Model Complexes for Ureases: A Dinickel(II) Complex with a Novel Asymmetric Ligand and Comparative Kinetic Studies on Catalytically Active Zinc,Cobalt, and Nickel Complexes

The dinuclear nickel(II) complex of the asymmetric ligand 1‐[N,N‐bis(2‐pyridylmethyl)amino]‐3‐[2‐(3,5dimethyl‐1H‐pyrazol‐1‐yl)ethoxy]‐2‐hydroxypropane (HL1) was prepared as a model for the active site of urease. The novel complex [Ni₂(L1)(MeCOO)(ClO₄)(EtOH)₂](ClO₄) · 0.5 Et₂O ( 1 ) crystallizes in the triclinic space group P 1 with a = 11.639(2) Å, b = 12.571(3) Å, c = 16.341(3) Å, α = 92.29°, β = 106.54°, and γ = 113.73°. The nickel ions (c.n. 6) are bridged by the alkoxy donor substituent of the ligand and an acetate anion. The dinuclear nickel(II), cobalt(II), and zinc(II) complexes of the ligands 1‐[N,N‐bis(2‐benzimidazolylmethyl)amino]‐3‐[2‐(3,5‐dimethyl‐1 H‐pyrazol‐1‐yl)ethoxy]‐2‐hydroxypropane (HL2), N‐methyl‐N,N',N'‐tris(2‐benzimidazolylmethyl)‐2‐hydroxy‐1,3‐diaminopropane (HL3), and N,N,N',N'‐tetrakis(2‐benzimidazolylmethyl)‐2‐hydroxy‐1,3‐diaminopropane (HL4) were investigated for their activity towards the hydrolysis of the test substrate p‐nitrophenyl acetate (npa) in ethanol‐water (1 : 1). The second‐order rate constants for the cleavage of npa were determined for all complexes. The profile of the pH dependence indicates that a hydroxide initially binds to the metal ion. The bound nucleophile subsequently attacks the test substrate. The results are discussed in terms of a refined model for the structure activity relationships of the dinuclear active site of urease.     

Synthesis,Crystal Structure and Properties of a 4,4′-Bipyridine Bridged Trigonal-Bipyramidal Copper Homobinuclear Complex with Tris(2-Aminoethyl)amine

The synthesis of the binuclear complex [(tren)Cu(4,4'-bipy)Cu(tren)] (ClO₄)₄ where tren = tris(2-aminoethyl) amine and 4,4'-bipy = 4,4'-bipyridine, is described. Single-crystal X-ray diffraction study of the homobinuclear complex shows that two copper(II) ions are bridged by 4,4'-bipyridine and each copper(II) ion is trigonal-bipyramidally coordinated, with tren occupying four sites [Cu-N = 2.030(2), 2.047(2), 2.078(2), and 2.119(2) Å respectively] and a bridging 4,4'-bipyridine in the apical position. The Cu-Cu distance is 11.11 Å. In variable-temperature ESR spectra, the presence of hyperfine structure suggest that some interaction exists between the two copper(II) ions. Temperature-dependent susceptibility studies indicate that it is a weak ferromagnetic interaction with 2J = 1.23 cm^-1.     

Crystal Structures of Alkali Metal Peroxodiphosphates

Peroxodiphosphates of alkali metals can be prepared from K₄P₂O₈, which is synthesized by electrolysis, in metathesis reactions with the corresponding perchlorates. Single crystals have been obtained by diffusion of methanol into aqueous solutions of the peroxodiphosphates. The crystal structures of Li₄P₂O₈·4H₂O (P2₁/n; a = 8.057(2) Å, b = 5.074(1) Å, c = 12.288(3) Å, β = 100.53(2)°; V = 493.9(2) ų; Z = 2), Na₄P₂O₈·18H₂O (at 130 K: P6₁; a = 9.0984(14) Å, c = 49.926(13) Å; V = 3579.2(12) ų; Z = 6) and K₄P₂O₈ (P2₁/c; a = 5.9041(15) Å, b = 10.254(2) Å, c = 7.356(2) Å, β = 99.05(3)°; V = 439.79(18) ų; Z = 2) have been determined by X‐ray diffraction. In the Li salt the cations are tetrahedrally coordinated by one water molecule and three oxygen atoms of the anions, whereas the Na salt is characterized by binuclear [Na₂(H₂O)₉]²⁺ complexes. At low temperatures, the latter undergoes a phase transition from a structure with disordered anions to a completely ordered phase. K₄P₂O₈ is solvent‐free and exhibits irregular cation coordination. The structure of the peroxodiphosphate anion is very similar in all compounds; the mean O–O distance is 1.49(1) Å. In addition, the structure determination of K₄(HPO₄)₂·3H₂O₂ (P2₁/n; a = 6.076(1) Å, b = 6.579(1) Å, c = 17.215(2) Å, β = 99.73(1)°; V = 678.26(17) ų; Z = 2), which can be mistaken for K₄P₂O₈, is presented.     

