Synthesis,structure and magnetic properties of 2-D and 3-D [cation]{M[Au(CN)2]3} (M = Ni, Co) coordination polymers

In order to study the templating effect of the cation and the resulting impact on the magnetic properties, reactions of M(II) salts with [cation][Au(CN)₂] were conducted, yielding a series of coordination polymers of the form [cation]{M[Au(CN)₂]₃} (cation = ⁿBu₄N⁺, PPN⁺ (bis(triphenylphosphoranylidene)ammonium); M = Ni(II) and Co(II)). The structures of ⁿBu₄N{M[Au(CN)₂]₃} and PPN{M[Au(CN)₂]₃} (M = Ni and Co) contain two distinct 3-D anionic frameworks of {M[Au(CN)₂]₃}⁻, hence the framework was sensitive to the cation, but not to the identity of the metal center. In ⁿBu₄N{M[Au(CN)₂]₃}, the metal centers are connected by [Au(CN)₂] units to form six 2-D (4, 4) rectangular grids that are fused through the M centers to yield a complex three-dimensional framework which accommodates the ⁿBu₄N⁺ cations. In PPN{M[Au(CN)₂]₃}, the framework adopts a simpler non-interpenetrated Prussian-blue-type pseudo-cubic array, with the PPN⁺ cations occupying each cavity; no reduction in dimensionality occurs despite the large cation size. In the presence of water, {Co(H₂O)₂[Au(CN)₂]₂} · ⁿBu₄N[Au(CN)₂] was obtained, a 2-D layered polymer that contains neutral sheets of {Co(H₂O)₂[Au(CN)₂]₂} which are separated by ⁿBu₄N[Au(CN)₂] layers; aurophilic interactions of 3.4250(13) Å and hydrogen-bonding connect the layers. The magnetic properties of all compounds were investigated by SQUID magnetometry. The Ni(II) polymers have similar magnetic behaviour, which are dominated by zero-field splitting with very weak antiferromagnetic interactions at low temperature (D ∼ 2–3 cm⁻¹, zJ < 1 cm⁻¹). The magnetic behaviour of all of the Co(II) polymers were found to be very similar, and dominated by single-ion effects (i.e. a large first-order orbital contribution). No significant magnetic coupling is observed in any of these coordination polymers, suggesting that the [Au(CN)₂] bridging unit behaves as a poor mediator of magnetic exchange in these high-dimensionality systems.     

Benign synthesis of N-(8-quinolyl)pyridine-2-carboxamide) ligand (Hbpq), and its Ni (II) and Cu (II) complexes. A fluorescent probe for direct detection of nitric oxide in acetonitrile solution based on Hbpq copper(II) acetate interaction

The ligand Hbpq = N-(8-quinolyl)pyridine-2-carboxamide) has been prepared using tetrabutylammonium bromide (TBAB) as an environmentally friendly reaction medium. Four new complexes of this ligand, [M(bpq)X] (M = Cu(II), X = SCN̄ (1), N₃̄ (2); M = Ni(II), X = SCN̄ (3), N₃̄ (4)), have also been synthesized and fully characterized. The crystal and molecular structures of [Cu(bpq)(NCS)]_n (1) have been determined by X-ray crystallography. Copper(II) ion adopts a distorted square pyramidal (4 + 1) coordination in this complex. Hbpq ligand shows a strong emission at 500 nm in acetonitrile solution. The emission is quenched in the presence of copper(II) acetate, apparently because of the formation of [Cu(L)(OAc)(H₂O)] complex. Introduction of nitric oxide (NO) into the acetonitrile solution at room temperature induces an increase in the fluorescence intensity, presumably due to the reduction of Cu(II) to Cu(I). This process is reversible and can form a basis for direct detection of NO.     

