A tetracopper(II) complex with N,N′-bis(picolinoyl)hydrazine

Synthesis, physical properties and X-ray structure of a hydrated tetranuclear copper(II) complex [Cu₄(μ-diph)₂(μ-H₂O)₂(O₂CCH₃)₄(H₂O)₂]·4H₂O with N,N′-bis(picolinoyl)hydrazine (H₂diph) are reported. The centrosymmetric complex has two types of copper(II) centres with distorted square-pyramidal N₂O₃ coordination spheres. The dinucleating trans planar diph²⁻ ligands are parallel to each other and act as N₂O-donor to one metal centre and N₂-donor to the other metal centre. The complex has a rectangular {Cu₄(μ-N-N)₂(μ-OH₂)₂} core with Cu···Cu distances as 4.834(1) and 3.762(1) Å. Solid state as well as solution electronic spectra show several transitions in the wavelength range 700-280 nm. The room temperature (298 K) solid state magnetic moment is 3.55 μ_B. The powder EPR spectra at 298 and 130 K are very similar and axial (g_∥ = 2.25 and g_⊥ = 2.08) in character.     

Deposition of iron titanate/titania ceramic composite thin films from a single molecular precursor

A heterobimetallic single molecular precursor, [Fe₂Ti₄(μ-O)₆(TFA)₈(THF)₆] (1) [TFA = trifluoroacetate, THF = tetrahydrofuran], was synthesized by the simple reaction of [Fe₃O(OAc)₆(H₂O)₃]NO₃·4H₂O [OAc = acetato] with tetrakis(2-ethoxyethanalato)titanium(IV) in the presence of trifluoroacetic acid in THF. The synthesized precursor was analyzed by melting point, CHN analysis, FTIR, single crystal X-ray diffraction and thermogravimetric analysis. Complex (1) crystallizes in the orthorhombic space group Pca2₁ with cell dimensions a = 19.2114(14), b = 20.4804(15) and c = 17.2504(12) Å, and the complex undergoes thermal decomposition at 490 °C to give a residual mass corresponding to an Fe₂TiO₅-TiO₂ composite mixture. The synthesized precursor was utilized for deposition of Fe₂TiO₅-TiO₂ composite thin films by aerosol-assisted chemical vapor deposition (AACVD) on glass substrates at 500 °C using argon as the carrier gas. Scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and X-ray powder diffraction (XRD) analyses of the thin films suggest the formation of good quality crystalline thin films of an Fe₂TiO₅-TiO₂ composite with an average grain size of 0.105-0.120 μm.     

Morphological and physiological adaptive traits of Mediterranean narrow endemic plants: The case of Centaurea gymnocarpa (Capraia Island,Italy)

A case study on Centaurea gymnocarpa Moris & De Not., a narrow endemic species, was carried out by analyzing its morphological, anatomical, and physiological traits in response to natural habitat stress factors under Mediterranean climate conditions. The results underline that the species is particularly adapted to the environment where it naturally grows. At the plant level, the above-ground/below-ground dry mass (1.73 ± 0.60) shows its investment predominately in the above-ground structure with a resulting total leaf area per plant of 1399 ± 94 cm². The senescent attached leaves at the base of the plant contribute to limit leaf transpiration by shading soil around the plant. Moreover, the dense C. gymnocarpa leaf pubescence, leaf rolling, the relatively high leaf mass area (LMA = 12.3 ± 1.3 mg cm⁻²) and leaf tissue density (LTD = 427 ± 44 mg cm⁻³) contribute to limit leaf transpiration, also postponing leaf death under dry conditions. At the physiological level, a relatively low respiration/photosynthesis ratio (R/P_N) in spring results from high R [2.26 ± 0.59 μmol (CO₂) m⁻² s⁻¹] and P_N [12.3 ± 1.5 μmol (CO₂) m⁻² s⁻¹]. The high photosynthetic nitrogen use efficiency [PNUE = 15.5 ± 0.4 μmol (CO₂) g⁻¹ (N) s⁻¹] shows the large amount of nitrogen (N) invested in the photosynthetic machinery of new leaves, associated to a high chlorophyll content (Chl = 35 ± 5 SPAD units). On the contrary, the highest R/P_N ratio (1.75 ± 0.19) in summer is due to a significant P_N decrease and increase of R in response to drought. The low PNUE [1.5 ± 0.2 μmol (CO₂) g⁻¹ (N) s⁻¹] in this season is indicative of a greater N investment in leaf cell walls which may contribute to limit transpiration. On the contrary, the low R/P_N ratio (0.05 ± 0.02) in winter is resulting from the limited enzyme activity of the respiratory apparatus [R = 0.23 ± 0.08 μmol (CO₂) m⁻² s⁻¹] while the low PNUE [3.5 ± 0.2 μmol (CO₂) g⁻¹ (N) s⁻¹] suggests that low temperatures additionally limit plant production. The experiment of the imposed water stress confirms that the C. gymnocarpa growth capability is in conformity with the severe conditions of its natural habitat, likewise as it may be the case with others narrow endemic species that have occupied niches with similar extreme conditions.     

