Synthesis,structure and photoluminescent properties for sensing nitro explosives of two new Zn(II) coordination polymers based on mixed tetrazolate and carboxylate ligands

Two novel Zn-based coordination polymer through employing of in-situ solvothermal techniques by using NO₂-bdc (2-nitroterephthalic acid), HL₁ = 1-(tetrazo-5-yl)-4-(triazo-1-yl)benzene, HL₂ = 1-(tetrazo-5-yl)-4-(triazo-1-yl)benzene and Zn(NO₃)₂·6H₂O to form [Zn₂(HL₁)₂(NO₂-bdc)]·0.5 (DMA)·CH₃OH·H₂O (1) and [Zn₂(μ₃-OH) (HL₂)·(NO₂-bdc)]·0.5 (DMA)·H₂O (2). The structures have been determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectra, powder X-ray diffraction (PXRD), and thermogravimetric (TG) analyses. In Compound 1, each Zn ion bridges one NO₂-bdc and two HL₁ ligands to yield infinite 2D layers, furthermore the aromatic π –π interactions link the adjacent layers yielding a 3D supramolecular structure. In compound 2, the HL₂ ligands link Zn ions to form a 2D Zn(HL) sheet firstly, and further connected by double NO₂-bdc pillars resulting in bi-pillared-layer type 3D frameworks. Moreover, 1 and 2 are luminescent with blue emission (λ_em = 440 nm and λ_em = 417 nm) in the solid-state. The fluorescent nature of 1and 2 inspired us to explore its potential application as a sensor for the detection of nitro explosives. The result reveals that 1 and 2 could be applied as a fluorescence sensor for NB (nitrobenzene) and 1,3-DNB (1,3-dinitrobenzene) with sensitivity and selectivity.     

Pillar-layered Zn–triazolate–carboxylate frameworks tuned by the bend angles of ditopic ligands

In the utilization of three ditopic ligands with different bend angles as pillars, we reported herein three pillar-layered Zn–triazolate–carboxylate frameworks, namely, [Zn₂(ATRZ)₂(BDC)]_n (1), [Zn₂(ATRZ)₂(TPDC)]_n·2nDMF (2) and [Zn₂(ATRZ)₂(ADDC)]_n (3) (ATRZ = 3-amino-1,2,4-triazole, H₂BDC = 1,4-benzenedicarboxylic acid, H₂TPDC = 2,5-thiophenedicarboxylic acid, and H₂ADDC = 1,3-adamantanedicarboxylic acid). Single crystal structural analyses demonstrate that different geometries of ditopic carboxylate pillars not only result in Zn–ATRZ layers adopting various corrugated configurations, but also give rise to 3,4-connected self-interpenetrated net of 1 and non-interpenetrated nets of 2 and 3. All these compounds exhibit high thermal stability and blue photoluminescence.     

Effect of coordination environment on the magnetic relaxation of mononuclear DyIII field-induced single molecule magnets

Two mononuclear Dy^III complexes [Dy(H₂TEG)(NO₃)₃]·[18-crown-6] (H₂TEG = triethylene glycol) (1) and [Dy(H₂TEG)Cl₃]·[18-crown-6] (2) have been prepared using H₂TEG as ligands. Magnetic studies revealed that both complexes show field-induced double magnetic relaxation behavior with energy barriers of 28 K and 54 K. Distinct magnetic dynamic properties observed in 1 and 2 are mostly attributed to the dissimilar coordination environments around Dy^III centers in these two complexes.     

Syntheses and characterizations of two-dimensional polymers based on tetraimidazole tetraphenylethylene ligand with aggregation-induced emission property

Two new coordination polymers [Co(TIPE)(H₂O)₂]·Hbtc·CH₃CN·3H₂O (1) and [Cd(TIPE)_0.5(m-bdc)(H₂O)]·CH₃OH·H₂O (2) (TIPE = tetra(3-imidazoylphenyl)ethylene, H₃btc = 1,3,5-benzenetricarboxylate, m-H₂bdc = 1,3-benzenedicarboxylate) have been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction, elemental analysis, IR, TGA, and PXRD. Furthermore, the luminescent properties of complexes 1, 2 and TIPE ligand have also been investigated in the solid at room temperature.     

