A non-aqueous organometallic route to highly monodispersed copper nanoparticles using [Cu(OCH(Me)CH2NMe2)2

Good quality, highly monodispersed capped copper metal nanoparticles have been synthesised in a non-hydrolytic approach using thermal decomposition of the Cu(II) precursor [Cu(OCH(Me)CH2NMe2)2] in a hot coordinating solvent without further reducing agents; the copper nanoparticles have been characterised by optical spectroscopy (UV/VIS), electron microscopy (TEM), electron diffraction (SAED), and dynamic light scattering (DLS).     

Inorganic-organic hybrids of the p,p'-diphenylmethylenediphosphinate, pcp2-. Synthesis, characterization, and XRPD structures of [Sn(pcp)] and [Cu(pcp)

Two new inorganic-organic polymeric hybrids [Sn(pcp)] and [Cu(pcp)], pcp=CH2(PhPO2)2(2-), have been synthesized and structurally characterized. The tin derivative has been obtained by reaction of the p,p'-diphenylmethylenediphosphinic acid (H2pcp) in water with SnCl2.2H2O, while the copper derivative has been synthesized through a hydrothermal reaction from the same H2pcp acid and Cu(O2CMe)2.H2O. The structures of these compounds have been solved "ab initio" by X-ray powder diffraction (XRPD) data. [Sn(pcp)] has a ladder-like polymeric structure, with tin(II) centers bridged by diphenylmethylenediphosphinate ligands, and alternating six- and eight-membered rings. The hemilectic coordination around the metal shows the tin(II) lone pair to be operative, resulting in significant interaction mainly with a C-C bond of one phenyl ring. The [Cu(pcp)] complex displays a polymeric columnar structure formed by two intersecting sinusoidal ribbons of copper(II) ions bridged by the bifunctional phosphinate ligands. The intersections of the ribbons are made of dimeric units of pentacoordinated copper ions. Crystal data for [Sn(pcp)]: monoclinic, space group P2(1)/c, a=11.2851(1), b=15.4495(6), c=8.6830(1) A, beta=107.546(1) degrees, V=1443.44(9) A, Z=4. Crystal data for [Cu(pcp)]: triclinic, space group P, a=10.7126(4), b=13.0719(4), c=4.9272(3) A, alpha=92.067(5), beta=95.902(7), gamma=87.847(4) degrees, V=685.47(7), Z=2. The tin compound has been characterized by 119Sn MAS NMR (magic-angle spinning NMR), revealing asymmetry in the valence electron cloud about tin. Low-temperature magnetic measurements of the copper compound have indicated the presence of weak antiferromagnetic interactions below 50 K.     

Novel Michael addition products of bis(amino acidato)metal(II) complexes: synthesis, characterization, dye degradation, and oxidation properties

Michael addition reactions of bis(amino acidato)metal(II) complexes (metal = copper, nickel, zinc; amino acid = glycine, dl-alanine, l-alanine) with acrylonitrile have been carried out under various experimental conditions in the absence of a base, resulting in mono- and disubstituted products in high yield, including partially hydrolyzed products. A reaction mechanism for the Michael addition on the nitrogen atom of the coordinated amino acid moiety, replacing the amino hydrogen atom(s), is proposed. All of the products have been characterized by Fourier transform infrared spectroscopy, electron paramagnetic resonance spectra, and elemental and electrochemical analyses. The single-crystal structures of bis( N-cyanoethylglycinato)copper(II) monohydrate ( 1a), diaquabis( N-cyanoethylglycinato)nickel(II), aquabis( N, N-dicyanoethylglycinato)copper(II) ( 2a), and bis[( N-propionamido- N-cyanoethyl)glycinato]copper(II) dihydrate ( 4a) have been confirmed by X-ray diffraction techniques. The products 1a, 2a, 4a, and bis( N-propionamidoglycinato)copper(II) monohydrate ( 3a) have been used as catalysts for the degradation of a phenol red dye and mild oxidation of various organic substrates in the presence of hydrogen peroxide. The monosubstituted complexes have been found to catalyze the reactions to a greater extent than the disubstituted complexes.     