Copper-cobalt oxide ceramic thin films from single source precursors: Preparation and characterization

Two heterobimetallic coordination complexes [Co(acac)Cu₂(bdmap)₂Cl₃]·C₇H₈ (1) and [Co(acac)Cu₂(bdmap)₂Cl₃]·3CH₂Cl₂ (2) [bdmap = 1,3-Bis(dimethylamino)-2-propanol and acac = 2,4-pentanedionate], have been synthesized by simple chemical technique and characterized by their melting points, elemental composition, FT-IR spectroscopy, mass spectrometry and single crystal X-ray analysis. Thermograms of both the precursors indicated their facile decomposition at relatively low temperature of 454 °C to give stable residual mixture of Cu and CoO. Both the precursors are utilized for the deposition of Cu-CoO thin films by aerosol-assisted chemical vapor deposition (AACVD) equipment at 450 °C on glass substrates that were subsequently characterized for their morphology and composition of the ceramic material. The scanning electron microscopy of copper-cobalt oxide films grown from both the precursors describe highly compact and smooth morphology with homogenously dispersed spherical particles with excellent adhesion properties to the substrates. The EDX analysis shows homogeneous distribution of metallic elements with Cu:Co ratio close to 2:1. Powder X-ray diffraction analysis of the films shows that they are composed of Cu/CoO composite and are crystalline in nature having particle size in the range of 0.3-0.8 μm.     

Dinuclear terephthalato-bridged copper(II) complexes: Syntheses, spectral and structural characterization, and magnetic properties

Herein, we report the syntheses, spectral and structural characterization, and magnetic behavior of four new dinuclear terephthalato-bridged copper(II) complexes with formulae [Cu₂(trpn)₂(μ-tp)](ClO₄)₂ · 2H₂O (1), [Cu₂(aepn)₂(μ-tp)(ClO₄)₂] (2), [Cu₂(Medpt)₂(μ-tp)(H₂O)₂](ClO₄)₂ (3) and [Cu₂(Et₂dien)₂(μ-tp)(H₂O)](ClO₄)₂ (4) where tp = terephthalate dianion, trpn = tris(3-aminopropyl)-amin, aepn = N-(2-aminoethyl)-1,3-propanediamine, Medpt = 3,3′-diamino-N-methyldipropylmine and Et₂dien = N,N-diethyldiethylenetriamine. The structures of these complexes consist of two μ-tp bridging Cu(II) centers in a bis(monodentate) bonding fashion. The coordination geometry of the Cu(II) ions in these compounds may be described as close to square-based pyramid (SP) with severe significant distortion towards trigonal bipyramid (TBP) stereochemistry in 1. The visible spectra of the complexes in aqueous solutions are in complete agreement with the assigned X-ray geometry around the Cu(II) centers. Also, the solid infrared spectral data for the stretching frequencies of the tp-carboxalato groups, the ν(COO⁻) reveals the existence of bis(monodentate) coordination mode for the bridged terephthalate ligand. The susceptibility measurements at variable temperature over the range 2-300 K are reported. Despite the same bonding mode of the tp bridging ligand, there has been observed slight antiferromagnetic coupling for the compounds 1 and 4 with J values of −0.5 and −2.9 cm³ K mol⁻¹, respectively, and very weak ferromagnetic coupling for 2 and 3 with J values of 0.8 and 10.1 cm³ K mol⁻¹, respectively. The magnetic results are discussed in relation to other related μ-terephthalato dinuclear Cu(II) published compounds.     