Synthesis,crystal structure,luminescence and thermal behavior of a new energetic zinc(II) compound

An energetic material [Zn₂(btzphda)₂(H₂O)₄(dpp)₂]·2DMF·4H₂O with high decomposition enthalpy of − 748.35 J/g was prepared by the reaction of H₂btzphda, dpp and Zn(NO₃)₂·6H₂O under solvothermal conditions, where btzphda = 1,4-bis(tetrazol-5-yl)benzene-N2,N2′-diacetato, dpp = 1.3-di(4-pyridyl)propane and DMF = N,N′-dimethylformamide. The luminescence properties of H₂btzphda and [Zn₂(btzphda)₂(H₂O)₄(dpp)₂]·2DMF·4H₂O were investigated at room temperature in the solid state (Hitachi F4600 spectrofluorometer). Furthermore, the thermal decomposition behavior of the compound is characterized by differential scanning calorimetry (DSC) and thermogravimetric-differential thermogravimetric (TG-DTG) analyses. The entropy of activation (ΔH), enthalpy of activation (ΔS) and the free energy of activation (ΔG) for the decomposition temperature were ΔH = 250.64 kJ/mol, ΔS = 222.75 J·mol^− 1·K^− 1 and ΔG = 134.10 kJ/mol.     

Self-assembly and magnetic behavior of 2-aldehyde-8-hydroxyquinolinate-based lanthanide complex

Self-assembly reaction of Ln(NO₃)_3.6H₂O, 2-aldehyde-8-hydroxyquinoline and histamine dihydrochloride affords two mononuclear complex [Ln(hma)(NO₃)₂(CH₃OH)]∙0.5C₄H₁₀ (Ln = Tb (1), Dy (2); Hhma = N-(2-(8-hydroxylquinolinyl)methane(2-(4-imidazolyl)ethylamine)). The structural analysis indicates that they are isomorphous where the Ln^3 + is ligated to one ligand, two nitrates and one methanol molecule. Variable temperature magnetic susceptibility studies reveal the presence of antiferromagnetic interactions in 2 and the dynamic measurement reveals that 2 displays single molecular magnet behavior below 10 K under an applied field of 2000 Oe.     

A pair of novel helical Zn(II) enantiomers constructed from l- and d-threonine Schiff bases: Synthesis,crystal structures and properties

Two novel homochiral helical Zn(II) coordination polymers, {[Zn₂(nap-l-thr)₂(H₂O)₂]·H₂O}_n (1) and {[Zn₂(nap-d-thr)₂(H₂O)₂]·H₂O}_n (2) (H₂nap-l-thr = N-(2-hydroxy-1-naphthylmethylidene)-l-threonine, H₂nap-d-thr = N-(2-hydroxy-1-naphthylmethylidene)-d-threonine) have been successfully synthesized and characterized by elemental analysis, IR, UV–visible and single-crystal X-ray diffraction. It is interesting to note that both complexes are a pair of enantiomers: 1 exhibits 1D right-handed helical chain of [Zn-COO⁻]_∞ and 2 is 1D left-handed helical chain of [Zn-COO⁻]_∞. There are various hydrogen bonds between the adjacent helical chains which result in a 2D homochiral supramolecular layer structure. Notably, under similar synthetic procedure by using the NO₃⁻, CH₃COO⁻, Cl⁻ salts of Zn^2 + ion as a starting reagent, and identical compounds were obtained. In addition, the chiral nature of complexes 1 and 2 are confirmed by the results of circular dichroism (CD) spectra measurements. Thermal stability and luminescence properties were also investigated.     

