Synthesis,characterization, structure and magnetic properties of azido-bridged nickel(II) and copper(II) complexes with a pyridylpyrazole-based ligand

A new pyridylpyrazole-containing tetradentate ligand, namely N,N-bis(3,5-dimethylpyrazol-1-ylmethyl)aminomethylpyridine (L), and two of its binuclear azido-bridged complexes, [Ni₂(L)₂(N₃)₂](ClO₄)₂·2EtOH (1) and [Cu₂(L)₂(N₃)₂](ClO₄)₂ (2), have been synthesized and characterized by physico-chemical and spectroscopic methods. The crystal structures of both complexes are reported. Each metal atom in the complexes has a MN₆ coordination environment with distorted octahedral geometry. Variable-temperature magnetic susceptibility measurements for complex (1) show typical antiferromagnetic behavior with J value −84.5 ± 1.3 cm⁻¹, whereas complex (2) has no magnetic interactions.     

Synthesis, structure and characterization of binuclear copper(Ⅱ) complexes

At room temperature, dibenzoyl peroxide undergoes oxidative addition reaction with metallic copper powder and pyridine N-oxide (triphenylphosphine oxide or 2,9-dimethyl-4,7-diphenyl-1,10-phenanthrolin) which affords the last products as binuclear copper(II) complexes, [Cu(C5H5NO)-(C6H5COO)2]2(1), [Cu(OPPh3)(C6H5COO)2]2(2) and [Cu(C6H5COO)(C26H2oN2)](3, C26H2oN2 is 2,9-dimethyl-4,7-diphenyl-1,10-phenanthrolin). The structure of the complexes were characterized by elemental analyses, IR spectra, TG-DTA and magnetic property. Crystals(1) are triclinic, space group P1,a=0.92617(36),b=1.06973(17), c=1.08813(29) nm, a=59.60(2)°, β=74.83(3)°,γ=72.80(2)°, V=0.880 nm3, Dc=1.520 g/cm3, Z=1, R=0.044, Rw=0.048, Mr=805.78, 3477 reflections with I > 3σ(I). Each copper(Ⅱ) ion is coordinated by two bridging bidentate benzoate ligands and one pyridine N-oxide or triphenylphosphine oxide to form dimeric binuclear molecules. The structure of the compound(1) shows a clear centre of symmetry.     

Binuclear copper(II) complexes of functionalized 1,2,4-triazoles: Synthesis,structure, and magnetic properties

Copper(II) coordination compounds with 3-(pyridin-2-yl)-5-(2-salicylideniminophenyl)-1H-1,2,4-triazole and 1,3-bis(5-(pyridin-2-yl)-1,2,4-triazole-3-yl)propane have been synthesized. The complexes have been studied by elemental and thermal analysis, IR and electron spectroscopy, electron paramagnetic resonance (EPR), and magnetochemistry. According to X-ray diffraction data, the complexes have binuclear structures in which metal cations are bonded via the nitrogen atoms of two bridging triazole rings.     

Mixed ligand complexes of copper(II) iminodiacetate with di- and tripeptides in solution

Calorimetric, potentiometric, and spectrophotometric studies on mixed ligand complexes of copper(II) iminodiacetate and simple di- and tripeptides (GlyGly, αAlaαAla, αAlaβAla, βAlaβAla, αAlaAsn, GlyGlyGly, AlaGlyGly) have been carried out in aqueous solution at 298.15 K and ionic strength of I = 0.5 (KNO₃). The thermodynamic parameters of formation of various mixed complexes have been determined. The probable coordination modes of the complex and peptide molecules in the mixed ligand complexes are discussed.     

