Synthesis,luminescence, and structural characterization of Zn and Cd coordination polymers of flexible bis(imidazolyl) derivatives

Coordination polymers [Zn(imc)(L¹)] · H₂O, (1, imc = iminodiacetate, L¹ = bis(N-imidazolyl)methane) [Zn(hba)₂(L²)]₂ · EtOH · 3H₂O, (2, hba = p-hydroxybenzoate, L² = bis(N-benzimidazolyl)methane), [Cd(mal)(H₂O)(L³)](3, L³ = 1,4-bis(N-imidazolyl)butane, mal = maleate) have been prepared and structurally characterized. Complex 1 consists of hexa-coordinated central Zn ions and exhibits 2D network structure. The Zn atoms in 2 have tetrahedral coordination geometry, and are linked by bis(imidazolyl) ligands into 1D chain structure. The cadmium ions in 3 are hepta-coordinated with pentagonal bipyramidal geometry. Complex 3 displays 2D grid structure. The TGA showed that the coordination polymers are stable up to 200 °C. All the three complexes are emissive at room temperature in their solid state.     

Synthesis and characterization of unusual heterotrinuclear Co(III)Ni(II)Co(III) hydrotris(3,5-dimethylpyrazolyl)borate complex with mixed 1,1-azide and pyrazolate bridges

An unusual heterotrinuclear complex [LCo(μ-L₁, 1-N₃)₂(μ-L₁)Ni(μ-1, 1-N₃)₂(μ-L₁)CoL] (1) was obtained by the reaction of the precursor of half-sandwich nickel(II) complex [LNi(HL₁)₂(N₃)] (2) and CoCl₂ · 6H₂O (L = hydrotris(3,5-dimethylpyrazolyl)borate; L₁ = 3,5-dimethylpyrazolate), the complex 1 was characterized by X-ray single-crystal diffraction, elemental analysis, IR, UV–vis spectra and magnetic properties.     

Coupling of cyclohexene oxide (CHO) and carbon disulfide (CS2) catalyzed by the asymmetric bis-Schiff-base Zn(II) complex

Based on the self-assembly of the asymmetric bis-Schiff-base ligand H₂L (H₂L = 4-((E)-(2-((E)-3,5-dibromo-2-hydroxybenzylideneamino)phenylimino)(phenyl)methyl-1-(4-chlorophenyl)-3-methyl-1H-pyrazol-5-ol) and Zn(OAc)₂·2H₂O, a new [Zn(L)] (1) was obtained and shown to efficiently catalyze the coupling of CHO (cyclohexene oxide) and CS₂ (carbon disulfide) in activation with [PPN]Cl (PPN⁺ = bis(triphenylphosphoranyidene)-ammonium), n-Bu₄NBr or n-Bu₄NI, where both poly[thio]carbonates and cyclic [thio]carbonates were produced, and the strong O/S exchange afforded the limited formation of trithiocarbonate in the cyclic [thio]carbonate byproducts.     

A new stable Cd(II)-framework for sensitive and selective detection of Cu2 + ions

A new water-stable 3D metal–organic framework (MOF), [Cd₂L₂]·NMP·MeOH (1, H₂L = 2-(3,5-dimethyl-1H-pyrazol-4-yl)-1,3-dioxoisoindoline-5,6-dicarboxylic acid, NMP = 1-methyl-2-pyrrolidinone) has been solvothermally synthesized and structurally characterized. 1 exhibits a 3D open-framework with a 2D metallic plane pillared by L^2 − fragments. Meanwhile, luminescent studies indicate that the luminescence intensity of 1 was strongly dependent on different metal ions. Most interestingly, 1 exhibited significantly quenching effect toward Cu^2 +, which implies that it may be used as a luminescent probe for the detection of Cu^2 +.     