A heterometallic approach for enhancing the net robustness of metal-organic framework

With the help of a heterometallic approach, an unstable channel-type framework {[Cu₄Cl(CPT)₄]·(NO₃)₃·5DMF}_n (1, HCPT = 4-(4H-1,2,4-triazol-4-yl)benzoic acid, DMF = N,N-Dimethylformamide) is structurally modified into a robust channel-type framework {[InCu(OH)(CPT)₂]·(NO₃)₂·(DMF)₄}_n (2) via embedding independent indium-based units into the Cu(II)-organic framework, in which the 1D In(III)-chains and 1D Cu(II)-chains coexist. Although both MOFs have similar framework structures, the activated heterometallic MOF 2 exhibits a BET surface area of 1032 m²/g, which is extraordinary high compared with that of the activated 1. In addition, the gas sorption property of MOF 2 around room temperature has also been investigated.     

A helical salicyladoxime-based manganese triangle chain with single-molecule magnet behavior

The reaction of 2-hydroxyphenylpropanone oxime (Et-H₂salox) with Mn(NO₃)₂·4H₂O, NEt₃ and 1,3-bis(4-pyridyl)propane-N,N′-dioxide (bppo) in EtOH/H₂O mixture afforded a one-dimensional coordination polymer with the formula [Mn₃O(Et-salox)₃(bppo)(MeOH)(H₂O)₃](NO₃)_0.5(Et-Hsalox)_0.5·MeOH·H₂O (1·MeOH·H₂O). 1·MeOH·H₂O had a manganese triangle structure, [Mn^III₃O]^7 +, which was used as a building unit for a subsequent assembly of an oximate and central oxide. The flexible bppo ligand linked the units, resulting in the formation of a 1D helical structure. Variable temperature direct current magnetic susceptibility measurements of complex 1·MeOH·H₂O were carried out. Exchange interactions of the metal centers of complex 1·MeOH·H₂O were examined, and the results indicate that both ferro- and antiferromagnetic interactions simultaneously coexist in 1·MeOH·H₂O, resulting in an S = 2 ground state. Moreover, complex 1·MeOH·H₂O shows the frequency dependence of the out-of-phase component in alternating current magnetic susceptibility measurements, indicating single-molecule magnet behavior with U_eff = 28 K and τ₀ = 1.8 × 10^− 9 s.     

A novel supramolecular adduct formed by CB[6]-based pseudo-rotaxane and hydrated Zn(II) ion

A novel supramolecular adduct of [C6N2(CB[6])]₃ · [Zn(H₂O)₆]Cl₂ · 14H₂O (1) is reported, where C6N2 = N,N′-bis(2-pyridylmethyl)-1,6-diaminohexane, CB[6] = Cucurbit[6]uril. It consists of a CB[6]-based pseudo-rotaxane and a six-hydrated Zn(II) ion, and forms an infinite 2D network and 3D spatial structure by hydrogen bonding interactions.     

Synthesis,structure and characterization of neat Zn2(OH)2 diamond-core chains linked through 2,2′,4,4′-biphenyl-tetracarboxylate

Reaction of 2,2′,4,4′-biphenyltetracarboxylic acid (2,4-H₄bptc), Zn(NO₃)₂ · 6H₂O in the presence of NaOH hydrothermally at 180 °C affords the first 2,4-H₄bptc complex [Zn₃(μ₃-OH)₂(2,4-bptc)]_n · 2nH₂O (1). Crystal structure indicates that 1 is Zn₂(OH)₂ diamond-core chains linked through 2,2′,4,4′-biphenyltetracarboxylate. 1 was characterized by TG, IR and fluorescence spectra. 1 is the first example of 2,4-H₄bptc complex and also first neat Zn₂(OH)₂ diamond-core chains.     