Synthesis, crystal structures and magnetic properties of tricyanomethanide-containing copper(II) complexes

The preparation, crystal structures and magnetic properties of the copper(II) complexes of formula [Cu(pyim)(tcm)(2)](n) (1), [Cu(bpy)(tcm)(2)](n) (2), [Cu(4)(bpz)(4)(tcm)(8)] (3), {[Cu(terpy)(tcm)].tcm}(n) (4) and {[Cu(2)(tppz)(tcm)(4)].3/2H(2)O}(n) (5) [pyim = 2-(2-pyridyl)imidazole, tcm = tricyanomethanide, bpy = 2,2'-bipyridine, bpz = 2,2'-bipyrazine, terpy = 2,2':6',2'-terpyridine and tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine] are reported. Complexes, 1, 2 and 4 are uniform copper(II) chains with single- (1 and 4) and double-(2) micro-1,5-tcm bridges with values of the intrachain copper-copper separation of 7.489(1) (1), 7.520(1) and 7.758(1) (2) and 7.469(1) A (4). Each copper atom in 1, 2 and 4 is five-coordinate with bidentate pyim (1)/bpy (2) and tridentate terpy (4) ligands and nitrile-nitrogen atoms from bridging (1,2 and 4) and terminal (1) tcm groups building a distorted square pyramidal surrounding. The structure of 3 is made up of neutral centrosymmetric rectangles of (2,2'-bipyrazine)copper(II) units at the corners, the edges being built by single- and double-micro-1,5-tcm bridges with copper-copper separations of 7.969(1) and 7.270(1) A, respectively. Five- and six-coordinated copper atoms with distorted square pyramidal and elongated octahedral environments occur in . Compound 5 is a neutral copper(II) chain with regular alternating bis-tridentate tppz and double micro-1,5-tcm bridges, the intrachain copper-copper distances being 6.549(7) and 7.668(1) A, respectively. The two crystallographically independent copper atoms in 5 have an elongated octahedral geometry with three tppz nitrogen atoms and a nitrile-nitrogen atom from a bridging tcm group in the equatorial positions, and two nitrile nitrogen atoms from a terminal and a bridging tcm ligand occupying the axial sites. The investigation of the magnetic properies of 1-5 in the temperature range 1.9-295 K has shown the occurrence of weak ferro- [J = +0.11(1) cm(-1) (2)] and antiferromagnetic interactions [J = -0.093(1) (1), -0.083(1) (4), -0.04(1) and 1.21(1) cm(-1) (3)] across the micro-1,5-tcm bridges and intermediate antiferromagnetic coupling [-J = 37.4(1) cm(-1) (5)] through bis-tridentate tppz. The values of the magnetic interactions are analyzed through simple orbital symmetry considerations and compared with those previously reported for related systems.     

Mono- and dinuclear copper(II) complexes with meta-phenylene-bridging ligands: Synthesis,structure and magnetic properties

The new double-Schiff-base ligand H₆ipa-bhea has been synthesized by condensation of a 4,6-diformylresorcinol derivative (ipa) with two equivalents of N,N-bis-(2-hydroxyethyl)ethylenediamine (bhea). Reaction with copper(II) perchlorate leads to the formation of two different products depending on the reaction conditions. The directed synthesis of either a mononuclear or dinuclear copper(II) complex is reported. The reaction in methanol results in the formation of a dinuclear complex [Cu₂(H₄ipa-bhea)](ClO₄)₂ (1). Whereas in the presence of water as solvent for the reaction, one imine side chain of the ligand is hydrolyzed regenerating the formyl moiety with the mononuclear complex [Cu(H₃hyforsa-bhea)]ClO₄ · 2H₂O (2) as final product. Subsequent reaction of complex 2 with N,N-bis-(pyridin-2-ylmethyl)ethylenediamine (unspenp) as additional amine component results in the formation of the mononuclear complex [Cu(Hhyforsa-unspenp)]ClO₄ (3). All complexes are characterized by IR spectroscopy, elemental analysis and X-ray crystallography. Temperature-dependent magnetic measurements on the dinuclear complex indicate weak antiferromagnetic exchange interactions between the copper(II) ions with a coupling constant of J = ?16.4 cm^?1. Density functional calculations have been used to evaluate the magnetic properties. The exchange coupling constant can be nicely reproduced with the use of the broken symmetry approach. The exchange pathway through the meta-phenylene-linkage is discussed in terms of a competitive spin-polarization and superexchange mechanism as well as geometrical changes at the copper(II) ions.     