Diiron and diruthenium aminocarbyne complexes containing pseudohalides: stereochemistry and reactivity

Acetonitrile is easily displaced from [Fe₂{μ-CN(Me)(R)}(μ-CO)(CO)(MeCN)(Cp)₂][SO₃CF₃] (R = 2,6-Me₂C₆H₃ (Xyl) (1a); Me (1b)) upon stirring in THF at room temperature in the presence of [NBu₄][SCN]. The resulting complexes trans-[Fe₂{μ-CN(Me)(R)}(μ-CO)(CO)(NCS)(Cp)₂] (R = Xyl (trans-2a); Me (trans-2b)) are completely isomerised to cis-[Fe₂{μ-CN(Me)(R)}(μ-CO)(CO)(NCS)(Cp)₂] (R = Xyl (cis-2a); Me (cis-2b)) when heated at reflux temperature. Similarly, the complexes cis-[M₂{μ-CN(Me)(R)}(μ-CO)(CO)(NCO)(Cp)₂] (M = Fe, R = Me (4a); M = Ru, R = Xyl (4b); M = Ru, R = Me (4c)) and cis-[M₂{μ-CN(Me)(R)}(μ-CO)(CO)(N₃)(Cp)₂] (M = Fe, R = Xyl (5a); M = Fe, R = Me (5b); M = Ru, R = Xyl (5c)) can be obtained by heating at reflux temperature a THF solution of [M₂{μ-CN(Me)(R)}(μ-CO)(CO)(MeCN)(Cp)₂][SO₃CF₃] (M = Fe, R = Xyl (1a); M = Fe, Me (1b); M = Ru, R = Xyl (1c); M = Ru, R = Me (1d)) in the presence of NaNCO and NaN₃, respectively. The reactions of 5 with MeO₂CCCCO₂Me, HCCCO₂Me and (NC)(H)CC(H)(CN) afford the triazolato complexes [M₂{μ-CN(Me)(R)}(μ-CO)(CO){N₃C₂(CO₂Me)₂}(Cp)₂] (M = Fe, R = Xyl (6a); M = Fe, R = Me (6b); M = Ru, R = Xyl (6c)), [M₂{μ-CN(Me)(R)}(μ- CO)(CO){N₃C₂(H)(CO₂Me)}(Cp)₂] (M = Fe, R = Me (7a); M = Ru, R = Xyl (7b)) and [Fe₂{μ-CN(Me)(Xyl)}(μ-CO)(CO){N₃C₂(H)(CN)}(Cp)₂] (8), respectively. The asymmetrically substituted triazolato complexes 7-8 are obtained as mixtures of N(1) and N(2) bonded isomers, whereas 6 exists only in the N(2) form. Methylation of 6-8 results in the formation of the triazole complexes [Fe₂{μ-CN(Me)(Xyl)}(μ-CO)(CO){N₃(Me)C₂(CO₂Me)₂}(Cp)₂][CF₃SO₃] (9), [M₂{μ-CN(Me)(R)}(μ-CO)(CO){N₃(Me)C₂(H)(CO₂Me)}(Cp)₂][CF₃SO₃] (M = Fe, R = Me (10a); M = Ru, R = Xyl (10b)) and [Fe₂{μ-CN(Me)(Xyl)}(μ-CO)(CO){N₃(Me)C₂(H)(CN)}(Cp)₂][CF₃SO₃], 11. The crystal structures of trans-2b, 4b · CH₂Cl₂, 5a, 6b · 0.5CH₂Cl₂ and 8 · CH₂Cl₂ have been determined.     

Dinuclear fumarato- and terephthalato-bridged copper(II) complexes: Structural characterization and magnetic properties