Preparation and characterization of copper sulfide nanoparticles from symmetrical [(Bu)2NC(S)NC(O)C6H3(3,5-NO2)2]2Cu(II) and [(Bu)2NC(S)NC(O)C6H4(4-NO2)]2Cu(II) complexes by thermolysis

Trigonal copper sulfide nanoparticles were synthesized from symmetrical [(Bu)₂NC(S)NC(O)C₆H₃(3,5-NO₂)₂]₂Cu(II) and [(Bu)₂NC(S)NC(O)C₆H₄(4-NO₂)]₂Cu(II) complexes by thermolysis in the presence of surfactant oleylamine. The symmetrical copper complexes were synthesized by reaction of copper(II) acetate with N-(3,5-dinitrobenzoyl)-N′,N′-dibutylthiourea and N-(4-nitrobenzoyl)-N′,N′-dibutylthiourea. The symmetrical copper complexes were characterized by FT-IR spectroscopy, elemental analysis, and mass spectrometry (MS-APCI). The single-crystal X-ray structure of [(Bu)₂NC(S)NC(O)C₆H₄(4-NO₂)]₂Cu(II) has been determined from single-crystal X-ray diffraction data. These metal complexes have been used as single source precursors for the preparation of copper sulfide nanoparticles. The deposited copper sulfide nanoparticles were characterized by X-ray powder diffraction and transmission electron microscopy.     

Hydrothermal Synthesis,Crystal Structure and Electrochemical Properties of the Copper(II) Complex [Cu_4O_4(phen)_4(ClC_6H_4COO)_2(H_2O)_2]·(H_2O)_3

1 INTRODUCTION As we all know, copper is a necessary trace element for human body. For example, a large number of bi- nuclear or multi-nuclear transition metallic complex- es exist in active centers of some metalloprotein[1]. In the 1960’s, Bertand and Bock et al[2] reported the first tetra-nuclear copper complex with Cu4O3 unit. In 1996, a cyclo-tetranucleate complex bridged by pyridine was synthesized by Zhang Hua etc[3]. In 1999, Tan Xiangshi and coworkers[4] presented a cubic tet…     

Corrosion inhibition performance of 2-ethyl phenyl-2, 5-dithiohydrazodicarbonamide on Fe (110)/Cu (111) in acidic/alkaline solutions: Synthesis,experimental, theoretical,and molecular dynamic studies

Herein, 2-ethyl phenyl-2,5-dithiohydrazodicarbonamide (2EPDCA) was synthesised and tested as a corrosion inhibitor for mild steel (MS) and copper (Cu) in 1 M HCl and 3.5% NaCl, respectively. Fourier transform infrared spectroscopy (FT-IR) and (NMR) nuclear magnetic resonance (¹H, ¹³C) were used to identify the chemical structure. Both experimental and computational approaches have been conducted to evaluate inhibitor efficiency on both metal systems. The electrochemical results showed that the 2EPDCA inhibition efficiency for MS systems was 95% at 1 × 10^?2 M, while in copper systems it was 97.5% at 1 × 10^?2 M. The Langmuir adsorption isotherm was fitted using adsorption surface coverage data, and for inhibitor in both systems, the kind of adsorption was mixed (physisorption and chemisorption). Through scanning electron microscopy (SEM), EDX, and atomic force microscopy (AFM) tests, we have confirmed the presence of the inhibitor molecules on the metal surface in both systems. Quantum chemistry simulations indicate that the superior corrosion inhibition efficacy of 2EPDCA on copper compared to mild steel surfaces is attributable to the former's greater electron donating propensity on copper. The adsorption of 2EPDCA molecules on Fe (110) and Cu (111) surfaces was further verified by molecular dynamic simulations, with the former having a greater adsorption energy. The results indicate that the corrosion inhibitor was effective even in harsh conditions, and it can be thought of as a novel corrosion inhibitor for mild steel and copper that provides good protection.     

