A luminescent europium metal–organic framework with free phenanthroline sites for highly selective and sensitive sensing of Cu2 + in aqueous solution

A luminescent europium metal–organic framework [Eu(HL)(L)(H₂O)₂]·2H₂O (1) (H₂L = (2,3-f)-pyrazino(1,10)phenanthroline-2,3-dicarboxylic acid) with uncoordinated phenanthroline nitrogen sites was hydrothermally synthesized. It exhibits highly sensitive and selective sensing of Cu^2 + in aqueous solution. To the best of our knowledge, complex 1 is the first luminescent Eu-MOF with uncoordinated phenanthroline nitrogen sites for selective sensing of Cu^2 + in aqueous solution. The probable sensing mechanism was discussed in detail.     

The first transition-metal metal–organic framework showing cation exchange for highly selectively sensing of aqueous Cu(II) ions

The anionic metal–organic framework (MOF), [NH₄]₂[ZnL]·6H₂O(1, L = 1,2,4,5-benzenetetracarboxylate), featuring the PtS-type net allows for [NH₄]⁺-to-(metal ions) cation exchange, and thus performs the potential of luminescent sensing of aqueous metal ions. To our best knowledge, polymer 1 presents the first transition-metal MOF suitable for luminescent sensing and the first MOF solid material for aqueous luminescent sensing.     

A luminescent coordination polymer with potential active site for the sensing of metal cation,anion and nitrobenzene explosive

A new 1D Zn-based coordination polymer (CP), {[Zn(HBTB)(pdp)]·H₂O} (1) (H₃BTB = 1,3,5-benzenetribenzoic acid and pdp = 2-(4,6-di(pyridine-2-yl)pyridine- 2-yl)pyridine), has been synthesized under solvothermal condition and structurally characterized. The compound displays intense luminescence in solid state at room temperature with high thermal stability. Interestingly, Luminescent studies indicate that 1 could be an efficient multifunctional fluorescence material for high sensitivity metal ions, anions and organic small molecules, especially for Cu^2 +, CrO₄^2 − and nitrobenzene (NB) by luminescent quenching. The probable quenching mechanism of different analytes was also discussed.     

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.     

Two new tetrazamacrocycle based Cu(II) complexes with 2D → 0D single-crystal to single-crystal transformation

Two new tetrazamacrocycle based compounds, namely, [Cu₆L₃(SO₄)₂]·SO₄·8H₂O (1) and [Cu₂L(SO₄)(H₂O)]^.2H₂O (2), have been prepared at different temperatures (H₂L = 10,21-dimethyl-3,6,14,17-tetraazatricyclo[17.3.18,12]tetracosa-1(23),8,10,12(24),19,21-hexaene-23,24-diolate). In 1, each SO₄^2 − anion bridges three [Cu₂L]^2 + cations to yield a hexagonal network, whereas in 2 each SO₄^2 − anion only links one [Cu₂L]^2 + cation to afford a discrete binuclear structure. Remarkably, the 2D network structure of 1 was transformed into the 0D structure of 2 in a single-crystal to single-crystal (SC–SC) fashion at room temperature.     

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.     

A new copper(II) selective fluorescence probe based on naphthalimide: Synthesis,mechanism and application in living cells

A new fluorescence probe L based on naphthalimide has been synthesized for selective and quantitative detection of Cu^2 + in CH₃CN:H₂O (4:1, v/v) solution. L exhibited a strong green fluorescence. Upon addition of 2 equiv. of Cu^2 +, the fluorescence emission shows a steady and smooth decrease until a plateau is reached with a 30-fold quenching of fluorescence intensity. In the presence of Cu^2 +, the absorbance peak of L maximum at 466 nm decreased, and a new absorption band at 600 nm appeared. Under the identical conditions, other physiological and environmental important metal ions induced negligible spectroscopic changes. The 1:2 stoichiometry binding mode of L with Cu^2 + was supported by the Benesi–Hildebrand analysis and ESI-MS spectra studies. The detection limit for Cu^2 + was estimated to be 64 ppb. Fluorescence microscopy experiments showed that L has practical application in living cells.     

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.     

New μ-oxo-bridged tetranuclear Cu(II) complex with Schiff-base ligand: Synthesis,crystal structure and magnetic properties

A new μ-oxo-bridged Cu(II) complex with cubane-like tetranuclear copper(II) complex, [Cu₄(L¹)₄] · 4H₂O (1) (H₂L¹ = 2-(3-methoxy-salicylidene-amino)-benzyl-alcohol), has been prepared, and structurally characterized by X-ray crystallography. Complex 1 crystallized in the monoclinic space group P₂₁/n and has a tetranuclear core of Cu₄O₄. The temperature dependence of magnetic susceptibility measurements shown that complex 1 exhibits a strong antiferromagnetic interaction with J = −103.4 cm⁻¹.     