Synthesis,characterization and fluorescence properties of hexanuclear zinc(II) complexes

Two hexanuclear zinc(II) complexes, [Zn₆(L¹)₂(μ₂-OH)₂(μ₂-CH₃COO)₈] · CH₃CN (1 · CH₃CN) and [Zn₆(L²)₂(μ₂-OH)₂(μ₂-CH₃COO)₈] · 4CH₃CN (2 · 4CH₃CN), where HL¹ = 4-methyl-2,6-bis(cyclohexylmethyliminomethyl)-phenol and HL² = 4-methyl-2,6-bis(1-naphthalylmethyliminomethyl)-phenol, have been synthesized and characterized by elemental analysis, FT-IR and fluorescence spectroscopic methods, and by X-ray diffraction analysis. In the asymmetric unit of complex 1, two of the three zinc atoms have pentacoordinate geometries and the other is tetrahedrally coordinated, whereas the three distinct Zn atoms in complex 2 adopt three different coordination environments, namely distorted octahedral, trigonal bipyramidal and tetrahedral. The fluorescence properties of the ligands and complexes have been investigated.     

Biological study and electrochemical characterization of Cu(II) and 1,8-bis-(2-pyridyl)-3,6-dithiaoctane (pdto) complex

Preliminary proliferation assays in human tumor cervix line HeLa, using the coordination compound [Cu(pdto)H₂O]²⁺ (pdto = 1,8-bis-(2-pyridyl)-3,6-dithiaoctane) and its precursors Cu(NO₃)₂ · 2.5H₂O and pdto, were carried out. The results showed that the copper complex has a behavior similar to that of the reference drug cis-platin. No biological activity for the non-coordinated ligand and the copper salt was found. It was established by cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy, that the complex [Cu(pdto)H₂O]²⁺ presents an electrochemical reversible Cu(II)/Cu(I) reduction, in acetonitrile solution, meanwhile, the copper salt Cu(NO₃)₂ · 2.5H₂O exhibited an electrochemical irreversible behavior. A comparison between biological and electrochemical results corresponding to [Cu(pdto)H₂O]²⁺ and Cu(NO₃)₂ · 2.5H₂O let us to proposed, the electrochemical reversibility, as one important factor in the antitumoral activity of the copper complex. Due to the nature of the studies presented in this work, other factors like intercalation properties with DNA cannot be neglected in the antitumoral activity of the complex.     

Low-dimensional quantum magnetic systems: Synthesis,structure and magnetic behavior of (2,5-dimethylpyrazine)copper(II) chloride and synthesis and magnetic behavior of bis(2,6-dimethylpyrazine)copper(II) chloride

The synthesis, X-ray structure and magnetic susceptibility of (2,5-dimethylpyrazine)copper(II) chloride (1), and the synthesis and magnetic susceptibility of (2,6-dimethylpyrazine)₂copper(II) chloride (2), are reported. Compound 1 crystallizes in the space group P2₁/c as a coordination polymer of Cu(II) ions bridged by 2,5-methylpyrazine. The resulting chains are magnetically linked via short chloride–chloride contacts. The magnetic susceptibility responds as a uniform Heisenberg chain (2J/k = −20(5) K) with a phase transition to three dimensional order near 5 K. Susceptibility data for compound 2 show that the compound is a linear chain coordination polymer with the copper ions linked by bihalide bridges. A fit to the model for a uniform Heisenberg chain yields 2J = −22.7(2) K.     

Coordination polymers incorporating copper(II) and manganese(II) centers bridged by pyridinedicarboxylate ligands: Structure and magnetism

Two heterobimetallic coordination polymers, [Cu(2,4-pydc)₂Mn(H₂O)₄]_x (1) and [Cu(2,5-pydc)₂Mn(H₂O)₂]_x · 4xH₂O (2), have been synthesized and structurally characterized by single crystal X-ray diffraction. Both compounds have extended 2-D sheet structures. In 1 the copper centers are linked in chains by double ligand bridges and these chains are cross-linked through the manganese coordination spheres and O–C–O bridges to form polymeric sheets. In 2 separate O–C–O bridged Cu and Mn chains are connected in an alternating array by additional ligand bridging to generate the overall 2-D structure. Analysis of magnetic data of 1 reveals that ferromagnetic exchange between the O–C–O bridged copper and manganese centers dominates the magnetic properties of this system. The magnetic data for 2 fit well to a model incorporating antiferromagnetic exchange in independent S = 1/2 and S = 5/2 linear chains with J(Cu) = −0.073 cm⁻¹ and J(Mn) = −0.32 cm⁻¹. Unlike the situation in 1, there is no evidence for heterometallic exchange. In both 1 and 2 the significant exchange occurs via O–C–O bridges. To study the effect of thermal dehydration on the magnetic properties of these systems, the compounds Cu(2,4-pydc)₂Mn · H₂O (1d) and Cu(2,5-pydc)₂Mn · H₂O (2d) were synthesized and studied.     

