Electrochemical Response Characteristics and Analytical Application of Papaverine Ion‐Selective Membrane Electrodes

Abstract

The construction and electrochemical response characteristics of poly(vinyl chloride) matrix ion‐selective electrodes (ISEs) for papaverine hydrochloride are described. The membranes incorporate ion association complexes of papaverine with tetraphenylborate {[B(C₆H₅)₄]^?}, picrate {[C₆H₂(NO₂)₃O]^?}, tetraiodomercurate [(HgI₄)]^2?, tetraiodobismuthate [(BiI₄)^?], Reinecke salt {[Cr(NH₃)₂(SCN)₄]^?} and heteropolycompounds of Keggin structure–molybdophosphoric acid [H₃(PMo₁₂O₄₀)], tungstophosphoric acid [H₃(PW₁₂O₄₀)], molybdosiliconic acid [H₄(SiMo₁₂O₄₀)], and tungstosiliconic acid [H₄(SiW₁₂O₄₀)] as electroactive materials for ionometric sensor controls. These ISEs show linear response for papaverine hydrochloride over the range from 1×10^?5 up to 5×10^?2 mol/l with cationic slopes from 42 up to 58 mV per concentration decade. These ISEs exhibit fast response time (up to 1 min), low determination limit (up to 1×10^?5 M), good stability (3–5 weeks) and reasonable selectivity. The ISEs were used for direct potentiometry and potentiometric titration {Na[B(C₆H₅)₄]} of papaverine hydrochloride in pharmaceutical preparations. Results with mean accuracy of 98.6±0.9% of nominal were obtained, which correspond well to data obtained with the European Pharmacopoeial method.     

Three organic–inorganic hybrid complexes based on the Wells–Dawson polyoxoanion

Three new organic–inorganic hybrid complexes based on the Wells–Dawson polyoxoanion, namely (H₂bpp)[Ni₂(bpp)₂(H₂O)₄(P₂W₁₈O₆₂)]·H₂O 1, [Cu₆(Hbpy)₆(bpy)₃(P₂W₁₈O₆₂)₂]·2H₂O 2 and (Him)₅[Cu(im)₂(P₂W₁₈O₆₂)]·4H₂O 3 [bpp = 1,3-bis (4-pyridyl) propane, bpy = 4,4′-bipyridine, im = imidazole] have been synthesized and characterized. Complex 1 exhibits a three-dimensional (6, 3)-connected framework with anatase topology constructed from [α-P₂W₁₈O₆₂]⁶⁻ clusters and [Ni(bpp)]²⁺ fragments. Each [α-P₂W₁₈O₆₂]⁶⁻ anion links to six nickel atoms through six terminal oxygen atoms from four polar and two equatorial WO₆ octahedra, which shows a novel coordination mode of a Wells–Dawson cluster with a transition-metal atom. Complex 2 displays an interesting one-dimensional double-chain structure built from [α-P₂W₁₈O₆₂]⁶⁻ clusters and [Cu₂(bpy)(Hbpy)₂]²⁺ fragments. To our knowledge, complex 2 represents the first double-chain organic–inorganic hybrid complex based on a Wells–Dawson-type cluster. Complex 3 possesses a one-dimensional zigzag chain structure constructed from [α-P₂W₁₈O₆₂]⁶⁻ anions and [Cu(im)₂]⁺ units through weak Cu···O interactions.     

