A novel Co-based metal–organic framework (MOF) with the formula of {[Co3(BIBT)3(BTC)2(H2O)2]·solvents} n (JXUST-2, where JXUST denotes Jiangxi University of Science and Technology, BIBT = 4,7-bi­(1H-imidazol-1-yl)­benzo-[2,1,3]­thiadiazole, and H3BTC = 1,3,5-benzenetricarboxylic acid) has been solvothermally prepared, which takes 3D structure with a rare 3,4,6-c topology and contains intramolecular hydrogen bonds. Interestingly, the sensing investigations suggest that JXUST-2 could be considered as a multifunctional fluorescence sensor toward Fe3+, Cr3+, and Al3+ via a turn-on effect with good reusability and detection limits of 0.13, 0.10, and 0.10 μM, respectively. The turn-on effect of JXUST-2 could be ascribed to an absorbance caused enhancement (ACE) mechanism. Notably, JXUST-2 is the first turn-on MOF fluorescent sensor for Fe3+, Cr3+, and Al3+ simultaneously.

Doping an organic crystal such as an inorganic semiconductor without having a bad influence on crystalline quality is a very difficult task because weak intermolecular interactions and lattice mismatches exist in organic condensed states. We report here the successful growth of tetracene and pentacene-doped trans-1,4-distyrylbenzene (trans-DSB) crystals with high crystalline quality, large size, and excellent optical properties. The doped concentration up to 10% can be achieved by controlling the temperature of the crystal growth zone. The first key point for the crystals with a high doping ratio is the choice of the host (trans-DSB) and guest (tetracene or pentacene) molecules with comparable crystal lattice structures, which ensure less lattice mismatch. The second key point is crystal growth at relative high temperatures by the physical vapor transport (PVT) method, which gives the guest molecules high kinetic energy to incorporate into the crystal lattice of the host. These doped crystals with slice shape and large size (millimeter scale) maintain ordered layer structures and crystal surface continuities, which are verified by X-ray diffraction (XRD) and atomic force microscopy (AFM) analysis. Efficient energy transfer from the host to the guest and the suppressing of the interaction among the guest molecules lead to color-tunable emission and high luminescent efficiencies (blue for undoped trans-DSB, η = 65 ( 4%; green for tetracene-doped trans-DSB, η = 74 ( 4%; red for pentacenedoped trans-DSB, η = 28 ( 4%). Steady-state and time-resolved fluorescence spectroscopy of undoped and doped crystals, and their amplified spontaneous emissions, have been investigated. These doped crystals are expected to be of interest for lightemitting transistors, diodes, and electrically pumped lasers.

A Zn II -based metal−organic framework (MOF) with a rare tcj topology has been solvothermally synthesized and displays relatively good thermal and chemical stabilities. Interestingly, the MOF can sensitively and selectively sense acetylacetone (acac) via a fluorescence enhancement effect with a detection limit of 0.10 ppm and good reusability, which demonstrates the first example of a MOF-based turn-on fluorescent sensor for acac.