The dinuclear dicarboxylato-bridged copper(II) complexes [Cu₂(TPA)₂(μ-tp)](ClO₄)₂ · H₂O (1), [Cu₂(TPA)₂(μ-fum)](ClO₄)₂ · 2H₂O (2) and [Cu₂(pmedien)₂(μ-fum)(H₂O)₂](ClO₄)₂ (3) (tp = terephthalate dianion, fum = fumarate dianion, TPA = tris(2-pyridylmethyl)amine and pmedien = N,N,N′,N″,N″-pentamethyldiethylenetriamine) were synthesized and structurally characterized by X-ray crystallography. The structures of the TPA complexes 1 and 2 consist of μ-tp or μ-fum bridging two Cu(II) centers in a bis(monodentate) bonding fashion. The coordination geometry around the Cu(II) ions in these compounds has a distorted trigonal bipyamidal geometry, TBP with four nitrogen atoms from the TPA ligand and a coordinated oxygen atom supplied by the carboxylate group of the bridged dicarboxylato ligand. Complex 3 has a distorted square pyramidal geometry achieved by the three N-atoms of the pmedien, one fum-carboxylate-oxygen and by an oxygen atom from a coordinated water molecule. The intradimer Cu…Cu distances in these complexes are 11.078(3), 8.663(4) and 9.520(3) Å for 1, 2 and 3, respectively. The electronic spectra of the complexes in aqueous solutions are in complete agreement with the assigned X-ray geometry around the Cu(II) centers. Also, analysis of the infrared spectral data for the ν(COO⁻) stretching frequencies of the tp-carboxalato groups reveals the existence of the bis(mondentate) coordination mode for the bridged dicarboxylato ligands in compounds 1 and 2. The susceptibility measurements at variable temperature over the 2-300 K range are reported. For 1-3, it has been observed slight antiferromagnetic coupling with J values of −0.8, −3.0 and −2.9 cm⁻¹, respectively.     

Barium acylpyrazolonate derivatives stabilized by O- and N-donor ligands: synthesis, spectral and structural characterization

New Ba acylpyrazolonate derivatives of formula [Ba(Q)₂(tetraglyme)] (HQ = HQ^tbu = 1-Ph-3-Me-4-C(O)CH₂Bu^t-5-pyrazolone; tetraglyme = 2,5,8,11,14-pentaoxapentadecane), [Ba(Q)₂(tmeda)₂] (HQ = HQ^tbu or HQ^piv, where HQ^piv = 1-Ph-3-Me-4-C(O)Bu^t-5-pyrazolone; tmeda = N,N,N′,N′-tetramethylethylenediamine), [Ba(Q)₂(pmdien)(H₂O)] (HQ = HQ^tbu or HQ^piv; pmdien = N,N,N′,N″,N″-pentamethyldiethylenetriamine) and [Ba(Q)₂(pmdien)(Meim)] (HQ = HQ^tbu or HQ^piv; Meim = 1-methylimidazole) have been synthesized and analytically and spectroscopically characterized. They are mononuclear air and solution stable compounds containing an eight-coordinated barium atom. The X-ray crystal structures of the hydrates [Ba(Q^tbu)₂(pmdien)(H₂O)] and [Ba(Q^piv)₂(pmdien)(H₂O)] show the water molecule directly bonded to Ba and involved in intermolecular H-bonding network. In the X-ray crystal structure of [Ba(Q^piv)₂(pmdien)(Meim)], the Meim ligand substitutes the water of previous derivatives and decreases the strength of intermolecular interactions, lowering the melting point. The derivative [Ba(Q^tbu)₂(pmdien)(NEt₃)] has been prepared from interaction of [Ba(Q^tbu)₂(pmdien)(H₂O)] with excess triethylamine in acetonitrile.     

Synthesis, X-ray crystal structure and magnetic study of the 1D {[Cu2(N,N,N′,N′-tetramethyl-ethylenediamine)2(μ-1,5-dca)2(dca)2]}n complex

Reaction of Cu(NO₃)₂ · 3H₂O, N,N,N′,N′-tetramethyl-ethylenediamine (L) and sodium dicyanamide (Nadca) in aqueous medium yields a complex the {[Cu₂L₂(μ-1,5-dca)₂(dca)₂]}_n complex, 1. Single crystal X-ray analysis reveals that complex 1 has a 1D infinite chain structure in which copper(II) ions are bridged by single dicyanamide anions in an end-to-end fashion. The coordination environment around copper(II) is distorted square pyramidal. Two among the four coordination sites of the basal plane are occupied by the nitrogen atoms of the diamine and two remaining sites are occupied by the terminal nitrogen atom of a bridging and of a monodentate dca anions. The fifth coordination site (apical) is occupied by a nitrogen atom from a bridging dca anion of an adjacent CuL(dca)₂ moiety, yielding the [Cu₂L₂(μ-1,5-dca)₂(dca)₂] dinuclear unit. Dimeric units are connected to each other by single μ-1,5-dicyanamido group to form infinite 1D chains which propagate parallel to the crystallographic c-axis. The variable temperature magnetic susceptibility measurements evidenced weakly antiferromagnetic interactions (J = −0.26 cm⁻¹) in {[Cu₂L₂(μ-1,5-dca)₂(dca)₂]}_n, 1.     