Synthesis and Electrochemical Properties of a New 1D Organic–Inorganic Hybrid Compound Based on Keggin-Type Heteropolyanions and Isopolyanions Decorated by Transition Metal Fragments

A new chain-like organic–inorganic hybrid compound composed of the heteropolyanions and isopolyanions, [{Cu^II(2,2′-bpy)}₆(Mo^VMo^VI ₅O₂₂)] [PMo^VI ₁₂O₄₀] · H₂O 1 (bpy = 2,2′-bipyridine) has been hydrothermally synthesized and characterized by elemental analysis, IR spectroscopy, TG analysis, XPS spectrum and single-crystal X-ray diffraction. Crystal data for compound 1: monoclinic, space group P _2(1)/c, a = 13.9382(14) Å, b = 20.0300(19) Å, c = 17.1757(17) Å, β = 94.054(2)°, V = 4783.2(8) ų, Z = 2. The Keggin-heteropolyanion [PMo₁₂O₄₀]^3? and the Cu-supporting isopolyanion [{Cu(2,2′-bpy)}₆(Mo₆O₂₂)]³⁺ building units are bridged through the O–Cu–O bridges into 1D infinite chain. Note that, the [{Cu(2,2′-bpy)}₆(Mo₆O₂₂)]³⁺ unit, which contains a rarely reported isopolyanion [Mo₆O₂₂]^9? decorated by six [Cu(2,2′-bpy)] fragments. Furthermore, the electrochemical behavior of a 1-modified carbon paste electrode (1-CPE) and its electrocatalytic reduction of nitrite were investigated.     

Formation and hydrolysis of gas‐phase [UO2(R)]+: R═CH3, CH2CH3, CH═CH2, and C6H5

The goals of the present study were (a) to create positively charged organo‐uranyl complexes with general formula [UO₂(R)]⁺ (eg, R═CH₃ and CH₂CH₃) by decarboxylation of [UO₂(O₂C─R)]⁺ precursors and (b) to identify the pathways by which the complexes, if formed, dissociate by collisional activation or otherwise react when exposed to gas‐phase H₂O. Collision‐induced dissociation (CID) of both [UO₂(O₂C─CH₃)]⁺ and [UO₂(O₂C─CH₂CH₃)]⁺ causes H⁺ transfer and elimination of a ketene to leave [UO₂(OH)]⁺. However, CID of the alkoxides [UO₂(OCH₂CH₃)]⁺ and [UO₂(OCH₂CH₂CH₃)]⁺ produced [UO₂(CH₃)]⁺ and [UO₂(CH₂CH₃)]⁺, respectively. Isolation of [UO₂(CH₃)]⁺ and [UO₂(CH₂CH₃)]⁺ for reaction with H₂O caused formation of [UO₂(H₂O)]⁺ by elimination of ·CH₃ and ·CH₂CH₃: Hydrolysis was not observed. CID of the acrylate and benzoate versions of the complexes, [UO₂(O₂C─CH═CH₂)]⁺ and [UO₂(O₂C─C₆H₅)]⁺, caused decarboxylation to leave [UO₂(CH═CH₂)]⁺ and [UO₂(C₆H₅)]⁺, respectively. These organometallic species do react with H₂O to produce [UO₂(OH)]⁺, and loss of the respective radicals to leave [UO₂(H₂O)]⁺ was not detected. Density functional theory calculations suggest that formation of [UO₂(OH)]⁺, rather than the hydrated U^VO₂⁺, cation is energetically favored regardless of the precursor ion. However, for the [UO₂(CH₃)]⁺ and [UO₂(CH₂CH₃)]⁺ precursors, the transition state energy for proton transfer to generate [UO₂(OH)]⁺ and the associated neutral alkanes is higher than the path involving direct elimination of the organic neutral to form [UO₂(H₂O)]⁺. The situation is reversed for the [UO₂(CH═CH₂)]⁺ and [UO₂(C₆H₅)]⁺ precursors: The transition state for proton transfer is lower than the energy required for creation of [UO₂(H₂O)]⁺ by elimination of CH═CH₂ or C₆H₅ radical.     

