Synthesis and magnetic properties of trinuclear copper(II) complexes bridged by dimethylglyoximate groups

Summary New three Cu^II-Cu^II-Cu^II homotrinuclear complexes have been synthesized, namely [Cu(dmg)₂{CuL}₂](ClO₄)₂ [L = 5-nitro-1,10-phenanthroline (5-NO₂-phen), 4,4-dimethyl-2,2-bipyridiine (DMbpy), tetramethylenediamine (TMDA) and dimethylglyoximate ion (dmg)^2-]. The magnetic susceptibilities of complexes (1) (L = 5-NO₂-phen) and (2) (L = DMbpy) were measured in the 4.2–300 K range, giving the parameters,J = -335cm^-1 (1) andJ= -327.5cm^-1 (2). The results demonstrate a very strong antiferromagnetic exchange interaction between the adjacent copper(II) ions.     

Novel dioximato-bridged chromium(III)-copper(II)-chromium(III) trinuclear complexes with ferromagnetic exchange interactions

Summary Two new dioximato-bridged trinuclear Cr^II-Cu^II-Cr^III complexes, [Cr(salen)-Cu(-BD)₂-Cr(salen)] (1) and [Cr(salen)-Cu(-FD)₂-Cr(salen)]-H₂O (2), have been prepared and characterized [salen^2– = N,N-ethylene- bis (salicylideneiminate), (-BD)^2– = -benzyldioximato and (-FD)^2– = -furildioximato]. Magnetic susceptibility measurements in the 4.2–300 K range demonstrated the operation of a ferromagnetic interaction between the adjacent Cr^III and Cu^II ions through oximato bridges in both (1) and (2). Based on spin Hamiltonians =–2J(₁₂+₂₃)(S₁=S₃=3/2,S₂=1/2) the exchange integrals (J) were evaluated as 3.19 and 5.38 cm^–1 for (1) and (2), respectively.     

O-phenylenebis(oxamato) bridged trinuclear copper(II) complexes: synthesis and magnetic properties

Summary Four new trinuclear copper(II) complexes bridged by o-phenylenebis(oxamato) (opba) and end-capped with 1,10-phenanthroline (phen), 5-nitro-1,10-phenanthroline (NO₂-phen), 2,2-bipyridyl (bipy) or 4,4-dimethyl-2,2-bipyridyl (Me₂bipy), {[Cu(opba)][Cu(L)]₂}(ClO₄)₂ (L = phen, NO₂-phen, bipy or Me₂bipy), have been synthesized and characterized. Based on i.r., elemental analyses, conductivity measurements and electronic spectra, oxamato-bridged structures consisting of three copper(II) ions in which each copper(II) ion has a square-planar environment are proposed. The temperature-dependent magnetic susceptibility of {[Cu(opba)][Cu(phen)]₂} (ClO₄)₂ has been studied in the 4.2–300 K range, giving the exchange integral J = -134.4cm^–1. The result revealed the operation of an antiferromagnetic spin-exchange interaction between the adjacent copper ions.     

Synthesis and magnetic properties of novel copper(II)-lanthanoid(III) heterobinuclear oxamido bridged complexes

Summary Seven novel -oxamido hetero-metal binuclear complexes have been prepared and characterized, namely [Cu(oxae)-Ln(NO₂-phen)₂ (ClO₄)](ClO₄)₂, where oxae denotes the N,N-bis(2-aminoethyl)oxamido dianion, NO₂-phen denotes 5-nitro-1,10-phenanthroline and Ln is Nd, Eu, Gd, Tb, Dy, Ho or Er. The magnetic susceptibility of [Cu(oxae)Gd(NO₂-phen)₂(ClO₄)](ClO₄)₂ was measured over a 4–300 K temperature range and the observed data were successfully simulated by an equation based on the spin Hamiltonian operator = -2J ₁·₂, giving the exchange integral for Gd^III J _(Cu-Gd) = -1.52cm^-1. This indicated a weak antiferromagnetic interaction between the Cu^II and Cd^III ions.Visiting scholar: Qufu Normal University.Visiting scholar: Tianjin Second Medical College.     

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.     

