Water‐Stable Coordination Polymers as Dual Fluorescent Sensors for Highly Oxidizing Anions Cr2O72− and MnO4−

Due to their striking optical properties, luminescent coordination polymers as sensors for the detection of hazardous species have drawn interest of researchers in consideration of the control of environmental pollution. In this work, the organic ligand 2‐(4‐((E)‐2‐(pyridine‐2‐yl)vinyl)styryl)pyridine (2‐bpeb), which possesses a large π‐conjugated system, was employed to react with d¹⁰ metal ions to obtain novel luminescent coordination polymers. Three complexes [Cd(2‐bpeb)_0.5(CNA)(H₂O)] ( CP1 ), [Cd(2‐bpeb)_0.5(NDC)] ( CP2 ) and [Zn(2‐bpeb)(BDC)] ( CP3 ) were synthesized successfully by introducing carboxylic acids of 4‐carboxycinnamic acid (H₂CNA), 2,6‐naphthalene dicarboxylic acid (H₂NDC) and 1,4‐benzenedicarboxylic acid (H₂BDC) as auxiliary ligands. Because of the existence of the large π‐conjugated system and d¹⁰ metal ions, all of these coordination polymers exhibit striking fluorescence properties. Impressively, all of them can function as sensors for the detection of highly oxidizing anions MnO₄^? and Cr₂O₇^2?, with an increased sensitivity for MnO₄^?.     

A Logic Fluorescent Chemosensor Based on Eu3+ Functionalized Cd-MOFs for Sensing Fe3+ and Cu2+ Synchronously

One of the most critical and yet unsolved issues is the effective monitoring of multiple heavy metal ions in complex systems through their specific function in fluorescence detection. In this work, luminescence-active cadmium base metal-organic frameworks (Cd-MOFs) based on the planar and rigid π-conjugated structure ligand benzo-(1,2;3,4;5,6)-tris (thiophene-2’-carboxylic acid) (H₃BTTC) was chosen. A series of sensing experiments demonstrated that the Cd-MOFs exhibits selective and sensitive response for Fe³⁺ and Eu³⁺ through fluorescence “turn off” and “antenna effect” respectively. In addition, the encapsulation of Eu³⁺ inside the Cd-MOFs (Eu³⁺@Cd-MOFs) led to an excellent probe with dual emission. To this end, a programmable fluorescence platform was developed to detect Fe³⁺ and Cu²⁺, in which the emission peaks of both the ligand and Eu³⁺ are completely quenched by Fe³⁺. The ratiometric detection of Cu²⁺ leads to a decrease in Eu³⁺ emission, while the ligand emission remains stable. To demonstrate the strategy, the fluorescence (Output) of Cd-MOFs, Eu³⁺@Cd-MOFs, and the analytes (Eu³⁺, Fe³⁺, and Cu²⁺, input) achieved elementary Boolean logic operations (OR, NOR, AND) and they constitute a logic fluorescent chemosensor to analyze Fe³⁺ and Cu²⁺ synchronously.     

Effect of Metal Ions on the Structures of Coordination Polymers Based on Biphenyl‐2,2′,4,4′‐Tetracarboxylate

Two new coordination polymers, {[Cd₂(btc)(2,2′‐bpy)₂] · H₂O}_n ( 1 ) and [Zn₂(btc)(2,2′‐bpy)(H₂O)]_n ( 2 ) (H₄btc = biphenyl‐2,2′,4,4′‐tetracarboxylic acid, 2,2′‐bpy = 2,2′‐bipyridine), were synthesized hydrothermally under similar conditions and characterized by elemental analysis, IR spectra, TGA, and single‐crystal X‐ray diffraction analysis. In complexes 1 and 2 , the (btc)^4– ligand acts as connectors to link metal ions to give a 2D bilayer network of 1 and a 3D metal‐organic framework of 2 , respectively. The differences in the structures are induced by diverging coordination modes of the (btc)^4– ligand, which can be attributed to the difference metal ions in sizes. The results indicate that metal ions have significant effects on the formation and structures of the final complexes. Additionally, the fluorescent properties of the two complexes were also studied in the solid state at room temperature.     