DNA and copper (II) governed fluorescence tuning of phenanthroline possessing Ru(II) complex. Interplay of electrostatic interactions

Tuning of the fluorescence properties of [Ru (bpy) ₂ (L₁)] ^2 + (1) [L₁ = 2-(2-methoxyphenyl)-1H–imidazo [4, 5-f] Kumar et al. (2010), Rawle et al. (1992) phenanthroline] by DNA and/or Cu^2 + ion have been investigated. Fluorescence of 1 gets enhanced upon binding to DNA owing to electrostatic interactions. The binding constant of 8.4 × 10⁴ has been evaluated. Cu^2 + ions though unable to alter the fluorescence intensity of free 1 but successfully sequestrate the DNA bound 1, evidently decreasing its fluorescence intensity. The reversibility of the sequestration process was ascertained by the recovery of the quenched fluorescence intensity via introduction of equimolar EDTA to the buffer system of DNA bound 1 and Cu^2 +.     

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.     

Design,structure and magnetic properties of a novel one-dimensional Mn(II) coordination polymer constructed from 4-pyridyl-NH-1,2,3-triazole

A one-dimensional manganese(II) complex, [Mn(L₂)]_n (1, HL = 4-pyridyl-NH-1,2,3-triazole), has been hydrothermally synthesized at 120 °C. In the structure of 1, the Mn(II) ions are octahedral coordinated and further bridged by L⁻ ligands, forming a rigid 1D ribbon coordination chain. Varieties of supramolecular interactions, such as hydrogen bonds and CH ⋯ π interactions, play an important role on the stabilization of the structures. As revealed by magnetic measurement, complex 1 displays weak antiferromagnetic interaction with θ = –4.83 K, the best fit using Fisher's 1D Heisenberg model gives the intrachain magnetic coupling constant J = –0.21 cm^− 1 above 30 K due to the neighboring Mn(N–N)₂Mn rings twisted in the angle of almost 90°.     

Construction and photoluminescence properties of two novel zinc(II) and cadmium(II) benzyl-tetrazole coordination polymers

Two new d¹⁰ coordination polymers, Zn(Beta)₂ (1) and Cd₂(Beta)₃Cl(H₂O) (2) (Hbeta = 5-benzyl-tetrazole) have been synthesized by the in situ [3 + 2] cycloaddition reaction of 5-benzylacetonitrile, sodium azide and MCl₂ [M = Zn (1); M = Cd (2)] under hydrothermal condition. Complex 1 is a coordination polymer comprised of numerous mildly undulated two-dimensional (2D) layers with a (4, 4) topological network; while complex 2 is a 3D coordination framework constructed from the interconnection of various helical chains through cadmium–chlorine bridges. Furthermore, the luminescence properties of two complexes have been investigated.     

Four-, six- and eight-coordinated lead(II) complexes with amine- or amide-type tripodal ligands

Three novel lead(II) complexes, [Pb(L¹)](ClO₄)₂ (1) (L¹ = tris(2-benzylaminoethyl)amine), [Pb(L²)₂](ClO₄)₂ (2) (L² = tris(4-phenyl-3-aza-2-oxobutyl)amine) and [Pb₂(L³)₂](ClO₄)₄ (3) (L³ = tris[3-aza-2-oxo-4-(2-pyridyl)butyl]amine) were synthesized and structurally characterized. All three complexes show different stoichiometries as well as coordination numbers of four in 1, eight in 2 and six in 3, respectively. Complex 1 displays a typical tripodal-type 1:1 (M:L) structure and 2 shows a sandwich-type 1:2 structure. The octa-dentate lead(II) ion in 2 is at the center of a dicapped trigonal prism. Complex 3 is revealed as a unique dinuclear 2:2 complex, in which two hexa-dentate lead(II) ions are linked by two carbonyl μ–O atoms forming a Pb₂(μ–O)₂ parallelogram-type moiety.     

Single-nodal linking for Zn2 +-Nd3 +-containing metallopolymer with efficient near-infrared (NIR) luminescence

Through the single-nodal copolymerization of MMA (methyl methacrylate) and a vinyl-containing complex monomer [Zn(L)(4-vinyl-Py)Nd(NO₃)₃] (2; H₂L = N,N′-bis(3-methoxy-salicylidene)ethylene-1,2-diamine; 4-vinyl-Py = 4-vinyl-pyridine) with the both ¹π-π* and ³π-π* sensitizing approach to Nd^3 + ion, the Zn^2 +-Nd^3 +-containing metallopolymer Poly(MMA-co-2) exhibits good physical properties including an attractive Nd^3 +-centered NIR sensitization efficiency (Φ^L_Nd = 1.22% and η = Φ^L_Nd/Φ^Nd_Nd = 82%).     