Dinuclear copper(II) complex and 1-D copper(II) complex with taurine Schiff base: synthesis,crystal structure,and properties

A dinuclear copper(II) compound, [Cu(btssb)(H₂O)]₂ · 4(H₂O) (1), and a 1-D chain copper(II) compound, [Cu(ctssb)(H₂O)] _n (2) [where H₂btssb is 2-[(5-bromo-2-hydroxy-benzylidene)-amino]-ethanesulfonic acid and H₂ctssb is 2-[(3,5-dichloro-2-hydroxy-benzylidene)-amino]-ethanesulfonic acid], were prepared and characterized. Compound 1 crystallizes in the monoclinic space group P2₁/c, with a = 10.109(2) Å, b = 20.473(4) Å, c = 6.803(1) Å, β = 100.32(3)°, V = 1385.1(5) ų, and Z = 2; R ₁ for 1796 observed reflections [I > 2σ(I)] was 0.0357. The geometry around each copper(II) can be described as slightly distorted square pyramidal. The Cu^II ··· Cu^II distance is 5.471(1) Å. Compound 1 formed a 1-D network through O–H ··· O hydrogen bonds and 1-D water chains exist. The 1-D chain complex 2 crystallizes in the triclinic space group P 1, with a = 5.030(2) Å, b = 7.725(2) Å, c = 17.011(5) Å, α = 92.706(4)°, β = 97.131(4)°, γ = 102.452(3)°, V = 638.6(3) ų, and Z = 2; R ₁ for 1897 observed reflections [I > 2σ(I)] was 0.0171. In 2, Cu(II) was also a slightly distorted square pyramid formed by two oxygens and one nitrogen from ctssb, one oxygen from another ctssb, and one water molecule. The complex formed a 1-D chain through O–S–O bridge of ctssb ligand. The 1-D chain further constructed a double chain through O?H ··· O hydrogen bonds.     

Synthesis,Crystal Structure,and Thermal Behaviour of Some New Copper Complexes with tridentate β-iminoketone ligands

The reaction of Cu(AcO)₂ · H₂O and tridentate β-iminoketone ligands yielded four new copper complexes: acetato{4-{[2-(dimethylamino)ethyl]amino}pent-3-en-2-onato}copper(II) ( 1 ), triacetato{4-{[3-(dimethylamino)-propyl]amino}pent-3-en-2-onato}dicopper(II) ( 2 ), {4-{[2-(dimethylamino)ethyl]amino}-1,1,1-trifluoropent-3-en-2-onato}( trifluoroacetato)copper(II) ( 3 ), and pentaacetato{4-{[3-(dimethylamino)propyl]amino}-1,1,1-trifluoropent-3-en-2- onato}tricopper(II) ( 4 ). All compounds were coloured and air-stable solids. The crystal structures of 1 and the dioxane adduct of 3 , μ-(1,4-dioxane)bis{{4-{[2-(dimethylamino)ethyl]amino}-1,1,1-trifluoropent-3- en-2-onato}(trifluoroacetato)copper(II)} ( 3a ), were determined. Complex 1 consists of dimeric units [{Cu(AcO)L}₂] in the solid state (L = β-iminoketonato ligand). In 3a , two [Cu(CF₃COO)L] are linked via the O-atoms of the coordinated solvent 1,4-dioxane. Compound 1 crystallized in the monoclinic space group P2₁/n with a formula unit in a cell having the dimensions a = 11.152(6)Å, b = 10.104(3)Å, c = 11.805(7)Å, and β = 99.02(4)Å, and compound 3a crystallized in the triclinic space group P1 with a formula unit in a cell having the dimensions a = 8.709(3)Å, b = 9.439(4)Å, c = 12.395(3)Å, α = 67.57(3)°, β = 77.01(2)°, and β = 84.17(3)°. Mass spectra (MS), thermal analysis (DTA/TG), and evaporation-rate measurements are reported for all compounds. The influence of fluorination on the structure and volatility will be discussed.     