Structures and magnetic properties of one-dimensional copper(II) complexes bridged with diazaaromatic rings

Seven kinds of polynuclear complexes of [Cu(hfac)₂] (Hhfac = 1,1,1,5,5,5-hexafluoropentane-2,4-dione) with diazaaromatic rings have been prepared. The crystal structures of [{Cu(hfac)₂(μ-L)}_n] (L = 2,5- and 2,6-dimethylpyrazines, propylpyrazine (prpyz), quinoxaline, phenazine, 4,6-dimethylpyrimidine, and 1,6-naphthyridine) have been determined. These complexes consist of a one-dimensional chain structure, and the geometry around the copper ion is approximately an octahedral structure. The relations between the magnetic properties and coordination structure were discussed from the magnetic measurements. In the μ-prpyz complex, one nitrogen atom is coordinated to a copper ion at an axial position, and at the same time the other coordinated at an equatorial site of a neighboring copper ion. This complex showed antiferromagnetic interaction with J/k_B = −0.086(3) K estimated from the Bonner–Fisher model. Weak magnetic interaction is caused by the somewhat long Cu–N distances due to the steric effect from the bridging ligands.     

Spectroscopic studies and crystal structure of tetrabutylammonium trichlorodimethylstannate(IV): Bu4NSnMe2Cl3

The structure of Bu₄NSnMe₂Cl₃ is found to be monomer, containing a 5-coordinated bipyramidal trigonal tin(IV) center. Crystals belong to the monoclinic space group C2/c, with unit-cell dimensions a = 26.633(4) Å; b = 9.880(2) Å; c = 21.510(2) Å; β = 114.82(2)°; Z = 8; D = 1.287 Mg/m³; R is refined to 0.0537 and R_w = 0.0642 for 3330 reflections (F > 2σ(F)).     

Crystal structures of Th(OH)PO4, U(OH)PO4 and Th2O(PO4)2. Condensation mechanism of MIV(OH)PO4 (M = Th,U) into M2O(PO4)2

Three new crystal structures, isotypic with β-Zr₂O(PO₄)₂, have been resolved by the Rietveld method. All crystallize with an orthorhombic cell (S.G.: Cmca) with a = 7.1393(2) Å, b = 9.2641(2) Å, c = 12.5262(4) Å, V = 828.46(4) Å³ and Z = 8 for Th(OH)PO₄; a = 7.0100(2) Å, b = 9.1200(2) Å, c = 12.3665(3) Å, V = 790.60(4) Å³ and Z = 8 for U(OH)PO₄; a = 7.1691(3) Å, b = 9.2388(4) Å, c = 12.8204(7) Å, V = 849.15(7) Å³ and Z = 4 for Th₂O(PO₄)₂. By heating, the M(OH)PO₄ (M = Th, U) compounds condense topotactically into M₂O(PO₄)₂, with a change of the environment of the tetravalent cation that lowers from 8 to 7 oxygen atoms. The lower stability of Th₂O(PO₄)₂ compared to that of U₂O(PO₄)₂ seems to result from this unusual environment for tetravalent thorium.     