Synthesis and magnetic properties of copper(II) bis(phenylsulphinyl)ethane complexes

Summary Two Cu^II complexes, [Cu₂(-L)Cl₄·H₂O (1) and Cu₂(-L)Cl₄ (2) [-L and -L = meso- and rac-PhS(O)(CH₂)₂S(O)Ph, respectively], were synthesized and characterized by elemental analysis, i.r. spectra and molar conductances. In each case, the Cu^II ion bonds to the 557-01 moiety through oxygen, and may be bridged by the ligand (-L or -L). From magnetic moment measurements at room temperature and variable temperature magnetic susceptibilities, we suggest that complexes (1) and (2) exhibit weak ferromagnetic behaviour.     

Synthesis,structures, and magnetic properties of two pyrazolato-bridged trinuclear copper(II) complexes

One nonlinear and one linear trinuclear copper(II) complex [Cu₃(dien)₂(pdc)₂CH₃OH]₂?·?6CH₃OH (1) and [Cu₃(pdc)₂(CH₃OH)₆(H₂O)₄] (2) were prepared and characterized structurally, where dien is diethylenetriamine and pdc^3? the trianion of 3,5-pyrazoledicarboxylic acid. Both complexes consist of 3,5-pyrazoledicarboxylato-bridged trinuclear copper(II) centers. In 1, copper(II) ions are five-coordinate in distorted square pyramids with bond angles 164.78° for Cu(1)–Cu(2)–Cu(3) and 164.51° for Cu(4)–Cu(5)–Cu(6). In 2, the three copper(II) ions are six-coordinate with elongated octahedral geometry. The trinuclear units of 1 and 2 interact through hydrogen bonds to form 3-D and 2-D supramolecular networks, respectively. Variable temperature magnetic susceptibility measurements show that 1 and 2 are antiferromagnetically coupled with J values of ?11.2 and ?13.3?cm^?1.     

Synthesis,spectral, magnetic and electrochemical properties of new dimeric copper(II) complexes

Four new ligands, bis-[3,5-disubstituted-2-hydroxybenzyl]-N-alkylamines (L¹–L⁴) with three potential donor sites, capable of forming dimeric copper(II) complexes have been prepared. The dimeric nature of the complexes has been confirmed by FAB mass spectral studies. Molar conductance studies indicate that the complexes are neutral. Electrochemical studies indicate that the complexes undergo quasi reversible two step single electron transfers at negative potentials (E_pc¹=−0.34 to −0.48 V, E_pc²=−0.59 to −0.72 V). Variable temperature magnetic studies indicate that the complexes are antiferromagnetically coupled (−2J=290 to 400 cm⁻¹). ESR spectral studies in DMF indicate that the complexes are dimeric and undergo dissociation on addition of pyridine.     

Cyclo(L-histidyl-L-histidyl)copper(II) complexes in aqueous solution

Summary The structure of the copper(II) complex cation with HISH₂ [HISH₂ = cyclo(L-histidyl-L-histidyl)] was determined from molecular weight data and n.m.r. and c.d. spectra in aqueous solution. Two HISH₂ moieties ligate to coppervia two nitrogen atoms of the imidazole rings giving rise to two 13-membered chelate rings in solution, a situation seen previously in the crystal.     