Linkers and coordinated solvent molecules; the two effective factors on formation of zinc oxide nanoparticles from metal–organic frameworks

The host and the apohost frameworks of Zn₂(ndc)₂(DMF)₂ ∙(H₂O)₄ (1 ∙ DMF ∙ H₂O) and Zn₂(bdc)₂(H₂O)₂ ∙(DMF)₂ (2·H₂O·DMF), (H₂ndc = 2,6-naphthalene dicarboxylic acid, H₂bdc = benzene-1,4-dicarboxylic acid and DMF = N,N-Dimethylformamide), were synthesized, characterized and subsequently used for preparing of ZnO nanoparticles. The morphology of initial precursors has direct influence on agglomeration tendency of resulting ZnO nanoparticles. Linkers and coordinated solvent molecules are the two effective factors on the formation of zinc oxide nanoparticles from these metal–organic frameworks.     

Synthesis,structure and near-infrared (NIR) luminescence of three solvent-induced pseudo-polymorphic complexes from a bimetallic Zn–Nd Schiff-base molecular unit

Three solvent-induced pseudo-polymorphic bimetallic Zn–Nd complexes [ZnNdL(OAc)(NO₃)₂(DMF)] · solvate (solvate: MeCN (1), THF (2), EtOH (3); H₂L = N,N′-bis(3-methoxy-salicylidene)phenylene-1,2-diamine) were obtained, and their solid NIR luminescence related to the packing structure from the intermolecular π–π interactions was discussed.     

Syntheses,topological analyses and magnetic properties of two 3D supramolecular nickel-organic frameworks constructed from 1,3,5-benzenetricarboxylate and flexible imidazole-based ligands

Two supramolecular nickel-organic frameworks, [Ni(HBTC)(bix)]_n (1) and [Ni₃(BTC)₂(mbix)₃(H₂O)₄]_n · 6nH₂O (2) (bix = 1,4-bis(imidazole-l-yl-methyl)benzene, mbix = 1,3-bis(imidazole-l-yl-methyl)benzene, and H₃BTC = 1,3,5-benzenetricarboxylate), have been hydrothermally prepared by the assembly of H₃BTC, Ni²⁺ with bix or mbix. Compound 1 shows a 2D layer structure, whose 3D supramolecular structure exhibits a fsc topology when hydrogen-bonging interactions between the adjacent layers are taken into account. Compound 2 manifests an unprecedented 2D (3, 4)-connected topological net. The 3D supramolecular framework of 2 is formed through π?π stacking interactions between the adjacent layers. The magnetic studies show that 1 features overall ferromagnetic property whilst 2 presents strong zero-field splitting (ZFS) when treated as a mononuclear model. Furthermore, the IR and TGA properties of 1 and 2 were also studied.     

Syntheses,structures, and magnetic properties of ethoxy-bridged dinuclear iron(III) complexes containing tetradentate ligands

Dinuclear iron(III) complexes, [(phenO)Fe(SO₄)]₂·2CH₃OH (1) and [(bpmapO)Fe(NO₃)]₂(NO₃)₂·3CH₃OH (2) have been prepared by the reaction of phenOH/bpmapOH and FeSO₄·7H₂O/Fe(NO₃)₃·9H₂O in methanol, respectively (phenOH = N-(2-pyridylmethyl)-N′-(2-hydroxyethyl)ethylenediamine, bpmapOH = N-(bis(2-pyridylmethyl)amino)-2-methylpropan-2-ol). Both complexes are ethoxy-bridged dinuclear species and the iron(III) ions in 1 and 2 have distorted octahedral geometries. Both complexes show strong antiferromagnetic interactions through the bridged ethoxy groups within the dimeric units.     

Construction of two-dimensional supramolecular structure containing water tetramer and octamer

The complex [Cd₂(phen)₄(p-phth)(H₂O)₂](p-phth) · 10H₂O (1) has been synthesized by the reaction Cd(NO₃)₂ with phen and p-phth (where phen = 1,10-phenanthroline, p-phth = p-phthalic acid) in a solution of ethanol and distilled water. The crystal structure was characterized by X-ray single-crystal diffraction and infrared spectrum. In 1, a novel 2D supramolecular structure was formed, containing water octamer and tetramer.     