The Coordination Chemistry of Iron with the 1,4‐Bis(2‐pyridyl‐methyl)piperazine Ligand

The behaviour of Fe^II and Fe^III ions in combination with the potential ligand 1,4‐bis(2‐pyridyl‐methyl)piperazine (BPMP) under anhydrous conditions has been investigated. BPMP has been reacted with FeCl₂, FeCl₃ and [Fe(OTf)₂(MeCN)₂]. This led to the isolation of four new complexes, which were fully characterized and structurally investigated by single crystal X‐ray diffraction. It turned out that in the presence of chloride co‐ligands Fe^III favours the tetradentate coordination mode of BPMP with the piperazine unit in a boat configuration, like for instance in [BPMP(Cl)Fe(μ‐O)FeCl₃] or [BPMP‐FeCl₂][FeCl₄], ( 1 ). However, the employment of FeCl₂ leads to the formation of a coordination polymer [BPMP‐FeCl₂]_n, ( 2 ), containing the piperazine ring in a chair configuration binding to two iron centres each. 2 can only be dissolved in very polar solvents like dmf which is capable of breaking up the polymeric structure under formation of [Cl₂(dmf)Fe(μ‐BPMP‐1κ²N,N:2κ²N,N))Fe(dmf)Cl₂]·2 dmf, ( 3 ). In contrast, using [Fe(OTf)₂(MeCN)₂] instead of FeCl₂ as the starting material leads to a mononuclear Fe^II complex with BPMP bound in the desirable tetradentate fashion: [BPMP‐Fe(OTf)₂], ( 4 ). Unlike other complexes with tetradentate N/py ligands the two residual ligands in 4 are bound almost trans to each other with the potential to adopt a cis orientation under oxidising conditions, and it will be interesting to exploit its catalytic properties in future.     

Hydrothermal Synthesis,Solid State Structure,and Thermal Properties of a Family of Isomorphous 1‐D Coordination Polymers Aggregated by Extensive Hydrogen Bonding: {[M(3,3′‐bpy)(H2O)4](SO4)·2H2O} (M = Co,Ni, Zn)

Hydrothermal synthesis has afforded a family of new coordination polymers incorporating 3,3′‐bipyridine (3,3′‐bpy), {[M(3,3′‐bpy)(H₂O)₄](SO₄)·2H₂O} (M = Co, Ni, Zn). The crystal structures revealed 1‐D undulating cationic ribbons of formulation {[M(3,3′‐bpy)(H₂O)₄]}_n²ⁿ⁺ with both unligated charge‐balancing sulfate anions and water molecules of crystallization entrapped by hydrogen bonding. The 1‐D ribbons run along the (101) crystal direction and further aggregate via extensive hydrogen bonding patterns. Thermal decomposition data were consistent with stepwise loss of water molecules of crystallization and aquo ligands followed by decomposition due to ligand removal.     

Syntheses and Structures of Three New Copper(II) Coordination Polymers Involving 2, 2‐(4, 6‐Dinitro‐1, 3‐phenylenedioxy)­diacetic Acid

Three copper(II) coordination polymers, namely, {[CuL(H₂O)₂] · 4H₂O}_n( 1 ), [CuL(H₂O)(DMF)]_n( 2 ), and [CuL(2, 2′‐bipy)(DMSO)] · DMSO ( 3 ) [H₂L = 2, 2′‐(4, 6‐dinitro‐1, 3‐phenyl‐enedioxy)diacetic acid] were synthesized in different solvents (H₂O, DMF, and DMSO). X‐ray single crystal diffraction studies show that both complexes 1 and 3 belong to triclinic crystal system and P$\bar{1}$ space group and complex 2 belongs to the monoclinic crystal system and P2₁/c space group. In three complexes, all the central Cu^II ions coordinate with the ligand, forming a square pyramidal configuration. Both complexes 1 and 2 show similar 1D chain‐like structure and the chains are further connected by hydrogen bonds, forming 3D frameworks. Complex 3 exhibits a 0D structure due to the introduction of the ligand 2, 2′‐bipy. In addition, the luminescence properties of these complexes were investigated.     

Fluorescent Sensing Properties of Three Coordination Polymers Constructed by 3,5‐Di(2′,5‐dicarboxylphenyl)pyridine Ligand

Three Cd^II coordination polymers (CPs), named as {[Cd₂(DDPP)(DMF)(H₂O)] · DMF}_n ( 1 ), {[Cd₂(DDPP)(H₂O)₂] · DMA · H₂O}_n ( 2 ), [Cd(H₂DDPP)]_n ( 3 ), based on 3,5‐di(2′,5‐dicarboxylphenyl)pyridine) (H₄DDPP), were synthesized under solvothermal methods. Structural analysis indicates that the H₄DDPP ligand of 1 – 3 adopt (κ₁‐κ₁)‐(κ₁‐κ₁)‐(κ₁‐κ₂)‐(κ₁‐κ₁)‐μ₈, (κ₁‐κ₁)‐(κ₁‐κ₂)‐(κ₁‐κ₂)‐(κ₁‐κ₁)‐μ₁₀, and (κ₀‐κ₀)‐(κ₁‐κ₂)‐(κ₁‐κ₂)‐(κ₀‐κ₀)‐μ₆ coordination modes, respectively. CP 1 is a 2‐nodal (4,8)‐c alb ‐ 4 , 8 ‐ Pbcn network. CP 2 is a 3D 4,8‐c flu/fluorite network. CP 3 displays a 2D layer, which is further connected with hycrogen‐bonding interactions between layers to form supramolecular framework. Moreover, the fluorescent features of 1 – 3 were studied in aqueous systems and the values of detection limit (DL) are also calculated by 3σ/k_sv. The results reveal that 1 – 3 have good ability on probing Cr^VI/Fe^III ions.     