Binuclear iron(III) complexes bridged by terephthalato groups

Six new μ-terephthalato iron(III) binuclear complexes have been prepared and identified: [Fe₂(TPHA)(L)₄]-(ClO₄)₄ [L = 2,2′-bipyridine (bpy); 1,10-phenanthroline (phen); 4,4′-dimethyl-2,2′-bipyridine (Me₂bpy); 5-methyl-1,10-phenanthroline (Me-phen); 5-chloro-1,10-phenanthroline (Cl-phen) and 5-nitro-1,10-phenanthroline (NO₂-phen)]; where TPHA = the terephthalate dianion. Based on the elemental analyses, molar conductance and magnetic moments of room-temperature measurements, and spectroscopic studies, extended TPHA-bridged structures consisting of two iron(III) ions, each in an octahedral environment, are proposed for these complexes. The [Fe₂(TPHA)(Me-phen)₄](ClO₄)₄ (1) and [Fe₂(TPHA)(phen)₄](ClO₄)₄ (2) complexes were characterized by variable temperature magnetic susceptibility (4–300 K) measurements and the observed data were successfully simulated by the equation based on the spin Hamiltonian operator, Ĥ = −2JŜ ₁ Ŝ ₂, giving the exchange integrals J = −1.05 cm⁻¹ for (1) and J = −9.28 cm⁻¹ for (2). This result indicates the presence of a weak antiferromagnetic spin-exchange interaction between the metal ions within each molecule. The influence of the terminal ligand methyl substituents on magnetic interactions between the metals is also discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Synthesis and ferromagnetic interaction in oxamido-bridged heterodinuclear copper(II)-chromium (III) complexes

Four μ- oxamido heterodinuclear complexes, [Cu (oxae) Cr (L)₂ ] (NO₃) ₃, where oxae denotes the N, N'bis (2-aminoethyl) oxamido dianion and L represents 1,10-phenanthroline (phen); 5-nitro-1,10-phenanthroline (NO_2-phen); 5-methyl-1, 10-phenanthroline (Me-phen) and 2, 2′-bipyridine (bpy), have been synthesized and characterized by elemental analyses, magnetic moments (at room temperature) and molar conductivity measurements and spectroscopy. It is proposed that these complexes have extended oxamido-bridged structures consisting of a copper (II) ion and a chromium (III) ion, which have a square planar environment and octahedral environment, respectively. The cryomagnetic properties of the [Cu(oxae)Cr(bpy)₂(NO₃)₃(1) and [Cu(oxae)Cr(phen)₂](NO₃)₃(2) complexes have been measured over the range of 4.2–300 K. The leastsquares fit of the experimental data based on the spin Hamiltonian, ? = - 2J?₁·?₂, the exchange integrals (J) were evaluated as +36.9 cm^?1 for 1 and +35.8 cm^?1 for 2. The reds have connived that the spin coupling between the adjacent copper (II) and chromium (III) ions through oxamido-bridge in both 1 and 2 is ferromagnetic.     

Synthesis and magnetic properties of binuclear cobalt(Ⅱ), nickel(Ⅱ) and copper(Ⅱ) complexes bridged by oxamidate group

Four binuclear Co(Ⅱ), Ni(Ⅱ) and Cu(Ⅱ) complexes bridged by oxamidate (oxd) group have been synthesized, namely Co2(byp)2(oxd)(ClO4)2 (1), Co2(Me2bpy)2(oxd)(ClO4)2.H2O (2), Ni2(bpy)2(oxd)(ClO4)2.2H2O (3) and Cu2(Me2bpy)2(oxd)(NO3)2 (4). (bpy=2,2'-bipyridyl, Me2-bpy=4,4'-dimethylbipyridyl, oxd=oxamidate) The complexes are characterized by IR, UV spectra, EPR and variable-temperature magnetic susceptibility (4-300 K). The susceptibility data for. complexes 1 and 3 were least-squares fit to the susceptibility equation derived from the spin Hamiltonian H=-2J . S1 . S2. The exchange integral, J, was found to be equal to -3.62 cm-1 in 1 and -1.82 cm-1 in 3. This indicates a weak antiferromagnetic spin exchange interaction between the metal ions.     

Synthesis, characterization and electrochemistry of ferrocenylselenolate bridged palladium(II) and platinum(II) complexes

The dimeric ferrocenyl-selenolate complexes of Pd and Pt, [{μ-η¹-Fe(η⁵-C₅H₄Se)₂}M(PⁿBu₃)]₂ (M = Pd 2, Pt 3), and the monomeric ferrocenyl(bis-selenolate) complex of platinum, [{η²-Fe(C₅H₄Se)₂}Pt(PⁿBu₃)₂] (4), have been prepared from 1,1′-bis(trimethylsilylseleno)ferrocene 1 and trans-MCl₂(PⁿBu₃)₂ and cis-PtCl₂(PⁿBu₃)₂, respectively. Complexes 2 and 3 contain two edge-sharing, square-planar metal centres forming a planar M₂Se₂ four-membered ring and exhibit two one-electron redox waves indicating electronic communication between the two Fe centers.     

