Characterization and magnetic properties of two novel copper(II) coordination polymers prepared by different synthetic techniques

Two novel ternary Cu(II) coordination polymers with formulas {[Cu(μ₂-AZPY)(H₂BTC)₂]}_n (1) and {[Cu(μ₂-AZPY)(μ₂-HBTC)(H₂O)]·AZPY}_n (2) (AZPY – trans-4,4′-azobis(pyridine), BTC – benzene-1,3,5-tricarboxylate) have been synthesized using the solvothermal or diffusion techniques, respectively. Compounds were characterized by single crystal X-ray diffraction, thermogravimetry, infrared spectroscopy, elemental analysis and AAS. Removal of water and AZPY from the framework of 2 was investigated by wide-angle X-ray scattering measurements during in-situ heating. A magnetic study showed on antiferromagnetic coupling in 1 and 2 and magnetic properties may be influenced by both crystal field (CF) and inter-molecular interactions. The effective magnetic moment decreases from the values μ_eff = 4.97 μ_B for 1 and μ_eff = 3.39 μ_B for 2 at T = 290 K to the values of μ_eff = 1.41 μ_B for 1 and μ_eff = 1.27 μ_B for 2 at T = 2 K. The origin of the observed behavior is discussed.     

A novel cobalt(II) acylpyrazolonate complex with intermolecular hydrogen bond: Synthesis,structure and properties

A new cobalt complex, [Co(L)₂·(H₂O)₂](HL = 4-hexanoyl-3-methyl-1-phenyl-1H -pyrazol-5(4H)-one), was synthesized by us. The complex was characterized by single crystal X-ray diffraction, IR, UV, fluorescence spectra and thermogravimetric analysis. The results of characterization showed that the crystal is monoclinic system with crystal parameters: a = 15.2439(12) Å, b = 7.4101(6) Å, c = 15.7381(18) Å, and Z = 2, S = 1.074. It was found that the Co²⁺ is located in the inversion center of the complex. The Co(II) had an ideal octahedral coordination environment with four oxygen atoms of HL ligands in the equatorial plane and two water molecules in axial positions. The complex exhibits yellow emission as the result of the fluorescence from the intraligand emission excited state.     

Tuning the valence of 3,3-di(1H-tetrazol-5-yl)pentanedioic acid: Solvothermal synthesis of Eu(III) and bimetallic Eu(III)/Cu(II) compounds

3,3-Di(1H-tetrazol-5-yl)pentanedioic acid (H₄dtzpda) with four acidic hydrogen atoms can display different valence when reacted with different metal ions. Solvothermal reactions of H₄dtapda with Eu(NO₃)₃·6H₂O or Eu(NO₃)₃·6H₂O/Cu(NO₃)₂·6H₂O afford [Eu(Hdtzpda)(H₂O)₄]·4H₂O (1) and [Eu₂Cu(dtzpda)₂(H₂O)₁₀]·6H₂O (2), respectively, where only three acidic hydrogen atoms of H₄dtzpda are deprotonated in compound 1 while all the four acidic ones are deprotonated in compound 2. In compound 1, Hdtzpda^3 − acts as a pentadentate ligand to bridge Eu(III) centers via the oxygen atoms of the carboxylate group while in compound 2, dtzpda^4 − is a hepadentate one via not only the oxygen atoms of the carboxylate group but also the nitrogen atoms of the tetrazole rings. The luminescence properties of the two compounds in the solid state show both intraligand and characteristic peaks of Eu^3 + at room temperature.     

Syntheses,structures, and luminescent properties of zinc(II) complexes assembled with aromatic polycarboxylate and 1,3-bis(1,2,4-triazol-1-yl)propane

Three new coordination compounds, {[Zn(btrp)(ip)]?2H₂O}_n (1), {[Zn(btrp)(hip)]?2H₂O}_n (2), and {[Zn_1.5(btrp)(btc)(H₂O)]?H₂O}_n (3) (btrp = 1,3-bis(1,2,4-triazol-1-yl)propane, H₂ip = isophthalate, H₂hip = 5-hydroxy isophthalate, H₃btc = benzene-1,3,5-tricarboxylic acid) have been prepared via solvothermal method and characterized by single crystal X-ray diffraction and elemental analysis. 1 possesses 2D (4. 4) net framewok. 2 is also a 2D infinite layer framework, and the resulting 2D structure is interconnected by hydrogen-bond and π…π interactions to lead to a 3D supramolecular architecture. 3 exhibits a novel 2D framework with three nonequivalent points, {5.6²}{5².6}{5⁴.8²}. The fluorescence properties of 1–3 have been studied at room temperature.     

