Oxamato-bridged trinuclear Ni(II)Cu(II)Ni(II) complexes with irregular spin state structures and a binuclear Ni(II)Cu(II) complex with an unusual supramolecular structure: crystal structure and magnetic properties

Four oxamato-bridged heterotrinuclear Ni(II)Cu(II)Ni(II) complexes of formula ([Ni(bispictn)](2)Cu(pba))(ClO(4))(2).2.5H(2)O (1), ([Ni(bispictn)](2)Cu(pbaOH))(ClO(4))(2).H(2)O (2), ([Ni(cth)](2)Cu(pba))(ClO(4))(2) (3), and ([Ni(cth)](2)Cu(opba))(ClO(4))(2).H(2)O (4) and a binuclear Ni(II)Cu(II) complex of formula [Cu(opba)Ni(cth)].CH(3)OH (5) have been synthesized and characterized by means of elemental analysis, IR, ESR, and electronic spectra, where pba = 1,3-propylenebis(oxamato), pbaOH = 2-hydroxyl-1,3-propylenebis(oxamato), opba = o-phenylenebis(oxamato), bispictn = N,N'-bis(2-pyridylmethyl)-1,3-propanediamine, and cth = rac-5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane. The crystal structures of 1, 3, and 5 have been determined. The structures of complexes 1 and 3 consist of trinuclear cations and perchlorate anions, and that of 5 consists of neutral binuclear molecules which are connected by hydrogen bonds and pi-pi interactions to produce a unique supramolecular "double" sheet. In the three complexes, the copper atom in a square-planar or axially elongated octahedral environment and the nickel atom in a distorted octahedral environment are bridged by the oxamato groups, with Cu.Ni separations between 5.29 and 5.33 A. The magnetic properties of all five complexes have been investigated. The chi(M)T versus T plots for 1-4 exhibit the minimum characteristic of antiferromagnetically coupled NiCuNi species with an irregular spin state structure and a spin-quartet ground state. The chi(M)T versus T plot for 5 is typical of an antiferromagnetically coupled NiCu pair with a spin-doublet ground state. The Ni(II)-Cu(II) isotropic interaction parameters for the five complexes were evaluated and are between 102 and 108 cm(-)(1) (H = -JS(Cu).S(Ni)).     

Syntheses and crystal structures of Zn(II) and Co(II) complexes with ofloxacin and enoxacin

[Zn(Ofl) · (H₂O)] · 2H₂O (1) and [Co(Enox)₂] · 4H₂O (2) were obtained by hydrothermal reactions. The solid-state structures have been characterized by IR spectroscopy and single crystal X-ray diffraction analyses. Complex 1 crystallizes in the triclinic system, space group P 1, with lattice parameters a = 9.2923(5), b = 11.3432(6), c = 17.7722(10) Å, α = 92.839(3), β = 94.826(3), γ = 91.909(3)°, V = 1863.01(18) ų, Z = 2, D _Calcd = 1.494 mg m^?3. The coordination environment around Zn²⁺ is a slightly distorted square pyramid. Complex 2 crystallizes in the triclinic system, space group P2(1)/c, with lattice parameters a = 5.97980(10), b = 21.4183(3), c = 13.1539(2) Å, V = 100.2810(10), Z = 2, D _Calcd = 1.526 mg m^?3, Co(II) ion is a distorted octahedral geometry.     

Syntheses and molecular structures of three Cu(II) complexes with tetradentate imine-phenols

Three Cu(II) complexes of N,N′-bis-(salicylidene)-1,3-diiminopropane (1), N,N′-bis-(salicylidene)-1,3-diimino-2,2-dimethylpropane (2), and N,N′-bis-(salicylidene)-1,5-diiminopentane (3) have been prepared and characterized by X-ray diffraction. All of the three complexes are four coordinated with Cu(II) in a tetrahedrally distorted square-planar geometry to two imine N atoms and two phenolate O atoms. Both 1 and 2 are monomeric with a 6-6-6 chelate ring structure and display the 2N2O donor atoms in a normal, tetradentate “cis” configuration. However, in 3 two Cu(II) ions coordinate with bis-bidentate Schiff-base ligands, such that the Cu atoms are bridged by the two ligands; about each Cu atom, the arrangement of the iminophenolate groups is trans. The CuN1O1 and CuN2O2 planes intersect to form dihedral angles of 24.7° and 34.8° for 1 and 2, respectively, while the dihedral angle of two bidentate chelate planes of 3 is 40.5°.     