Synthesis, structure and magnetic properties of oligometallic systems derived from di- and trinuclear copper(II) amido-oximate complexes

Three heterometallic complexes [M(H(2)O)(n)][Cu(3)L(2)(H(2)O)] (M = Mn(2+), Co(2+) or Ba(2+)) and one dinuclear compound (CuDien)(CuL{H(2)O}) were prepared by interaction of anionic compounds Cu(3)L(2)(2-) or CuL(2-) with the corresponding cations (H(4)L = 1,9-dicyano-1,9-bis(hydroximino)-3,7-diazanonane-2,8-dione; Dien = 1,5-diamino-3-azapentane). The complexes [M(H(2)O)(n)][Cu(3)L(2)(H(2)O)] have a polymeric structure, formed via oligomerization of Cu(3)L(2)(2-) units and additionally, in the case of the Ba-salt, by binding of Cu(3)L(2)(2-) units through Ba(2+). Antiferromagnetic interactions occur in all the complexes, while for [Co(H(2)O)(6)][Cu(3)L(2)(H(2)O)] there is evidence of some ferromagnetic ordering at low temperatures. The values of J are lower in magnitude than for similar, previously reported systems, which is attributed to the electron-withdrawing effect of the ligand cyano groups.     

Inorganic-metalorganic hybrids based on copper(II)-monosubstituted Keggin polyanions and dinuclear copper(II)-oxalate complexes. Synthesis, X-ray structural characterization, and magnetic properties

Reaction of in situ generated copper(II)-monosubstituted Keggin polyoxometalates and copper(II)-bipyridine-oxalate complexes in the corresponding alkaline acetate buffer led to the formation of hybrid metal organic-inorganic compounds K(2)[{SiW(11)O(39)Cu(H(2)O)}{Cu(2)(bpy)(2)(H(2)O)(2)(mu-ox)}(2)].14H(2)O (1), K(14)[{SiW(11)O(39)Cu(H(2)O)}{Cu(2)(bpy)(2)(mu-ox)}](2)[SiW(11)O(39)Cu(H(2)O)].55H(2)O (2), (NH(4))(4)[{SiW(11)O(39)Cu(H(2)O)}{Cu(2)(bpy)(2)(mu-ox)}].10H(2)O (3), and Rb(4)[{SiW(11)O(39)Cu(H(2)O)}{Cu(2)(bpy)(2)(mu-ox)}].10H(2)O (4). Their structures have been established by single-crystal X-ray diffraction. The main structural feature of these compounds is the presence of copper(II)-monosubstituted alpha-Keggin polyoxoanions as inorganic building blocks, on which the mu-oxalatodicopper metalorganic blocks are supported. Compound 1contains the discrete hybrid polyanion [{SiW(11)O(39)Cu(H(2)O)}{Cu(2)(bpy)(2)(H(2)O)(2)(mu-ox)}(2)](2)(-), whereas the polymeric hybrid polyanion [{SiW(11)O(39)Cu(H(2)O)}{Cu(2)(bpy)(2)(mu-ox)}(2)](n)(4)(n)(-) gives a monodimensional character to compounds 2-4. Magnetic and EPR results are discussed with respect to the crystal structure of the compounds. DFT calculations on both the [Cu(2)(bpy)(2)(H(2)O)(4)(mu-ox)](2+) cationic complex and the metalorganic blocks have been performed in order to determine the optimized geometry and the magnetic coupling constants, respectively.     

Synthesis,crystal structures and magnetic properties of nitronyl nitroxide radical-coordinated copper(II) complexes

Transition Metal Chemistry - The coordination compound constructed for nitronyl nitroxide radical NIT-Ph-4-Br and CuII(hfac)2(H2O)2 building blocks...     

Synthesis,characterization and function of ternary copper(II) complexes

Ternary complexes of glycine, alanine, -alanine, serine and ethylenediamine with copper iminodiacetate have been prepared and characterized by their i.r., u.v.-vis. and e.s.r. spectra. The data suggest that the complexes possess axial symmetry and a distorted octahedral configuration in aqueous solution. The H2O molecule on the axial copper site can be replaced by O2–. The bonding parameters, which fall between 0.84 and 0.88, indicate that the bonds between copper(II) and the ligands possess more ionic character. The ternary complex containing serine displays the highest catalytic activity in dismutation of the superoxide radical O2–. This activity may be explained on the basis of the stabilization of CuII-O2– by hydrogen bonding.     