Novel two-dimensional Co(II) and Cd(II) coordination polymers with intriguing net topologies

Three new two-dimensional coordination polymers were constructed from 2,6-bis(imidazole-1-yl)pyridine (2.6-bip), terephthalic acid (1,4-bdcH₂), and M(NO₃)∙nH₂O (M = Co, Cd). [M(2,6-bip)(1,4-bdc)] (1: M = Co; 2: M = Cd) were prepared under hydrothermal condition, whereas [Cd(2,6-bip)(1,4-bdc)∙xDMF] (3) was obtained under solvothermal condition in DMF solvent. Single-crystal X-ray analyses revealed the first example of a 2D 4-connected net of 6⁶ topology in 1 and 2 and a rare 2D 4,5-connected net of 4,5 L20 topology in 3. All these complexes were thermally robust and emissive in solid-states. This work confirmed the versatility of using hingelike 2,6-bip as a linker and the importance of solvent effect in the process of framework formation.     

Microporous metal–organic frameworks constructed by Cu(I)/Zn(II), Tpt and 1,4-benzenedicarboxylate

Two novel metal–organic frameworks, [Cu(tpt)(bdc)_1/2]_n · nH₂O (1) and [Zn(tpt)(bdc)_1/2I]_n (2) (tpt = 2,4,6-tris(4-pyridyl)-1,3,5-triazine, H₂bdc = 1,4-benzenedicarboxylic acid), have been prepared by hydrothermal reactions. In complex 1, Cu(I) center is in a trigonal coordination environment with bidentate tpt coordinating Cu(I) atoms to form 1D zigzag chains, and bdc ligand links the zigzag chains to form a 2D layered structure. In complex 2, Zn(II) center is in a trigonal–pyramidal environment with bidentate tpt coordinating Zn(II) atoms to form zigzag chains, and bdc links the zigzag chains to form metal–organic framework which contains interesting hexagonal nano-channels.     

Synthesis,reactivity, and X-ray structural characterization of a vanadium(III) oxidation pre-catalyst, (CpPOEtCo)VCl2(DMF)

Vanadium complexes are extensively used in the chemical industry as oxidation catalysts. During the course of our investigations into vanadium oxidation catalysis, the rich reactivity of a vanadium(III) scorpionate analogue complex, (CpP^OEtCo)VCl₂(DMF) (1), was investigated. The octahedrally coordinated 1 was prepared by mixing vanadium(III) chloride with Na(CpP^OEtCo) in DMF. The crystal structure of 1 has been determined through X-ray diffraction. Complex 1, C₂₀H₄₂Cl₂CoNO₁₀P₃V, crystallizes in the monoclinic space group P2₁/c with a = 38.566(9) Å, b = 9.499(2) Å, c = 18.149(4) Å, and β = 100.485(4)° with Z = 8. Complex 1 was found to be an effective pre-catalyst for the oxidation of 3,5-di-tert-butylcatechol to 3,5-di-tert-butylquinone. The reactivity studies, oxidative catalytic ability, as well as X-ray structural characterization of (CpP^OEtCo)VCl₂(DMF) will be discussed. ((CpP^OEtCo) = [η⁵-cyclopentadienyltris(diethylphosphito-κ¹P) cobaltate(III)⁻; DMF = N,N-dimethylformamide).     

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).     

Selective adenine/cytosine cations in one-dimensional coordination polymers of manganese (II) and copper (II) 2,3-pyridinedicarboxylates

One-dimensional coordination polymer {[1H,9H-ade]₂[MnL₂]?4H₂O}_n (1) and {[1H,3H-cyt]₂[CuL₂]?6H₂O}_n (2) (ade = adenine, cyt = cytosine, L = dianion of 2,3-pyridinedicarboxylic acid) are selectively synthesized and variable-temperature magnetic susceptibility measurements revealed weak antiferromagnetic interactions within the chains of 1 and 2 (J = ? 0.29 cm^? 1 for 1 and J = ?0.03 cm^? 1 for 2, according to the ? 2J_ijS_iS_j HDvV Hamiltonian formalism).     

