Crystal structure and magnetic properties of heterometallic trinuclear Cu2Ni complex containing macrocyclic ligands

One novel heterometallic trinuclear complex of macrocyclic oxamide [Ni(CuL)₂(HBTC)H₂O] (I) (H₂L = 2,3-dioxo-5,6,14,15-dibenzo-1,4,8,12-tetraazacyclopentadeca-7,13-dien; H₃BTC = 1,3,5-benzenetricarboxylic acid) has been solvothermally synthesized and structurally characterized by elemental analysis, IR spectroscopy, XRD, and single-crystal X-ray diffraction. The crystals crystallize in the monoclinic system, space group P2₁/c, a = 11.435(3), b = 20.646(5), c = 18.430(5) Å, β = 94.131(4)°. The structure of I has oxamido-bridged trinuclear [Cu ₂ ^II Ni^II] units and consists of two-dimensional supramolecular architecture formed by strong intermolecular hydrogen bonds. Furthermore, the magnetic properties of complex I was investigated and discussed in detail.     

Two linear trinuclear clusters with bridging triazole: crystal structure and magnetism

Two linear trinuclear clusters, [Co₃(L)₆(H₂O)₆](ClO₄)₆ (1) and [Ni₃(L)₆(H₂O)₆](ClO₄)₆?·?3H₂O (2) (L?=?4-(4-hydroxyphenyl)-1,2,4-triazole), obtained by the reactions of M(ClO₄)₂?·?6H₂O and 4-(4-hydroxyphenyl)-1,2,4-triazole have been isolated and structurally characterized. The two isostructural clusters, linear hexapositive trimers, are linked by three N1,N2-1,2,4-triazoles to the divalent central and terminal metal ions. The magnetic behaviors of the clusters were investigated from 1.8 to 300?K. Magnetic susceptibility measurements reveal antiferromagnetic exchange interactions between the metal centers in the clusters. The magnetic data were analyzed by using linear trinuclear modes with S?=?3/2 and S?=?1 for 1 and 2, respectively. Further studies were performed by accounting spin–orbital coupling for 1 and involving zero-field splitting within the ground state for 2.     

Crystal structure and magnetic behaviour of a trinuclear copper(II) complexes with bridging nitronyl nitroxides

Summary [Cu(hfac)₂]₃(NITR)₂ (hfac = hexafluoroacetylacetonate, NITR = 2-R-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, R = 4-methoxyphenyl) has been prepared and its crystal structure determined. In the centrosymmetric complex, the central copper atom has an elongated octahedral geometry, the terminal ones square pyramidal. The magnetic measurements of the complex show that the metal-radical coupling is antiferromagnetic.Author to whom all correspondence should be directed.     

Lanthanide class of a trinuclear enantiopure helical architecture containing chiral ligands: synthesis, structure, and properties

The pinene-bipyridine carboxylic derivatives (+)- and (-)-HL, designed to form configurationally stable lanthanide complexes, proved their effectiveness as chiral building blocks for the synthesis of lanthanide-containing superstructures. Indeed a self-assembly process takes place with complete diastereoselectivity between the enantiomerically pure ligand L(-) and Ln(III) ions (La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er), thus leading to the quantitative formation of a trinuclear supramolecular architecture with the general formula [Ln(3)(L)(6)(mu(3)-OH)(H(2)O)(3)](ClO(4))(2) (abbreviated as tris(Ln[L](2))). This class of C(3)-symmetrical compounds was structurally characterized in the solid state and solution. Electrospray (ES) mass spectrometric and (1)H NMR spectroscopic analyses indicated that the trinuclear species are maintained in solution (CH(2)Cl(2)) and are stable in the investigated concentration range (10(-2)-10(-6) m). The photophysical properties of the ligand HL and its tris(Ln[L](2)) complexes were studied at room temperature and 77 K, thus demonstrating that the metal-centered luminescence is well sensitized both for the visible and near-IR emitters. The chiroptical properties of tris(Ln[L](2)) complexes were investigated by means of circular dichroism (CD) and circularly polarized luminescence (CPL). A high CD activity is displayed in the region of pi-pi* transitions of bipyridine. CPL spectra of tris(Eu[(+)-L](2)) and tris(Tb[(+)-L](2)) present large dissymmetry factors g(em) for the sensitive transitions of Eu(III) ((5)D(0)-->(7)F(1), g(em)=-0.088) and Tb(III) ((5)D(4)-->(7)F(5), g(em)=-0.0806). The self-recognition capabilities of the system were tested in the presence of artificial enantiomeric mixtures of the ligand. (1)H NMR spectra identical to those of the enantiomerically pure complexes and investigations by CD spectroscopic analysis reveal an almost complete chiral self-recognition in the self-assembly process, thus leading to mixtures of homochiral trinuclear structures.     