Molecular and Low‐dimensional Coordination Compounds of Copper(II) and 3, 5‐Dimethylpyrazole — Synthesis,Crystal Structure,and Properties

Three 3, 5‐dimethylpyrazole (pz*) copper(II) complexes, [Cu(pz*)₄(H₂O)](ClO₄)₂ ( 1 ), [Cu(pz*)₂(NCS)₂]·H₂O ( 2 ), and [Cu(pz*)₂(OOCCH=CHCOO)(H₂O)]·1.5H₂O ( 3 ), have been synthesized and characterized with single crystal X‐ray structure analysis. 1 crystallizes in the tetragonal space group, 14/m, with a = 14.027 (3) Å, c = 16.301 (5) Å, and Z = 4. 2 crystallizes in the monoclinic space group, P2₁/c, with a = 8.008 (3) Å, b = 27.139 (9) Å, c = 8.934 (3) Å, β = 106.345 (6)°, and Z = 4. 3 crystallizes in the triclinic space group, P1¯, with a = 7.291 (9) Å, b = 10.891 (13) Å, c = 11.822 (14) Å, α = 80.90 (2)°, β = 79.73(2)°, γ = 70.60(2)°, and Z = 2. In 1 , one water molecule and four pz* ligands are coordinated to Cu^II. Two [Cu(pz*)₄(H₂O)]²⁺ units are connected to ClO₄^— via hydrogen bonds. One lattice water molecule is found in the unit cell of 2 , which forms an one‐dimensional chain via intermolecular hydrogen bonds with the N‐H atom of pz*. In 3 , the oxygen atom of the coordinated water molecule is connected with two C=O groups of two neighbouring maleic acid molecules to form a linear parallelogram structure. Another C=O group of maleic acid forms a hydrogen bond with the N‐H atom of pz* to create a two‐dimensional structure. The spectroscopic and bond properties are also discussed.     

Synthesis,Spectroscopic and Electrochemical Studies of Isomeric Dichloro-bis-[ N (1)-Alkyl-2-(Arylazo)Imidazole]-Osmium(II). Single Crystal X-ray Structures of Blue-Violet Dichloro-Bis-[ N (1)-Methyl-2-(Arylazo)Imidazole]-Osmium(II) Species

1-Alkyl-2-(arylazo)imidazoles (p-R-C₆H₄-N=N-C₃H₂N₂X, abbreviated as RaaiX, R = H(a), CH₃(b), Cl(c); X = N(1)-CH₃ (1), N(1)-CH₂-C₆H₅ (2)) have been reacted with (NH₄)₂[OsCl₆] and OsCl₂(RaaiX)₂ species isolated in two isomeric forms, blue-violet (3, 5) and red-violet (4, 6). IR spectra show two x (Os-Cl) modes and support a cis-OsCl₂ configuration. X-ray diffraction methods were used to determine structures of blue-violet isomers. In terms of the three coordination pairs around Os(II), Cl, Cl, N, N (N(imidazole), N) and N', N' (N(azo), N') the blue-violet isomers have a cis-trans-cis (ctc) configuration. ¹H NMR data for the red-violet complexes (isomers B) and results concerning analogous ruthenium(II) complexes indicate isomer B to have cis-cis-cis (ccc) configuration. Absorption spectra show an intense MLCT band at ca 580 nm along with two weak bands at 800 and 1000 nm. Cyclic voltammetry shows quasi-reversible Os(III)/Os(II) and Os(IV)/Os(III) couples at 0.4-0.6 V and 1.3-1.5 V versus SCE and ill-defined azo reductions. The X-Ray structures show unusually long N=N bond lengths, 1.31-1.32 Å, elongated by some 0.06 Å compared to the free ligand value. Os(II) prefers to bind N(azo) (Os-N(azo), 1.98 Å) rather than N(imidazole) (Os-N(imidazole), 2.03 Å). EHMO calculations of ctc-OsCl₂ (MeaaiMe) and comparison with the ruthenium(II) complex account for the MLCT transitions in terms of a metal-dominated HOMO to a ligand-dominated LUMO shift.     