Cd(II), Zn(II), and Pd(II) complexes of an isoindoline pincer ligand: consequences of steric crowding

The sterically crowded isoindoline pincer ligand, 6'-MeLH, prepared by condensation of 4-methyl-2-aminopyridine and phthalonitrile, exhibits very different reaction chemistry with Cd2+, Zn2+, and Pd2+. Three different ligand coordination modes are reported, each dependent upon choice of metal ion. This isoindoline binds to Cd2+ as a charge-neutral, zwitterionic, bidentate ligand using imine and pyridine nitrogen atoms to form the eight-coordinate fluxional complex, Cd(6'-MeLH)2(NO3)2. In the presence of Zn2+, however, loss of a pyridine arm occurs through solvolysis and tetrahedrally coordinated complexes are formed with coordination of pyrrole and pyridine nitrogen atoms. Reaction with Pd2+ produces the highly distorted, square planar complex Pd(6'-MeL)Cl in which a deprotonated isoindoline anion coordinates as a tridentate pyridinium NNC pincer ligand.     

New oxamato-bridged trinuclear Cu(II)-Cu(II)-Cu(II) complexes with hydrogen-bond supramolecular structures: synthesis and magneto-structural studies

Three oxamato-bridged copper(II) complexes of formula [(Cu(H(2)O)(tmen)Cu(tmen))(mu-Cu(H(2)O)(Me(2)pba))](n)((PF(6))(2))(n).2nH(2)O (1), [(Cu(H(2)O)(tmen)Cu(NCS)(tmen))(mu-Cu(H(2)O)(Me(2)pba))](2)(ClO(4))(2).4H(2)O (2), and [(Cu(H(2)O)(tmen)Cu(NCS)(tmen))(mu-Cu(H(2)O)(Me(2)pba))](2)(PF(6))(2).4H(2)O (3), where Me(2)pba = 2,2-dimethyl-1,3-propylenebis(oxamato) and tmen = N,N,N',N'-tetramethylethylenediamine, have been synthesized and characterized. Their crystal structures were solved. Complex 1 crystallizes in the monoclinic system, space group P2(1), with a = 15.8364(3) A, b =8.4592(2) A, c = 15.952 A, beta = 101.9070(10) degrees, and Z = 2. Complex 2 crystallizes in the monoclinic system, space group P2(1)/c, with a = 6.69530(10) A, b = 18.2441(3) A, c = 31.6127(5) A, beta = 90.1230(10) degrees, and Z = 4. Complex 3 crystallizes in the monoclinic system, space group P2(1)/c, with a = 6.68970(10) A, b = 18.150 A, c = 32.1949(4) A, beta = 90.0820(10) degrees, and Z = 4. The three complexes have a central core in common: a trinuclear Cu(II) complex with the two terminal Cu(II) ions blocked by N,N,N',N'-tetramethylethylenediamine. The structure of complex 1 consists of trinuclear cationic entities connected by hydrogen bonds to produce a supramolecular one-dimensional array. The structure of complexes 2 and 3 consist of trinuclear cationic entities linked by pairs by hydrogen bonds between the water molecule of the central Cu(II) and one oxygen atom of the oxamato ligand of the neighboring entity, forming a hexanuclear complex. The magnetic properties of the three complexes were studied by susceptibility vs temperature measurement. For complexes 1-3 the fit was made by the irreducible tensor operator (ITO). The values obtained were J(1) = -386.48 cm(-1) and J(2) = 1.94 cm(-1) for 1, J(1) = -125.77 cm(-1) and J(2) = 0.85 cm(-1) for 2, and J(1) = -135.50 cm(-1) and J(2) = 0.94 cm(-1) for 3. In complex 1, the coordination polyhedron of the terminal Cu(II) atoms can be considered as square pyramidal; the apical positions are filled by the oxygen atom from a water molecule in the former and a F atom of the hexafluorophosphate anion in the latter showing a quasi-planar [Cu(CuMe(2)pba)Cu] network. For complexes 2 and 3, the square pyramidal environment of the terminal Cu(II) ions was strongly modified. To our knowledge, this is the first time that the longest distance (apical) in complexes with oxamato derivatives and bidentate amines as blocking ligands has been reported in one of the oxamato arms. The great difference in J(1) values between 1 and the other two complexes is interpreted as an orbital reversal of the magnetic orbitals of the terminal Cu(II) ions in 2 and 3.     

