Significant positional isomeric effect of zwitterionic ligands on the construction of two different 2D and 3D Pb(II) coordination polymers

Hydrothermal reactions of PbCl₂ with two positional isomers of asymmetric zwitterionic ligands 1-carboxylatomethylpyridinium-3-carboxylate (HL³) and 1-carboxylatomethyl-pyridinium-4-carboxylate (HL⁴) result in the formation of two coordination polymers (CPs) [Pb(L³)Cl] (1) and [Pb_1.5(L⁴)₂Cl(H₂O)] (2), respectively. CPs 1 and 2 were characterized by elemental analysis, IR, powder X-ray diffraction, and single-crystal X-ray diffraction. 1 and 2 exhibit the 2D (4,4)-connected and 3D (3,4,4,5)-connected novel topological networks with (4³.6².8) and (4².12⁴)(4².6)₂(4³.6.8⁴.10²)₂(4⁶)₂ point symbols, respectively, which reveal the significant positional isomeric effect of the zwitterionic ligands on the construction of CPs. Their thermal and photoluminescent properties were also investigated.     

Two novel Cd(II)-based coordination polymers constructed from isomeric double betaine ligands: Syntheses,structures and fluorescent properties

Two novel Cd^2 + based coordination compounds based on two isomeric double betaine ligands (1,4-Bis(4-carboxylatopyridinium-1-methylene)benzene (H₂L₁Cl₂) and 1,4-Bis(3-carboxylatopyridinium-1-methylene)benzene (H₂L₂Cl₂)) were synthesized, structurally and optically characterized. Both compounds show two dimensional sheet architectures with different features depending on structural motifs that ranging from helical chain to linear chain, and the spatial arrangements of coordinated ligands as well as their unlike coordination modes. They further exhibit the way how three dimensional supramolecular isomers form via weak interactions. Meanwhile, two compounds exhibit intense fluorescence attributing to the ligands' emissions with stokes shift.     

Two 3D coordination polymers constructed from flexible desymmetric carboxylate and neutral nitrogen ligands

Two coordination polymers based on a flexible desymmetric ligand precursor H₂L have been synthesized, that is, [Ni(L)(dpe)_3/2] H₂O (1), [Ni₂(H₂O)(L)₂(bpp)₂] H₂O (2), [H₂L = 4,4′-(phenylazanediyl)dibenzoic acid, dpe = 1,2-di(pyridin-4-yl)ethane, bpp = 1,3-di(pyridin-4-yl)propane]. These complexes were characterized by elemental analysis, IR spectroscopy, X-ray single-crystal and power diffraction. In addition, the second nonlinear optical properties of 2 were measured.     

Synthesis and crystal structure of three dimensional complex from copper(II) and 1,2,4,5-benzenetetracarboxylate

A copper(II) complex {[Cu(H₂btc) (H₂O)₃]₂(H₄btc)(C₅H₁₁N)₂ · 3H₂O}_n (1) has been synthesized and characterized structurally (H₄btc=1,2,4,5-benzenetetracarboxylic acid). Open channels were formed and can accommodate piperidine molecules. TGA data show that guest water and piperidine molecules are lost at 130 °C.     

A 3D cadmium(II) coordination polymer constructed from new β-diketone-functionalized pyridinecarboxylate and 4,4′-bipyridine ligands

A new cadmium(II) coordination polymer [Cd₂(L)₂(bpy)]_n·nCH₃OH (1) (H₂L = 2-(3-oxo-3-phenylpropionyl)-6-pyridinecarboxylic acid N-oxide, bpy = 4,4′-bipyridine), has been synthesized from the reaction of H₂L, 4,4′-bipyridine with CdSO₄·8/3H₂O. Compound 1 is an exceptional non-interpenetrating three-dimensional framework and contains double helical chains and rare cross bpy configuration. Interestingly, these helical chains can span two different directions on other alternate layers. Compound 1 shows intense photoluminescence at room temperature.     

Solvent-induced supramolecular isomers: Two dimensional coordination polymers constructed by Cu(II) and fluconazole

Two Cu(II)–fluconazole supramolecular isomers 1 and 2 formulated as (flu)₂Cu(SCN)₂ (flu = fluconazole) have been synthesized and structurally characterized by single crystal X-ray diffraction. Different solvent media lead to the different binding modes of anion SCN⁻ and the flexible C–C chain of fluconazole has been rotated in the two isomers. Complex 1 exhibits a two dimensional square grid-like layer and complex 2 exhibits a two dimensional framework with a parquet motif. Different H-bonds and stacking modes are observed in the two isomers. Complex 1 is nonemissive, whereas complex 2 exhibits photoluminescence property.     