No abstract

Herein, through a dual-ligand strategy, we report eight isorecticular lanthanide(III) furan-2,5-dicarboxylic acid metal−organic frameworks (Ln-MOFs) with the general formula {[Ln(2, Gd (3), Tb (4), Dy (5), Ho (6), Er (7), and Yb (8); 2,5-FDA 2− = furan-2,5-dicarboxylate and Glu 2− = glutarate; x = 0.5 for 1, 2, and 4 and x = 0 for 3 and 5−8], synthesized under solvothermal conditions by using an N,N′-dimethylformamide/H 2 O mixed solvent system. Crystallographic data reveal that all eight Ln-MOFs 1−8 crystallize in the orthorhombic Pnma space group. All of the MOFs are isostructural as well as isomorphous with distorted monocapped squareantiprismatic geometry around the Ln1 metal center. In Ln-MOFs 1−8, the 2,5-FDA 2− and Glu 2− ligands exhibit μ 2 -κ 4 ,η 1 :η 1 :η 1 :η 1 and μ 3 -κ 5 ,η 2 :η 1 :η 1 :η 1 coordination modes, respectively. Topologically, assembled Ln-MOFs 1−8 consist of the 2D cem topological type. The designed Ln-MOFs 1−8 are further explored for structure-corroborated density functional theory study. Meanwhile, room temperature photoluminescence properties of Ln-MOFs 2 and 4 and magnetic properties of Ln-MOFs 3 and 5 have been explored in detail. A highly intense, ligand-sensitized, Ln 3+ f−f photoluminescence emission is exhibited by Ln-MOFs 2 [Eu 3+ (red emission)] and 4 [Tb 3+ (green emission)]. Magnetic studies suggest weak antiferro-and ferromagnetic interactions between adjacent Gd III ions in Ln-MOF 3, thereby displaying a large magnetocaloric effect. The magnetic data measured at T = 2 K and ΔH = 30 kOe depict that the −ΔS m value per unit mass reaches 32.1 J kg −1 K −1 , which is larger than most of the Gd III -based complexes reported. The alternating-current susceptibility measurements on Ln-MOF 5 revealed that out-of-phase signals are frequency-and temperature-dependent under both 0 and 2 kOe direct-current fields, thereby suggesting a typical slow magnetic relaxation behavior with two relaxation processes. This is further supported by the Cole−Cole plots at 2.4−6 K.

The design and preparation of novel multifunctional lanthanide metal–organic frameworks (Ln-MOFs) have been arisen widespread attention. In particular, Ln-MOFs have shown great luminescence potential in chemical sensing. Herein, a new benzothiadiazole-based Eu-MOF {[(CH3)2NH2]­[Eu­(BTDB)2]·2H2O} n (JXUST-11) was obtained based on 4,4′-(benzo­[c]­[1,2,5]­thiadiazole-4,7-diyl)­dibenzoic acid (H2BTDB), which exhibits a chain-based three-dimensional framework. Moreover, JXUST-11 is considered as a photoluminescent sensor to identify Al3+ and Ga3+ ions by fluorescence enhancement with the detection limits of 2.9 and 10.2 ppm, severally. Importantly, Al3+ and Ga3+ can be discerned with the naked eye by color change under a natural lamp. In addition, a portable MOF film based on JXUST-11 was developed for Al3+ and Ga3+ detection. This is the first Ln-MOF that can be employed as a naked-eye fluorescent probe to identify Ga3+. Interestingly, JXUST-11 is also capable of detecting Al3+ and Ga3+ in living cells.

No abstract

A family of chiral 3d−4f heterometallic complexes, namely, [Zn 2 Ln(R,R-L) 2 (H 2 O) 4 ](ClO 4 ) 3 ) [Ln = Dy (1), Tb ( 3 5), Tb (7)], and [Zn 2 Ln 2 (S,S-L) 2 (CO 3 ) 2 (NO 3 ) 2 ]•2CH 3 OH [Ln = Dy (6), Tb (8)] {H 2 L = cyclohexane-1,2-diylbis(azanediyl)bis-(methylene)bis(2-methoxyphenol)}, has been synthesized and characterized. Crystal structure analysis reveals that complexes 1− 4 are isostructural trinuclear clusters crystallized in chiral space group C2 2 2 1 , and 5−8 are isostructural tetranuclear clusters crystallized in chiral space group P1. Interestingly, the adjacent [ZnLn] units within the tetranuclear cluster in 5−8 are bridged by two carbonate anions via in situ incorporation of CO 2 from air. Magnetic measurements indicate that complexes 1 and 3 exhibit field-induced single-molecule magnet behavior with energy barriers (U eff ) of 22.46 and 38.70 K (or 41.87 K), respectively. Complex 5 displays typical SMM behavior with U eff = 19.61 K under zero dc field, while for complex 7, no obvious out-of-phase signals are observed even under 2 kOe dc field, the absence of SMM behavior. The solid-state luminescence studies reveal that all complexes display the characteristic fluorescence emission of lanthanide ions. Furthermore, the Kurtz−Perry measurements reveal these complexes are potential nonlinear optical materials.