Pyridazine-bridged copper(I) complexes of bis-bidentate ligands: tetranuclear [2 x 2] grid versus dinuclear side-by-side architectures as a function of ligand substituents

Eight bis-bidentate Schiff-base ligands, derived from 3,6-diformylpyridazine and substituted amino-benzenes, have been prepared. A variety of electron donating/withdrawing and/or sterically demanding/undemanding substituents were employed. Two ligands and five of the six pure copper(I) complexes have been structurally characterised. The sterically unhindered ligand derived from 3,5-difluoroaniline, (m,m-F), was almost completely flat whereas the very sterically hindered ligand derived from trimethylaniline, (o,o,p-Me), was severely twisted. The only dinuclear side-by-side complex obtained, [Cu(I)(2)((o-Ph))(2)](PF(6))(2), was of the ligand derived from 2-aminobiphenyl. All five of the other complexes are believed to be [2 x 2] tetranuclear grid complexes, and this was unequivocally shown to be the case for four of these complexes, [Cu(I)(4)((p-Me))(4)](PF(6))(4), [Cu(I)(4)((o,p-Me))(4)](PF(6))(4), [Cu(I)(4)((m,m-F))(4)](PF(6))(4) and [Cu(I)(4)((m,m-Cl))(4)](PF(6))(4). In all cases the copper(I) centres are substantially distorted from tetrahedral, with the most severe distortion present in the side-by-side complex. In the absence of any special effects, tetracopper(I) [2 x 2] grid architectures are observed to be the favored outcome for 1 : 1 reactions of these bis-bidentate ligands with copper(I) ions. Only when the aromaticity of the ligand was extended by employing a phenyl substituent on the phenyl rings, (o-Ph), did a dicopper(I) side-by-side architecture result. Cyclic voltammetry in acetone revealed that the free ligands did not undergo reduction until potentials below -0.8 V, whereas between three and four reversible one electron reductions were observed, between +0.16 and -0.71 vs. AgCl/Ag, for the tetranuclear copper(I) [2 x 2] grid complexes. The redox potentials observed for these complexes are highly dependent on the nature of the ligand phenyl ring substituent(s). The side-by-side complex had one irreversible reduction process, E(pc)ca.-0.5 V.     

铜(Ⅱ)-羟肟络合物的电子自旋共振谱研究

本文报导芳香族羟肟铜(Ⅱ)络合物的电子自旋共振(ESR)谱的研究。讨论了这类配位体上取代基的电子效应对络合物中铜(Ⅱ)的超精细分裂常数A_(Cu)值的影响,以及A_(Cu)值与这些配位体萃取铜的分配系数的关系。     

Synthesis,structure, and second-order nonlinear optical properties of copper(II) and palladium(II) acentric complexes with N-salicylidene-N'-aroylhydrazine tridentate ligands

Two new N-salicylidene-N'-aroylhydrazines ligands have been prepared: N-4-diethylaminosalicylidene-N'-4-nitrobenzoyl-hydrazine (L(1)) and N-4-diethylaminosalicylidene-N'-4-(4-nitrophenylethylidene)-benzoyl-hydrazine (L(2)). The ligands are properly functionalized with strong electron donor-acceptor groups and are of potential interest in second-order nonlinear optics (NLO). Dimeric copper(II) and palladium(II) complexes with L(1) and L(2) have been prepared, and, starting from these, mononuclear acentric adducts with pyridine as a further ligand have been prepared and characterized. The X-ray structures of three adducts are also reported. The NLO activity of the adducts has been determined by EFISH measurements giving mubeta values up to 1500 x 10(-48) esu for an incident wavelength of 1.907 microm.     

Synthesis, crystal structure, magnetic properties and theoretical studies on a one-dimensional polynuclear copper(II) complex [Cu2(mu1,3-SCN)2(mu'1,3-SCN)2(MPyO)2]n

A new one-dimensional polynuclear copper(II) complex [Cu(2)(mu(1,3)-SCN)(2)(mu'(1,3)-SCN)(2)(MPyO)(2)](n)(where MPyO = 4-methylpyridine N-oxide) has been synthesized and its crystal structure determined by X-ray crystallography. In the complex there exist two kinds of bridging coordination modes, namely, mu(1,3)-SCN(-) equatorial-equatorial (EE) bridging ligand and micro'(1,3)-SCN(-) equatorial-axial (EA) bridging ligand. Two micro(1,3)-SCN(-) EE bridging ligands coordinate two copper(II) ions in a binuclear unit, and the S atoms from the micro'(1,3)-SCN(-) EA bridging ligands as axial coordinated atoms link the binuclear units into one-dimensional chains. The ESR spectra have been investigated, and variable temperature (4-300 K) magnetic measurements were analyzed using a binuclear Cu(ii) magnetic interaction formula and indicate the existence of strong antiferromagnetic coupling with 2J=- 216.00 cm(-1) between bridged copper(II) ions. Density functional calculations have been carried out on this binuclear unit, yielding a similar singlet-triplet splitting. The mechanism of strong antiferromangetic interaction is revealed according to the calculations.     