Two clusters-based coordination polymers constructed from conformation-flexible cyclohexanetetracarboxylate and chelating bipyridyl ligands

Two new coordination polymers, [Co₃(μ₇-CTA)(bipy)(μ₃-OH)₂(μ₂-H₂O)]·3H₂O (1) and [Mn₂(μ₆-CTA)(bipy)(H₂O)₂]·H₂O (2), have been prepared by a flexible cyclohexane-1,2,4,5-tetracarboxylic acid (H₄CTA) with a chelating co-ligand, 2,2’-bipyridine (bipy). Complex 1 is a two-dimensional (2D) structure based on unusual hexanuclear cluster (Co₆) nodes and CTA linkers, while 2 exhibits a 1D chain based on dinuclear cluster (Mn₂) units and CTA linkers. Structural analysis revealed that the conformation of H₄CTA in 1 exhibits a (a,e,e,a) fashion and transforms to a thermodynamically more stable conformation (e,a,e,e) type in 2. 1 and 2 showed antiferromagnetic interactions.     

1D and 3D arrays of isomeric cadmium(II) diphosphonates constructed from N,N-dimethylaminomethane-1,1-diphosphonate ligand

Two isomeric cadmium(II) diphosphonates built up from corner-sharing CdO₆ octahedra and CPO₃ tetrahedra, with the same formula of [Cd(H₃L)₂] (H₄L = (CH₃)₂N–CH(PO₃H₂)₂), have been synthesized and structurally characterized. Compound 1 shows a 1D chain structure in which the adjacent Cd²⁺ ions are doubly bridged by two equivalent H₃L^? anions, whereas compound 2 exhibits a novel non-centrosymmetric 3D framework which is formed by a pillared-layer array, with one type of H₃L^? anions participating in the construction of a 2₁-symmetry layer and the other type of H₃L^? anions acting as pillars.     

pH dependent synthesis of structurally diverse praseodymium(III) coordination polymers based on isomeric ligands

Reactions of two isomeric ligands, 5-(n-pyridyl)tetrazole-2-acetato potassium salt (Kn-pytza, n = 2,4) and PrCl₃·6H₂O under solvothermal conditions, afforded three new complexes, [Pr(2-pytza)(SO₄)(H₂O)₃]·H₂O(1), [Pr(4-pytza)₃(H₂O)₂]·2H₂O (2) and [Pr₄(4-pytza)₅(OH)₄(H₂O)₇Cl]Cl₂·4H₂O (3), whose structures are controlled by not only the different positions of the nitrogen atom of the pyridine ring but also the pH value of the solvent system. These compounds have been characterized by elemental analysis, IR and single crystal X-ray diffraction. The X-ray analysis reveals that compound 1 is a two dimensional layer structure made up of a Pr₂O₆ binuclear unit and the tridentate bridging SO₄^2 − ligand; compound 2 is an unusual one dimensional ladder like chain structure consisting of a Pr₂O₁₀ binuclear unit and 4-pytza which acts as a tetradentate ligand via the pyridine-N and the carboxylate group in a μ_1,1,3-COO bridging mode while compound 3 is an unprecedented two dimensional network composed of a tetranuclear cubane-shaped Pr₄(OH)₄^8 + cluster (SBU) and tridentate 4-pytza via the pyridine-N and the carboxylate group in a μ_1,3-COO bridging mode. Various hydrogen bonds exist to assemble the 1D chains or 2D layers into 3D supramolecular network structures. Furthermore, the luminescence properties investigated at room temperature in the solid state show only intraligand emission for 1 and both intraligand and characteristic peaks of Pr^3 + for either compound 2 or 3.     