Synthesis,crystal structure,and magnetic properties of a linear trinuclear Cu(II) complex

A new linear trinuclear Cu(II) complex, [Cu₃(NTA)₂(4,4′-bpt)₄(H₂O)₂]?·?10H₂O (H₃NTA?=?nitrilotriacetic acid, 4,4′-bpt?=?4-amino-3,5-bis(4-pyridyl)-1,2,4-triazole) (1), was obtained from evaporation of an aqueous solution containing Cu(NO₃)₂?·?6H₂O, 4,4′-bpt, nitrilotriacetic acid (H₃NTA), and NaOH. 1 was characterized using single-crystal X-ray diffraction, IR, and elemental analysis. In the trimer, the three linear copper ions are bridged by two NTA carboxylate groups in a syn–anti conformation and connected by 4,4′-bpt to produce a 1-D array. Temperature-dependent magnetic susceptibilities reveal the presence of weak antiferromagnetic exchange between metal centers.     

Crystal structure and magnetic properties of a linear tetranuclear CoII cluster

Polynuclear complexes are an important class of inorganic functional materials and are of interest particularly for their applications in molecular magnets. Multidentate chelating ligands play an important role in the design and syntheses of polynuclear metal clusters. A novel linear tetranuclear Co^II cluster, namely bis{μ₃‐(E)‐2‐[(2‐oxidobenzylidene)amino]phenolato}bis{μ₂‐(E)‐2‐[(2‐oxidobenzylidene)amino]phenolato}bis(1,10‐phenanthroline)tetracobalt(II), [Co₄(C₁₄H₁₁NO₂)₄(C₁₂H₈N₂)₂], was prepared under solvothermal conditions through a mixed‐ligand synthetic strategy. The structure was determined by X‐ray single‐crystal diffraction and bulk purity was confirmed by powder X‐ray diffraction. The complex molecule has a centrosymmetric tetranuclear chain‐like structure and the four Co^II ions are located in two different coordination environments. The Co^II ions at the ends of the chain are in a slightly distorted octahedral geometry, while the two inner Co^II ions are in five‐coordinate distorted trigonal bipyramidal environments. A magnetic study reveals ferromagnetic Co^II…Co^II exchange interactions for the complex.     

A cross-coupling strategy for the synthesis of dimetallic assemblies containing mixed bipyridine-terpyridine bridging ligands: luminescence and energy transfer properties

Tris-bidentate complexes of the form [Ir(N[symbol: see text]C)2(N[symbol: see text]N)]+ and [Ru(N[symbol: see text]N)3]2+ incorporating a boronic acid substituent (N[symbol: see text]C=2-phenylpyridyl, N[symbol: see text]N=a 2,2'-bipyridyl ligand), are cross-coupled with bromo-substituted bis-terpyridyl ruthenium and iridium complexes to generate heterometallic assemblies comprising bpy-phi(n)-tpy bridges; they display efficient energy transfer from Ir(III) to Ru(II).     

Synthesis,structure and magnetic properties of a trinuclear π-cyclopentadienylniobium complex containing the formate,hydroxylic and oxygen bridges

The trinuclear complex [C₅H₅NbOOCH]₃ (OH)₂ (O)₂ was prepared by heating C₅H₅Nb(CO)₃PPh₃ with anhydrous HCOOH in xylene. The niobium atoms are located at the vertices of an almost regular triangle with short Nb?Nb distance equal to 3.14». The electronic configuration of niobium is d¹. Analysis of the magnetic properties and location of the niobium atoms indicated that they bind only by the formate, hydroxylic and oxygen bridges instead of by direct NbNb bonds.     

Influence of multi-atom bridging ligands on the electronic structure and magnetic properties of homodinuclear titanium molecules

The electronic structure and magnetic properties of homodinuclear titanium(III) molecules with bridging ligands from groups 14, 15, and 16 are examined. Single- and multireference methods with triple-zeta plus polarization basis sets are employed. Dynamic electron correlation effects are included via second-order multireference perturbation theory. Isotropic interaction parameters are calculated, and two of the complexes studied are predicted to be ferromagnetic based on multireference second-order perturbation (MRMP2) theory, using the TZVP(fg) basis set. Zero-field splitting parameters are determined using spin-orbit coupling obtained from complete active space (CAS) self-consistent field (SCF) and multiconfigurational quasi-degenerate perturbation theory (MCQDPT) wave functions. Three Breit-Pauli-based spin coupling methods were employed: full Breit-Pauli (HSO2), the partial two-electron method (P2E), and the semiempirical one-electron method (HSO1).     

Synthesis and structure of new dinuclear palladium complex containing no bridging ligands

Oxidation of the mononuclear semiquinonediimine complex [(NPh)(NH)C₆H₄]₂Pd with silver trifluoromethanesulfonate afforded the diamagnetic dinuclear dicationic palladium complex {[(NPh)(NH)C₆H₄]₂Pd}₂(O₃SCF₃)₂ with a Pd...Pd distance of 3.267(1) . The complex was structurally characterized, and its spectroscopic and electrochemical properties were studied.     