Calix[4]arene-based 1,3-diconjugate of salicylyl imine having dibenzyl amine moiety (L): synthesis, characterization, receptor properties toward Fe2+, Cu2+, and Zn2+, crystal structures of its Zn2+ and Cu2+ complexes, and selective phosphate sensing by the [ZnL

A calix[4]arene conjugate bearing salicylyl imine having dibenzyl moiety (L) has been synthesized and characterized, and its ability to recognize three most important essential elements of human system, viz., iron, copper, and zinc, has been addressed by colorimetry and fluorescence techniques. L acts as a sensor for Cu(2+) and Fe(2+) by exhibiting visual color change and for Zn(2+) based on fluorescence spectroscopy. L shows a minimum detection limit of 3.96 ± 0.42 and 4.51 ± 0.53 ppm and 45 ± 4 ppb, respectively, toward Fe(2+), Cu(2+), and Zn(2+). The in situ prepared [ZnL] exhibits phosphate sensing among 14 anions studied with a detection limit of 247 ± 25 ppb. The complexes of Zn(2+), Cu(2+), and Fe(2+) of L have been synthesized and characterized by different techniques. The crystalline nature of the zinc and copper complexes and the noncrystalline nature of simple L and its iron complex have been demonstrated by powder XRD. The structures of Cu(2+) and Zn(2+) complexes have been established by single crystal XRD wherein these were found to be 1:1 monomeric and 2:2 dimeric, respectively, using N(2)O(2) as binding core. The geometries exhibited by the Zn(2+) and the Cu(2+) complexes were found to be distorted tetrahedral and distorted square planar, respectively. The iron complex of L exists in 1:1 stoichiometry as evident from the mass spectrometry and elemental analysis.     

Heteroleptic Cu(II) dipyrromethene complexes linked via hydrogen bonds, coordinative bonds, and covalent bonds: probing the coordination environment by electron paramagnetic resonance spectroscopy

meso-Phenyldipyrromethene acetylacetonato copper(II) complexes [Cu(dpm-C6H4R)(acac)] (dpm-C6H4R = phenyl-substituted dipyrromethene, acac = acetylacetonato) with different substituents R at the phenyl moiety were synthesized. These substituents determine the mode of assembly into polymeric chains, namely, via hydrogen bonds, coordinative bonds, or covalent bonds (by immobilization on a polymer). Although the primary coordination sphere around the copper center is essentially identical for all complexes reported in this study (square-planar geometry with N2O2 coordination), subtle differences due to the different microenvironments have been observed in their structures, properties, and reactivity as probed by IR spectroscopy, electron paramagnetic resonance spectroscopy, magnetic measurements, thermal analyses, density functional theory calculations, and reaction with pyridine.     

Formation of Cu and Cu2O nanoparticles by variation of the surface ligand: preparation, structure, and insulating-to-metallic transition

Copper and copper (I) oxide nanoparticles protected by self-assembled monolayers of thiol, carboxyl, and amine functionalities [X(CH(2))(n)-CH(3), where X can be -COOH, -NH(2), or -SH] have been prepared by the controlled reduction of aqueous copper salts using Brust synthesis. The optical absorption spectrum (lambda(max)=289 nm) is found to be invariant with the nature of the capping molecule while the particle shape and distribution are found to depend strongly on it. A comparison of the protection efficiency for different capping agents such as dodecanethiol (DDT), tridecylamine (TDA), and lauric acid (LA) suggests that although zerovalent Cu is initially formed for dodecanethiol, all other cases allow oxidation to Cu(2)O nanoparticles. Despite the variation in particle size and relative stability, nanoparticles have been found to form oxides after a few days, especially for the case of LA and TDA surface capping. For all the samples studied, the size has been found to be 4-8 nm by high-resolution transmission electron microscopy. The protective ability is found to be better for dodecanethiol SAM (similar to the case of Au and Ag nanoparticles), while the order of capping efficiency varies as Cu-DDT>Cu-TDA>Cu-LA. In the present study we also demonstrate a reversible metal-insulator transition (MIT) in capped nanoparticles of Cu using temperature-dependent electrical resistivity measurement. However, the LA-capped sample does not show any such transition, possibly due to the oxide formation.     