Syntheses,structures of Mn(II), Ni(II), Cu(II) and Zn(II) coordination complexes based on 3,4,5-trifluorobenzeneseleninic acid and N-donor ligands

Abstract

Five new coordination complexes [Mn^II (L₁)₂(4,4′-bpy)]_n (1), [Ni^II (L₁)₂(4,4′-bpy)]_n (2), [Zn^II (L₁)₂(4,4′-bpy)]_n (3), [Cu^II (L₁)₂(phen)₂]Cl₂ (4) and [Cu^II ₂(L₁)₂(2,2′-bpy)₂]Cl₂ (5) (HL₁?=?3,4,5-trifluorobenzeneseleninic acid, 4,4′-bpy = 4,4′-bipyridine, 2,2′-bpy = 2,2′-bipyridine and phen = 1,10-phenanthroline), have been synthesized and characterized by single-crystal X-ray diffraction, powder X-ray diffraction (PXRD), elemental analysis and IR spectroscopy. Complexes 1–3 display similar layers structures. In 1–3, the adjacent layers are further connected through π···π interactions to form three-dimensional supramolecular structures. Complexes 4 and 5 show a dimer containing an eight-membered ring. The dimer extends into three-dimensional supramolecular structures through π···π interactions, C–H···F and C–H···Cl interactions.     

Syntheses and structures of Zn(II) and Ni(II) complexes of 4-N-(acetylacetone amine)acetophenone thiosemicarbazone

A new ligand, 4-N-(acetylacetone amine)acetophenone thiosemicarbazone (HL, 1), was synthesized by condensation of p-aminoacetophenone with thiosemicarbazide and acetylacetone. Treatment of HL with zinc acetate and nickel acetate afforded ZnL₂ (2) and NiL₂?·?DMF (3). The crystal structures of 1, 2 and 3 have been determined by single-crystal X-ray diffraction. 2 and 3 have similar structures, in which metal atom is coordinated in a distorted tetrahedral configuration, and L^? coordinates to zinc(II) or nickel(II) through the azomethine nitrogen and the thiolato sulfur atom.     

Cu(I) and Zn(II) complexes of 7-azaindole-containing scorpionates: structures, luminescence and fluxionality

A new scorpionate borate ligand K[HB(7-azain)3](1, 7-azain = 7-azaindolyl) has been obtained from the reaction of KBH4 with excess 7-azaindole. The scorpionate ligand 1 was found to be able to form complexes with Zn(II) and Cu(I) ions. Complex 2 with the formula [BH(7-azain)3](ZnCl) has been obtained from the reaction of ZnCl2 with 1. Complex 3 with the formula [BH(7-azain)3][Cu(PPh3)] has been obtained from the reaction of [Cu(PPh3)2(CH3CN)2][BF4] with . The crystal structures of 1-3 have been determined by single-crystal X-ray diffraction analyses which revealed that has a dimeric structure linked together by two K+ ions, 2 has a symmetric tripodal structure with all three 7-azaindolyl groups being coordinated to the Zn(II) center, and 3 has an asymmetric structure with two of the 7-azaindolyl groups being coordinated to the Cu(I) center and the third 7-azaindolyl group uncoordinated. Variable temperature 1H NMR experiments established that 3 is highly dynamic in solution involving a rapid exchange between the coordinated and the non-coordinated 7-azaindolyl groups. All three compounds display blue emission in the solid state at ambient temperature. However, in solution at ambient temperature, compounds 1 and 2 display bright blue emission while compound 3 has no emission at all. At 77 K, solutions of all three compounds display blue-green phosphorescent emission with a long decay lifetime (> 2 ms).     