A three-dimensional (3,4)-connected network of 658 topology containing hexagonal channels constructed from cadmium(II) and 5-aminoisophthalate

The hydrothermal reaction of H₂aip (aip²⁻=5-aminoisophthalate) and Cd(II) acetate dihydrate yields an unprecedented three-dimensional (3,4)-connected network, [Cd(aip)(H₂O)] · H₂O, with 6⁵8 topology and interesting photoluminescent behaviour in the solid state.     

MLCT interaction in [Rh(II)2(CO3)4]4 −( x L)

Complexes of the type [Rh^II₂(CO₃)₄(H₂O)L]^n − with L = N-methylpyrazinium⁺ and 1-heptyl-4-(4-pyridinyl)pyridinium⁺ cations display intense long-wavelength (Rh(II) to L) MLCT absorptions. With L = H₂O, MLCT absorptions are not identified, but the photoreactivity of the complex in aqueous solution supports the assumption that (Rh(II) to CO₃^2 −) MLCT excited states are accessible. Upon irradiation with white light, Rh(II) is photooxidized while carbonate is reduced to CO. The efficiency of this photolysis is very low. However, the occurrence of this photoredox reaction is, nevertheless, of general interest with regard to the photochemical reduction of CO₂.     

A lead(II)-orotate coordination polymer with a new coordination mode: Synthesis,structure and luminescent property

A lead(II) orotate complex [Pb(HOr)(H₂O)]_n (1), (H₃Or = orotic acid) was synthesized under hydrothermal condition and characterized by X-ray diffraction, IR, solid-state photoluminescence and thermogravimetric analysis. Lead atom in 1 is in a holodirected eight-coordinated polyhedron and the orotate ligand exhibits a new and unique hexametallic coordination mode. The lead complex shows a 6,6-connected (4⁸, 6⁶, 8)(4¹³, 6²) topology. The complex exhibits photoluminescence at 546 nm (λ_ex = 350 nm).     

Synthesis,structure, and luminescence of a novel lead(II) coordination polymer with 1,2-phenylenediacetic acid

A coordination polymer [Pb₂(phda)₂]_n (H₂phda = 1,2-phenylenediacetic acid) was synthesized and characterized by single crystal X-ray diffraction. The complex has a (6, 6)-connected 2D framework with topology of (4¹⁵), in which Pb²⁺…π interaction is observed. The 2D framework is further assembled by C–H…π interactions, resulting in a 3D supramolecular network. The fluorescence of the complex is assigned to the intraligand π^?–π transition and the ligand-to-metal charge transfer.     

Structural characterization of ferromagnetic bridged-acetato and -dichlorido copper(II) complexes based on bicompartmental 4-t-butylphenol

The reaction of Cu(II) salts with 2,6-bis[bis(2-pyridylmethyl)aminomethyl]-4-t-butylphenol (L^t-Bu-OH) afforded two bridged-phenoxido/hydroxido complexes. The dinuclear bridged acetate species [Cu₂(μ-L^t-Bu-O)(μ-CH₃COO)](PF₆)₂ (1) and the 1D polymeric doubly-bridged-chlorido {[Cu₂(μ-L^t-Bu-OH)(μ-Cl)₂](ClO₄)₂·4H₂O}_n (2). The two complexes were structurally characterized. Both complexes revealed ferromagnetic interactions; moderate in complex 1 (J = + 30.8 cm^− 1) and very weak (J = + 2.25 cm⁻¹) in 2.     

Synthesis,structure, stability and DNA cleavage activities of three Cr(III) complexes with salicylate and ammonium ligands

Complexes [Cr(III)(SA)(en)₂]⁺ (1), [Cr(III)(SA)(DETA)(H₂O)]⁺ (2) and [Cr(III)(SA)(TETA)]⁺ (3) were synthesized (H₂SA = salicylic acid, en = ethylenediamine, DETA = diethylenetriamine, TETA = triethylenetetramine). Kinetics studies show that 2 is the most instable one among these complexes. In addition, only 2 is found to be a very efficient catalyst of the cleavage of PBR322 DNA in the absence of any added cofactor. The degradation rate from supercoiled form to nicked form was 1.05 ± 0.081 h^− 1 (10^− 5 M) at pH 7.4 and 37 °C. Thiobarbituric acid-reactive substances assay shows 2 fail to produce OH causing any degradation of deoxyribose ring even in the presence of ascorbic acid. Ethidium bromide displacement assay suggests that only 2 can kick out EB from the groove of DNA. The interaction with DNA causes a blue shift of the d → d transition spectra of 2.     