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 and characterization of oxo-bridged, trinuclear, six-coordinate mixed-carboxylato complexes of chromium (III)

Mixed-carboxylato β-diketonato complexes of chromium (III) (R=C₁₃H₂₇, C₁₅H₃₁ or C₁₇H₃₅ and L=CH₃OH) [Cr₃O(OOCR)₃(dike)₃L₃]⁺ have been synthesized by enforced substitution reactions of [Cr₃O(OOCCH₃)₇(H₂O)] first with straight chain fatty acids (myristic, palmitic or stearic acid) and then with β-diketones (Hβ-dike) like acetylacetone(Hacac) or benzoylacetone(Hbzac) in toluene under reflux. These are new type of oxo-bridged chromium(III) complexes in which one ligand is a fatty acid while the other one is a β-diketone. The complexes were characterized by elemental analyses, spectral (infrared, electronic, FAB mass and powder XRD) studies, molar conductance and magnetic susceptibility measurements. Bridging coordination modes for both carboxylate and β-diketonate anions were indicated by presence of ν_asym(Cr₃O) vibrations in the infrared spectra. Trinuclear nature of the complexes and their structural features have been discussed on the basis of physicochemical studies.     

Synthesis and magnetism of 2-hydroxy-1,3-propanediylbis-(oxamato) bridged trinuclear copper(II) complexes

Summary Four novel trinuclear copper(II) complexes have been synthesized, namely {[Cu(pbaOH)][Cu(L)]₂}(ClO₄)₂, where pbaOH = 2-hydroxy-1,3-propanediylbis(oxamato) and L is 1,10-phenanthroline (phen), 5-nitro-1,10-phenanthroline (NO₂-phen), 2,2-bipyridyl (bipy) or 4,4-dimethyl-2,2-bipyridyl (Me₂bipy). Based on i.r. and electronic spectra, elemental analyses, and conductivity measurements oxamato-bridged structures consisting of three copper(II) ions, in which each copper(II) ion has a square-planar environment, are proposed. The temperature-dependent magnetic susceptibility of {[Cu-(pbaOH)][Cu(phen)]₂}(ClO₄) ₂ has been studied in the 4.2–300 K range, giving the exchange integral J=- 111.9cm^–1. The result revealed the operation of an antiferromagnetic spin-exchange interaction between adjacent copper ions.     

Molecular tricorns: self-assembly of trinuclear palladium(II) complexes

Cyclometalation of the ligand 1,3-bis(1-alkylbenzimidazol-2-yl)benzene (1) with palladium carboxylates leads to a trimeric complex [Pd(3)(ligand)(3)(carboxylate)(3)] (3). Studies in solution show that the trinuclear core is stable but that the carboxylates are labile, undergoing intra- and intermolecular exchange on an NMR time scale. The structural analogue of 1, 2,6-bis(1-alkylbenzimidazol-2-yl)pyridine (4), gives only the mononuclear species [Pd(4)(carboxylate)(2)], characterized by X-ray diffraction. This complex forms a trimer if one carboxylate is labilized by the addition of strong acid; the resulting trinuclear species is readily cleaved by nucleophiles but can include weakly basic anions within its cavity.     

Synthesis and magnetic properties of new nickel(II)-copper(II)-nickel(II) trinuclear complexes with irregular spin-state structure

Summary Four novel heterotrinuclear complexes were prepared, namely {[Ni(L)₂]₂[Cu(pba)]}(ClO₄)₂, where pba = pro-pylene-1,3-bis(oxamato) and L = 1,10-phenanthroline (phen), 5-nitro-1,10-phenanthroline (NO₂-phen), 2,2-bipyridyl (bpy), 4,4-dimethyl-2,2-bipyridyl (Me₂bpy). Based on i.r., elemental analyses, conductivity measurements and electronic spectra oxamato-bridged structures are proposed for these complexes, consisting of two nickel(II) ions, each in a distorted octahedral environment, and a copper(II) ion in a square planar environment, respectively. The temperature dependence of the magnetic susceptibility of {[Ni(phen)₂]₂[Cu(pba)]}(ClO₄)₂·H₂O was studied in the 4–300 K range, giving the exchange integral J = - 106 cm^–1. TheX _scm T versusT plot exhibited a minimum at ca. 98 K, characteristic of this kind of coupled polymetallic complex with an irregular spin-state structure. E.s.r. spectra of these complexes clearly indicated a strong rhombicity withg ₁ = 5.20,g ₂ = 2.29 andg ₃ = 2.02 (approximately), which agrees with an anisotropicS = ±1/2 Kramer doublet in the ground state.     