Synthesis,crystal structure and thermal behaviour of [La(hfa)3(Phen)2] (hfa = hexafluoroacetylacetonate,Phen = o-phenanthroline)

The mixed ligand complex [La(hfa)₃(Phen)₂] (I) was obtained by the interaction of La(hfa)₃ and Phen; its composition does not depend on the stoichiometry of the reagents. According to the X-ray single crystal analysis data, complex I crystallizes in the monoclinic space group P2₁/n, with a = 13.583(3) Å, b = 16.959(3) Å, c = 18.860(4) Å, β = 94.71(3)° and Z = 4. The structure of I consists of isolated mononuclear molecules, the coordination number of La being 10. Thermal behaviour and composition of the vapor phase have been studied for I by thermal analysis and mass-spectrometry using a Knudsen cell. The mixed ligand complex I was found to sublime congruently in the temperature range 370–460 K: [La(hfa)₃(Phen)₂]_(s) = [La(hfa)₃(Phen)]_(g) + Phen_(g), Δ_rH⁰(T) = 316.2 ± 1.8 kJ/mol.     

New metastable hybrid phase,Zn2(OH)2(C8H4O4), exhibiting unique oxo-penta-coordinated Zn(II) atoms

The metastable phase (phase 1) Zn(OH)₂(tp)₂ (tp = C₈H₄O₄^2?) was found to be an intermediate forming during the hydrothermal synthesis of Zn₃(OH)₄tp (phase 2). Its structure has been determined ab initio from synchrotron powder diffraction data and refined with the Rietveld method: space group P2₁/c, a = 3.48856(2) Å, b = 5.84645(2) Å, c = 22.1331(1) Å, β = 103.46(1)°, D_x = 2.488 g/cm³, R_p = 0.10, R_B = 0.095 (402 independent reflections). The structures of the two analogues were compared. Whereas a mixed coordination of the zinc atoms was found in phase 2, phase 1 exhibits only penta-coordinated Zn(II). Moreover, different optical properties were observed, Zn₂(OH)₂(tp) showing photoluminescence at 378 nm under λ_ex = 316 nm.     

Heterobimetallic Cu(II)–Hg(II) polynuclear complexes containing Hg(SCN)42− unit – Synthesis,spectroscopic investigations,X-ray studies and magnetic properties

Three novel heterobimetallic polymers with Hg(SCN)₄^2? as a linker have been synthesised and characterized by means of IR, EPR, magnetic measurements and single crystal X-ray. All the obtained compounds [Cu(bpzm)Hg(SCN)₄]_n (1), [Cu(bdmpzm)Hg(SCN)₄]_n (2) and [Cu(dpa)Hg(SCN)₄]_n (3) form supramolecular framework structures. The 1 creates a three-dimensional coordination polymer, and 2 and 3 form two-dimensional nets extending along crystallographic (0 1 0) plane. Each octahedrally coordinated Cu(II) atom of 1 connects to four mercury ions through four thiocyanate bridges, and each Hg(II) ion is bridged with four copper ions via four thiocyanate bridges. The Cu(II) ions of 2 and 3 display a pyramidal coordination geometry, and they are connected to three mercury ions through three thiocyanate bridges, one thiocyanate ion is nonbridging group.     

Versatile binding properties of di-pyridyl ligands with Cu(II) complexes: The syntheses,structural characterization and thermal analysis of six new species