Synthesis,Structure, and Physicochemical Studies of Hexakis(2,4‐dimethylanilinium) Cyclohexaphosphate Hexahydrate

Chemical preparation, crystal structure, thermal analysis, IR absorption, and NMR studies are given for a new organic cyclohexaphosphate, the hexakis(2,4‐dimethylanilinium) cyclohexaphosphate hexahydrate ((2,4‐Me₂C₆H₃NH₃)₆P₆O₁₈?6 H₂O). This compound crystallizes in the monoclinic space group P2₁/n, with cell parameters a=10.914(4) Å, b=11.198(3) Å, c=25.670(2) Å, β=95.05(4)°, Z=2, and V=3124(2) ų. Its crystal structure is determined and refined to a final R=0.054 for 4627 independent reflections. The atomic arrangement can be described as a layer organization built by P₆O₁₈‐ring anions and H₂O molecules. Between these layers are located the organic groups that form H‐bonds with O‐atoms of the P₆O₁₈ rings and H₂O molecules. Determination of the geometric characteristics of the H‐bonds show the existence in this structure of four particularly strong H‐bonding contacts (1.75, 1.76, 1.78, and 1.87 Å).     

Synthesis and structural characterization of binuclear ytterbium(III) complexes with 2-amino and 3-amino benzoic acid

Two novel homobinuclear ytterbium(III) complexes, [Yb₂(2AMB)₆(H₂O)₄] · 2C₂H₆O (I) and Yb₂(3AMB)₆(H₂O)₄] · 3H₂O (II) (2AMB = 2-aminobenzoic acid, 3AMB = 3-aminobenzoic acid) have been synthesized and characterized by elemental analysis, infrared spectroscopy, thermogravimetric analysis and X-ray crystallography (CIF files CCDC nos. 950103 (I), 921652 (II)). Complex I crystallizes in triclinic space group \(P\bar 1\) and complex II crystallizes in monoclinic space group P2₁/n. X-ray analysis shows that both complexes (I, II) have the dinuclear structure. The central Yb³⁺ ions in both complexes are eight-coordinated adopting distorted YbO₈ dodecahedral geometry. Each Yb³⁺ ion is coordinated to two O atoms from bridging carboxylate, four O atoms from the chelating carboxylate ligands and two O atoms of water molecules. The crystal structure of I and II are stabilized by N-H…O, O-H…O, O-H…N, and C-H…O hydrogen bonds, C-H…π interactions and weak π-π stacking interactions.     

X-ray powder structure determination of Li6P6O18·3H2O

Preparation, characterization by X-ray diffraction, IR absorption, DTA-GTA analysis and ab-initio crystal structure determination are reported for a new lithium cyclohexaphosphate hydrate Li₆P₆O₁₈·3H₂O. It crystallizes in a trigonal (rhomboedral) cell (space group R 3¯m No 166, Z = 6) with a = 15.7442(2) Å, c = 12.5486(2) Å. X-ray powder diffraction pattern data was refined by Rietveld profile technique and lead to R_Bragg = 0.09. The crystal structure of Li₆P₆O₁₈·3H₂O is built up from [P₆O₁₈]^6- ring anions, having the 3m symmetry, alternating along the 3¯ axis with rings made of six LiO₄ tetrahedra and six LiO₅ pseudo square pyramids sharing common edges.     

Quecksilber(II)‐chlorid‐ und ‐iodid‐Komplexe von Dithia‐ und Tetrathiakronenethern