Synthesis,structure, and DNA-binding studies of a new tetracopper(II) complex bridged by dissymmetrical N-benzoato-N′-(2-aminoethyl)oxamide

A new oxamido-bridged tetracopper(II) complex, [Cu₄(oxbe)₂(bpy)₂](ClO₄)₂ · 2H₂O, where H₃oxbe and bpy stand for N-benzoato-N′-(2-aminoethyl)oxamide and 2,2′-bipyridine, has been synthesized and characterized by elemental analyses, molar conductivity, infrared and electronic spectra, and single-crystal X-ray diffraction. It crystallizes in triclinic system, space group P-1, with crystallographic data: a = 7.829(5) Å, b = 12.680(5) Å, c = 13.420(5) Å, α = 104.665(5)°, β = 95.275(5)°, γ = 106.931(5)°, and Z = 1. The circular tetranuclear copper(II) cation [Cu₄(oxbe)₂(bpy)₂]²⁺ with an embedded center of inversion is assembled by a pair of cis-oxbe-bridged dinuclear copper(II) units through coordination between carboxyl and copper(II). One copper(II) is located in a slightly distorted square-planar environment, while the other is in a distorted square-pyramidal geometry. In the crystal structure, abundant hydrogen bonds and aromatic stackings link the tetranuclear copper(II) units into an overall 3-D framework. Interactions of the tetranuclear copper(II) complex with herring sperm DNA (HS-DNA) are investigated by using UV absorption and fluorescence spectra, electrochemical techniques, and viscometry. The results suggest that the tetranuclear copper(II) complex interacts with DNA by intercalation with an intrinsic binding constant of 1.47 × 10⁵ mol^?1 L.     

Synthesis and Characterization of Binuclear (μ-Oxalato) Copper(II) Complexes with N,N′-Diethylethylenediamine or N,N,N′-Trimethylethylenediamine

Three new binuclear w -oxalato copper(II) complexes of composition [(Cu(N,N' -dieten) H₂O)₂ox](ClO₄)₂ ·H₂O (1) (N,N'-dieten = N,N'-diethylethylenediamine, H₂ox = oxalic acid), [(Cu(trimeen)H₂O)₂ox](ClO₄)₂·2H₂O (2) (trimeen = N,N,N'-trimethylethylenediamine) and [(Cu(trimeen)H₂O)₂ox](NO₃)₂ ·2H₂O (3) have been isolated from the reactions of Cu(ClO₄)₂ ·6H₂O (or Cu(NO₃)₂ ·3H₂O), the appropriate amine and Na₂ox in water and have been characterized by IR and electronic spectroscopy and magnetic measurements. The crystal structure of [(Cu(N,N' -dieten)H₂O)₂ ox](ClO₄)₂.H₂O (1) has been determined by single-crystal X-ray analysis. The structure of ( 1 ) consists of binuclear cations [(N,N'-dieten)H₂O)Cu(ox)Cu(N,N'-dieten)H₂O)]²⁺, perchlorate anions and water molecules of crystallization. The copper atom is coordinated by two oxygen atoms of the oxalato ligand, two nitrogen atoms belonging to N,N'-dieten and one oxygen atom of water in a distorted square-pyramidal arrangement. The temperature dependence of magnetic susceptibilities (78-293 K) was measured for 1-3 . Magnetochemical measurements show that copper(II) ions in these compounds are antiferromagnetically coupled with J = -172 cm^-1, -172 cm^-1 and -168 cm^-1 (H = -2JS ₁ S ₂, S ₁= S ₂ = 1/2) for 1, 2 and 3, respectively.     