Structures and photoluminescence of coordination polymers assembled from bifunctional ligand containing both tetrazole and imidazole groups

Three new coordination polymers, namely, {[Cu₂(IPT)(SO₄)(OH)(H₂O)]·H₂O}_n (HIPT = 5-(4-(1H-imidazol-1-yl)phenyl)- 1H-tetrazolate, 1), {[Cd₂(IPT)(NPA)(OH)]·H₂O}_n (H₂NPA = 5-nitroisophthalic acid, 2), and {[Zn₂(IPT)(IDC)(H₂O)]·3H₂O}_n (H₃IDC = 1H-imidazole-4,5-dicarboxylic acid, 3), were assembled from a bifunctional organic ligand containing both tetrazole and imidazole groups with/without the aid of carboxylate coligands. Compound 1 possesses 2D structure built by 1D [Cu₂(IPT)(SO₄)(OH)]_n secondary building blocks and IPT⁻ linkers. The 2D networks are linked into 3D supramolecular framework via water chains in helical conformation. Compound 2 displays 3D pillar-layer framework with 2D layers based on tetranuclear Cd(II) SBUs and NPA^2 − pillars. Compound 3 exhibits a 3D framework constructed from the interconnection of 1D [Zn-IDC]_n chains and binuclear Zn₂(IPT)₂ rings. The thermal stabilities of porous compound 3 and luminescent properties of compounds 2 and 3 have also been studied in detail. They exhibit intense solid-state fluorescent emissions at room temperature.     

Luminescence sensing of an unusual tetranodal 3-connected topology of Cu(I)-MOF

A new Cu(I)-based complex with chemical formulae [Cu₄Cl_0.24(CN)_3.76(L)] (1), (L = 1,3,5-tris(1-imidazolyl) benzene) has been synthesized and structurally characterized. Compound 1 shows an unusual tetranodal 3-connected topology and is self-penetrating – 0-membered shortest circuits. It shows that 1 can work as highly sensitive sensors to Cu^2 + and nitrobenzene (NB) explosive by luminescent quenching. This study shows that 1 could be a useful luminescent sensor for metal ions and organic small molecules.     

An unusual emissive and colorimetric copper (II) detection by a selective probe based on a pseudo-crown cysteine dye: Solution and gas phase studies

An off-on-off emissive and colorimetric probe L, based on a Pseudo-Crown cysteine dye was designed for Copper (II). Compound L was studied in solution and in gas-phase (MALDI-MS) over alkaline, alkaline, earth-alkaline and transition metal ions (Li⁺, Na⁺, K⁺, Ca^2 +, Mg^2 +, Zn^2 +, Cu^2 +, Co^2 +, Ni^2 +, Pb^2 +, and Hg^2 +) in organic media. The recognition of Cu^2 + by L lead to red/dark red colored complexes, one emissive L₂Cu and another LCu, less emissive. In regards to fluorescent quantum yield in both cases an increase respective to L was visualized (2 fold for LCu and 7 fold for L₂Cu). The paramagnetic nature of both complexes was proved by the synthesis of both complex species, as well as, through ¹H NMR and FTIR. Compound L demonstrate to be able to detect and quantify the minimal amounts of 1.3 μM/3.3 μM of Cu^2 +.     

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.     

A new 3D cobalt(II) complex with left- and right-handed helical channels

A new 3D complex, {[Co(btec)_0.5(imb)(H₂O)]∙1.5H₂O}_n (1) (imb = 2-(1H-imidazol-1-methyl)-1H-benzimidazole, H₄btec = 1,2,4,5-benzenetetracarboxylic acid) has been synthesized by solvothermal technique. X-Ray diffraction analysis indicates that complex 1 displays a 3D framework with left- and right-handed helical channels and very high porous, which can be simplified as a 4,4,4-connected 3D topology with a Schläfli symbol of (3² · 10³ · 11)(3² · 10⁴)(3² · 10³ · 11). Moreover, its IR spectra, PXRD patterns, thermogravimetric curves, and luminescent emissions were studied at room temperature.     

Three novel bismuth-based coordination polymers: Synthesis,structure and luminescent properties

Three novel bismuth-based coordination polymers, [(CH₃)₂NH₂][Bi(pdc)(bdc)]·2DMF, [(CH₃)₂NH₂][Bi(tdc)₂]·1.5DMF and [Bi(bpdc)₂H₂O]·xGuest (compounds 1–3) (H₂pdc = 3,5-pyridinedicarboxylic acid, H₂bdc = 1,4-benzenedicarboxylic acid, H₂tdc = 2,5-thiophenedicarboxylic acid, H₂bpdc = 4,4′-biphenyldicarboxylic acid), have been successfully synthesized under solvothermal conditions and characterized by single crystal X-ray diffraction. Compounds 1 and 2, which are constructed by 9-coordinated or 8-coordinated Bi^3 +, feature three-dimensional structures with hms and dia topology, respectively. However, 5-coordinated Bi^3 + based compound 3 is a two-dimensional layered structure. Compound 1 can tune emissive performance by doping different lanthanide ions Tb^3 +, Eu^3 + and Dy^3 +. Furthermore, detection of nitro explosives is investigated. All of the compounds are characterized by elemental analysis, IR spectrum and thermogravimetric analysis.     