Synthesis,structure and luminescent property of a new Zn(II) coordination polymer with isolated tetrahedral {Zn4O} clusters as building subunits

A new luminescent Zn(II) coordination polymer, namely [Zn₄(L)₂(μ₄-O)(H₂O)₂(DMF)]_n (1 H₃L = biphenyl-3,4,5-tricarboxylic acid, DMF = N,N′-dimethyl formamide) has been synthesized by combining the H₃L ligand with Zn(II) salts under solvothermal conditions. Single-crystal X-ray diffraction analysis reveals that 1 features μ₄-oxygen-bridged tetrahedral {Zn₄O} clusters as building subunits, which are further bridged by L^3 − ligands into a complicated three-dimensional (3D) architecture. Topological analysis reveals that it can be reduced into a (3, 6)-connected topological network with the schläfli symbol of {4 · 6²}₂{4² · 6⁹ · 8⁴}. In addition, the luminescent property of 1 was also investigated in the solid state at room temperature.     

Hetero-trinuclear near-infrared (NIR) luminescent ZnLn2 (Ln = Nd,Yb or Er) complexes based on monomer ZnL Schiff-base precursor and o-vanillin

With the monomer [Zn(L¹)(H₂O)] (1) complex in situ formed by the deprotonated hexadentate Salen-type Schiff-base ligand H₂L¹ (H₂L¹ = N,N′-bis(3-methoxy-salicylidene)cyclohexane-1,2-diamine) and Zn(NO₃)₂ as the precursor, series of the hetero-trinuclear ZnLn₂ complexes [ZnLn₂(L¹)₂(L²)(NO₃)₂Cl] (Ln = Nd, 2; Ln = Yb, 3; Ln = Er, 4 or Ln = Gd, 5) were obtained from the further reaction with LnCl₃ (Ln = Nd, Yb Er or Gd) and the second o-vanillin (HL²) ligand, respectively. The photophysical properties of complexes 2–4 showed that the characteristic near-infrared (NIR) luminescence of Ln^3 + ions with two emission centers and emissive lifetimes in microsecond ranges, was sensitized from the excited state (both ¹LC and ³LC) of mixed H₂L¹–HL² ligands.     

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.     

In situ synthesis and dielectric properties of copper(II) and nickel(II) chiral Schiff base complexes

Two chiral Schiff base-containing complexes, [Cu(L¹)](ClO₄)₂·H₂O (1, L¹ = (S,S)-N1,N2-bis((1H-imidazol-4-yl)methylene)cyclohexane-1,2-diamine) and [Ni(L²)₂](ClO₄)₂ (2, L² = (S,S)-N1-((1H-imidazol-4-yl)methylene)cyclohexane-1,2-diamine) were synthesized from the reaction mixture of 1H-imidazole-4-carbaldehyde, (S,S)-1,2-diaminocyclohexane and Cu(ClO₄)₂·6H₂O or Ni(ClO₄)₂·6H₂O in methanol. Single-crystal X-ray diffraction analyses reveal that the in situ generated chiral Schiff base ligands L¹ and L² are bisubstituted and monosubstituted, respectively, corresponding to the different metal ions Cu^II and Ni^II. Variable-frequency and -temperature dielectric properties of 1 and 2 have been studied.     

Crystal structures and visible-light excited photoluminescence of N-methyl-4,4′-bipyridinium chloride and its Zn(II) and Cd(II) complexes

A new approach has been used to synthesize MQ⁺ ligand (MQ⁺ = N-methyl-4,4′-bipyridinium) by the reaction of 4,4′-bipyridine and chloroacetic acid, and the structure of (MQ)Cl·H₂O (1) was first determined. Three new complexes containing MQ⁺, (MQ)CdI₃ (2), (MQ)ZnI₃ (3), and [(MQ)ZnCl_1.53I_1.47]₂(MQ)ZnCl_1.68I_1.32 (4), were successfully obtained via a solution or hydrothermal method by reaction of MI₂ (M = Cd, Zn) with 1, and each of which exhibits an isolated structure, with each metal atom coordinated by one MQ⁺ ligand and three terminal halogen atoms. Compounds 123–4 all display photoluminescence in the visible region under visible-light excitation, and the origins of the emissions have been assigned to ILCT for 1 and the combination of ILCT and LLCT for 23–4.