A Water Stable CdII‐based Metal‐Organic Framework as a Multifunctional Sensor for Selective Detection of Cu2+ and Cr2O72– Ions

A water stable tetrazolate‐containing metal‐organic framework, [Cd₂(L)(OH)(H₂O)₂]_n ( 1 ) [H₃L = 5‐(4‐(tetrazol‐5‐yl)phenyl)isophthalic acid], was synthesized under solvothermal conditions and structurally characterized. Compound 1 displays a three dimensional porous network with one dimensional tubular channels based on trinuclear cluster [Cd₃(μ₃‐OH)N₄C] units. Notably, 1 exhibits highly sensitive response to Cu²⁺ and Cr₂O₇^2– through luminescence quenching effects with the detection limit of 0.666 ppm for Cu²⁺ and 0.846 ppm for Cr₂O₇^2–, respectively. The possible mechanism of the luminescence quenching was discussed in detail.     

2D LnIII(Nd/La)‐AgI Heterometallic and TmIII Homometallic Coordination Polymers Based on Pyridine Dicarboxylate ­Ligands

Two 2D 4d‐4f heterometallic coordination polymers, [LnAg(Py26DC)₂(H₂O)₃] · 3H₂O [Ln = Nd ( 1 ), La ( 2 ); H₂Py26DC = pyridine‐2,6‐dicarboxylic acid], and one 2D lanthanide homometallic coordination polymer, [Ln(Py25DC)(ox)_0.5(H₂O)₂] [Ln = Tm ( 3 ); H₂Py25DC = pyridine‐2,5‐dicarboxylic acid; ox = oxalate], were synthesized and characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis, and single‐crystal X‐ray diffraction analysis. Both complexes 1 and 2 are isostructural and exhibit 3‐connected 2D heterometallic layer structures with the Schläfli symbol of (8² · 10), whereas complex 3 represents an extended 2D homometallic network structure with (4,4) topology.     

Quervernetzung lamellarer Schichten mit Hilfe von (O–H…O)‐Wasserstoffbrücken: Strukturen von M⊕⊖N(SO2C6H4‐4‐COOH)2 (M⊕ = K⊕, Rb⊕, Cs⊕)

Structures of Ionic Di(arenesulfonyl)amides. 4. Cross‐Linking Lamellar Layers by O–H…O Hydrogen Bonds: Structures of M^⊕⊖N(SO₂C₆H₄‐4‐COOH)₂ (M^⊕ = K^⊕, Rb^⊕, Cs^⊕) Syntheses and low‐temperature X‐ray crystal structures are reported for M^IN(SO₂C₆H₄‐4‐COOH)₂, where M = K (monoclinic, space group P2₁/c, Z = 4, Z′ = 1), M = Rb (monoclinic, P2₁, Z = 4, Z′ = 2), or M = Cs (monoclinic, P2₁/c, Z = 4, Z′ = 1). The three compounds are examples of layered inorgano‐organic solids where the inorganic component is comprised of metal cations and N(SO₂)₂ groups and the outer regions are formed by the 4‐carboxy substituted phenyl rings of the folded anions. In the two‐dimensional coordination networks, K^⊕ and Cs^⊕ adopt irregular and chemically distinct [MN₁O₇] octacoordinations, whereas the independent Rb^⊕ cations attain irregular nonacoordinations of type [RbN₂O₇] or [RbO₉] respectively. The crystal packings of the compounds are governed by self‐assembly of parallel layers through exhaustive hydrogen bonding between carboxylic acid groups, resulting in a dense array of cyclic (COOH)₂ motifs within the interlamellar regions.     

