Four novel mixed-ligand metal−organic frameworks (MOFs), [Zn5(μ3-OH)2(BTA)2(tp)3]
n
(1), [Zn(BTA)(chdc)0.5]
n
(2), [Zn(BTA)(ap)0.5]
n
(3), and [Zn(BTA)(gt)0.5]
n
(4) (BTAH = benzotriazole, H2tp = terephthalic acid, H2chdc = 1,4-cyclohexanedicarboxylic acid, H2ap = adipic acid, and H2gt = glutaric acid), have been synthesized by the reaction of zinc(II)
chloride and BTAH with four different aromatic/aliphatic binary acids under similar hydrothermal conditions. All these compounds
are fully structurally characterized by elemental analysis, IR, single-crystal X-ray crystallography, and the bulk new materials were
further identified by X-ray powder diffraction. Their compositional stability and photoluminescence properties were further investigated
to establish the structure−properties relationships. Structural analysis reveals that 1 is a scarcely reported eight-connected three-dimensional (3-D) self-penetrating MOF with pentanuclear zinc clusters as secondary building units (SBUs); 2 is a 3-D infinite
network with empty 34-membered hexanuclear zinc(II) metallamacrocycle channels; 3 and 4 are 3-D meso-racemic coordination
polymers with a one-dimensional Zn-BTA helix chain motif, in which alternative right- and left-hand helical chains are linked
together via ap for 3 and gt for 4. The much higher compositional stability up to 436 °C and strong solid-state luminescence emissions
suggest that 1−4 are good candidates for light emission materials.
The first 2D aggregate, {[Cd 3 (l 3 -ade) 2 (ap) 2 (H 2 O) 2 ] . 1.5H 2 O} n (1) (where adeH = adenine; H 2 ap = adipic acid), with trinuclear Cd(II) as secondary building units, has been successfully synthesized, the compound shows scarce coordination modes (tridentate l 3 -N3,N7,N9 for ade and hexadentate g 1 :g 2 :g 2 :g 1 for flexible ap) and a novel crystal packing arrangement, exhibiting strong fluorescent emission properties.
A unique tetranuclear Cu(II)-based 2D aggregate containing 26-membered Cu(II)ade macrocycles, [Cu(4)(DMF)(6)(mu(4)-ade)(2)(mu(2)-Cl)(2)Cl(4)](n) (1; Hade = adenine, DMF = N,N-dimethylformamide), was isolated by the reaction of CuCl(2) and Hade in a mixed DMF-methanol medium and structurally characterized by X-ray crystallography, elemental analysis, Fourier transform infrared, fluorescence spectroscopy, and thermogravimetry-differential thermal analysis techniques. Unexpectedly, the adeninate in 1 represents an unprecedented tetradentate mu(4)-N1,N3,N7,N9-bridging mode, which significantly contributes to both the aggregate of four Cu(II) cores within the subunit and the extension of the 2D covalent framework. Additionally, 1 displays the intense Hade-based fluorescence emission in solution at room temperature.
Characteristically strong photoluminescence with high quantum yield and long emission lifetime plays vital roles for the sensing performance of functional lanthanide complexes. To enhance the energy transfer efficiency through the ligand-field effect, three lanthanide-based coordination polymers formulated as {[Ln(H 2 O)(TPA)(ox)]•0.5H 2 O} n (Ln-CPs, Ln = Eu, Tb, and Gd) were solvothermally synthesized via employing 6-(1H-1,2,4-triazol-1-yl)pyridine-2-carboxylate (TPA) and oxalate (ox) as antenna and bridging ligands. These obtained Ln-CPs were structurally and photophysically characterized, and the sensing capacity and feasible application of two luminescent Ln-CPs were further investigated. The three Ln-CPs are crystallographically isostructural, exhibiting (4 4) layers assembled from centrosymmetric {Ln 2 (TPA) 2 } dimers and pairs of ditopic ox 2− linkages. Resulting from the conjugated TPA − chromophore and distorted Ln III coordination configuration, highly effective energy migration from the longer-lived triplet state of TPA − to Ln III is observed, endowing Eu-CP and Tb-CP to display bright red and green luminescence with an unexceptionable emission quantum yield up to 89% and 71%. Furthermore, the Tb-CP shows fast and effective responses toward the biomarkers of carcinoid cells with a strong Stern−Volmer quenching constant (K SV ) and low detection limit (LOD) of 8.95 × 10 3 M −1 and 0.72 μM for 5-hydroxy tryptamine as well as 1.18 × 10 4 M −1 and 0.95 μM for 5-hydroxy-3-indoleacetic acid. Instead, the red-emitting Eu-CP can differentiate quercetin effectively with K SV = 1.82 × 10 4 M −1 and LOD = 0.58 μM. Furthermore, luminescent ink with strong anti-counterfeiting ability and long-term stability is developed, representing the promising practice of Ln-CPs as functional materials.
By reaction of CuCl 2 with H 4 btc (H 4 btc ϭ 1,2,4,5-benzenetetracarboxylic acid) in mixed N,N-dimethylformamide (DMF) and methanol solution, a new two-dimensional (2-D) copper(II) complex [Cu(btc) 0.5 (DMF)] n (1) based on the paddlewheel-like [Cu 2 (-CO 2 ) 4 (DMF) 2 ] building blocks has been synthesized, which is different from those previous Cu-btc(II) coordination polymers obtained in water medium. Four carboxylate groups of (btc) 4Ϫ anion in 1 consistently exhibit bidentate bridging coordination
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