Three cobalt (II) complexes with triethylenetetraaminehexaacetic acid: From binuclear complex to 3d-4f coordination polymers

The cobalt(II)–lanthanide(III) heteronuclear complexes [Ln(H₂O)₄Co₂(TTHA)(SCN)₂]·H₃O⁺ (H₆TTHA = triethylenetetraaminehexaacetic acid, Ln = La(2), Ce(3)) have been synthesized based on a binuclear building block of [Co₂(H₂TTHA)(H₂O)₂] in [Co₂(H₂TTHA)(H₂O)₂]·4H₂O (1). Single-crystal structures show that complex 1 is a binuclear complex, containing the [Co₂(H₂TTHA)(H₂O)₂] unit as a useful building block. Adding the La^3 + and Ce^3 + ions to this synthesis system, two new 3d-4f mixed complexes 2 and 3 were obtained. Complexes 2 and 3 show 3D framework, comprising an infinite 1D (one-dimensional) chain based on heterometallic Ln₂Co₂ (Ln = La(2), Ce(3)). Further investigations such as IR spectra, UV–vis spectra, TGA, XRD and magnetic properties were studied.     

Construction of a new 3D Zn(II) coordination polymer with (4,6)-connected topology: Synthesis,structure and luminescence

A new coordination polymer of {[Zn₂(odpa)(IP)]·4H₂O}_n (1) (H₄odpa = 3,3′,4,4′-oxydiphthalic acid and IP = 1-H-imidazo[4,5-f][1,10]-phenanthroline), is reported. The 3D (4,6)-connected {4⁴∙6²∙8⁸∙12}{4⁴∙6²} topology net is formed by IP and odpa ligands in 1. Interestingly, the IP ligand acts as a tridentate mode and extends the resulting 3D feature. The luminescence study indicates that the title compound emits bright red fluorescence.     

Three unique MOFs constructed by 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene and dicarboxylates: From rhombic tetrameric zinc(II) 2D layer to 2D + 2D → 3D polycatenated frameworks

Three metal–organic networks, namely, [Zn₂(Hnip)(4-bpdb)(nip)₂(μ₃-OH)] (1), {[Zn(tbip)(4-bpdb)_1.5]·CH₃OH}_n (2), and {[Ni(1,3-bdc)(4-bpdb)]·2H₂O}_n (3) (4-bpdb = 1.4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene, H₂nip = 5-nitroisophthalic acid, H₂tbip = 5-tert-butylisophthalic acid, and 1,3-H₂bdc = 1,3-benzenedicarboxylic acid) are synthesized under hydrothermal conditions. The structure of 1 is built around uncommon rhombic {Zn₄} clusters with double T_d and double O_h Zn(II) geometries, which extend into a 2D network by the rigid deprotonated H₂nip and 4-bpdb bridges. Meanwhile, 2 presents a novel 2D → 3D parallel polycatenated framework assembled from 2D bilayers with cuboids as the fundamental building units. Compound 3 features an interesting 2D → 3D inclined polycatenated network based on 4⁴-sql subunits. Moreover, the thermal stabilities, photoluminescence, and magnetic properties of the compounds are also discussed.     

Synthesis,structure, and properties of dinuclear copper (II) complex with a (H2O)12 cluster

A novel pyrazole complex, namely [Cu₂(4,4′-bpy)₂(2,2′-bpy)(L)₂]·6H₂O has been synthesized under mild condition (4,4′-bpy = 4,4′-bipyridine, 2,2′-bpy = 2,2′-bipyridine). We report the structural evidence in the solid state of discrete water hexamers chair-like conformation. These units were found to act as supramolecular glue in the aggregation of dinuclear copper (II) complex to give a three dimensional network through hydrogen-bonding. The preliminary investigation on the electrochemical property and fluorescence property of the complex are presented.     

Two new luminescent Cd(II)/Zn(II) metal–organic frameworks for exceptionally selective detection of picric acid explosives

Two new coordination polymers, {[Cd(BIDPT)(oba)]·0.5H₂O}_n (1) and {[Zn(BIDPT)(4,4′-sdb)]·2.25H₂O}_n (2) (BIDPT = 4,4′-bis(imidazol-l-yl)diphenyl thioether, H₂oba = 4,4′-oxydibenzoic acid, 4,4′-H₂sdb = 4,4′-sulfonyldibenzoic acid), have been solvothermally synthesized and characterized. Both 1 and 2 show 2-fold interpenetrating 3D frameworks with {6⁵ ∙ 8} cds and {6⁶} dia topology, respectively. These two coordination polymers show strong luminescence and their luminescence could be quenched by a series of nitro explosives. Importantly, they exhibit very highly sensitive and selective detection of picric acid compared to other nitro explosives.     

