Oxotris(oxalate)niobate(V): An oxalate delivery agent in the design of building blocks

<p>This work concerns the oxalate delivery process that occurs when using (NH₄)₃[NbO(C₂O₄)₃]·6H₂O as a suitable oxalate source in the synthesis of two compounds, [Cu(dmphen)(C₂O₄)(H₂O)] (<b>1</b>) and [{Cu(dmphen)(CH₃OH)}₂(μ-C₂O₄)](ClO₄)₂ (<b>2</b>) (dmphen = 2,9-dimethyl-1,10-phenanthroline). {[Fe{HB(pz)₃}(CN)₂(μ-CN)]₂[{Cu(dmphen)}₂(μ-C₂O₄)]}∙<i>x</i>CH₃OH (<b>3</b>) (2.0 ≤ <i>x</i> ≤ 2.4) was obtained by reacting <b>2</b> and PPh₄[Fe{HB(pz)₃}(CN)₃]∙H₂O [ = tetraphenylphosphonium and  = tris(pyrazolyl)borate]. Crystal structures of <b>1</b>–<b>3</b> have been determined by single-crystal X-ray diffraction experiments: <b>1</b> is a mononuclear trigonal bipyramidal copper(II) species, <b>2</b> is a centrosymmetric oxalato-bridged dicopper(II) complex, and <b>3</b> consists of centrosymmetric tetranuclear units with intramolecular iron–copper and copper–copper distances around 5.010(1) and 5.1833(9) Å, respectively. Variable-temperature magnetic measurements of <b>2</b> and <b>3</b> were carried out from 50 to 350 (<b>1</b>) and 1.9 to 300 K (<b>3</b>). A strong antiferromagnetic interaction between copper(II) ions occurs in <b>2</b> (<i>J</i> = −340 cm⁻¹, the spin Hamiltonian being defined as ). Analysis of the magnetic data of <b>3</b> shows magnetic interactions across the oxalate (<i>J</i>₁ = −341 cm⁻¹) and single cyanide (<i>J</i>₂ = +12.9 cm⁻¹) … (<i>J</i>₂ = +12.9 cm⁻¹) bridges . Simple symmetry considerations of the interacting magnetic orbitals in <b>2</b> and <b>3</b> provide a clear picture of the exchange pathways involved in these complexes.</p

Difluorodioxophosphate-Based Hollow Hexanuclear Lanthanide(III) Clusters Decorated with Tetrathiafulvalene Ligands

The galvanostatic reaction of the [4,5-bis­(2-pyridyl-<i>N</i>-oxidemethylthio)]-4′,5′-methyldithiotetrathiafulvalene ligand with lanthanide ions in the presence of hexafluorophosphate (PF₆^–) anions afforded the highest-nuclearity lanthanide clusters decorated by tetrathiafulvalene-based ligands thanks to the original partial hydrolysis of the PF₆^– anions in difluorodioxophosphate (PO₂F₂^–) bridging ligands

Alkaline Ion-Modulated Solid-State Supramolecular Organization in Mixed Organic/Metallorganic Compounds Based on 1,1′-Ethylenebis(4-aminopyridinium) Cations and Bis(oxamate)cuprate(II) Anions

Three new coordination compounds of formula (edap)₂­[Cu­(opba)]₂­·4H₂O (<b>1</b>), (edap)­[{Na₂(H₂O)₄}­{Cu₂(opba)₂}]­·2H₂O (<b>2</b>), and (edap)­[{K₂(H₂O)₂}­{Cu₂(opba)₂}]­·3H₂O (<b>3</b>) (edap = 1,1′-ethylenebis­(4-aminopyridinium) and opba = 1,2-phenylenebis­(oxamate)) were synthesized through the metathesis reaction involving A₂[Cu­(opba)] (A = Li⁺, Na⁺, and K⁺) and (edap)­Cl₂·2H₂O. Crystal structures of <b>1</b>–<b>3</b> and edap­(IO₃)₂­·4H₂O compound were elucidated by single crystal X-ray diffraction. Compounds <b>1</b>–<b>3</b> are built up from dinuclear copper­(II) entities, {[Cu­(opba)]₂}^4– with an asymmetric bis­(monatomic oxygen) bridge resulting from the parallel “out-of-plane” disposition of the planar mononuclear [Cu­(opba)]^2–. They possess distinct supramolecular arrangements of varying dimensionality (<i>n</i>D with <i>n</i> = 0 (<b>1</b>), 1 (<b>2</b>), and 2 (<b>3</b>)) in the solid state depending on the nature of the coordinated alkaline ion present alongside edap²⁺ counterions. While the {[Cu­(opba)]₂}^4– building blocks are well-isolated in <b>1</b>, they form either double chains or corrugated layers due to the coordination of the Na⁺ or K⁺ ions in <b>2</b> and <b>3</b>, respectively. Magnetic properties of <b>1</b>–<b>3</b> show a very weak antiferromagnetic coupling between the Cu^II ions through a double monatomic (μ-O) bridge (−<i>J</i> = 1.63(9) (<b>1</b>), 2.29(2) (<b>2</b>), and 1.65(3) cm^–1 (<b>3</b>)), the Hamiltonian being defined as <i><b>H</b></i> = −(<i><b>S</b></i>_{<i><b>1</b></i>}·<i><b>S</b></i>_{<i><b>2</b></i>}) + <i>g βH</i>(<i><b>S</b></i>_{<i><b>1</b></i>} + <i><b>S</b></i>_{<i><b>2</b></i>})