The solid complex Zn(CF3)Br·2DMF as an alternative reagent for the preparation of both, trifluoromethyl and pentafluoroethyl copper, CuCF3 and CuC2F5

Trifluoromethylcopper and pentafluoroethylcopper are prepared conveniently via the reaction of the solid complex Zn(CF₃)Br·2DMF with copper(I) bromide in N,N-dimethylformamide. The reactions of both copper species with 2,4-dinitrochlorobenzene, 4-iodonitrobenzene, 4-nitrobenzyl iodide, 4-bromobenzoic acid ethyl ester, 4-iodobenzoic acid ethyl ester, 2-iodopyridine and 2-iodopyrimidine have been studied. The structure of 2,4-dinitrotrifluoromethylbenzene has been elucidated.     

Ferromagnetism in malonato-bridged copper(II) complexes. Synthesis,crystal structures,and magnetic properties of [[Cu(H2O)3][Cu(mal)2(H2O)]]n and [[Cu(H2O)4]2[Cu(mal)2(H2O)]][Cu(mal)2(H2O)2][[Cu(H2O)4][Cu(mal)2(H2O)2][(H2mal = malonic acid)

Three malonato-bridged copper(II) complexes of the formulas [[Cu(H2O)3][Cu(C3H2O4)2(H2O)]]n (1), [[Cu(H2O)4]2[Cu(C3H2O4)2(H2O)]] [Cu(C3H2O4)2(H2O)2][[Cu(H2O)4][Cu(C3H2O4)2(H2O)2]] (2), and [Cu(H2O)4][Cu(C3H2O4)2(H2O)2] (3) (C3H2O4 = malonate dianion) have been prepared, and the structures of the two former have been solved by X-ray diffraction methods. The structure of compound 3 was already known. Complex 1 crystallizes in the orthorhombic space group Pcab, Z = 8, with unit cell parameters of a = 10.339(1) A, b = 13.222(2) A, and c = 17.394(4) A. Complex 2 crystallizes in the monoclinic space group P2/c, Z = 4, with unit cell parameters of a = 21.100(4) A, b = 21.088(4) A, c = 14.007(2) A, and beta = 115.93(2) degrees. Complex 1 is a chain compound with a regular alternation of aquabis(malonato)copper(II) and triaquacopper(II) units developing along the z axis. The aquabis(malonato)copper(II) unit acts as a bridging ligand through two slightly different trans-carboxylato groups exhibiting an anti-syn coordination mode. The four carboxylate oxygens, in the basal plane, and the one water molecule, in the apical position, describe a distorted square pyramid around Cu1, whereas the same metal surroundings are observed around Cu2 but with three water molecules and one carboxylate oxygen building the equatorial plane and a carboxylate oxygen from another malonato filling the apical site. Complex 2 is made up of discrete mono-, di-, and trinuclear copper(II) complexes of the formulas [Cu(C3H2O4)2(H2O)2]2-, [[Cu(H2O)4] [Cu(C3H2O4)2(H2O)2]], and [[Cu(H2O)4]2[Cu(C3H2O4)2(H2O)]]2+, respectively, which coexist in a single crystal. The copper environment in the mononuclear unit is that of an elongated octahedron with four carboxylate oxygens building the equatorial plane and two water molecules assuming the axial positions. The neutral dinuclear unit contains two types of copper atoms, one that is six-coordinated, as in the mononuclear entity, and another that is distorted square pyramidal with four water molecules building the basal plane and a carboxylate oxygen in the apical position. The overall structure of this dinuclear entity is nearly identical to that of compound 3. Finally, the cationic trimer consists of an aquabis(malonato)copper(II) complex that acts as a bismonodentate ligand through two cis-carboxylato groups (anti-syn coordination mode) toward two tetraaqua-copper(II) terminal units. The environment of the copper atoms is distorted square pyramidal with four carboxylate oxygens (four water molecules) building the basal plane of the central (terminal) copper atom and a water molecule (a carboxylate oxygen) filling the axial position. The magnetic properties of 1-3 have been investigated in the temperature range 1.9-290 K. Overall, ferromagnetic behavior is observed in the three cases: two weak, alternating intrachain ferromagnetic interactions (J = 3.0 cm-1 and alpha J = 1.9 cm-1 with H = -J sigma i[S2i.S2i-1 + alpha S2i.S2i+1]) occur in 1, whereas the magnetic behavior of 2 is the sum of a magnetically isolated spin doublet and ferromagnetically coupled di- (J3 = 1.8 cm-1 from the magnetic study of the model complex 3) and trinuclear (J = 1.2 cm-1 with H = -J (S1.S2 + S1.S3) copper(II) units. The exchange pathway that accounts for the ferromagnetic coupling, through an anti-syn carboxylato bridge, is discussed in the light of the available magneto-structural data.     