A 3d‐4f Complex Constructed by the Assembly of a Cationic Template, [Cu(en)2]2+, and a 3D Anionic Coordination Polymer, [Sm2(C2O4)3(C5O5)(H2O)2]2–

A three‐dimensional (3D) 3d‐4f complex, [Cu(en)₂][Sm₂(C₅O₅)(C₂O₄)₃(H₂O)₂] · 8H₂O ( 1 ) (en = ethylenediamine, C₅O₅^2– = dianion of 4,5‐dihydroxycyclopent‐4‐ene‐1,2,3‐trione), were prepared via the in‐situ ring‐opening oxidation reaction of croconate in the presence of the template‐directed complex, [Cu(en)₂]²⁺ cation. The structural characterization determined by X‐ray diffraction determination reveals that the 3D anionic coordination polymer of [Sm₂(C₂O₄)₃(C₅O₅)(H₂O)₂]^2– in 1 can be describe in terms of in‐plane 2D honeycomb‐like [Sm₂(C₂O₄)₃] layered frameworks bridged by oxalate with bis‐chelating mode, being mutually interlinked via the bridge of μ_1,2,3,4‐croconate ligands with bis‐chelating coordination mode to complete the 3D open framework, which gives rise to 1D channels with pore size of 14.023 × 11.893 Å (longest atom–atom contact distances) along the b axis. The structure‐directing complex, [Cu(en)₂]²⁺, and solvated water molecules are resided into these honeycomb‐type hexagonal channels. The thermal stability of 1 was further studied by TGA and in‐situ powder X‐ray diffraction measurement.     

[Ph2P(O)CH2Im][F3B(μ‐OH)BF3]. Erste strukturanalytische Charakterisierung des Hexafluoro(μ‐hydroxo)diborat‐Ions [1]

[Ph₂P(O)CH₂Im][F₃B(μ‐OH)BF₃]. First Structural Characterization of the Hexafluoro(μ‐hydroxo)diborate Ion [1] The hexafluoro(μ‐hydroxo)diborate ion has been isolated as it's Ph₂P(O)CH₂Im salt [Im = 2‐(1, 3, 4, 5‐tetramethylimidazolio)] ( 2 ) through basic hydrolysis of [Ph₂P(OBF₃)CH₂Im]BF₄ ( 1 ). The crystal structure of 2 · CH₂Cl₂ reveals the presence of ion pairs linked by unsymmetrical O‐H‐O hydrogen bonds.     

Fabrication of a Fe2O3 Nanoparticles Implantation‐modified Electrode and its Applications in Electrochemical Sensing

A novel Fe₂O₃ modified indium tin oxide electrode (Fe₂O₃/ITO) was fabricated by iron ion‐implantation method first, and then annealed at 300 °C. Fe₂O₃/ITO reveals good catalytic performance toward hydrogen peroxide (H₂O₂) in phosphate buffer solution due to the Fe(II)/Fe(III) redox couple. Amperometric response shows a linear dependency on the H₂O₂ concentration ranging up to 360 μM with a detection limit of 0.3 μM. Moreover, electrocatalytic activity based on rarely reported higher oxidation states of iron (tentatively assigned to Fe(IV)) was shown to allow the reliable detection of glucose and cysteine. The results show promising application potential of the proposed electrode.     

Sapphyrin Supramolecules through C−H⋅⋅⋅S and C−H⋅⋅⋅Se Hydrogen Bonds—First Structural Characterization of meso- Arylsapphyrins Bearing Heteroatoms

An unprecedented coupling reaction of heteroatom-containing tripyrranes leads to the formation of core-modified sapphyrins 1 and 2 , which self-assemble in the solid state to form supramolecular ladders. Weak C−H⋅⋅⋅S and C−H⋅⋅⋅Se hydrogen-bonding interactions in addition to C−H⋅⋅⋅N hydrogen bonds are responsible for the observed structures.     

(Δ)[Fe(II)(phen)3]2+ Filled in the Chiral Cavitiy Constituted by {(Δ)[Fe(III)(C2O4)3](NH42+)(DMF)(H2O)32−}n

A chiral coordination compound {(Δ)[Fe(II)(phen)₃][(Δ)Fe(III)(C₂O₄)₃](NH₄)(H₂O)₃(DMF)}_n (phen = 1,10‐phenanthroline), (DMF = N,N'‐Dimethylformamide), has been synthesized, and the structure has been revealed by infrared spectroscopy and X‐ray single‐crystal diffraction. The framework consists of two chiral subunits. One subunit (Δ)[(Fe(III)(C₂O₄)₃]^3? which as host anion forms a chiral porous three‐dimensional supermolecular network with lattice water, lattice DMF and lattice ammonium cation through hydrogen bonds. And then the other is Δ[Fe(II)(phen)₃]²⁺ which as guest cation fills in the chiral cavity located in the previously mentioned host porous network.     