Difluorodioxophosphate-Based Hollow Hexanuclear Lanthanide(III) Clusters Decorated with Tetrathiafulvalene Ligands

The galvanostatic reaction of the [4,5-bis­(2-pyridyl-<i>N</i>-oxidemethylthio)]-4′,5′-methyldithiotetrathiafulvalene ligand with lanthanide ions in the presence of hexafluorophosphate (PF₆^–) anions afforded the highest-nuclearity lanthanide clusters decorated by tetrathiafulvalene-based ligands thanks to the original partial hydrolysis of the PF₆^– anions in difluorodioxophosphate (PO₂F₂^–) bridging ligands

Crystal Engineering Applied to Modulate the Structure and Magnetic Properties of Oxamate Complexes Containing the [Cu(bpca)]⁺ Cation

This work deals with the crystal engineering features of four related copper­(II)-based compounds with formulas {[{Cu­(bpca)}₂­(H₂ppba)]·1.33DMF­·0.66DMSO}_<i>n</i> (<b>2</b>), [{Cu­(bpca)­(H₂O)}₂­(H₂ppba)] (<b>3</b>), [{Cu­(bpca)}₂­(H₂ppba)]­·DMSO (<b>4</b>), and [{Cu­(bpca)}₂­(H₂ppba)]­·6H₂O (<b>5</b>) [H₄ppba = <i>N</i>,<i>N</i>′-1,4-phenylenebis­(oxamic acid) and Hbpca = bis­(2-pyridylcarbonyl)­amide] and how their distinct molecular and crystal structures translate into their different magnetic properties. <b>2</b> and <b>3</b> were obtained through the hydrolytic reaction of the double-stranded oxamato-based dipalladium­(II) paracyclophane precursor of formula [{K₄(H₂O)₂}­{Pd₂(ppba)₂}] (<b>1</b>) with the mononuclear copper­(II) complex [Cu­(bpca)­(H₂O)₂]⁺, either in a water–DMSO–DMF solvent mixture or in water, respectively. The straightforward reaction of the neutral H₄ppba molecule with [Cu­(bpca)­(H₂O)₂]⁺ in a water–DMSO mixture afforded compound <b>4</b>, whereas compound <b>5</b> resulted from the reaction between the copper­(II) complex and the K₂ppba salt in water. The [Pd₂(ppba)₂]^4– tetraanionic unit which is present in <b>1</b> has a [3,3] metallacyclophane-type motif connected by two N–Pd–N bonds. This entity acts as a ligand toward partially hydrated potassium­(I) cations through its outer oxamate oxygens leading to a neutral three-dimensional network. The structure of <b>2</b> consists of neutral chains made up of double oxo­(carboxylate-oxamate)-bridged di­[{bis­(2-pyridylcarbonyl)­amidate}­copper­(II)] units are which connected by the extended H₂ppba^2– ligand, each of its oxamate fragments adopting a bidentate/outer monodentate coordination mode. Compounds <b>2</b>–<b>5</b> are neutral and centrosymmetric dicopper­(II) complexes which have in common the presence of peripheral bpca ligands and H₂ppba^2– as a bridge with each of its monoprotonated oxamate groups exhibiting rare monodentate (<b>3</b>) and bis-bidentate (<b>4</b> and <b>5</b>) coordination modes. Compounds <b>2</b>, <b>4</b>, and <b>5</b> share the same basic [{Cu­(bpca)}₂­(H₂ppba)] unit, but besides the difference in the cocrystallization solvent molecules and synthetic strategies, they feature very different crystal structures. To better understand the role of palladium­(II) ions in the formation of <b>2</b> and <b>3</b>, some studies were carried out using different mixtures of solvents such as water, DMSO, and DMF which revealed a major importance of DMF in the formation of <b>2</b> and the dependence on the palladium­(II) ions in the formation of <b>3</b>. A reaction pathway leading to the formation of <b>2</b> and <b>3</b> is then proposed. The variable-temperature (2.0–300 K) magnetic susceptibility measurements of <b>2</b>, <b>4</b>, and <b>5</b> revealed the occurrence of weak ferro- [<i>J</i> = +0.70 cm^–1 (<b>2</b>)] and antiferromagnetic interactions [<i>J</i> = −0.90 (<b>4</b>) and −0.79 cm^–1 (<b>5</b>)], the spin Hamiltonian being defined as <b>H</b> = −<i>J</i><b>S</b>₁·<b>S</b>₂. The different nature and strength of the magnetic coupling along this unique series of compounds are discussed in the light of the structural data, and they are compared with those of related dicopper­(II) systems