Syntheses, structures, and photoluminescence of two Cd(II) coordination polymers constructed from analogue (pyridyl)imidazole derivative and polycarboxylate acid

Two novel Cd(II) coordination frameworks based on a semirigid asymmetric ligand L and aromatic multi-carboxylate ligands, {[Cd₂L(btc)(H₂O)₂]·5H₂O}_n (1) and [Cd₂L₂(bdc)]_n (2) (L = (4-((2-(pyridine-2-yl)-1H-imidazol-1-yl)methyl)benzoic acid, H₃btc = 1,3,5-benzenetricarboxylic acid, H₂bdc = 1,3-benzenedicarboxylic acid), have been hydrothermally synthesized, and structurally characterized by elemental analysis, IR spectroscopy, single-crystal X-ray crystallography. Due to various coordination modes and conformations of the semirigid asymmetric ligand, and carboxylate containing co-ligands, therefore, the two complexes exhibit structural and dimensional diversity. Complex 1 exhibits a novel 2D (3, 5)-connected network structure with (3·5²)(3²·5³·6⁴·7) topology. Complex 2 exhibits a novel 3D CdSO₄ topology, which is formed from different dinuclear cadmium units. In addition, the photoluminescence properties of the free ligand L, and complexes 1 and 2 were studied in the solid state at room temperature.     

Construction of three new mixed-ligand Zn(II) coordination polymers based on nitrogen-containing heterotopic ligands and carboxylate co-ligands

Reactions of Zn(II) salts, presynthesized 5-(4-(1H-imidazol-1-yl)phenyl)-1H-tetrazolate (HIPT) and various carboxylate ligands result to three new coordination polymers (CPs), namely, [Zn₂[(IPT)₂(ox)]}_n (H₂ox = oxalic acid, 1), [Zn₂(IPT)₂(mNBDC)]_n (H₂mNBDC = 5-nitroisophthalic acid, 2), and [Zn₂(IPT)(CA)(H₂O)]_n (H₃CA = citric acid, 3). Compound 1 can be seen as constructed from 2D [Zn(IPT)]_n layers with (6,3) topology and pillared by ox^2 −. It is a 3D (3,4)-connected framework with InS topology. Compound 2 has 2D bilayer structure based on 2D [Zn(IPT)]_n single layer and mNBDC^2 − linkers. Compound 3 is a 3D pillar-layer framework built by Zn–CA bilayers and IPT⁻ pillars. The results showed that the coordination modes, configurations of IPT⁻, and the structure of carboxylate co-ligands have great influence on the structures of the final network. The choice of carboxylate can decide the result of CPs in Zn–IPT chains/net subunits plus carboxyl linkers or Zn–carboxylate chains/net subunits plus IPT⁻ linkers. The thermal stabilities and luminescent properties of selected compounds have also been studied.     

Three Cu(II) coordination polymers with novel bi-triazole ligand: Synthesis,structure and EPR properties

Three Cu(II) coordination polymers: [Cu(XL)(NO₃)₂]_n (1), {[Cu(XL)(4,4′-bpy)(NO₃)₂]·CH₃CN}_n (1a) and {[Cu(XL)₃](NO₃)₂·3.5H₂O}_n (2) have been synthesized mainly based on a novel bi-triazole ligand N,N′-bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxdiimide bi(1,2,4-triazole) (XL) and characterized by X-ray crystallography, EPR spectra, elemental analyses, FT-IR spectra and PXRD patterns. Structure analyses reveal that compounds 1 and 1a exhibit 1D chains, and compound 2 features a 2D cationic framework. Additionally, the Cu(II) ions with various coordination environment in compounds 1, 1a and 2 exhibit different EPR properties.     

Construction of three Cd(II) coordination polymers based on extended pyridyl-tetrazolyl-bifunctional ligands: Structures and luminescent properties

Reactions of Cd(II) with three new pyridyl-tetrazole-bifunctional ligands, 3-(4-(1H-tetrazol-5-yl)phenyl)pyridine (HL¹), 4-(3-(1H-tetrazol-5-yl)phenyl)pyridine (HL²), and 3-(3-(1H-tetrazol-5-yl)phenyl)pyridine (HL³) resulted in three Cd(II) coordination polymers (CPs), namely, [CdL¹₂]_n (1), [CdL²₂]_n (2), and [CdL³₂(H₂O)]_n (3). Although the geometry of L¹ and L² is quite different, the coordination modes of Cd(II) ion and ligand, as well as the SBUs in compounds 1 and 2 are quite similar, thus give rise to 3D frameworks with same (3,6)-connected ant topology. Compound 3 is a 3D framework composed of 1D helical chains and features as (3,5)-connected tcj topology. The results showed that the topologies are largely dependent on the coordination angle between two coordination groups. The thermal stabilities and luminescent properties of compounds 1–3 have also been studied.     