Mono, di and polynuclear Cu(II)-azido complexes incorporating N,N,N reduced schiff base: syntheses, structure and magnetic behavior

Three kinds of copper(II) azide complexes have been synthesised in excellent yields by reacting Cu(ClO₄)₂ · 6H₂O with N,N-bis(2-pyridylmethyl)amine (L¹); N-(2-pyridylmethyl)-N′,N′-dimethylethylenediamine (L²); and N-(2-pyridylmethyl)-N′,N′-diethylethylenediamine (L³), respectively, in the presence of slight excess of sodium azide. They are the monomeric Cu(L¹)(N₃)(ClO₄) (1), the end-to-end diazido-bridged Cu₂(L²)₂(μ-1,3-N₃)₂(ClO₄)₂ (2) and the single azido-bridged (μ-1,3-) 1D chain [Cu(L³)(μ-1,3-N₃)]_n(ClO₄)_n (3). The crystal and molecular structures of these complexes have been solved. The variable temperature magnetic moments of type 2 and type 3 complexes were studied. Temperature dependent susceptibility for 2 was fitted using the Bleaney-Bowers expression which led to the parameters J = −3.43 cm⁻¹ and R = 1 × 10⁻⁵. The magnetic data for 3 were fitted to Baker’s expression for S = 1/2 and the parameters obtained were J = 1.6 cm⁻¹ and R = 3.2 × 10⁻⁴. Crystal data are as follows. Cu(L¹)(N₃)(ClO₄): Chemical formula, C₁₂H₁₃ClN₆O₄Cu; crystal system, monoclinic; space group, P2₁/c; a = 8.788(12), b = 13.045(15), c = 14.213(15) Å; β = 102.960(10)°; Z = 4. Cu(L²)(μ-N₃)(ClO₄): Chemical formula, C₁₀H₁₇ClN₆O₄Cu: crystal system, monoclinic; space group, P2₁/c; a = 10.790(12), b = 8.568(9), c = 16.651(17) Å; β = 102.360(10)°; Z = 4. [Cu(L³)(μ-N₃)](ClO₄): Chemical formula, C₁₂H₂₁ClN₆O₄Cu; crystal system, monoclinic; space group, P2₁/c; a = 12.331(14), b = 7.804(9), c = 18.64(2) Å; β = 103.405(10)°; Z = 4.     

Octahedral hexanuclear complexes involving light lanthanide ions

Two new hexanuclear complexes involving two of the lightest lanthanide ions have been synthesized and structurally described. Their chemical formula is [Ln₆(μ₆-O)(μ₃-OH)₈(NO₃)₆(H₂O)₁₄] · 2NO₃ · 2H₂O with Ln = Pr or Nd. The structure has been solved for the Pr³⁺-containing compound. It crystallizes in the monoclinic system, space group P21/n (no. 14) with a = 12.4163(2) Å, b = 10.51210(10) Å, c = 16.0389(2) Å, β = 95.7810(6)° and Z = 4. The chemical and thermal stabilities of both the compounds have been studied. These studies reveal that they can be used as molecular chemical precursors for further materials synthesis. To the best of our knowledge, this praseodymium-containing hexanuclear complex is the first ever reported.     

Three azido-, alk/phenoxido- and acetato-bridged tetranuclear nickel complexes featuring defective double-cubane

Three new tetranuclear nickel(II) complexes of general formula [Ni₄(L)₂(N₃)₂(CH₃COO)₂(CH₃O)₂]₂·xCH₃OH·yH₂O (HL = HL¹, HL² and HL³; x = 0, y = 1 for 1; x = 2, y = 0 for 2 and x = 2, y = 4 for 3) were synthesized and characterized by single crystal X-ray diffraction and magnetic measurements. Single crystal X-ray studies reveal that all three complexes exhibit similar tetranuclear face-shared defective double-cubane structure, having azido-, alk/phenoxido- and acetato-bridges. Magnetic susceptibility measurements on the complexes in the range of 300-2 K indicate ferromagnetic coupling between the metal ions. The slightly different magnetic behaviors observed are probably caused by subtle structural differences between the respective [Ni₄O₄N₂] cores induced by ligand variation.     