Selective Wrapping of Few-Walled Carbon Nanotubes by a Serpent-Like Heterobimetallic Coordination Polymer

In this work, selective interactions between the constituents of the composite CNT@MnCu (<b>2</b>) prepared using carbon nonotubes (CNTs) (<b>1</b>) and the heterobimetallic chain [MnCu­(opba)]_<i>n</i> (MnCu), opba = <i>o</i>-phenylenebis­(oxamate), were studied mainly by resonance Raman spectroscopy and high-resolution transmission electron microscopy (HRTEM). An apparent interaction between CNTs and MnCu complex with the wrapping of the former by the heterobimetallic complex was observed in the microscopy images. The resonance Raman data suggest that the interations between MnCu complex and the CNTs are selective, occurring mainly with metallic CNTs independently of the diameter and excitation energy. However, for semiconducting CNTs, these interactions solely occur with tubes having diameters higher than ca. 1.47 nm

Solvent effects on the dimensionality of oxamato-bridged manganese(II) compounds

<p>Two new oxamate-containing manganese(II) complexes, [{Mn(H₂edpba)(H₂O)₂}₂]_n (<b>1</b>) and [Mn(H₂edpba)(dmso)₂]∙dmso∙CH₃COCH₃∙H₂O (<b>2</b>) (H₄edpba = <i>N,N′</i>-ethylenediphenylenebis(oxamic acid) and dmso = dimethylsulfoxide), have been synthesized and the structures of <b>1</b> and <b>2</b> were characterized by single crystal X-ray diffraction. The structure of <b>1</b> consists of neutral honeycomb networks in which each manganese(II) is six-coordinate by one H₂edpba²⁻ ligand and two carboxylate–oxygens from two other H₂edpba²⁻ ligands building the equatorial plane. Each manganese is connected to its nearest neighbor through two carboxylate(monoprotonated oxamate) bridges in an <i>anti</i>-<i>syn</i> conformation. A dmso solution of single crystals of <b>1</b> was placed under acetone atmosphere affording <b>2</b>, whereas putting <b>2</b> in equimolar water:ethanol mixture results in <b>1</b>. The molecular structure of <b>2</b> is made up of mononuclear manganese(II) units which are interlinked by weak C–H⋯π and edge-to-face π-stacking interactions leading to supramolecular chains along the crystallographic <i>b</i> axis. Magnetic measurements reveal the occurrence of an antiferromagnetic coupling between two manganese(II) ions through <i>anti-syn</i> carboxylate bridges for <b>1</b> [<i>J</i> = −1.18 cm⁻¹, the Hamiltonian being defined as <b><i>H</i> </b>= −<i>J</i> <b><i>S</i></b>₁^.<b><i>S</i></b>₂] and very weak intrachain ferromagnetic interactions in <b>2</b> [<i>J</i> = + 0.046 cm⁻¹, <b><i>H</i></b> = −<i>J</i> ∑_i<b><i>S</i></b>_i^.<b><i>S</i></b>_i + 1].</p

Influence of Copper(II) and Nickel(II) Ions in the Topology of Systems Based on a Flexible Bis-Oxamate and Bipyridine Building Blocks