Synthesis,structure and characterization of binuclear copper(I) complexes

Binuclear copper(I) complexes [Cu(dppm)(NO3)]2 (1), dppm=Ph2PCH2PPh2, [Cu(dppm)(2,9-Me2Phen)]2(NO3)2 (2), [Cu(dppm)(I)]2 (3) and [Cu(dppm)(py)]2(NO3)2 (4), (py=pyridine) have been synthesized by ligand reduction of cupric nitrate with dppm in EtOH and characterized by elemental analyses, molecular weight determination, t.g.a., 31P-n.m.r spectra; their electronic conductivities and c.v. waves have also been measured. The results show that dppm coordinates as a bridging bidentate ligand to the CuI atoms, and that NO3 behaves as a monodentate ligand or free ion in the newly prepared complexes.     

Synthesis,spectral and magnetic properties of binuclear copper(II)/nickel(II) and copper(II) complexes bridged by glyoximate groups

Three new dinuclear complexes, [(tmen) (H2O)2Ni (Hdmg)(dmg)Cu]·ClO4, [(dien)(H2O)Ni (Hdmg)(dmg) Cu]·ClO4 and [(tmen)Cu(Hdmg)(dmg) Cu] ClO4·H2O (H2dmg=dimethylglyoxime, tmen=tetramethylene diamine), have been prepared. Variable-temperature- magnetic susceptibility measurements (75–300K) on the complexes reveal the presence of intramolecular antiferromagnetic interactions through the oximate bridges. The formation of mononuclear, dinuclear complexes has been confirmed by spectrophotometry.     

Synthesis, crystal structure, and magnetic properties of oxime-bridged polynuclear Ni(II) and Cu(II) complexes

Two new polynuclear complexes [Ni6(amox)6(mu6-O)(mu3-OH)2](Cl2).6H2O and [Cu3(amox)3(mu3-OH)(mu3-Cl)](ClO4).4H2O (amox- = anion of 4-amino-4-methyl-2-pentanone oxime) have been synthesized and characterized structurally and magnetically. The Ni(II) complex contains a novel Chinese-lantern-like Ni6 cage centered by an oxo ion. It contains the nearest octahedral Ni(II)...Ni(II) separation (<2.8 A) and exhibits strong antiferromagnetic properties. The Cu(II) complex has a cyclic trinuclear copper(II) core bridged by both mu3-OH(-) and mu3-Cl(-) ions. The magnetic susceptibilities of both antiferromagnetic complexes were fitted by using approximate models.     

Synthesis,characterization and crystal structure of ternary chloroacetate,dichloroacetate and trichloroacetate copper(II) complexes

Three binuclear ternary copper(II) chloroacetate complexes with OP(OMe)₃ were prepared, and the configurations of the copper(II) dichloroacetate and trichloroacetate complexes were converted from a square-planar structure into a binuclear cage structure during the reaction. The crystal structure of Cu₂(ClCH₂CO₂)₄[OP(OMe)₃]₂ were determined by single-crystal X-ray diffraction. The i.r. spectra show that the carboxylate groups behave as bridging bidentate ligands in Cu₂(ClCH₂CO₂)₄(H₂O)₂ (1), Cu₂(ClCH₂CO₂)₄[OP(OMe)₃]₂ (4), Cu₂(Cl₂CHCO₂)₄-[OP(OMe)₃]₂ (5) and Cu₂(Cl₃CCO₂)₄[OP(OMe)₃]₂ (6), and as monodentate ligands in Cu(Cl₂CHCO₂)₂(H₂O)₂ (2) and Cu(Cl₃CCO₂)₂(H₂O)₂ (3). The electronic reflectance spectra in the solid state suggest a square pyramidal coordination environment around the copper(II) atom in (1), (4), (5) and (6), and a square-planar coordination environment in (2) and (3). Room temperature X-band e.s.r. spectra of powdered samples studied indicate the presence of electron coupling of copper(II) ions in (1), (4), (5) and (6).