Mercury(II) Chloride and Iodide Complexes of Dithia‐ and Tetrathiacrown Ethers The complexes [(HgCl₂)₂((ch)₂30S₄O₆)] ( 1 ), [HgCl₂(mn21S₂O₅)] ( 2 ), [HgCl₂(ch18S₂O₄)] ( 3 ) and [HgI(meb12S₂O₂)]₂[Hg₂I₆] ( 4 ) have been synthesized, characterized and their crystal structures were determined. In [(HgCl₂)₂((ch)₂30S₄O₆)] two HgCl₂ units are discretely bonded within the ligand cavity of the 30‐membered dichinoxaline‐tetrathia‐30‐crown‐10 ((ch)₂30S₄O₆) forming a binuclear complex. HgCl₂ forms 1 : 1 “in‐cavity” complexes with the 21‐membered maleonitrile‐dithia‐21‐crown‐7 (mn21S₂O₅) ligand and the 18‐membered chinoxaline‐dithia‐18‐crown‐6 (ch18S₂O₄) ligand, respectively. The 12‐membered 4‐methyl‐benzo‐dithia‐12‐crown‐4 (meb12S₂O₂) ligand gave with two equivalents HgI₂ the compound [HgI(meb12S₂O₂)]₂[Hg₂I₆]. In the cation [HgI(meb12S₂O₂)]⁺ meb12S₂O₂ forms with the cation HgI⁺ a half‐sandwich complex.     

Effect of N-donor sites of bis-pyridyl-bis-amide ligands on the architectures of three Anderson-type polyoxometalate-based metal–organic complexes

Three polyoxometalate-based metal–organic complexes [Co₂(H₂O)₆(TeMo₆O₂₄)](3-H₂dpyb)·2H₂O (1), [M₂(4-Hdpyb)₂(H₂O)₆(TeMo₆O₂₄)]·6H₂O [M = Co (2), Zn (3); 3-dpyb = N,N′-bis(3-pyridinecarboxamide)-1,4-butane, 4-dpyb = N,N′-bis(4-pyridinecarboxamide)-1,4-butane] have been hydrothermally synthesized and characterized by elemental analysis, IR, TG, powder diffraction and single-crystal X-ray diffraction analysis. The structure of complex 1 consists of 1D [Co₂(H₂O)₆(TeMo₆O₂₄)] inorganic chains, which are joined together by the 3-dpyb ligands through weak hydrogen bonds to generate a 2D supramolecular network. Complexes 2 and 3 are isostructural; each [TeMo₆O₂₄]^6? (TeMo₆) polyoxoanion chelates either two cobalt or two zinc atoms to generate the discrete complexes [Co₂(4-Hdpyb)₂(H₂O)₆(TeMo₆O₂₄)] and [Zn₂(4-Hdpyb)₂(H₂O)₆(TeMo₆O₂₄)], respectively. The electrochemical properties, electrocatalytic and photocatalytic activities of the complexes have been investigated.     

Zur thermischen Dehydratisierung von Lithiumdihydrogenphosphat, -hydrogendiphosphat und -cyclophosphat-Hydraten

Thermal Dehydration of Lithium Dihydrogenphosphate, -Hydrogen-diphosphate, and -Cyclophosphate Hydrates On heating lithium dihydrogenphosphate, LiH₂PO₄, is converted to lithium polyphosphate, (LiPO₃)_n · H₂O [2–5]. Seeding LiH₂PO₄ with lithium cyclohexaphosphate, Li₆P₆O₁₈, the thermal dehydration proceeds structurally controlled to pure Li₆P₆O₁₈. On heating lithium hydrogen-diphosphate, Li₃HP₂O₇, reacts to Li₄P₂O₇ form III and lithium cyclotetraphosphate, Li₄P₄O₁₂ form II , which ist converted to Li₆P₆O₁₈ at higher temperatures. The thermal dehydration of Li₂H₂P₂O₇ and of the cyclophosphate hydrates Li₃P₃O₉ · 3 H₂O, Li₄P₄O₁₂ · (8 and 6) H₂O, Li₆P₆O₁₈ · (6 and 4) H₂O and Li₈P₈O₂₄ · (10 and 6) H₂O are described.     