Syntheses and thermal reactivities of tetradentate metalloenediynes of Cu(II) and Zn(II)

The syntheses and Bergman cyclization temperatures of disubstituted tetradentate enediyne ligands based on a dibenzylethylenediamine backbone are reported relative to the corresponding Cu(II) and Zn(II) analogues. For these compounds, the R-groups dimethylamine (dma), pyridine (py), quinoline (quin), and 3-oxypyridine (pyO) have been symmetrically and asymmetrically incorporated at the alkyne termini positions directly (0:0) or via a methylene spacer (1:0, 0:1, 1:1). Electron paramagnetic resonance (EPR) reveals that all Cu(II) complexes are monomeric with near axial symmetry and g-values (g(x) approximately 2.04, g(y) approximately 2.09 g(z) approximately 2.25) representative of tetragonal Cu(II) geometries. The hyperfine splitting parameter A(z) values are approximately 170 x 10(-)(4) cm(-)(1), which is consistent with distorted 4-coordinate, or weakly 6-coordinate, structures. In contrast, solution conductivity measurements show that Zn(II) complexes with rigid py or quin ligands (e.g., py-py 0:0, py-quin 0:0) behave as 1:4 electrolytes indicative of dimeric, bridging enediyne structures. Consequently, these Zn(II) complexes have very high Bergman cyclization temperatures (>290 degrees C), while their less rigid, 1:1 analogues (<185 degrees C) and monomeric Cu(II) counterparts (110-136 degrees C) have markedly lower cyclization temperatures. The results underscore the important consequences metal center structure plays in influencing Bergman cyclization temperatures of metalloenediynes.     

Syntheses,structures and luminescent properties of two Zn(II) complexes of N-2-nitrobenzenesulfonyl-glycine acid

Two luminescent zinc coordination complexes [Zn₂(2-NBS-gly)₄(H₂O)₄]?·?2H₂O (1), and Zn(Im)₂(2-NBS-gly)₂ (2), (2-NBS-glyH?=?N-2-nitrobenzenesulfonyl-glycine acid, Im?=?imidazole) have been synthesized and their crystal structures determined by X-ray crystallography. The Zn(II) in 1 is a five-coordinate geometry and can be described as a slightly distorted square-pyramid; complex 2 is four-coordinate, forming a distorted tetrahedron. Through hydrogen bonding, complex 1 forms a 2-D network and complex 2 forms a zigzag chain. Fluorescent analyses show that both 1 and 2 exhibit photoluminescence in the solid state and may be potential candidates for photoactive materials.     

New Ni(II)Cu(II)Ni(II) trinuclear complexes with an 5=3/2 high-spin ground

Four new heterotrinuclear complexes have been synthesized and characterized, namely {[Ni(L)₂]₂[Cu(opba)]}(ClO₄)₂, where opba denotes o-phenylenebis(oxamato) and L stands for 1,10-phenanthroline(phen) (1), 5-nitro-l,10-phenanthroline(NO₂-phen) (2), 2,2′-bipyridyl(bpy) (S) and 4,4′-dimethyl-2,2′-bipyridyl(Me₂bpy) (4). The temperature dependence of the magnetic susceptibility of {[Ni(phen)₂]₂[Cu(opba)]}(ClO₄)₂3H₂O has been studied in the 4–300 K range, giving the exchange integral J—109 cm^?1. The HMT vs. T plot exhibits a minimum at about 100 K, characteristic of this kind of coupled polymetallic complex with an irregular spin-state structure.     