Structure and EPR spectra of binuclear copper(II) complexes with acyldihydrazones of benzenedicarboxylic acids and 5-substituted 2-hydroxyacetophenones

Binuclear copper(II) complexes with acyldihydrazones of 1,3- or 1,4 benzenedicarboxylic acid and 5-methyl- or 5-bromo-2-hydroxyacetophenone in which coordination polyhedra are connected by an aromatic bridge have been synthesized and studied. The structure of the copper(II) complex with diacylhydrazone of isophthalic acid and 2-hydroxy-5-methylacetophenone (H₄L) of composition [Cu₂L · 3Py] was studied by X-ray diffraction. The crystals are monoclinic: a = 12.1996(12) Å, b = 17.7295(17) Å, c = 17.9339(17) Å, β = 109.7450(10)°, space group P2₁/n, Z = 4. The complex is of the “dimer of dimers” type and contains two binuclear subunits that bind together into a centrosymmetric dimer owing to the coordination of the copper cation to the phenoxyl oxygen atom of a neighboring binuclear molecule to form the Cu₂O₂ moiety, in which the copper atoms are 3.409 Å apart. The distance between the copper(II) cations in the binuclear subunit is 8.56 atoms (2N + O) of the doubly deprotonated acylhydrazone moiety and the nitrogen atom of the pyridine molecule. One of the copper cation is additionally coordinated to an extra pyridine molecule so that its coordination sphere is completed to a tetragonal pyramid. The second copper atom is involved in additional interaction with the phenoxyl oxygen atom of the neighboring molecule. The EPR spectra of solutions of the binuclear complexes show an isotropic signal of four HFS lines (g _o = 2.065–2.143, a _Cu = 52.1–66.5 × 10^?4 cm^?1) typical of mononuclear copper(II) complexes.     

Complex Species in Aqueous Solutions of 4-Chloro-1,2-Phenylenediamine-N,N,N′,N,'-Tetraacetic Acid with Magnesium(II), Calcium(II), Strontium(II), Barium(II), Zinc(II) and Cadmium(II)

Abstract

The coordination in aqueous solution of 4-chloro-1,2-phenylenediamine-N',N',N',N'-tetraacetic acid (4-Cl-o-PDTA) with Be(II) and with the transition metal cations cobalt(II), nickel(II) and copper(II) was reported in earlier publications.^1,2 In this note a study is presented of the coordination in aqueous solution (25°C, 1 = 0.1 M in KC1) of 4-CI-o-PDTA acid with magnesium(II), calcium(II), strontium(II), barium(II), zinc(II) and cadmium(II).     

Crystal Structure and Superoxide Dismutase Activity of [Cu(Imidazole)2(Quinoline)Cl2]·0.5[Cu(Imidazole)4Cl2]

The preparation, spectroscopic properties and crystal structure of (bis-imidazole)quinoline-copper(II) dichloride [Cu(Im)₂(quin)Cl₂] (Im = imidazole, quin = quinoline) and tetraimidazole-copper(II)-dichloride [Cu(Im)₄Cl₂] are reported. Both cocrystallize on the triclinic system, space group P-1, with cell constants a = 8.095(5) Å, b = 12.141(5) Å, c = 13.847(5) Å, α = 108.816(5)°, β = 104.173(5)°, γ = 94.965(5)° and Z = 2. In the [Cu(Im)₂(quin)Cl₂] complex the copper(II) ion is coordinated to two imidazole molecules, to one quinoline and two chlorine ions, with the copper(II) ion in a distorted trigonal bipyramidal coordination geometry. In the [Cu(Im)₄Cl₂] complex, the copper(II) ion has a distorted octahedral coordination geometry. The superoxide dismutase mimetic activity of the complexes was investigated using the indirect xanthine-xanthine oxidase-nitroblue tetrazolium method and compared to that of the native enzyme.     

COPPER CATALYZED HYDROLYSIS OF TRIAZINE: SYNTHESIS AND STRUCTURE OF Cu(HN = CHNHCH = NH)2(ClO4)2

Abstract

Reaction of Cu(ClO₄)₂·6H₂O with 1,3,5-triazine in 95% ethanol resulted in partial hydrolysis of the triazine ring and isolation of bis(1,3,5-triaza-1,4-pentadieno) copper(II) perchlorate, (1). Compound 1 crystallizes as violet needles. Crystal data for Cu(HN = CHNHCH = NH)₂(ClO₄)₂ are: monoclinic, space group: C2/c, a = 13.342(3), b = 11.186(2), c = 18.045(4) Å, β = 99.09(3)°, V = 2659.3(10) ų, Z = 8, D_calc = 2.021 Mg/m³, μ = 2.096 mm^?1, F(000) = 1624, MoK_α (γ = 0.71069Å), R = 0.063 for 1597 unique observed [≥Fα3σ(F)] reflections and 196 parameters. The bis-chelated copper(II) ion contains a planar coordination geometry with Cu-N_(ave) = 1.97Å and the perchlorate ions weakly coordinated (Cu - 0 = 2.84Å) in the axial positions.     