Single crystals of the mononuclear bis-oxamate nickel­(II) complex [Ni­(bipy)­(H₂edpba)]·dmso (<b>1</b>) are obtained by reacting [Ni­(bipy)­Cl₂]·H₂O and the flexible K₂(H₂edpba) ligand [bipy = 2,2′<b>-</b>bipyridine; H₄edpba = <i>N</i>,<i>N</i>′-2,2′-ethylenediphenylenebis­(oxamic acid)]. The reaction of <b>1</b> with copper­(II) ions resulted in two products in which the replacement of the nickel­(II) ion by copper­(II) took place: the chain compound [Cu­(bipy)­(H₂edpba)]_<i>n</i>·3<i>n</i>H₂O·<i>n</i>dmso [dmso = dimethyl sulfoxide] (<b>2</b>) and the analogous chain compound without dmso crystallization molecules [Cu­(bipy)­(H₂edpba)]_<i>n</i>·1.5<i>n</i>H₂O (<b>3a</b>) in its polycrystalline form. The reaction of [Cu­(bipy)­Cl₂] and K₂(H₂edpba) yielded single crystals of [Cu­(bipy)­(H₂edpba)]_<i>n</i>·1.5<i>n</i>H₂O (<b>3b</b>). The H₂edpba^2– ligand exhibits the <i>anti</i> conformation in <b>1</b>, <b>2</b>, and <b>3b</b>, but it adopts different coordination modes: terminal bis-bidentate (<b>1</b>) and bridging bis-bidentate (<b>2</b> and <b>3b</b>) through the two pairs of carbonyl-oxygen atoms of the two oxamate arms. Magnetic susceptibility measurements carried out on a polycrystalline sample of <b>3b</b> in the temperature range 1.9–295 K showed the occurrence of very weak intrachain antiferromagnetic interactions [<i>J</i> = −0.40 cm^–1, the Hamiltonian being defined as <i><b>H</b></i> = −<i>J</i> ∑_<i>i</i><i><b>S</b></i>_<i>i</i>·<i><b>S</b></i>_<i>i</i>+1], in agreement with the large values of the copper–copper separation [8.308(3) Å]

Palladium(II)–Copper(II) Assembling with Bis(2-pyridylcarbonyl)amidate and Bis(oxamate) Type Ligands

Five new complexes of formula K₄[Pd₂(mpba)₂] · 4H₂O (<b>1</b>), {[K₄(H₂O)­(dmso)]­[Pd₂(mpba)₂]} (<b>2</b>), {[Cu­(bpca)]₄[Pd₂(mpba)₂]} · 6H₂O (<b>3</b>), {[Cu­(bpca)]₂[Pd­(opba)]} · 1.75dmso · 0.25H₂O (<b>4</b>), {[Cu­(bpca)]₂[Pd­(opba)]}_<i>n</i> · <i>n</i>dmso (<b>5</b>) [H₄mpba =1,3-phenylenebis­(oxamic acid), H₄opba = 1,2-phenylenebis­(oxamic acid), Hbpca = bis­(2-pyridylcarbonyl)­amide, and dmso = dimethyl sulfoxide] have been prepared and investigated by infrared spectroscopy, thermal analysis, single crystal X-ray diffraction, and magnetic susceptibility techniques. The structure of <b>2</b> consists of a [Pd₂(mpba)₂]^4– anionic entity in which the palladium­(II) cations are coordinated by two mpba ligands resulting in a dipalladium­(II) unit that acts as a ligand toward potassium­(I) cations leading to a neutral three-dimensional network. Compound <b>3</b> is a neutral hexanuclear complex where the dinuclear [Pd₂(mpba)₂]^4– unit adopts a tetrakis­(bidentate) coordination mode toward four [Cu­(bpca)]⁺ end-cap entities. This compound can be viewed as a “dimer of trimers” in which two Cu^II–Pd^II–Cu^II trinuclear units are connected by two mpba ligands. Compounds <b>4</b> and <b>5</b> have in common the presence of a [Pd­(opba)]^2– unit, which acts as a bis­(bidentate) ligand toward two [Cu­(bpca)]⁺ entities to afford neutral heterotrinuclear Cu^II–Pd^II–Cu^II motifs that are interlinked through weak double (<b>4</b>) and single (<b>5</b>) out-of-plane copper­(II) to carbonyl­(bpca)-oxygen atoms leading to uniform linear (<b>4</b>) and zigzag (<b>5</b>) chains of heterobimetallic trinuclear units. The investigation of the magnetic properties of <b>3</b>–<b>5</b> in the 1.9–300 K temperature range reveals the presence of very weak antiferromagnetic interactions between the copper­(II) ions. The nature and magnitude of these magnetic interactions are discussed in terms of orbital symmetry considerations

Magnetic Poles Determinations and Robustness of Memory Effect upon Solubilization in a Dy^III-Based Single Ion Magnet

The [Dy­(tta)₃(L)] complex behaves as a single ion magnet both in its crystalline phase and in solution. Experimental and theoretical magnetic anisotropy axes perfectly match and lie along the most electro-negative atoms of the coordination sphere. Both VSM and MCD measurements highlight the robustness of the complex, with persistence of the memory effect even in solution up to 4 K