Synthesis,crystal structure and photoluminescent properties of a 3D Zn(II) coordination polymer

A new 3D coordination polymer [NH₂(CH₃)₂]₂[Zn₇L₄(DMF)₂(H₂O)₃]·19H₂O (1) (L = 2,3′,5,5′-biphenyl tetracarboxylic acid) has been solvothermally synthesized and structurally characterized by IR, elemental analysis and single-crystal X-ray diffraction. Single-crystal X-ray diffraction studies indicate that 1 exhibits 3D framework with a one-dimensional (1D) channel. The luminescence properties have been studied, and the results showed that 1 displays strong fluorescent emissions both in the solid state and in methanol suspension at room temperature. More interesting, the addition of Fe^3 + causes the fluorescence intensity of 1 to be weakened, which implies that it may be used as luminescent probes of Fe^3 +.     

Co-existence of heterometallic Zn2Er and ZnEr arrayed chromophores for the sensitization of near-infrared (NIR) luminescence

With the Zn-Schiff-base [ZnL(Py)] from the simple Salen-type Schiff-base ligand H₂L (H₂L = N,N′-bis(salicylidene)ethylene-1,2-diamine) as the precursor, two co-crystallized heterometallic (Zn₂Ln and ZnLn array) complexes [Zn₂Ln(L)₂(Py)₂(NO₃)₂]·[ZnLn(L)(Py)(NO₃)₃(H₂O)]·NO₃·mMeOH·nS (Ln = Er(1), S = CH₃CN, m = 2, n = 1 or Gd(2), S = H₂O, m = 1, n = 3) were obtained by the further reaction with Ln(NO₃)₃·6H₂O, respectively. The result of their photophysical properties shows the intramolecular effective energy transfer has been demonstrated in the Zn₂Er and ZnEr arrayed complex 1, and the co-existence of different chromophores should be a potentially new way to the fine-tuning properties of NIR luminescence from Er³⁺ ions.     

Construction of three isostructural 3d–4f microporous coordination frameworks based on mixed nicotinate and oxalate ligands

The self-assembly of nicotinic acid and sodium oxalate with mixed 3d–4f metal salts under hydrothermal conditions gave three isostructural 3D 3d–4f coordination polymers, [LnCu(nic)₂(ox)] · xH₂O [Ln = La, x = 1 (1); Ln = Eu, x = 2 (2); Ln = Gd, x = 2 (3)] [ox = oxalate, nic = nicotinate]. All three structures exhibit same unusual 3D microporous heterometallic coordination frameworks that are built up by rare tetranuclear Ln₂Cu₂ clusters and mixed ox and nic linkers. Furthermore, the luminescent property of complex 2 has also been investigated.     

A novel 3D Zn(II) coordination polymer for highly luminescent sensing of nitro compounds

A novel 3D coordination polymer [Zn_2.5(L)(trz)₂(H₂O)₂]·2H₂O (1) (H₃L = 5-(4-carboxybenzyloxy)isophthalic acid, trz = 1,2,4-triazole) has been synthesized hydrothermally. Compound 1 displays a 3D (3,8)-connected net with (5³)₂(5⁸·6⁴·7⁸·8⁴·9⁴) topology. The luminescent property of 1 dispersed in different solvents as well as nitro compounds have been investigated systematically, demonstrating high detection sensitivity via a fluorescence quenching mechanism.     

Assembly of one 2D layer and two 3D pillared-layer structures derived from metal ions and 5-(pyridin-4-yl)isophthalic acid with or without pillars

Three new coordination polymers, [Mn(L)(H₂O)₂]₂·5H₂O (1), [Cu(L)(4,4′-bipy)]₂·H₂O (2) and [Pb(L)(4,4′-bipy)_0.5] (3) (H₂L = 5-(pyridin-4-yl)isophthalic acid; 4,4′-bipy = 4,4′-bipyridine) have been synthesized and characterized by IR, thermogravimetric analysis, X-ray powder diffraction and X-ray single crystal diffraction. Complex 1 shows a 2D layer structure which stacks with the other ones to form 1D channels to hold 1D water chains. Complex 2 displays a 3D + 3D → 3D polycatenation network. 3 shows a unique 2D + 2D → 3D polycatenation net in which each Pb center has a hemidirected coordination geometry due to the existence of “inert pair effect”. The thermal and luminescent properties of 1–3 were also examined.