An unprecedented seven-connected coordination network based on octanuclear supertetrahedral lead(II) cluster as a secondary building unit

A novel two-dimensional (2D) lead(II) coordination polymer, {[(Me₂NH₂)₄[Pb₈(μ₄-O)(1,2,3-btc)₆]]₂·6DMF·2H₂O}_n (1) (1,2,3-H₃btc = benzene-1,2,3-tricarboxylic acid; DMF = N,N-dimethylformamide; Me₂NH₂⁺ = the countercationic dimethylammonium ion, generated in situ via the hydrolysis of the solvent DMF), was synthesized solvothermally and fully characterized by single crystal X-ray diffraction, thermogravimetry and solid-state luminescence analysis. Structural analysis reveals that complex 1 contains an unusual octanuclear tetrahedron @ tetrahedron lead(II) secondary building units (SBUs) [Pb₈(μ₄-O)(O₂C)₁₈] and is extended topologically into a rare uninodal 7-connected framework structure. At room temperature, 1 in the solid-state exhibits strong emission peak at 495 nm originated from ligand to metal charge transfer (LMCT) between delocalized π bonds of carboxylate groups and p orbitals of lead(II) centers.     

Two helical one-dimensional copper(II) coordination polymers based on N-(2-hydroxylbenzyl)glycine and N-(2-hydroxylbenzyl)-l-alanine: Syntheses,crystal structures and magnetic studies

Two new helical Cu(II) coordination polymers, [Cu(2,2′-bpy)(Hsgly)]Cl · 2H₂O(H₂sgly = N-(2-hydroxylbenzyl)glycine) (1) and [Cu(2,2′-bpy)(Hsala)](NO₃) · 2H₂O(H₂sala = N-(2-hydroxylbenzyl)-l-alanine) (2) were synthesized. Single crystal X-ray diffraction analysis indicated that both complexes showed helical chains arrangement of Cu(II) centers bridged by carboxyl groups. The magnetic measurements showed complex 1 exhibited ferromagnetic interaction while there was no interaction between the Cu(II) centers in complex 2.     

Three-dimensional fourfold interpenetrated (10, 3)-b nickel(II) framework with 5-(isonicotinamido)isophthalate

A new three-dimensional nickel(II) metal-organic framework [Ni(INAIP)(H₂O)₂]_n · nH₂O (1) [H₂INAIP = 5-(isonicotinamido)isophthalic acid] was synthesized under hydrothermal conditions, and characterized by single-crystal X-ray structure determination, thermogravimetric analysis, X-ray powder diffraction, IR and magnetic studies. The compound 1 has (10, 3)-b topology with not well known fourfold interpenetration, in which both Ni(II) atoms and INAIP^2? ligands act as three-connected nodes.     

Synthesis and chemical reactivity of an Fe(III) metallacrown-6 towards N-donor Lewis bases

The iron(III) 18-azametallacrown-6 [Fe(ashz)(EtOH)]₆ (1) (ashz^3 − = trianionic derivative of N-acetylsalicylhydrazide), prepared upon reaction of [Fe₃(μ₃-O)(Piv)₆(H₂O)₃](Piv) (Piv = Bu^tCOO⁻) with H₃ashz, reacts with N-heterocyclic Lewis bases (B = pyridine, 4-methyl pyridine, 3-amino pyridine or imidazole), leading to the stable adducts [Fe(ashz)(B)]₆ (2 to 5, respectively) upon replacement of the labile ethanol ligand. All the compounds were characterized by elemental analysis, IR and ESI–mass spectroscopies and, for complexes 1 and the 3-amino pyridine adduct 4, also by X-ray crystallography. In both 1 and 4, the stereochemistry of the ligand imposes a propeller configuration of the metal cation which exhibits alternating Λ/Δ forms.     

Synthesis,crystal structure and magnetic properties of a new cyanide-bridged mixed-valence copper(I)/copper(II) clathrate

A unique cyanide-bridge mixed-valence Cu^I/Cu^II clathrate of formula [Cu^I₂(CN)₃][{Cu^II(tren)}₂(μ-CN)](CF₃SO₃)₂ [tren = tris(2-aminoethyl)amine] containing cyanide-bridged [{Cu^II(tren)}₂(μ-CN)]^3 + binuclear cations stacked between anionic honeycomb layered copper(I) cyanide networks, was synthesized and structurally characterized by single crystal X-ray diffraction. Variable-temperature magnetic susceptibility studies showed that the cyanide bridge mediates a strong antiferromagnetic interaction between the copper(II) centers (J = − 160 cm^− 1, the spin Hamiltonian being defined as H = −J S_A⋅S_B).