Syntheses,Structures, and Luminescent Properties of d10 Coordination Polymers with 2‐(4‐Carboxyphenyl)‐imidazo[4, 5‐f]‐1, 10‐phenanthroline and 1, 3‐Benzenedicarboxylate Derivatives

Four Zn^II/Cd^II coordination polymers (CPs) based on 2‐(4‐carboxy‐phenyl)imidazo[4, 5‐f]‐1, 10‐phenanthroline (HNCP) and different derivatives of 5‐R‐1, 3‐benzenedicarboxylate (5‐R‐1, 3‐BDC) (R = NO₂, H, OH), [Zn(HNCP)(5‐NO₂‐1, 3‐BDC)]_n ( 1 ), [Cd(HNCP)(5‐NO₂‐1, 3‐BDC)]_n ( 2 ), [Zn(HNCP)(1, 3‐BDC)(H₂O)₂]_n ( 3 ), and {[Zn(HNCP)(5‐OH‐1, 3‐BDC)(H₂O) · H₂O}_n ( 4 ) were synthesized under hydrothermal conditions. Compounds 1 – 4 were determined by elemental analyses, IR spectroscopy, and single‐crystal and powder X‐ray diffraction. Compounds 1 and 2 are isomorphous, presenting a 4‐connected uninodal (4, 4)‐sql 2D framework with threefold interpenetration, which are further extended into the three‐dimensional (3D) supramolecular architecture through π ··· π stacking interactions between the aryl rings of 5‐NO₂‐1, 3‐BDC. Compared to compound 1 , 3 is obtained by using different reaction temperatures and metal‐ligand ratios, generating a 3D framework with –ABAB– fashion via π ··· π stacking interactions. Compound 4 is a 1D chain, which is further extended into a 3D supramolecular net by hydrogen bonds and π ··· π stacking interactions. The thermogravimetric and fluorescence properties of 1 – 4 were also explored.     

PbADC and PbADC·H2O: Two Coordination Polymers with Acetylenedicarboxylate (ADC2–) as Bridging Ligand

Single crystals of PbADC ( 1 ) and PbADC · H₂O ( 2 ) formed at the phase boundary of an aqueous silica gel containing acetylenedicarboxylic acid (HOOC–C≡C–COOH, H₂ADC) and an aqueous solution containing Pb(NO₃)₂. By choosing different concentrations of Pb(NO₃)₂, compounds 1 and 2 were obtained as phase pure products. Additionally, 1 was obtained by grinding Pb(CH₃COO)₂ · 3H₂O with H₂ADC resulting in a polycrystalline sample. The crystal structures of 1 (I4₁/amd, Z = 4; SrADC type structure) and 2 (P2₁/c, Z = 4, new structure type) were solved and refined from X‐ray single crystal data. Compound 1 exhibits a three‐dimensional framework structure: lead cations with a diamond‐like arrangement are interconnected by bridging ADC^2– ligands. In 2 double‐layers are formed by lead cations, bridging ADC^2– anions, and water molecules. These layers are held together by hydrogen bonds through water molecules and oxygen atoms of the ADC^2– ligands. Suspending 1 for 24 h in water at ambient conditions leads to the formation of 2 , which can be converted to 1 again by careful dehydration at approx. 400 K in vacuo. This reversible reaction can be structurally interpreted as a topochemical reaction, which transforms a 3D coordination network into a 2D network structure and vice versa, as both crystal structures show noticeable structural similarities.     

Synthesis and Structural Analysis of ϵ‐Fe2O3

Powder material of ?‐Fe₂O₃ was obtained by thermal decomposition of the clay mineral nontronite and subsequent isolation of the ferric oxide by leaching the silicate phases. Additionally, crystals of ?‐Fe₂O₃ were grown as precipitates by internal oxidation of a Pd₉₆Fe₄ alloy. Analysis of the precipitate crystals by electron diffraction yields an orthorhombic crystal system and space group Pna2₁ ab initio. X‐ray diffraction data of the powder containing small amounts of Al substituting Fe were refined by the Rietveld method. The refinement yields lattice parameters a = 507.15 pm, b = 873.59 pm and c = 941.78 pm, and atom positions. ?‐Fe₂O₃ is isostructural with κ‐Al₂O₃, AlFeO₃, and GaFeO₃ having an anion stacking sequence /ABAC/, and 1/4 of the cations in tetrahedral co‐ordination. Some strongly distorted FeO₆ octahedrons with one large Fe‐O distance, which may be considered as a 5+1 co‐ordination, appear to be characteristic for ?‐Fe₂O₃. The structure shows elements known from silicates and oxyhydroxides of iron, respectively.