Meng-Chang Shen

Syntheses, spectroscopy and crystal structure of several binuclear silver(I) cryptates

Abstract Three binuclear silver(I) cryptates were synthesized by template condensation of tris(3-aminopropyl)amine with 5-R-2- methoxy-l,3-phenylenedialdehyde (R=CH3O, CH3 or Br) and characterized by physical measurements (solution electrical conductivity, 1H NMR, IR and electronic spectra). The crystal structure of the cryptate of L1 (R=CH3O) was determined by X-ray diffraction and presents a novel basket structure for the cation [Ag2L1]2+ in which both silver(I) centres possess three coordinate environments. The crystal is monoclinic, space group Cc, C48H68Cl2N8O15Ag2, Mr=1283.75, a=11.349(2), b=29.16(1), c=17.506(6) A, β=102.38(2)°, Z=4, R=0.063 and Rw=0.071 for 3693 reflections. Each Ag atom locates at the top of a trigonal pyramid distorted from a planar triangle composed of one bridgehead tertiary nitrogen and two imino nitrogens. Only two bridging chains of the cryptand coordinate to the metals, another does not. The internuclear distance Ag(1)···Ag(2) is 7.468(12) A. All cryptates possess similar spectroscopic features.

A novel saddle-form macrocyclic barium complex—synthesis, characterization, mechanism and X-ray crystal structure

Abstract A novel saddle-form macrocyclic barium complex was synthesized by cyclo-condensation of diformylpyridine with [BaL1(ClO4)2]·3H2O. In the complex crystal [BaL2(ClO4)2(H2O)]·MeOH·1.5H2O, two perchlorate anions are cis-coordinated to barium(II), and the coordinated water molecule is located on the opposite side to the perchlorate anion. 1H NMR and ES MS spectra were used to characterize its structure in methanol solution. The mechanism of the reaction was discussed.

A study on a novel superoxide dismutase mimic bis(dioxotetraamine) copper(II) complex — kinetics of catalytic dismutation of superoxide anion by pulse radiolysis and solution equilibrium

Abstract A mimic of Cu2Zn2SOD has been investigated in detail. Its stability in solution has been obtained by the solution equilibrium study of N,N′,N″,N‴-tetra(2-aminoethyl)-1,1,2,2,-ethanetetraamide with copper ions. The kinetics of catalytic dismutation of superoxide anions by copper(II) complex [Cu2(H−4L)] was studied using pulse radiolysis. The rate constant of catalytic dismutation of O2− was determined to be Kcat = 2.81 × 108 (pH = 7.8) and 1.63 × 108 mol−1 dm3 s−1 (pH = 8.3) and the mechanism of catalytic dismutation of O2− was suggested. The kcat values have been compared with those of other Cu2Zn2SOD (SOD = superoxide dismutase) mimics. The experimental results show that the novel mimic exhibits high activity and stability at about pH = 7.8.

SYNTHESIS AND X-RAY CRYSTAL STRUCTURE OF A MACROCYCLIC BINUCLEAR CADMIUM(II)COMPLEX WITH SIDE CHAIN

Abstract The binuclear cadmium(II) macrocyclic complex was synthesized by [2+2] Schiff base condensation of tris(3-aminopropyl)amine (trpn) with sodium 2,6-diformyl-4-methylphenolate (sdmp) in the presence of Cd 2+ . The crystal structure of the complex [Cd 2 L](ClO 4 ) 2 ·H 2 O·0.5CH 3 OH has been determined by X-ray diffraction. The crystal is orthorhombic, space group Aba 2, a =16.163(6), b =17.714(6), c =16.027(6) A, Z =4, V =4589(5) A 3 , F (000)=2220, R =0.048, R w =0.060. Each cadmium locates at the center of a distorted octahedron composed of three oxygens in the phenoxy groups and three nitrogens in trpn. The coordination of the phenoxy oxygens and terminal amino groups enchanced the stability of the complex.

Abnormal electrochemical behavior of copper–zinc superoxide dismutase on mercury electrodes

The electrochemical behavior of porcine superoxide dismutase (PESOD) on mercury electrodes was investigated by cyclic voltammetry and direct current polarography in the absence of mediators for the first time. It is interesting and abnormal that PESOD displays two pairs of redox adsorbed peaks in the CV diagram, which are located in the potential regions of the disulfide bonds of many proteins reported by some authors, but we attributed them to the redox peaks of copper(II) and zinc(II) by reconstitution of PESOD. The apparent numbers of electrons in the reduction process were obtained by polarography and the electrode process was discussed.