Dinuclear cobalt and manganese squarate complexes with bidentate N-donor ligand: syntheses, crystal structures, spectroscopic, thermal and voltammetric studies

The crystal structures of [M₂(phen)₄(H₂O)₂(C₄O₄)]· C₄O₄· 8H₂O [M = Co²⁺ (1), Mn²⁺ (2); phen: 1,10-phenanthroline] complexes have been prepared and characterized by IR spectroscopy, thermal analysis and single X-ray diffraction techniques. Their structures consist of [Co₂(phen)₄(H₂O)₂(C₄O₄)]²⁺ (1) and [Mn₂(phen)₄(H₂O)₂(C₄O₄)]²⁺ (2) dinuclear cobalt(II) and manganese(II) cations, uncoordinated C₄O ₄ ^2? (SQ^2?) dianion and crystalization water molecules. In both complexes the metal ions have distorted octahedral geometry. The squarate adopts the μ-1,3 (1) and (2) bis(monodentate) coordination modes, the intradimer M–M separation being 8.053(7) Å (1) and 8.175(4) Å (2), respectively, while the other squarate acts as a counter anion. The voltammetric behaviour of complexes (1) and (2) was investigated in DMSO (dimethylsulfoxide) solution by cyclic voltammetry using n-Bu₄NClO₄ as supporting electrolyte. The complexes exhibit both metal and ligand centred electroactivity in the potential ?±1.75 V versus Ag/AgCl reference electrode. The dianion SQ^2? is oxidized in two consecutive steps to the corresponding radical monoanion and neutral form.     

Topologisch und elektronisch bemerkenswerte „reduzierte”︁ Cluster des Typs [V18O42(X)]n− (X = SO4, VO4) mit Td-Symmetrie und davon abgeleitete Cluster [V(18–p)As2pO42(X)]m− (X = SO3, SO4, H2O; p = 3, 4)

Reduced Clusters with Remarkable Topological and Electronic Properties of the Type of [V₁₈O₄₂(X)]^n? (X = SO₄, VO₄) with T_d-Symmetry and Related Clusters [V_(18—p)As_2pO₄₂(X)]^m? (X = SO₃, SO₄, H₂O; p = 3, 4) The novel cluster-compounds Na₆[V₁₈O₄₂H₉(VO₄)] · 21 H₂O, (NH₄)₈[V₁₈O₄₂(SO₄)] · 25 H₂O, K₆[V₁₅As₆O₄₂(H₂O)] · 8 H₂O, (NH₄)₆[V₁₄As₈O₄₂(SO₃)], (NH₄)₆[V₁₄As₈O₄₂(SO₄)] and [N(CH3)₃]₄[₄V₁₄As₈0₄₂(H₂0)] were prepared and characterized by IR- and UV/Vis/NIR-spectroscopy, magnetic measurements and complete crystal structure analysis. For structural data see Inhaltsübersicht. Topological relations to the rhombicuboctahedron spanned by 24 0-atoms of the genuine hypothetical a-Keggin ion, at which the square planes are capped by V?O or As₂O groups, are discussed. Of particular interest are the ?extended”? Keggin ions [V₁₈O₄₂(X)]ⁿ- (X = SO₄ VO₄), (formaly derived from the hypothetical genuine a-Keggin ion by addition of six V?O groups) which have quite different electron populations in spite of the same structure of their cluster shells.     

Two New Benzoate‐di(methylcyclopentadienyl)ytterbium(III) Complexes: [Yb(MeCp)2(O2CC6F5)]2 and [Yb(MeCp)2(O2C‐o‐HC6F4)]2

Transparent orange crystals of [Yb(MeCp)₂(O₂CC₆F₅)]₂ and [Yb(MeCp)₂(O₂C‐o‐HC₆F₄)]₂ were obtained by oxidation of Yb(MeCp)₂ with M(O₂CR) (M = ¹/₂ Hg, Tl; R = C₆F₅, o‐HC₆F₄) in tetrahydrofuran. They have a dimeric structure with bridging bidentate (O, O')‐benzoate groups and eight coordinated ytterbium. Both crystallise isotypic in the orthorhombic space group Pbca. Room temperature as well as low temperature single crystal X‐ray investigations show the o‐H/F positions in [Yb(MeCp)₂(O₂C‐o‐HC₆F₄)]₂ not to be ordered.     