Synthesis, structures, electrochemistry and properties of dioxo-molybdenum(VI) and -tungsten(VI) complexes with novel asymmetric N2OS, and partially symmetric N2S2, NOS2N-capped tripodal ligands

A new class of asymmetric N-capped (dianionic/trianionic) tripodal proligands [H_x(Lⁿ)] (x = 2, n = 1-6; x = 3, n = 7, 8) which possess pendant arms with N₂OS, N₂S₂ or NOS₂ donor groups and with different chelate ring sizes {5,5,5} or {5,6,5} has been prepared. Treatment of these ligands with [WO₂Cl₂(dme)] (dme = 1,2-dimethoxyethane) in the presence of base (triethylamine or KOH) leads to the formation of cis-dioxotungsten(VI) complexes of the types [WO₂(Lⁿ)] (n = 1-6) and K[WO₂(Lⁿ)] (n = 7, 8). Reaction of these tetradentate ligands with [MoO₂(acac)₂] (acac = acetylacetonate) gives the corresponding Mo(VI) analogues [MoO₂(Lⁿ)] (n = 1-6) and K[MoO₂(Lⁿ)] (n = 7, 8). Moreover, a new five coordinate dioxomolybdenum(VI) complex with an NS₂ tridentate ligand [MoO₂(L⁹)] has been synthesised using similar procedure. All these compounds have been spectroscopically characterised and the molecular structures of [MoO₂(Lⁿ)] (n = 2, 6) and [WO₂(L⁶)] have been established by X-ray diffraction analysis. The electrochemistry and the catalytic activity for oxidation of allylic and benzylic alcohols of these dioxo complexes have also been investigated.     

Oxidative nuclease activity of ferromagnetically coupled μ-hydroxo-μ-propionato copper(II) complexes [Cu3(L)2(μ-OH)2(μ-propionato)2] (L = N-(pyrid-2-ylmethyl)R-sulfonamidato, R = benzene, toluene, naphthalene)

Three doubly-bridged, trinuclear copper(II) compounds with hydroxo and carboxylato bridges, ^∞₁[Cu₃(L1)₂(μ-OH)₂(μ-propionato)₂](1), [Cu₃(L2)₂(μ-OH)₂(μ-propionato)₂(DMF)₂] (2) and ^∞₁{[Cu₃(L3)₂(μ-OH)₂(μ-propionato)₂]} [Cu₃(L3)₂(μ-OH)₂(μ-propionato)₂(DMF)₂]} (3) [HL1 = N-(pyrid-2-ylmethyl)benzenesulfonylamide, HL2 = N-(pyrid-2-ylmethyl)toluenesulfonylamide, HL3 = N-(pyrid-2-ylmethyl)naphthalenesulfonylamide], have been synthesized and characterized. 1 is built from [Cu₃(L1)₂(μ-OH)₂(μ-propionato)₂] clusters. Each unit contains three copper(II) with two different coordination environments: the terminal centers are square-base pyramidal whereas the central copper is square planar. 2 presents a similar square-base pyramidal geometry in the terminal centers, but the central copper is six-coordinate. 3 shows an unusual 1D coordination polymer comprised of two distinct building blocks: one similar to that found in 1 and the other similar to that found in 2. The magnetic susceptibility measurements (2-300 K) reveal a ferromagnetic interaction between the Cu(II) ions with J values of 76.0, 55.0, and 48.0 cm⁻¹ for 1, 2, and 3, respectively. Emission spectroscopy, thermal denaturation, viscosimetry and cyclic voltammetry show an interaction of the complexes with DNA through the sugar-phosphate backbone. All three Cu(II) complexes were found to be very efficient agents of plasmid DNA cleavage in the presence of ascorbato or mercaptopropionic acid. Both the kinetics and the mechanism of the cleavage reaction have also been examined.     