Coordination polymers from 1-D to 3-D assembled from disulfonate ligands: Structures and luminescent properties

Four rare earth organodisulfonate coordination polymers, {[Tb₂(phen)₄(nds)₃(H₂O)₂]·4H₂O}_n (1), {[Ln(phen)(nds)(OH)]}_n[Ln = Sm (2), Nd (3)], {[Tb(phen)₂(nds)_0.5(OH)·H₂O]·(nds)_0.5}_n (4), were synthesized under the solvothermal conditions by using ligands 2,6-naphthalenedisulfonate (L = nds) and 1,10-phenanthroline (L′ = phen). Single-crystal X-ray diffraction reveals that compounds 1 and 4 exhibit different 1-D and 2-D crystal structures just owing to the single difference of stoichiometric ratio of the reactants in the synthesis process. Compounds 2 and 3 show 3-D structures with similar Ln coordination mode. Besides, the photoluminescent property in solid state of 1 was investigated in detail.     

Assembly of a pcu topological porous Cd-trimesate framework with free carboxylic acid group: Sorption and luminescent property

A six connected 3D porous coordination polymer {[Cd(HBTC)(BPz)]·3EtOH}_n (1) (H₃BTC = benzene-1,3,5-tricarboxylic acid, BPz = 3,3′,5,5′-tetramethyl-4,4′-bipyrazole) has been synthesized from mild solvothermal reaction of Cd(NO₃)₂·4H₂O with BPz and H₃BTC in ethanol. Complex 1 is a thermally stable microporous MOF having (Cd₂(COO)₂) as the secondary building unit (SBU) with a six connected pcu topology. The pores of the polymer are decorated with free COOH groups which show moderate N₂ sorption (38 cc g^− 1) at 77 K with a BET surface area of 129 m² g^− 1. Complex 1 also exhibited photoluminescent property in solid state with λ_max at 396 nm.     

Template-assisted self-assembly: Synthesis,structures, and magnetic properties of lanthanide(III)-cobalt(II) coordination complexes constructed with deprotonated 3,5-pyridinedicarboxylic acid ligand

Two new 3d-4f complexes, [LnCo(3,5-pdc)₂(3,5-Hpdc) (H₂O)₇]·H₂O (Ln = Gd 2, La 3; 3,5-pdcH₂ = pyridine-3,5-dicarboxylic acid), have been synthesized by the self-assembly of Ln(III) oxides, 3,5-pdcH₂ and the template molecule [Co(3,5-pdc)(H₂O)₅]·H₂O (1) under hydrothermal conditions. Heterometallic complexes 2 and 3 are isostructural with supracyclic units containing four Ln(III) ions and two Co(II) ions, in which Co(II) and Ln(III) are linked by the deprotonated 3,5-pdcH₂ ligands in three kinds of bridging modes. The weak antiferromagnetic coupling of complex 2 and 3 imply that the large 3,5-pdc bridges with the greater separation ( > 7 Å) cannot lead to long range magnetic ordering, the strength of d_n-f_n exchange coupling increasing with decreases the size of the lanthanide ion.     

1D chain lanthanide coordination polymers with 6-hydroxynicotinic acid: Crystal structures and luminescent properties

Four new lanthanide coordination polymers {[Ln(HL)₂(H₂O)₅] · HL ·  H₂O}_n (Ln = Sm for 1, Eu for 2, Tb for 3 and Dy for 4) (H₂L = 6-hydroxynicotinic acid) have been synthesized and characterized by elemental analysis, FT-IR spectra and X-ray single-crystal diffraction. They all exhibit 1D chain structure, which are further linked via hydrogen bonds to form 3D supramolecular architecture. Luminescent properties of these lanthanide coordination polymers are studied.