A study on some alkaline earth metal cryptates: Synthesis, characterization, crystal structure and solution structure

Abstract Three alkaline earth metal cryptates (Barium(II), Strontium(II), Calcium(II)) were synthesized by (2+3) template condensation of tris(3-aminopropyl)amine with 2,6-diformylpyridine and characterized by some physical methods. The solution structure of [BaL]2+ (L=cryptand) was studied by electrospray mass spectrometry, 1H-13C NMR and molecular dynamics method based on analysis of 1H NMR NOE spectrum. The crystal structure presents a tricapped trigonal prism structure in which barium(II) is enclosed within the macrobicycle and is nine-coordinated by six imino nitrogen atoms and three pyridyl nitrogen atoms.

SYNTHESIS AND X-RAY CRYSTAL STRUCTURE OF A NEW μ2-PHENOXY OXYGEN BRIDGED BINUCLEAR CADMIUM(II) CRYPTATE

Abstract A new tris(phenoxy oxygen) bridged bicadmium(II) polyaza cryptate has been synthesized by the [2 + 3] Schiff-base condensation of tris(3-aminopropyl)amine (trpn) with sodium 2,6-diformyl-4-chlorophenolate (sdcp) in the presence of Cd(ClO4)2 6H2O. The crystal structure of the cryptate [Cd2L](ClO4)CH3OH has been determined by X-ray methods. Crystals are monoclinic, space group P21/n with a = 16.076(4), b = 15.900(3), c = 18.590(4) A, β = 95.100(14)°, Z = 4, V = 4719(4) A3, F(000) = 2360, Dc = 1.649 g cm−3, μ = 11.9 cm−1, R = 0.0581, Rw . = 0.0682. Each cadmium(II) atom is bonded to three mU2-phenoxy oxygen atoms, three amine atoms and one bridgehead nitrogen atom. The coordination geometry around the Cd(II) is considered as being a capped trigonal prism.

Synthesis and x-ray crystal structure of a 24-membered macrocyclic binuclear cadmium(ii) complex with pendant arms

Abstract A new binuclear cadmium(II) macrocyclic complex has been synthesized by [2 + 2] Schiff base condensation of tris(2-aminoethyl)amine (tren) with sodium 2, 6-diformyl-4-bromo-phenolate (sdbp) in the presence of Cd2+ ion. The crystal structure of the complex [Cd2L](ClO4)2 0.5CH3OH has been determined by X-ray methods. Crystals are mono-clinic, space group P21 /c with a = 11.633(15), b = 16.370(2), c = 21.193(2) A, β = 96.121(12)°, Z= 4, V= 4013.0(8) A3, F(000) = 2180, Dc., = 1.841 g cm−3, μ = 32.46 cm−1, R = 0.049, Rw = 0.069. Two cadmium(II) ions are bridged by two μ2-phenoxy oxygen atoms. Each cadmium lies in a N4O2 coordination environment. Coordination geometry around Cd(II) is a capped trigonal bipyramid. Coordination of phenoxy oxygens and terminal amino groups enhances the stability of the complex.

The Synthesis of Three μ2-Phenoxy Oxygen Bridged 24-Membered Macrocyclic Binuclear Cadmium(II) Complexes and the X-Ray Crystal Structure of one of them

Abstract Three binuclear cadmium(II) macrocyclic complexes have been synthesized by [2+2] Schiff base condensation of tris(2-aminoethyl)amine (tren) with sodium 2,6-diformyl-4-R-phenolate (R = CH3, L1, R = Br, L2, R = Cl, L3) in the presence of Cd(CIO4)2·6H2O. The crystal structure of the complex [Cd2L2](CIO4)2·0.5CH3OH has been determined by X-ray diffraction. The crystal is monoclinic, space group P21/c, with a = 11.633(15) A, b = 16.370(2) A. c = 21 193(2) A, β = 96.121(12)°, Z = 4, V = 4013.0(8) A3, F(000) = 2180, R = 0.049, and Rw = 0.069. The crystal structure, spectral characterization and molar conductivity show that two cadmium(II) ions are bridged by two μ2-phenoxy oxygen atoms Each cadmium(II) ion is located in a N4O2 coordination environment. The coordination geometry around the Cd(II) is a capped trigonal bipyramid. The coordination by phenoxy oxygens and terminal amino groups enhances the stability of the complex.

Synthesis and X-ray crystal structure of the first pentanuclear silver(I) cluster of the polyaza cryptands

A new silver(I) polyaza cryptate [Ag5L][BF4]2·H2O is synthesized and shown by X-ray crystallographic structure determination to consist of a pentanuclear silver(I) cluster incorporated in a polyaza cryptand.