Unprecedented formation of binuclear copper(II) complex with a perylene derived ligand by the oxidative reaction

A new perylene-pendent tridentate ligand, N-(3-perylenylmethyl)-N,N-bis(2-pyridylmethyl)amine (perbpa) 1 and its Cu(II) complex, [Cu(perbpa)Cl₂] (2) were prepared and structurally characterized by the X-ray diffraction method. In the packing structure of ligand 1, perylene groups were aggregated to form a π-π stacked layer of dimerized pelylene moieties similar to the packing of pristine perylene. This result suggests both that the π-π interactions among the perylene moieties predominate for the arrangement of perbpa molecules in the crystal and that this ligand is a good candidate for constructing electron conducting path. A complex 2 was prepared from the ligand 1 and a copper(II) chloride dehydrate. Complex 2 had a mononuclear and 5-coordinate distorted square pyramidal structure with a perbpa and two coordinated chloride ions. The chemical oxidation of 2 by iodine resulted in the unprecedented binuclear Cu(II) species, [Cu₂(μ-Cl)₂(perbpa)₂](I₃)₂, 3·(I₃)₂. An X-ray crystal structure analysis of 3·(I₃)₂ revealed the binuclear structure bridged by the chloride ions. A temperature dependent magnetic susceptibility measurement of 3 showed a weak ferromagnetic exchange interaction with S = 1 ground state, g = 2.12 and J = +1.17 cm⁻¹, based on H = −2JS₁ · S₂. The UV-Vis absorption and the EPR spectra of 3 showed that the perylene groups are not oxidized. These results indicate a couple of Cu(II) constructed S = 1 ground state with intermolecular ferromagnetic interaction. The electrochemical study suggested that the crystallization of 3·(I₃)₂ was initiated by the oxidation of the N,N-bis-(2-pyridylmethyl)amino (bpa) groups of 2 by I₂.     

Synthesis of a novel pyridine-diamino bridged diphosphine ligand and its macrocyclic metal complexes

A novel long chain diphosphine ligand with a pyridine-diamino bridge, 2,6-bis(N-benzyl-N-diphenylphosphinomethylamino)pyridine (PNP1), was prepared conveniently using the Mannich reaction of HPPh₂ with paraformaldehyde and 2,6-bis(N-benzylamino)pyridine in high yield. Reactions of the ligand with metal complexes, M(COD)Cl₂ (M = Pd, Pt), M(CH₃CN)₄ClO₄ (M = Cu, Ag) and M(CO)₆ (M = Mo, W) afforded the corresponding 10-numbered monometallic macrocyclic complexes with an uncoordinated pyridyl bridge. The monometallic chelate PdCl₂(PNP1) continued to react with Ag⁺ or Cu⁺ giving the μ-Cl bridged bicyclic metallic complex (μ-Cl)₂[PdCl(PNP1)]₂. The diphenylphosphine group coordinated with metal ion in cis-form in all the 10-numbered macrocyclic metal complexes. Ligand PNP1 and another known analogous 2,6-bis(N-diphenylphosphinoamino)pyridine (PNP2) reacted with Au(SMe₂)Cl giving the corresponding bimetallic Au₂Cl₂(PNP1) and Au₂Cl₂(PNP2), respectively. The latter bimetallic complexes continued to react with Ag⁺ and diphosphine ligand to give the corresponding bimetallic macrocyclic complexes Au₂(ligand)₂(ClO₄)₂. All the complexes were characterized and the structures of some complexes were confirmed by X-ray single crystallography determination.     

Hydrogen-bonded copper(II) and nickel(II) complexes and coordination polymeric structures containing reduced Schiff base ligands

Complexes [Cu(HSas)(H₂O)] · 2H₂O (H₃Sas = N-(2-hydroxybenzyl)-l-aspartic acid) (1), [Cu(HMeSglu)(H₂O)] · 2H₂O (H₃MeSglu = (N-(2-hydroxy-5-methylbenzyl)-l-glutamic acid) (2), [Cu₂(Smet)₂] (H₂Smet = (N-(2-hydroxybenzyl)-l-methionine) (3), [Ni(HSas)(H₂O)] (4), [Ni₂(Smet)₂(H₂O)₂] (5), and [Ni(HSapg)₂] (H₂Sapg = (N-(2-hydroxybenzyl)-l-aspargine) (6) have been synthesized and characterized by chemical and spectroscopic methods. Structural determination by single crystal X-ray diffraction studies revealed 1D coordination polymeric structures in 2 and 4, and hydrogen-bonded network structure in 5 and 6. In contrast to previously reported coordination compounds with similar ligands, the phenol remains protonated and bonded to the metal ions in 2 and 4, and also probably in 1. However, the phenolic group is non-bonded in 6.     