Synthesis and crystal structure of ((NH3CH2CH2)3N)2P6O18·6H2O

Chemical preparation and crystal structure are given for a new cyclohexaphosphate: ((NH₃CH₂CH₂)₃N)₂P₆O₁₈·6H₂O. This compound is triclinic P¯1 with the following unit-cell parameters: a = 10,281(1)Å, b = 11.083(1)Å, c = 9.307(2)Å, α = 103.83(1) °, β = 108.56(1) °, γ = 68.11(1) °, Z = 1, V = 924.2(3)ų and pcal. = 1.582 g.cm⁻³. Its atomic arrangements contain layers built by P₆O₁₈ ring anions spreading in the plans (001). Between these layers are located the organic groups which form hydrogen bonds with oxygen atoms of P₆O₁₈ rings and water molecules. Crystal structure has been solved and refined to R = 0.028 using 4540 independent reflections. The thermal behavior has been investigated and interpreted by comparison with IR absorption spectroscopy and X-ray diffraction experiments.     

Etude thermique et thermodynamique du cyclohexaphosphate de lithium Li6P6O18·5H2O

We report in this paper the results of our thermal and thermodynamic investigation on lithium cyclohexaphosphate, Li₆P₆O₁₈·5H₂O between 298 and 1007 K. The different transitions with respect to temperature (successive dehydrations, solid-solid transition and melting) were studied with the help of differential thermal analysis and thermogravimetry. The different phases were characterized by X-ray diffraction and by infrared absorption. Finally, the enthalpy of these phasesvs. temperature was measured by isothermal drop calorimetry. Their heat capacities as well as the enthalpies of dehydration, of solid-solid transition and of melting were deduced. We pointed out that the lithium cyclohexaphosphate loses a molecule of water at 333 K (54.3 kJ·mol^?1), three molecules of water at 413 K (151 kJ·mol^?1) and the last one at 488 K (50.6 kJ·mol^?1). The anhydrous lithium cyclohexaphosphate, Li₆P₆O₁₈, give the polyphosphate, LiPO₃, at 708 K (second order transition) and melt at 933 K (24.6 kJ·mol^?1).     

Assembly of four copper(II)–2,2′-biimidazole complex-supported Strandberg-type phosphomolybdates

Four Strandberg-type phosphomolybdate-based Cu(II) complexes of 2,2′-biimidazole (C₆H₆N₄, H₂biim) and H₂O molecules, namely [Cu(H₂biim)₂(H₂O)][Cu(H₂biim)₂(HPO₄)₂(Mo₅O₁₅)]·2H₂O (1), [{Cu(H₂biim)(H₂O)}₂{μ-Cu(H₂biim)(H₂O)}(P₂Mo₅O₂₃)]₂·20H₂O (2), [Cu(H₂biim)₂][{Cu(H₂biim)(H₂O)₂}{Cu(H₂biim)₂}(HPO₄)(PO₄)(Mo₅ O₁₅)]₂·20H₂O (3), and [Cu(H₂biim)₂(H₂O)][Cu(H₂biim)₂(HPO₄)₂(Mo₅O₁₅)]·6H₂O (4) have been synthesized and characterized by physico-chemical and spectroscopic methods. Single-crystal X-ray diffraction analysis reveals that compound 1 consists of a mono-supporting heteropolyoxoanion [Cu(H₂biim)₂(H₂P₂Mo₅O₂₃)]²⁻and an isolated [Cu(H₂biim)₂(H₂O)]²⁺ cation. Compound 2 is composed of two tetra-supporting heteropolyoxoanions linked via two Cu(II) complex fragments. In compound 3, there exist two symmetrical bi-supported polyoxoanion clusters and an isolated [Cu(H₂biim)₂]²⁺ fragment lying in the center of the clusters. Compound 4 is also constructed from a [Cu(H₂biim)₂(H₂P₂Mo₅O₂₃)]²⁻ polyoxoanion and a [Cu(H₂biim)₂(H₂O)]²⁺ cation, but it has a different space group and packing interactions compared with compound 1.     