A novel series of 4,4′-bipyridine- and 1,2-bis(4-pyridyl)ethane-Cu(II) complexes were synthesized using a variety of amine ligands (DPA = di(2-pyridylmethyl)amine, Medpt = 3,3′-diamino-N-methyldipropylamine, Hbpca = bis(2-pyridylcarbonyl)amine, TPA = tris(2-pyridylmethyl)amine) and cyclen = 1,4,7,10-tetraazacyclododecane). Different complexes were obtained including mononuclear [Cu(cyclen)(4,4′-bipy)](ClO₄)₂ (1), dinuclear {[Cu(μ₂-bpca)(4,4′-bipy)(H₂O)]ClO₄}₂ (2), [Cu₂(DPA)₂(μ₂-4,4′-bipy)(ClO₄)₄)]·H₂O (3), [Cu₂(cyclen)₂(μ₂-bpe)](ClO₄)₄ (4) and [Cu₂(TPA)₂(μ₂-bpe)](ClO₄)₄ (5) and the 1-D polymer, {[Cu(Medpt)(μ₂-4,4′-bipy)](ClO₄)₂}_n (6). In the 1–6 samples, cooling up to 100 K produces only the expected, minor, changes in cell constants given no space group changes. Therefore, data for the 100 K structures are reported only. Single-crystal X-ray crystallography reveals the monodentate coordination of the 4,4′-bipy in 1 and 2, and the bridged nature of the di-pyridyl ligands in the dinuclear complexes 2–5 and in the polymeric complex 6. In this series, structures 3–6 consist of the 4,4′-bipy or bpe bridging the two Cu(II) centers, the coordination by the tri- or the tetra-N donors of the amine, and the ClO₄^? groups as counter ions in 4–6 complexes. In the complexes 3–6, the Cu···Cu distances across the bridged di-pyridyl ligands were found to be greater than 11 Å. The magnetic properties of complex 3 reveal no evidence for magnetic coupling between the two Cu(II) centers (J = ?0.58 cm^?1).     

Copper azine compounds: Synthesis,structure and magnetic analyses of Cu(phenazine)Cl2, (phenazinium)2CuCl4 · H2O,and [Cu(phenazine)Cl2 · H2O]2

Three compounds composed of phenazine and copper chloride have been prepared and studied by infrared spectroscopy, X-ray diffraction, and variable temperature magnetization. The compounds synthesized and studied are: Cu(phenazine)Cl₂ (1), (phenazinium)₂CuCl₄ · H₂O (2), and [Cu(phenazine)Cl₂ · H₂O]₂ (3). Compounds 1 and 2 are described as antiferromagnetic Heisenberg chains with exchange constants ∣J∣/k_B = 33.8 K and 8.6 K, respectively.     

Syntheses,crystal structures and properties of dinuclear copper(I) complexes

Two dinuclear molecule-bridged Cu(I) complexes, (μ-bpym)[Cu(PPh₃)Cl]₂ (1), [(μ-bpym)(CuL)₂](ClO₄)₂·(CH₃CN)₂(H₂O) (2) (bpym = 2,2′-bipyrimidine, L = (R)-(+)-2,2′-bis(diphenylphospho)-1,1′-dinaphthalene) have been synthesized and characterized. The molecular structures of the two new dinuclear compounds exhibit bridging of two copper(I) centers by the symmetrically bis-chelating bpym ligand. Intriguingly, compound 1 features a remarkable “intramolecular organic sandwich” configuration where the central 2,2′-bipyrimidine bridging ligand interacts in π/π/π fashion with two phenyl rings from the coligands above and below the central plane, while chiral compound 2 exhibits second-order nonlinear optical effect and temperature-dependent luminescence. Upon decreasing the temperature from 298 to 10 K, compound 2 shows a red light emission.     

Synthesis and structure of a bimetallic hybrid inorganic/organic layered coordination polymer with an octamolybdate cluster variant trapped between the α and δ isomeric forms

Hydrothermal combination of CuSO₄, MoO₃, and 4-phenylpyridine (4-phpyr) in a 1:4:4.5 ratio under basic conditions afforded purple crystals of {[Cu(4-phpyr)₄]₂(Mo₈O₂₆)·4-phpyr} (1), which were analyzed by spectroscopy and single crystal X-ray diffraction. The asymmetric octamolybdate clusters in 1 adopt an intermediate structural variant between the known α and δ isomeric forms, with four octahedral and three tetrahedral molybdenum coordination spheres, along with one molybdenum atom in a highly distorted square pyramidal environment. Paddle-wheel shaped [Cu(4-phpyr)₄]²⁺ cations link adjacent {α/δ-Mo₈O₂₆}⁴⁻ clusters into a 2-D layered rhomboid grid coordination polymer. Uncoordinated 4-phpyr molecules lie in incipient voids in the interlamellar regions. The structure of 1 illustrates the utility of sterically bulky coordination complexes in the stabilization of intermediate conformations during energetically facile polyoxometallate isomer interconversion. Crystallographic data: triclinic, P1, a = 13.717(3) Å, b = 13.728(3) Å, c = 14.809(3) Å, α = 109.251(4)°, β = 107.670(4)°, γ = 92.005(4)°, V = 2480.0(9) Å³, R₁ = 0.0637, wR₂ = 0.1054.     