Gemischtligandkomplexe des Technetiums. XV. Zur Reaktion von [TcNCl2(Me2PhP)3] mit Dialkyldithiocarbamaten und N,N-Dialkylthiocarbamoylbenzamidinen

Mixed-ligand Complexes of Technetium. XV. The Reaction of [TcNCl₂(Me₂PhP)₃] with Dialkyldithiocarbamates and N,N-Dialkylthio-carbamoylbenzamidines [TcN(Cl)(Me₂PhP)₂(Et₂dtc)], [TcN(Me₂PhP)(Et₂dtc)₂], and [TcN(Et₂dtc)₂] can be prepared by stepwise ligand exchange reactions starting from dichlorotris(dimethylphenylphosphine)nitridotechnetium(V), [TcNCl₂(Me₂PhP)₃], and diethyldithiocarbamate. In contrast to this, only one intermediate, [TcN(Cl)(Me₂PhP)₂(HEt₂tcb)], could be isolated during the reaction with N,N-Diethlthiocarbamoylbenzamidine, which yields the bis chelate [TcN(HEt₂tcb)₂]. [TcN(Me₂PhP)(Et₂dtc)₂] crystallizes in the monoclinic space group P2₁/c; a = 17.369(5) Å, b = 15.024(1) Å, c = 9.906(3) Å, β = 76.47(1)º, Z = 4. The phosphine is coordinated equatorially. The multiply bonded nitrogen ligand (Tc? N(1) 1.624(3) Å) strongly labilizes the trans positioned donor atom (distance Tc? S(4) 2.826(1) Å). [TcN(HEt₂tcb)₂] crystallizes in the triclinic space group P1 with a = 9.749(4) Å, b = 11.264(4) Å, c = 12.359(4) Å, α = 75.34(2)º, β = 79.69(2)º, γ = 87.55(2)º, Z = 2. The metal is five-coordinate with the nitrido donor atom occupying the apex of a square pyramid. It's basal plane is formed by the cis-coordinated chelate ligands. The technetium is situated over the basal plane by about 0.6 Å. The Tc?N distane was found to be 1.610(5) Å.     

A cobalt(III) compound of a 13‐membered cyclic tetra­amine: trans‐(12,12‐dimethyl‐1,4,7,10‐tetra­aza­cyclo­tetra­decane)diisothio­cyanato­cobalt(III) tetra­isothio­cyanato­zinc(II) ethanol solvate

The title compound, [Co(NCS)₂(C₁₁H₂₆N₄)]₂[Zn(NCS)₄]·C₂H₅OH, has two similar cations with the Co^III atom coordinated in a planar fashion by the 13‐membered cyclic tetra­amine, in the 1R,4S,7R,10S configuration, and with trans isothio­cyanate ligands. The six‐membered chelate ring is in a chair conformation, with one axially and one equatorially oriented methyl substituent [mean Co—N = 1.948 (2) Å]. The `opposite' chelate ring (N<sup>4</sup> and N<sup>7</sup>) is in an eclipsed conformation [mean Co—N = 1.928 (2) Å], and the `side' chelate rings have gauche conformations. The mean Co—N_NCS distance is 1.928 (2) Å. Both cations have one Co—N—C group nearly linear and the other appreciably bent, with mean Co—N—C angles of 178.7 (1) and 160.4 (1)°, respectively. The [Zn(NCS)₄]²⁻ anion is approximately tetra­hedral, with Zn—N = 1.951 (1)–1.986 (1) Å, N—Zn—N = 104.5 (1)–111.9 (1)° and Zn—N—C = 152.5 (1)–179.4 (1)°. One NH group is hydrogen bonded to the ethanol O atom and the other NH groups are bonded to thio­cyanate S atoms, forming a network.     