Supramolecular Systems Based on Ca2+, [Mo3O2S2Cl6(H2O)3]2s-, [Mo3S4Cl6.75Br0.25(H2O)2]3s- and Cucurbit[6]uril

Adducts of cucurbit[6]uril with Ca²⁺ and trinuclear cluster chloroaquacomplexes (H₉O₄)₂(H₇O₃)₂[(Ca(H₂O)₅)2(C₃₆H₃₆N₂₄O₁₂)]Cl₈·0.67H₂O (1) and [(Ca(H₂O)₅)₂(C₃₆H₃₆N₂₄O₁₂)]× [Mo₃O₂S₂Cl₆(H₂O)₃]₂·13H₂O (2) are obtained and structurally characterized. The structures of both compounds contain polymeric [Ca(H₂O) _n ]₂² CB[6]∞ cations that form infinite columns; the space between them is filled with Cl^s- (1) and [Mo₃O₂S₂Cl₆(H₂O)₃]^2s- (2). A new (H₇O₃)₂(H₅O₂)× [Mo₃S₄Cl_6.25Br_0.25(H₂O)₂](C₃₆H₃₆N₂₄O₁₂)·CH₂Cl₂·6H₂O complex (3) is also obtained and structurally characterized.     

Four inorganic–organic hybrid complexes built from tetravanadate and macrocyclic oxamide

Four inorganic–organic hybrid compounds, [M₂(CuL)₄(V₄O₁₂)]·2H₂O (M?=?Co (1), Mn (2)), [Mn₂(NiL)₄(V₄O₁₂)]·2H₂O (3), and [Zn₂(CuL)₄(V₄O₁₂)]·2CH₃OH·2H₂O (4) (M′L, H₂L?=?2,3-dioxo-5,6,14,15-dibenzo-1,4,8,12-tetraazacyclo-pentadeca-7,13-dien), have been synthesized and characterized by elemental analysis, IR, UV, fluorescence spectra, and X-ray diffraction analysis. Single-crystal X-ray analysis reveal that both [V₄O₁₂]^4? and M₂V₄ adapt a chair-like configuration in four structures. The cyclovanadate group [V₄O₁₂]^4? is a tetradentate bridging ligand linking two [M(M′L)₂]²⁺ fragments, producing centroantisymmetric heterometallic hexanuclear [M₂M′₄] complexes. The variable-temperature magnetic susceptibility measurements (2–300?K) of 1 and 2 show weak antiferromagnetic interactions.     

New nine-coordinate (NH4)3[YbIII(ttha)]·5H2O and eight-coordinate (NH4)[YbIII(pdta)(H2O)2]·5H2O complexes: Structural determination