Copper (II)-supported polyethylenimine-functionalized magnetic graphene oxide as a catalyst for the green synthesis of 2-arylquinazolin-4(3H)-ones

A novel copper (II) catalyst supported on polyethylenimine-functionalized magnetic graphene oxide (denoted Cu@PEI-MGO) has been developed and applied for the cyclization of benzylacetamide with 2-aminobenzamide to afford 2-arylquinazolin-4(3H)-ones in acetonitrile as an inexpensive, non-toxic and reusable solvent medium. Cu@PEI-MGO was characterized by transmission electron microscopy, scanning electron microscopy, thermo-gravimetric analysis, and Fourier-transform infra-red spectroscopy.     

Structural and photophysical studies of trans-AB(2)C-substituted porphyrin ligands and their zinc and copper complexes

trans-AB(2)C porphyrins with A = C(6)H(4)-COOR, C = C(6)H(4)-NX(2) and B = C(6)H(5) (R = CH(3), H; X = O, H) have been synthesised by a rational high-yield procedure (1a-1d) and their zinc(ii) and copper(ii) complexes have been prepared (2a-2d, 3a-3d ).1a, 2a .THF and 3a display different distortions of the porphyrin core as shown by single crystal X-ray crystallography and NSD analyses. The Soret and Q bands of free-base and metalated porphyrins with mixed electron donating and withdrawing substituents (NH(2)/COOR) are red-shifted as are the corresponding emission bands of free-base and zinc porphyrins. The electronic asymmetry revealed by spectrocopy is rationalised by DFT calculations.     

Synthesis, X-ray structure and properties of a new nitrite-bound copper(II) complex with 2-(3,5- dimethylpyrazol-1-ylmethyl)pyridine in a CuN4(O) coordination

Synthesis and characterization of a nitrite-bound copper(II) compound [CuL⁴)₂(ONO)]ClO₄ have been achieved (L⁴ = 2-(3,5-dimethylpyrazol-1-ylmethyl)pyridine]. The bidentate ligand L⁴ provides a pyridine and a pyrazole donor site; however, they are separated by a methylene spacer. The complex has been structurally characterized and it belongs to only a handful of complexes having nitrito-bound mononuclear copper(II) centre. The metal atom has a distorted square pyramidal geometry with the copper atom displaced from the equatorial plane by 0.25 Å. In MeCN solution the green complex exhibits a broad ligand-field transition at 655 nm with a shoulder at 675 nm and in dichloromethane-toluene glass (80 K) it exhibits an EPR spectral feature characteristic of the unpaired electron in the d_x²−y² orbital. Variable-temperature (80–300 K) magnetic susceptibility measurements in the solid state as well as room temperature measurement in MeCN solution reveal mononuclear magnetically dilute copper(II) centre. When examined by cyclic voltammetry (MeCN solution) it displays electrochemically irreversible Cu^II---Cu^I response [cathodic peak potential, E_pc (V vs saturated calomel electrode (SCE)): −0.32]. An oxidative response is observed at 1.14 V, probably due to bound-nitrite oxidation and is partially removed to generate a solvated complex at the electrode surface. The latter species gives rise to reversible Cu^II---Cu^I redox response [ ].     