Structural Relationships between the Hemiporphyrazine Macrocyclic Ligand and its Metal Complexes. II.: Planar Neutral Ligand,C26H16N8, and Four Isomorphous Metal Complexes, [M(C26H16N8)(H2O)], M=Mn(II), Co(II), Cu(II), Zn(II)

Crystal and molecular structures of the planar neutral ligand, C₂₆H₁₆N₈, and the four isomorphous five-coordinated metal complexes, [M(C₂₆H₁₆N₈)(H₂O)], M = Mn(II), Co(II), Cu(II), Zn(II), have been determined from three-dimensional X-ray diffraction data. The free ligand hpH₂, C₂₆H₁₆N₈, belongs to the P 2₁/c space group with Z=2, a=4.142(3), b=23.736(6), c=10.338(3) Ä, β=94.66(6)°. The metal complexes monohydrate Mhp-H₂O all belong to the orthorhombic Pcab space group with Z=8. The dimensions are roughly 8.8×19.3×23.7 ų. In each structure, the macrocyclic ligand has an almost planar conformation which differs from the saddle shaped ligand hydrate (hpH₂·H₂O) and the nickel complex [Nihp]⁵. The distances from the center of the macrocyclic ring to the nitrogen atom of the free ligand are 1.907(6) and 2.245(6)Å. The coordination geometry in these four complexes is square pyramidal with a water molecule as an axial ligand. The bond distances of M(II)-O(H₂O), M(II)-N1 (imine), M(II)-N3 (pyridine) are: 2.19(1), 2.00(2), 2.27(2)Å respectively for the manganese complex; 2.08(1), 1.97(1), 2.23(1)Å for the cobalt complex; 2.33(1), 1.92(3), 2.18(1)Å for the copper complex; 2.110(5), 1.964(6), 2.252(6)Å for the zinc complex. The variation of metal-ligand distances can be correlated to the metal d orbital occupancy. A comparison with similar ligands will be presented.     

Synthesis,Crystal Structure and Magnetic Properties of a Two-Dimensional Heterometallic Assembly ∣[Mn(salen)]∣2∣[Ni(CN)4∣·1/2H2O

A heterometallic assembly, [Mn(salen)]₂[Ni(CN)₄ ]·1/2H₂O (where salen=N, N'-ethylene-bis(salicylideneiminato)-dianion), has been prepared from the reaction of [Mn(salen)H₂O]ClO₄ ·H₂O with K₂ [Ni(CN)₄ ]·H₂O in methanol/water. The compound crystallizes in the tetragonal space group P 4/ncc with the cell dimensions of a =14.604(2) Å, c =16.949(3) Å, and Z=4. The compound assumes a two-dimensional distorted square network structure, formed from Ni―CN―Mn(salen)―NC―Ni linkages with dimensions of Ni―C = 1.867(7)Å, Mn―N - 2.312(6) Å, Mn―N―C - 163.8(6)° Ni―C―N = 178.4(6)°. The two metal atoms Ni(II) and MN(III) have square and slightly distorted octahedral arrangements, respectively. Magnetic susceptibility measurements indicate the presence of an intramolecular antiferro-magnetic interaction and gives a Mn―Mn exchange integral of ?3.2cm^?1.     

The synthesis,crystal structures and infrared spectra of bis(2,2′-bipyridyl)mononitratozinc(II) hexafluorophosphate and bis(2,2′-bipyridyl)mononitratozinc(II) perchlorate: A comparison with existing [Zn(chelate)2(OXO)][Y] and [Cu(chelate)2(OXO)][Y] complexes of known crystal structure