Syntheses,crystal, molecular structures,and solution studies of Cu(II), Co(II), and Zn(II) coordination compounds containing pyridine-2,6-dicarboxylic acid and 1,4-pyrazine-2,3-dicarboxylic acid: comparative computational studies of Cu(II) and Zn(II) complexes

Structural Chemistry - Three new coordination compounds of Cu(II), Co(II), and Zn(II) based on different dicarboxylic acids formulated as (AcrH)[Cu(pydc)(pydcH)]·5H2O (1)...     

Syntheses, crystal structures and magnetic properties of two dicopper(II) complexes and a zigzag 1-D Cu(II) complex of a bidentate pyridyl-pyrazole ligand

Two new dinuclear copper compounds, [Cu₂(pypz)₂(N₃)₂(NO₃)₂] (1) and [Cu₂(pypz)₂(OH)₂(NO₃)₂] (2), and one 1-D polymeric Cu(II) complex, [Cu(pypz)(dca)₃]_n (3) [‘pypz’ = (3,5dimethyl-1-(2′-pyridyl)pyrazole) and dca = (dicyanamide)], have been synthesized and characterized crystallographically and spectroscopically. Complex 1 is pseudo-octahedral, adjacent Cu atoms are connected by a pair of μ(1,1) azido groups and the structure is stabilized by π-π interactions between two pyridyl moieties from two different neighboring complex molecules. Complexes 2 and 3 are square pyramidal. The hydroxo bridged complex 2 is further stabilized through H-bonding. The 1-D polymeric chain of 3 is bridged by an end-to-end dicyanamide bridge and it propagates along the crystallographic b axis, whilst the polymer chains are stacked one upon another along the crystallographic c axis. Low temperature magnetic measurement shows that complexes 1 and 2 are ferromagnetic (J values are 30.81 and 14.79 cm⁻¹, respectively), whereas due to larger Cu-Cu distances, complex 3 shows weak ferromagnetism.     

Syntheses and structures of mononuclear and binuclear transition metal complexes (Cu,Zn, Ni) with (salicylideneglycine and imidazole)

Four transition metal (Cu(II), Zn(II) and Ni(II)) complexes with a Schiff-base ligand (salicylideneglycine) have been synthesized. All complexes have been characterized by elemental analysis, IR spectra and UV-vis spectroscopy. Single-crystal analyses were performed with (C₉H₇NO₃)Cu(C₃H₄N₂) (1), (C₉H₇NO₃)Zn(C₃H₄N₂)₂ (2), (C₉H₇NO₃)₂Ni₂(C₃H₄N₂)₄ (3) and (C₉H₇NO₃)Ni(C₃H₄N₂)₂(C₄H₅N₂O) · CH₃OH · 0.5H₂O (4) and fluorescence spectra and thermogravimetric analyses were also carried out. Structural analyses show that 1, 2 and 4 have similar coordinated modes with the tridentate amino-Schiff-base ligand, but differ from the binuclear nickel complex 3. The tridentate amino-Schiff-base ligand contains aliphatic nitrogen, phenoxy, and carboxylic oxygen as three donor atoms. In addition, inter- and intra-molecular hydrogen bonds are also discussed.     

Synthesis, crystal structures and spectroscopic properties of two novel oxamido-bridged trinuclear complexes [Cu2M] (M = Cu, Zn)

Based on the complex ligand CuL (H₂L = 2,3-dioxo-5,6:14,15-dibenzo-7,13-diphenyl-1,4,8,12-tetraazacyclo-pentadeca-7,13-diene), two novel oxamido-bridged trinuclear complexes have been prepared. They are of the formula Cu(CuL)₂(ClO₄)₂ · 4C₂H₅OH (1) and [(CuL)₂Zn(C₂H₅OH)₂](ClO₄)₂ · 2C₂H₅OH (2). The crystal structures of the two complexes have been determined by X-ray crystallography. In complex (1), the central Cu is in a complete square-planar environment, bonding to four oxygen atoms of the oxamido macrocyclic ligand, while in complex (2), the Zn center is six-coordinate in an octahedral geometry, the four oxygen donors from macrocyclic ligand form the basal plane and the axial positions are occupied by other oxygen atoms from C₂H₅OH molecules. The spectroscopic properties have been investigated and the EPR spectra have been simulated by WINEPR and SimFonia programs.     