Syntheses, crystal structures, magnetic properties, and EPR spectra of tetranuclear copper(II) complexes featuring pairs of "roof-shaped" Cu2X2 dimers with hydroxide, methoxide, and azide bridges

Hydroxo- and methoxo-bridged tetranuclear copper(II) complexes of the tetramacrocyclic ligand 1,2,4,5-tetrakis(1,4,7-triazacyclonon-1-ylmethyl)benzene (Ldur), have been prepared from [Cu4Ldur(H2O)8](ClO4)8.9H2O (1). Addition of base to an aqueous solution of 1 gave [Cu4Ldur(mu2-OH)4](ClO4)4 (2). Diffusion of MeOH into a DMF solution of 2 produces [Cu4Ldur(mu2-OMe)4](ClO4)4.HClO4.2/3MeOH (3), a complex which hydrolyzes on exposure to moisture regenerating 2. The structurally related azido-bridged complex, [Cu4Ldur(mu2-N3)4](PF6)4.4H2O.6CH3CN (4), was produced by reaction of Ldur with 4 molar equiv of Cu(OAc)2.H2O and NaN3 in the presence of excess KPF6. Compounds 2-4 crystallize in the triclinic space group P1 (No. 2) with a = 10.248(1) A, b = 12.130(2) A, c = 14.353(2) A, alpha = 82.23(1) degrees, beta = 80.79(1) degrees, gamma = 65.71(1) degrees, and Z = 1 for 2, a = 10.2985(4) A, b = 12.1182(4) A, c = 13.9705(3) A, alpha = 89.978(2) degrees, beta = 82.038(2) degrees, gamma = 65.095(2) degrees, and Z = 1 for 3, and a = 12.059(2) A, b = 12.554(2) A, c = 14.051(2) A, alpha = 91.85(1) degrees, beta = 98.22(1) degrees, gamma = 105.62(1) degrees, and Z = 1 for 4. The complexes feature pairs of isolated dibridged copper(II) dimers with "roof-shaped" Cu2(mu2-X)2 cores (X = OH-, OMe-, N3-), as indicated by the dihedral angle between the two CuX2 planes (159 degrees for 2, 161 degrees for 3, and 153 degrees for 4). This leads to Cu.Cu distances of 2.940(4) A for 2, 2.962(1) A for 3, and 3.006(5) A for 4. Variable-temperature magnetic susceptibility measurements indicate weak antiferromagnetic coupling (J = -27 cm(-1)) for the hydroxo-bridged copper(II) centers in 2 and very strong antiferromagnetic coupling (J = -269 cm(-1)) for the methoxo-bridged copper(II) centers in 3. Pairs of copper(II) centers in 4 display the strongest ferromagnetic interaction (J = 94 cm(-1)) reported thus far for bis(mu2-1,1-azido)-bridged dicopper units. Spectral measurements on a neat powdered sample of 4 at 33.9 GHz or 90 Ghz confirm the spin-triplet ground state for the azido-bridged copper(II) pairs.     

Template Synthesis,Crystal Structure,and Spectroscopic Characterization of [N,N′-Bis(2-pyridylmethylene)-1,3-diamino-2-methyl-2-nitropropane] copper(II) Perchlorate

In a facile carbon-acid condensation reaction of bis(2-aminomethylpyridine)copper(II) with nitroethane and formaldehyde in basic MeOH the N,N′-bis(2-pyridylmethylene)-1,3-(diamino-2-methyl-2-nitropropane)copper(II) cation is produced in essentially quantitative yield. The perchlorate salt crystallizes in space group P2₁en, a = 9.083(2), b = 15.198(3), c = 16.025(3). Cu(II) is essentially four-coordinate, though there are weak axial interactions to the perchlorate O-atoms. There is a large tetrahedral distortion from the least-squares plane through the Cu and four N donors; with the Cu(II) in the plane, N-atoms are up to 0.25 Å above or below. Solution spectroscopy confirms that the solution structure of the cation is qualitatively the same as in the solid. The complex and its precursor have been investigated by room-temperature magnetic-moment measurement, voltammetry, and by IR, electronic, and electron spin resonance spectroscopy.