Supramolecular networks of dinuclear copper(II): Synthesis, crystal structure and magnetic study

The complexes [Cu₂(ox)(phen)₂(H₂O)₂](NO₃)₂ (1), [Cu₂(sq)(pmdien)₂(H₂O)₂](ClO₄)₂ (2) and {[Cu₃(pdc)₃(4,4′-bipy)_1.5(H₂O)_2.25] · 2.5(H₂O)}_n (3) [phen = 1,10-phenanthroline; pmdien = N,N,N′,N′,N″-pentamethyldiethylenetriamine; 4,4′-bipy = 4,4′-bipyridine; ox = oxalate dianion; sq = squarate dianion and pdc = pyridine 2,6-dicarboxylate] have been synthesized and characterized by X-ray single crystal structure determination, low temperature magnetic measurement and thermal study. Structure determination reveals that 1 and 2 are dinuclear copper(II) complexes bridged by oxalate and squarate dianions, respectively, while 3 is a hexanuclear species formed by three Cu(pdc)(H₂O)-(4,4′-bipy)-Cu(pdc)(H₂O) fragments, connected through long Cu-O(pdc) bonds in a centrosymmetric arrangement. In complex 1 H-bonds occurring between the coordinated water molecules and lattice nitrate anions result in eight-membered ring clusters with the concomitant formation of 1D supramolecular chain. The adjacent chains undergo π-π stacking forming a 2D architecture. In the crystal of 3 an extensive H-bonding scheme gives rise to a 3D supramolecular network. Low temperature magnetic study shows a strong antiferromagnetic coupling in 1 (J = −288 ± 2 cm⁻¹, g = 2.21 ± 0.01, R = 1.2 × 10⁻⁶); and a very weak interaction in 2 and 3, the best-fit parameters being: J = −0.21 cm⁻¹, g = 2.12 ± 0.01, R = 1.1 × 10⁻⁶ (2) and J = −1.34 cm⁻¹ ± 0.1, g = 2.14 ± 0.01, R = 1.2 × 10⁻⁶ (3) (R defines as .     

Rh and Ir dibenzo[a,e]cyclooctatetraene complexes: Chloro, hydroxo, and mixed Au oxo complexes

New and improved procedures are reported for the synthesis of [M(DBCOT)(μ-Cl)]₂ (M = Rh, Ir; DBCOT = dibenzo[a,e]cyclooctatetraene) from MCl₃(H₂O)_x or [M(COD)(μ-Cl)]₂ and DBCOT. Treatment of [M(DBCOT)(μ-Cl)]₂ with [(LAu)₃(μ-O)]BF₄(L = PPh₃, P^tBu₃) yields the mixed-metal oxo complexes [M(DBCOT)(μ⁴-O)(AuL)₂]₂(BF₄)₂. Dimeric [Rh(DBCOT)(μ-OH)]₂ is obtained from the reaction of [M(DBCOT)(μ-Cl)]₂ with KOH in EtOH/H₂O. All complexes except [Rh(DBCOT)(μ-Cl)]₂ have been structurally characterized by single crystal X-ray diffraction.     

Synthesis and crystal structure of a cis-oxime-oximate bridged tetra coordinated open-book shaped new dicopper(II/II) complex [Cu2(μ-Hdmg)2(Hdmg)]ClO4: First report of unusual oxime OH bridging

Reaction of Cu(ClO₄)₂ · 6H₂O with dimethylglyoxime (H₂dmg) and triethylamine (pH ∼ 4-5) at room temperature affords oxime bridged dicopper(II/II) complex of formula [Cu₂(μ-Hdmg)₂(Hdmg)]ClO₄ · H₂O (1) (H₂dmg = dimethylglyoxime). The complex has been characterized by single-crystal X-ray diffraction analysis. The structure consists of one dinuclear complex cation, [Cu₂(μ-Hdmg)₂(Hdmg)], and one anion. Two copper(II) ions at a distance of 3.558 Å are bridged by one oxime and one oximate groups in cis arrangement. The geometry around each copper atom is square planar with an overall open-book type arrangement of these planes. The average copper-oxygen distance is (1.953 Å) and the average copper-nitrogen distance is 2.003 Å. The Cu-O(oxime) distance (1.963 Å) is higher than the Cu-O(oximate) distance (1.942 Å) due to different protonation label. The room temperature value of χ_MT for the title complex (χ_M being the molar magnetic susceptibility for two copper atoms) is low (ca. 0.42 cm³ K mol⁻¹) (μ_eff = 1.52 μ_B). The UV-Vis spectrum of the complex shows a characteristic broad band at 470 nm.