4H(2)O](n), which can be named as polymeric bis(ethylenediamine)copper(II) (ethylenediamine)copper(II) octacyanotungstate(IV) tetrahydrate or penta-micro-cyano-tricyanotris(ethylenediamine)dicopper(II)tungsten(IV) tetrahydrate, consists of two half [Cu(en)(2)](2+) cations (Cu(2+) on inversion centres), a [Cu(en)](2+) cation and a [W(CN)(8)](4-) ion, together with four water molecules. The latter Cu(II) site is coordinated by five N atoms from an en ligand and by three cyanides in a distorted square-pyramidal geometry. The Cu(II) atoms of the two [Cu(en)(2)](2+) cations reside in an elongated octahedral coordination environment, and one of them is localized at a centre of inversion. The W atom is coordinated by eight cyano groups in an irregular square antiprism. Five of these act as bridging units connecting the W and the three Cu atoms, to form an infinite three-dimensional porous network containing a zigzag ladder structure.

Crystal structures and magnetic properties of two octacyanometalate-based tungstate(v)???copper(ii) bimetallic assembliesElectronic supplementary information (ESI) available: ORTEP drawing of the asymmetric unit for 2; packing diagrams for 1 and 2; temperature dependence of ??M???1 for 1; field dependence of the magnetization for 2; temperature dependence of the magnetization with ZFCM and FCM for 1 and 2, respectively. See http://www.rsc.org/suppdata/nj/b1/b110635j/

Two novel cyanide-bridged bimetallic assemblies based on octacyanotungstate as the building block, [Cu(tn)2]2[W(CN)8](OH)·H2O (1) and {[Cu(dien)]2[W(CN)8](OH)·3H2O}∞ (2) (tn = 1,3-diaminopropane; dien = diethylenetriamine), have been prepared and their magnetic properties studied. The X-ray analysis shows that the structure of 1 consists of a trinuclear unit, Cu(tn)2–N–C–W(CN)6–C–N–Cu(tn)2, which acts as a basic component that is connected through weak axial Cu⋯N–C–W interactions to form a two-dimensional sheet network. In the structure of 2, each W(CN)8 fragment connects four Cu(dien) groups through two types of W–C–N–Cu linkages in a –(A–B)n– pattern along the diagonal lines of the a and b axes to form an infinite 2-D layer structure. Magnetic susceptibility data demonstrate that the magnetic behavior of both 1 and 2 is characteristic of ferromagnetic interactions onto which weak antiferromagnetic interactions are superimposed.

A novel binucleating macrocyclic ligand with two alcohol pendants.

A novel binucleating 24-membered macrocyclic ligand, 6,20-bis(2-hydroxyethyl)-3,6,9,17,20,23-hexazatricyclo[23.3.1.1(11,15)]triaconta-1(29),11(30),12,14,25,27-hexaene (L), was synthesized and crystallized as the tetrahydrobromide salt, i.e. 6,20-bis(2-hydroxyethyl)-6,20-diaza-3,9,17,23-hexaazoniatricyclo[23.3.1.1(11,15)]triaconta-1(29),11(30),12,14,25,27-hexaene tetrabromide tetrahydrate, C28H50N6O2(4+)*4Br(-)*4H2O. A crystallographic inversion center is located in the macrocyclic cavity and the two hydroxyethyl pendants are on opposite sides of the macrocyclic plane. The benzene rings of the macrocycle are parallel to each other and a pi-pi-stacking interaction exists between the benzene rings of adjacent macrocycles, which are separated by 3.791 (9) A. An infinite intermolecular hydrogen-bond network stabilizes the crystal.

The crystal structure of a new double hydroxyethyl-bridged dizinc(II) complex with macrocyclic ligand

Abstract A new dizinc(II) complex with 6,20-bis(2-hydroxyethyl)-3,6,9,17,20,23-hexaaza-tricyclo [23,3,1,111,15]-triaconta-1(29),11(30),12,14,25,27-hexaene (L) was synthesized and characterized. The crystal structure of [Zn2H−2L](ClO4)2 has indicated that both Zn2+ ions are in penta-coordination environment with distorted trigonal bipyramid consisting of three N atoms from diethylenetriamine moieties, one internal O atom of the hydroxyethyl pendant, one intermolar O atom from another hydroxyethyl pendant, and the separation of Zn⋯Zn is 3.05 A. The two aromatic rings are parallel to each other, with the centroid–centroid distance 9.21 A. ES–MS spectra showed the main species of [Zn2H−2L]2+, [Zn2H−2L(H2O)2]2+, and [Zn2H−2L(ClO4)]+. The hydrolysis of 4-nitrophenyl acetate catalyzed by [Zn2H−2L]2+ in 10% (v/v) CH3CN at 25 °C, with I=0.10 (NaNO3) and pH 9.0, has shown a second-order rate constant of 0.021 M −1 s −1 .

Synthesis, characterization and catalytic ATP-hydrolysis of two tetrairon(III) complexes bridged by succinate/terephthalate with tris(2-benzimidazolylmethyl) amine

Two new tetranuclear iron(III) complexes, [Fe4(TBA)4(μ-O)2(μ4-Suc)](ClO4)4(OH)2·1.5CH3CN·2C2H5OH·6H2O (1) and [Fe4(TBA)4(μ-O)2(μ4-Tp)](ClO4)6·3C2H5OH·6H2O (2) (Suc = succinate, Tp = terephthalate, TBA = tris(2-benzimidazolylmethyl)amine) have been prepared and characterized by various physicochemical techniques. X-Ray crystallography reveals complex 1 contains equivalent two μ-oxo-μ-carboxylate diiron(III) centers bridged by a succinate acting as a tetradentate ligand linked to four iron atoms, forming a tetranuclear core [Fe4(TBA)4(O)2(Suc)]6+, in which each iron atom has an N4O2 donor set with distorted octahedral geometry and each of the two diiron(III) centers contains two iron atoms with a distinct coordination environment. Magnetic behaviors indicate the presence of a stongly antiferromagnetic coupling in the two complexes with the exchange coupling constants J = −114.27(8) cm−1 for 1 and J = −119.52(6) cm−1 for 2. The NMR spectra imply that the structures in the solid state are retained in solution. The two tetranuclear complexes exhibit similar cyclic voltammograms, i.e. there are three irreversible two-electron redox peaks at Ec = 0.247, −0.233 V; Ea = 0.354 V for 1 and Ec = 0.307, −0.166 V; Ea = 0.526 V for 2. The preliminary study on the hydrolysis of adenosine 5′-triphosphate (ATP) followed by 31P NMR spectroscopy shows that the two complexes can catalyze the hydrolysis of ATP.