In order to extend the number of [Zn(chelate)₂(OXO)][Y] complexes, with chelate =2,2″ bipyridyl, 1,10 phenanthroline and 2,2″-bipyridylamine and (OXO)^-=(ONO)^-, (O₂NO)^-, (O₂CCH₂)^- and (O₂CH)^-, the crystal structures and infrared spectra of [Zn(bipy)₂(O₂NO)][PF₆], (9) and [Zn(bipy)₂(O₂NO)][ClO₄], (10) have been determined. Both zinc(II) complexes involve a slightly elongated cis-distorted ZnN₄O₂ chromophore.The slight elongation contrasts with the more significant compressed cis-distorted octahedral CuN₄O₂ chromophore of the corresponding copper(II) structures. The Zn‐O bonds in (9) are 2.186(3) and 2.351(3)Å (ΔO0.165(3)Å), while the corresponding Zn‐O(1) and Zn‐O(2) bonds in (10) are 2.194(2) and 2.355(2)Å (ΔO0.161(2)Å), respectively. The mean Zn‐O bond distance in (9) is 2.269(3) and 2.275(2)Å in (10). Although the significant cis-distortion of the Zn‐O distances is comparable to the analogous Cu‐O distances, the ΔO values are notably smaller. The thermal ellipsoids of (9) and (10), which are slightly asymmetric (ΔO ≈ 0.16Å), are small and isotropic. Such differences reflect the spherical symmetry of the d ¹⁰ zinc(II) configuration relative to the nonspherical symmetry of the d ⁹ copper(II) ion.The ZnN₄O₂ chromophores of (9) and (10) are similar, indicating the isomorphous and isostructural nature of the complexes. Both complexes have a common back-angle or magic angle of α≈117°, in contrast to the bipyam complexes where the back-angle is much less at ≈105°, related to the conformation of the floppier bipyam chelate ligand.     

Spectroscopic studies and X-ray crystal structures of charge-transfer complexes of 1,4,7-trithiacyclononane with diiodine

1,4,7-Trithiacyclononane ([9]aneS₃) reacts with molecular diiodine in CH₂Cl₂ to form a 1:1 adduct. The formation constant and the thermodynamic parameters of this adduct have been determined by UV-visible spectra of several solutions at the temperatures of 15, 20, 25, 30, and 35°C. The ¹³C NMR spectra show that adducts with higher ligand/diiodine molar ratios are formed. Two neutral charge-transfer molecular compounds having formula 2[9]aneS₃ · 4I₂ ( I ) and [9]aneS₃ · 3I₂ · ( II ) have been obtained as crystals. The crystals of I are triclinic (a = 8.498(2) Å, b = 13.984(4) Å, c = 14.898(6) Å, α = 65.57(2)°, γ = 89.19(2)°, γ = 81.26(2)°, Z = 2, space group P1; R = 0.025) and contain units formed by two [9]aneS₃ molecules connected by a diiodine molecule; one [9]aneS₃ binds two other diiodine molecules, while the second binds only one other diiodine molecule. The crystals of II are monoclinic (a = 13.810(2) Å, b = 9.829(4) Å, c = 16.198(6) Å, β = 113.41(2)°, Z = 4, space group P2₁/c; R = 0.019) and contain molecules of [9]aneS₃ binding three diiodine molecules. FT-Raman spectra in the characteristic v(I–I) region, carried out on the solid adducts, are discussed in comparison with the structural parameters.     

A new two-dimensional polymeric copper(II) complex bridged both by oxamidate and azide groups: synthesis,structure and DNA binding properties

A new two-dimensional polymeric copper(II) complex, [Cu₂(heae)(N₃)₂] _n , where heae stands for the dianion of N,N′-bis(N-hydroxyethylaminoethyl)oxamide, has been synthesized and characterized by elemental analysis, molar conductivity measurement, IR, electronic spectral studies and single-crystal X-ray diffraction. The compound crystallizes in the monoclinic system, P2₁/c space group with crystallographic data: a = 9.1588(18) Å, b = 6.6238(13) Å, c = 14.602(3) Å and Z = 2. The X-ray analysis reveals a two-dimensional copper(II) polymeric coordination network constructed by bis-tridentate chelated [Cu(trans-heae)Cu]²⁺ building blocks and end-on azido ligands. The environment around the copper(II) atom can be described as a square-based pyramid. The azido bridge is very asymmetric with one Cu–N bond distance short and the other long. The Cu ··· Cu separations through μ-trans-oxamidate and μ-azido bridges are 5.2996(13) Å and 4.2464(7) Å, respectively. The copper(II) complex is a polymer in the solid state, whereas in solution it exists as discrete neutral binuclear copper(II) species. Coordination mode of the azide in solution is proved by electronic spectra. The DNA-binding properties of the binuclear copper(II) species were investigated by emission spectral and electrochemical techniques, indicating the binuclear copper(II) complex binds to HS-DNA via a groove mode.