A 3D (3,8)-connected net based on the tetranuclear Cu4 units constructed from mixed organic ligands

Under hydrothermal conditions, a new polynuclear Cu(II) complex, [Cu₂(nip)(ina)(μ₃-OH)]₂·H₂O (1) (H₂nip = 5-nitroisophthalic acid, Hina = isonicotinic acid) has been synthesized with mixed organic ligands. Single crystal X-ray analysis reveals that complex 1 displays a three-dimensional (3D) structure based on the tetranuclear Cu₄ units. In the structure of 1, two pairs of symmetry-related Cu(II) ions are connected by six carboxyl and two μ₃-OH groups to generate the tetranuclear Cu₄ units, which are connected by the mixed ligands into a 3D framework. Topology analysis reveals a (3,8)-connected tfz-d net for 1. Magnetic studies display antiferromagnetic behavior for 1. And thermogravimetric analysis of 1 has also been investigated.     

Ionothermal syntheses of two coordination polymers constructed from 5-sulfoisophthalic acid ligands with 1-n-butyl-3-methylimidazolium tetrafluoroborate ionic liquid as solvent

Two coordination polymers, namely, [Co(IM)₆][Co₂(SIP)₃] (1) (IM = imidazole, H₃SIP = 5-sulfoisophthalic acid) and [BMIM]₂[Cd₂(SIP)₃] (2) (BMIM = 1-n-butyl-3-methylimidazolium) were synthesized in ionothermal reactions by using ionic liquid 1-n-butyl-3-methylimidazolium tetrafluoroborate as solvent. Single-crystal X-ray analyses revealed that 1 has an anionic 1D polymeric chain charge balanced by an uncommon [Co(IM)₆]²⁺ cation. Complex 2 features an anionic 2D layer containing unique tetranuclear [Cd₄(CO₂)₆(SO₃)₂] cluster wherein the four Cd atoms are co-planar. The imidazolium cation [BMIM]⁺ of the ionic liquid acting as charge compensating agent intercalated into the [Cd₂(SIP)₂]^2n? interlayers in structure 2. The rich ionic environments of the ionic liquid may be particularly helpful in the formation of the anionic frameworks of 1 and 2.     

Solvothermal synthesis of 1D and 2D cobalt(II) and nickel(II) coordination polymers with 2,5-dihydroxy-p-benzenediacetic acid

1D cobalt(II) and nickel(II) coordination polymers {[Co(dba)(H₂O)₄] · H₂O}_n (1) and {[Ni(dba)(H₂O)₄] · H₂O}_n (2) (H₂dba = 2,5-dihydroxy-p-benzenediacetic acid) were synthesized under low temperature solvothermal condition. When 4,4′-bipyridine (bpy) was introduced to the synthetic systems of 1 and 2, respectively, two novel 2D coordination polymers {[Co(dba)(bpy)] · 0.5H₂O}_n (3) and [Ni(dba)(bpy)(H₂O)₂]_n (4) with different structures were obtained. All of the compounds were characterized by elemental analysis, FT-IR, UV–Vis spectra and single crystal X-ray diffraction.     

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.     

Syntheses and characterizations of two new pillared-layer coordination polymers constructed from lanthanides and mixed O-donor ligands

Two new pillared-layer frameworks have been obtained through self-assembly of 4,4′-azobenzene dicarboxylatic acid (4,4′-H₂ABDC), oxalate, hydroxyl and LnCl₃(Ln = Sm, Eu) under hydrothermal environment and characterized by TGA, IR spectroscopy, element analyses, and X-ray single crystal diffraction. The X-ray structure analyses reveal that the oxalates link the Ln(III) to form metal layers, and 4,4′-ABDC ligands work as pillars to connect adjacent layers to further extend into 3D frameworks. Their magnetic studies show that the two compounds have typical anti-ferromagnetic behaviors.     

Two Pb(II) coordination polymers constructed from dicarboxamido-(2-pyridyl)-pyridine by varying ratios of mixed solvents

Through varying the volume ratio of mixed solvent, we obtained two distinct polymers {[Pb₆(2,6-pda)₆] · H₂O}_n (1) (2,6-pda = 2,6-pyridyldicarboxylate) and [Pb(mpcp)(OAc)]_n (2) (mpcp = methyl-6-(pyridin-2-ylcarbamoyl)picolinate) by reaction of Pb(OAc)₂ · 3H₂O and 2,6-dicarboxamido-(2-pyridyl)-pyridine (H₂dcapp) decomposed through lead-induced hydrolysis. Photoluminescence investigations reveal that both polymers display enhanced emissions in contrast to the free ligand, respectively.