Synthesis,crystal structure and standard molar enthalpy of formation of bis(trans-bis(N,N-dimethyl-(1-(R)-phenyl-2-(S)-methyl-2-aminoethoxy-N,O))-copper(II)) heptahydrate

A novel complex, bis(trans-bis(N,N-dimethyl-(1-(R)-phenyl-2-(S)-methyl-2-aminoethoxy-N,O))-copper(II)) heptahydrate (abbreviated as Cu₂(C₁₁H₁₆NO)₄·7H₂O(cr)), was synthesized by the method of liquid phase reflux. The composition and structure of the complex were characterized by chemical analysis, elemental analysis, FTIR, and X-ray crystallography. A reasonable thermochemical cycle was designed based on the preparation reaction of the coordination compound, and standard molar enthalpies of dissolution of reactants and products were measured by an isoperibol solution-reaction calorimeter. Finally, the standard molar enthalpy of formation of the complex Cu₂(C₁₁H₁₆NO)₄·7H₂O(cr) was determined to be ?(4525.22 ± 13.71) kJ · mol^?1 in accordance with Hess’s law.     

Ce(H2O)(PO4)3/2(H3O)1/2(H2O)1/2, a second entry in the structural chemistry of cerium(IV) phosphates

A cerium(IV) phosphate has been prepared using precipitation methods and its structure has been solved by single crystal X-ray diffraction (R₁ = 0.0292 for 3092 reflections with I>2σ(I) and wR₂ = 0.0540). Ce(H₂O)(PO₄)_3/2(H₃O)_1/2(H₂O)_1/2 crystallises in the monoclinic space group C2/c (a = 15.7058(17) Å, b = 9.6261(9) Å, c = 10.1632(4) Å, ß = 121.623(7)°, and V = 1308.4 (2) Å³). Its structure is based on a negatively charged 3D framework, made of cerium atoms connected by PO₄ tetrahedra. There are two types of PO₄ units; one shares only corners with the cerium coordination polyhedra while the other one shares edges and corners. This structure also includes hydronium cations, to balance the framework charge, and water molecules. One special feature of this 3D framework is the formation of interconnected tunnels which extend along the c axis and contain the hydronium cations and the water molecules. This open framework and the presence of cationic species in the tunnels are in perfect agreement with the previously reported ion exchange properties.     

Spin crossover behavior in two-dimensional bimetallic coordination polymer FeII(3-bromo-4-picoline)2[AuI(CN)2]2: Synthesis,crystal structures,and magnetic properties

A new novel 2D network bimetallic Fe^IIAu^I spin crossover coordination compound based on 3-bromo-4-picoline and bridged cyano ligands, {Fe^II(3-bromo-4-picoline)₂[Au^I(CN)₂]₂}_n (1), has been synthesized and characterized by elemental analyses and IR, using single-crystal X-ray analysis at 293 K and at 90 K and magnetic measurements. The Fe^II ions in 1 have octahedral FeN₆ coordination geometries, which are linked by a [Au^I(CN)₂]^? unit at the equatorial plane to form a polymeric 2D sheet architecture. The two pyridine rings coordinate at the axial positions. The structure of 1 comprises parallel 2D arrays and the layers interact by pairs, defining bilayers with strong binuclear aurophilic Au?Au interactions. Furthermore, intermolecular Au?Br and Br?Br distances in 1 are significantly smaller than the sums of the van der Waals radii. Variable-temperature (2–300 K) magnetic susceptibility measurements of 1 have been performed to determine behaviors of spin transition. The susceptibility data of 1 indicates that about 50% of the HS states are changed to LS states at 75 K. The Fe–N bond distances at 90 K show that ratio of high spin states agree with the SQUID data.