The (NH₄)₃[Yb^III(ttha)]·5H₂O (I) (H₆ttha = triethylenetetramine-N,N,N′,N″,N‴,N‴-hexaacetic acid) and (NH₄)[Yb^III(pdta)(H₂O)₂]·5H₂O (II) (H₄pdta = propylenediamine-N,N,N′,N′-tetraacetic acid) complexes are synthesized by heat-refluxing and acidity-adjusting methods, and their structures are determined by single crystal X-ray diffraction techniques. These two complexes are all mononuclear structures. The complex I crystallizes in ttha monoclinic crystal system with the P2₁/c space group. The central Yb^III ion is nine-coordinated only by one the ligand, and one non-coordinate carboxyl group is left. The crystal data are as follows: a = 10.321(4) ?, b = 12.744(5) ?, c = 23.203(9) ?, β = 91.082(6)°, V = 3051(2) ?³, Z = 4, D _c = 1.754 g/cm³, μ = 3.150 mm⁻¹, F(000) = 1636, R = 0.0357, and wR = 0.0672 for 6203 observed reflections with I ≥ 2σ(I). The YbN₄O₅ part in the [Yb^III(ttha)]³⁻ complex anion forms a pseudo-monocapped square antiprismatic polyhedron. The complex II is coordinated with one pdta ligand and two water molecules, which form an eight-coordinate structure, and crystallizes in the triclinic crystal system with the P[`1]P\bar 1 space group. The YbN₂O₆ part in the [Yb^III(pdta)(H₂O)₂]⁻ complex anion makes a pseudo-square antiprismatic polyhedron. The crystal data are as follows: a = 9.8923(9)?, b = 10.9627(10) ?, c = 12.2618(11) ?, α = 67.284(5)°, β = 70.956(6)°, γ = 68.741(5)°, V = 1115.97(18) ?³, Z = 2, D _c = 1.843 g/cm³, μ = 4.264 mm⁻¹, F(000) = 618, R = 0.0177, and wR = 0.0409 for 4036 observed reflections with I ≥ 2σ(I).     

Nuclease activity of redox/non-redox active binuclear transition metal mixed-polypyridine complexes: [M2(1,4-tpbd)(diimine)2(H2O)2]4+, M = Zn,Co, Ni,Cd, diimine = phen,bpy, dafo

Seven new transition metal complexes formulated as [M₂(1,4-tpbd)(diimine)₂(H₂O)₂]⁴⁺ [M = Zn, Co, Ni, Cd; 1,4-tpbd = N,N,N′,N′-tetrakis(2-pyridylmethyl)benzene-1,4-diamine; diimine is a N,N-donor heterocyclic base like 1,10-phenanthroline (phen), 2,2′-bipyridine (bpy), 4,5-diazafluoren-9-one (dafo)] have been synthesized and structurally characterized by X-ray crystallography: [Zn₂(1,4-tpbd)(phen)₂(H₂O)₂]⁴⁺ (1), [Zn₂(1,4-tpbd)(bpy)₂(H₂O)₂]⁴⁺ (2), [Co₂(1,4-tpbd)(phen)₂(H₂O)₂]⁴⁺ (3), [Ni₂(1,4-tpbd)(phen)₂(H₂O)₂]⁴⁺ (4), [Ni₂(1,4-tpbd)(bpy)₂(H₂O)₂]⁴⁺ (5), [Ni₂(1,4-tpbd)(dafo)₂(H₂O)₂]⁴⁺ (6) and [Cd₂(1,4-tpbd)(phen)₂(H₂O)₂]⁴⁺ (7). Single crystal diffraction reveals that the metals in the complexes are all in a distorted octahedral geometry. The interactions of the seven complexes with calf thymus DNA (CT-DNA) have been investigated by UV absorption, fluorescence, circular dichroism spectroscopy and viscosity measurements. The apparent binding constants (K_app) are calculated to be 5.2?×?10⁵ M^?1 for 1, 1.05?×?10⁵ M^?1 for 2, 5.76?×?10⁵ M^?1 for 3, 4.57?×?10⁵ M^?1 for 4, 1.29?×?10⁵ M^?1 for 5, 1.7?×?10⁵ M^?1 for 6, 2.53?×?10⁵ M^?1 for 7, the binding propensity to the calf thymus DNA in the order: 3 (Co-phen) > 1 (Zn-phen) > 4 (Ni-phen) > 7 (Cd-phen) > 6 (Ni-dafo) > 5 (Ni-bpy) > 2 (Zn-bpy). Furthermore, these complexes display efficient oxidative cleavage of supercoiled DNA; the Zn(II)/H₂O₂ and Cd(II)/H₂O₂ systems efficiently cleave DNA attributed to the peroxide ion coordinated to the Zn(II) and Cd(II), which enhanced their nucleophilicity, this is rare.