Synthesis, crystal structure and magnetic properties of an enneanuclear manganese cluster containing mixed chelating ligands

A new mixed-valence [Mn₉] cluster of formulae [Mn₉O(OH)₃Cl₄(N₃)₃(hmp)₆(dpkd)₃]·1.5CH₃CN·3H₂O (1·1.5CH₃CN·3H₂O, where hmp⁻ and dpkd²⁻ are the anion of 2-hydroxymethylpyridine and the dianion of the gem-diol form of the dpk, respectively) has been synthesized and characterized by single-crystal X-ray diffraction, IR spectra, elemental analysis and magnetic measurements. Single-crystal structural analysis shows that complex 1 contains a [Mn₉] core with a new structural topology in the Mn clusters, in which the centered six Mn^III atoms compose a trigonal antiprism and the peripheral residual three Mn^II atoms can be seen as the skirt hem of this antiprism. DC magnetic susceptibility studies indicate that the overall antiferromagnetic interactions between Mn ions are present in the cluster. Fitting the data of magnetization and extrapolation of the χ_M′T suggest the spin ground states of S = 3.5, and no out-of-phase (χ_M″) signals are present in the alternating current (AC) susceptibility.     

Crystal structure, magnetic property and thermal analysis of a novel manganese complex with phenyldicarboxylate and benzidine ligands

A new complex [Mn₂(C₁₂H₁₂N₂)₃(C₁₄H₈O₄)₂ (C₂H₅OH)₂] _n (where C₁₄H₈O₄ is 2,2′-bi-phenyldicarboxy- late, bpda; C₁₂H₁₂N₂ is benzidine), has been solvothermally synthesized at 443 K and characterized by the elemental analyses, IR, and the single crystal X-ray diffraction analysis. The title complex crystallizes in the triclinic system, space group P-1, with a=9.472 (4) Å, b=12.638(5) Å, c=13.434(5) Å, and Z=1. The compound consists of one-dimensional S-shaped subchains which interlinked by μ₃-2,2′-bpda into a 2-D sheet. The lattice alcohol molecules are located between the layers of the sheet. The magnetic susceptibility has been measured and indicates possible antiferromagnetic coupling between adjacent Mn(II). Based on the TGA curve, the thermal decomposition mechanism of the compound has also been discussed.     

Synthesis, structure and magnetic properties of linear heterobimetallic trinuclear Mn2Ln (Ln = Eu, Gd, Dy) complexes

The reaction of (S)P[N(CH(3))N[double bond, length as m-dash]CH-C(6)H(3)-2-OH-3-OCH(3)](3) with a Mn(II) salt followed by a Ln(III) salt (Ln = Eu, Gd and Dy), afforded linear heterometallic complexes [L(2)Mn(2)Ln](+) that showed interesting magnetic properties.     

Crystal structure and magnetic properties of dicarboxylate-bridged linear chain Mn(II) complexes

Two manganese(II) complexes, [Mn(mtm)(CH₃OH)₂(H₂O)]_n (1) and [Mn₂(mtm)₂(2,2′-bipy)₂]_n (2) (bipy=bipyridine, mtm=[bis(methylthio)methylene]malonate) were synthesized and characterized by X-ray crystallography. Structure of 1 consists of octahedral manganese(II) species which are extended by carboxylate bridges in syn–anti fashion along the c-axis. Chains of 1 are associated by hydrogen bonding among coordinating water and methanol molecules and carboxylate oxygen atoms, forming two-dimensional structures. The crystallographic asymmetric unit of 2 comprises two [Mn(2,2′-bipy)(mtm)] units in which Mn(II) atoms are bridged by μ₂-oxygens from carboxylate to form Mn₂O₂ rhombus. The dimeric units are linked doubly by second carboxylates in syn–anti fashion, resulting in a chain structure. The antiferromagnetic coupling of Mn(II) ions in 1 (−0.2 cm⁻¹) and 2 (−1.57 cm⁻¹) was determined from variable-temperature magnetic susceptibility data in the temperature range of 2–300 K.     

Synthesis,crystal structure and magnetic properties of a new macrocyclic trinuclear CuII-CuII-CuII complex

A new oxamido-bridged trinuclear copper(II) complex [(CuL)₂Cu](ClO₄)₂·0.5H₂O (L?=?the dianion of 2,3-dioxo-5,6,14,15-dibenzo-7,13-bis(ethoxycarbonyl)-1,4,8,12-tetraazacyclotetradeca-7,12-diene) has been synthesized by self-assembly and characterized. X-ray diffraction analysis reveals that the title complex is monoclinic, space group P2₁, with a?=?16.213(5), b?=?9.811(3), c?=?18.802(6)?Å, β?=?96.790(5)°. The central copper(II) ion lies in a distorted octahedral environment. Terminal coppers have square pyramidal coordination geometry. Magnetic measurements show there is strong antiferromagnetic interaction between the central and the terminal Cu(II) ions.