4,4'-联吡啶、吡嗪和咪唑桥联铜、镍配合物的合成和磁性

合成了六个含氮杂环桥联配合物: [Ni(salal)2(4,4'-bipy)]n、[Ni(Et-dtp)2(4,4'-bipy)]n、[Cu(acac)2(4,4'-bipy)]n、[Cu(TTA)2(pyz)]n、[Cu(TTa)(Im)]n和[Cu(Im)2]n, 用元素分析、IR、MS、ESR和热重分析对它们的结构和性质作了表征。吡嗪配合物的晶体结构显示, 吡嗪配位于拉伸八面体的轴向位置, 桥联Cu(TTA)2形成一维无限链状结构。变温磁化率表明, 4,4'-联吡啶和吡嗪配合物的磁性遵从Curie-Weiss定律, 分子内没有明显的磁交换作用。咪唑配合物中存在着较强的反铁磁性交换作用, 磁交换常数分别为-75和-107cm^-^1。对4,4'-联吡啶、吡嗪和咪唑传递磁交换的性质作了讨论。     

Synthesis, characterization and magnetism of binuclear cobalt (II) complexes bridged by tetracarboxylato groups

Three new binudear cobalt (II) complexes with extended te-tracarboxylato- bridge have been synthesized and characterized, namely [Co2 (PMTA) (bpy)4] (1), [Co2(PMTA)-(phen)4] (2) and [Co2(PMTA) (NO2phen)4] (3), where PMTA represents the tetraanion of pyroniellitic acid, and bpy, phen, NO2-phen denote 2,2'-bipyridine, 1,10-phenan-throline; 5-nirto-1, 10-plienanthroline, respectively. Based on elemental analyses, molar conductivity measurements, IR and electronic spectra studies, it is proposed that these complexes have PMTA-bridged structures and consist of two cobalt (II) ions, each in a distorted octahedral environment. These complexes were further characterized by variable temperature magnetic susceptibility measurements (4-300 K) and the observed data were successfully simulated by the equation based on the spin Hamiltonian operator, giving the exchange integral J = - 1.02 cm-1 for 1, J = -1.21 cm-1 for 2 and J = - 1.18 cm-1 for 3, respectively. These results revealed the operation of antiferromagneti     

Synthesis and properties of some chromium(III) β-diketonate complexes

Summary Equimolar quantities of CrCl₃ · 3THF and-diketones, -dkH, react to yield CrCl₂(-dk) · 2THF and CrCl₂(-dk) · THF complexes in coordinating and noncoordinating solvents respectively. For 1 : 2 and 1 : 3 molar ratios of reactants, derivatives of general formulae CrCl(-dk)₂ and Cr(-dk)₃ (where-dkH = acerylacetrrnc, benzoylacetonc and dibenzoylmethane) have been isolated. All complexes have been characterized by elemental analysis, molecular weights and by i.r. spectra.     

Cyclopentadienyl mesityl complexes of chromium(II) and chromium(III)

Chromium(III) mesityl complexes were synthesized by protonolysis of chromocene with 1,3-diisopropylimidazolium chloride or DBU hydrochloride, salt metathesis with MesMgBr, and single electron oxidation with iodine.     

N2 Laser-excited luminescence of antiferromagnetically coupled trinuclear chromium(III) complexes

Exchange interaction parameters in several trinuclear chromium(III) complexes [Cr₃O(R-COO)₆(H₂O)₃]X·nH₂O (R = CH₃, C₂H₅) are determined in the study of luminescence, time-resolved luminescence (TRS ), and decay time measurements over the temperature range 4–100°K. The presence of four inequivalent trinuclear clusters and a luminescence anomaly at 25 and 55°K are observed in the basic chromium(III) acetate prisms. Magnetic anomalies reported earlier should be attributed to the distortion and disordering of the hydrogen-bonded channels in crystals at low temperatures.     

Synthesis, structures, and magnetic properties of carboxylate-bridged trinuclear complexes based on low-spin manganese(III)/iron(III) building blocks

Four linear trinuclear transition metal complexes have been prepared and characterized. The complexes [M^II(MeOH)₄][Fe^III(L)₂]₂·2MeOH (M = Fe (1) or Ni (2)), [Co^II(EtOH)₂(H₂O)₂][Fe^III(L)₂]₂·2EtOH (3), and [Mn^II(phen)₂][Mn^III(L)₂]₂·4MeOH (4) (H₂L = ((2-carboxyphenyl)azo)-benzaldoxime, phen = 1,10-phenanthroline) possesses a similar syn–anti carboxylate-bridged structure. The terminal Fe(III) or Mn(III) ions are low spin, and the central M(II) ions are high spin. Magnetic measurements show that antiferromagnetic interactions were present between the adjacent metal ions via the syn–anti carboxylate bridges. The antiferromagnetic coupling between low-spin Fe(III) and Ni(II) is unusual, which has been tentatively assigned to the structural distortion of Fe(III).