Syntheses of phenoxo-bridged Zn(II) and metallamacrocyclic Hg(II) complexes of organochalcogen (Se,Te) substituted Schiff-bases: structure and DNA-binding studies of Zn(II) complexes

The coordination of organochalcogen (especially Se and Te) substituted Schiff-bases L¹H, L²H, L³H, and L⁴H toward Zn(II) and Hg(II) has been studied. Reactions of these ligands with ZnCl₂ in 1?:?1 molar ratio gave binuclear complexes [{2-[PhX(CH₂) _n N?=?C(Ph)]-6-[PhCO]-4-MeC₆H₂O}₂Zn₂Cl₂] (where X?=?Se, n?=?2 (1); X?=?Se, n?=?3 (2); X?=?Te, n?=?2 (3); and X?=?Te, n?=?3 (4)) with partial hydrolytic cleavage of proligands. In these complexes, two partially hydrolyzed ligand fragments coordinate tridentate (NOO) with two Zn's. Reaction of HgBr₂ with L¹H and L²H in 1?:?1 molar ratio gave monometallic complexes [C₆H₂(4-Me)(OH)[2,6-{C(Ph)?=?N(CH₂) _n Se(Ph)}₂HgBr₂]] (n?=?2 (5) or 3 (6)) and under similar conditions with L³H and L⁴H gave bimetallic complexes [C₆H₂(4-Me)(OH)[2,6-{C(Ph)?=?N(CH₂) _n Te(Ph)}₂Hg₂Br₄]] (n?=?2?(7) or 3 (8)) in which the ligands coordinate with metal through selenium or tellurium, leaving the imino nitrogen and phenolic oxygen uncoordinated. The proligands L¹H, L²H give 14- or 16-membered metallamacrocycles through Se–Hg–Se linkages and L³H, L⁴H give 16- or 18-membered metallamacrocycles through Te–Hg–Br–Hg–Te linkages. All the complexes were characterized by elemental analyses, ESIMS, FTIR, multinuclear NMR, UV-Vis, and conductance measurements. The redox properties of the complexes were investigated by cyclic voltammetry (CV). Complexes 1–4 exhibited ligand-centered irreversible oxidation processes. Complexes 5 and 6 showed metal-centered quasi-reversible single electron transfer, whereas dinuclear complexes 7 and 8 displayed two quasi-reversible, one-electron transfer steps. A single-crystal X-ray structure determination of 1 showed that the coordination unit is centrosymmetric with Zn(II) in square-pyramidal coordination geometry and the two square pyramids sharing an edge. The Zn?···?Zn separation is 3.232?Å. The DNA-binding properties of 1 and 3 with calf thymus DNA were explored by a spectrophotometric method and CV.     

Syntheses and structures of Mn(II), Co(II), and Zn(II) complexes of 1,3-diterpyridyl-substituted p-tert-butylcalix[4]arene

The calix[4]arene-based podand which incorporates two terpyridine functions in 1,3-alternate positions with flexible propylene spacers at lower rim has been prepared and subjected to complexation studies with some transition metal ions. Single-crystal structures of Mn(II), Co(II), and Zn(II) complexes were determined by X-ray diffraction. These metal complexes are formed with a 2?:?1 ratio of metal and ligand. Coordination of each metal is five-coordinate distorted trigonal-bipyramidal geometry by three nitrogen atoms from a terpyridyl unit and two chloride atoms.