Xuan Shen

Four MOFs with 2,2′-dimethoxy-4,4′-biphenyldicarboxylic acid: syntheses, structures, topologies and properties

Four novel metal–organic frameworks, [MnL(DMF)]n (1), [NiL(H2O)2(DMF)]n (2), [Cu2L2(H2O)2]·6H2O·2DMF (3), and Na2(Me2NH2)4[Cd7L10]·9H2O·17Me2NH·2DMF (4), were successfully synthesized in solvothermal conditions using 2,2′-dimethoxy-4,4′-biphenyldicarboxylic acid (H2L) as the ligand. The X-ray crystallography analysis reveals that MOF 1 exhibits a 3D framework with sra topology, while MOF 2 shows a 2D network with sql topology though they possess a similar secondary building unit (SBU) [MO6] (M = Mn for 1 and Ni for 2). MOF 3 reveals an unprecedented 4-fold interpenetrated 3D framework with lvt topology constructed from only planar 4-connected nodes ([Cu2(CO2)4] SBUs) with the rigid dicarboxylic acids. MOF 4 features an unique acentric 3D/3D hetero-interpenetrated framework built from two different nodes (4- and 8-connected), different chemical compositions [Cd(CO2)4 and Cd3(CO2)8], and different topology of networks (66 and 424·64) and contains an inorganic 1D chain consisting of a Na+ and three Cd2+ ions. The solid state 113Cd NMR spectrum indicates that 4 has three 6-, 7-, and 8-coordinated Cd2+ ions with chemical shifts at δ −25.3, −41.2 and −83 ppm, respectively. MOF 3 has two kinds of 1D channels with diameters of 11 A and 7 A and exhibits a selective gas adsorption for CO2–N2 and CH4–N2. MOF 4 shows a selective adsorption for cationic dyes and a nonlinear SHG activity (ca. 0.8 times that of urea).

An unprecedented 3D/3D hetero-interpenetrated MOF built from two different nodes, chemical composition, and topology of networks

An exceptional acentric MOF material with two-fold hetero-interpenetrated nets consisting of a 3D diamond network (mononuclear Cd(CO2)4 node) and a 3D CsCl framework (trinuclear Cd3(CO2)8 node) has been constructed, which contains 6-, 7-, 8-coordinated Cd2+ ions and shows a high thermal stability (>420 °C) and SHG activity.

Novel 3D lanthanide-organic frameworks with an unusual infinite nanosized ribbon [Ln3(μ3–OH)2(–CO2)6]+n (Ln = Eu, Gd, Dy): syntheses, structures, luminescence, and magnetic properties

Three novel lanthanide-organic frameworks, [Ln3(μ3–OH)2L2(HCO2)3(H2O)2]·H2O (Ln = Eu (1), Gd (2), Dy (3); H2L = 3,3′-dimethoxy-4,4′-biphenyldicarboxylic acid), have been prepared by the solvothermal reaction of Ln(NO3)3·6H2O and H2L in DMF/H2O mixed solvent. Crystallographic data show that 1–3 are isomorphous and crystallize in the monoclinic space groupP21/c. Each complex contains a rare infinite nanosized ribbon [Ln3(μ3–OH)2(–CO2)6]+n with three crystallographically distinct Ln(III) ions: two nine-coordinated and one eight-coordinated. The nanosized ribbons are interconnected through HCO2− anions and L2− linkers to yield a 3D framework. Furthermore, 1 exhibits strong red luminescence upon 343 nm excitation. The investigation of the magnetic properties shows the weak antiferromagnetic coupling between Gd(III) ions in 2 but ferromagnetic coupling between the Dy(III) ions in 3.

Two 3D metal–organic frameworks with different topologies, thermal stabilities and magnetic properties

Two novel 3D metal–organic frameworks, [ML]n (M = Co, 1; Mn, 2) were successfully prepared in solvothermal conditions using 3,3′-dimethoxy-4,4′-biphenyldicarboxylic acid (H2L) as the ligand. X-Ray crystallography analysis reveals that MOF 1 crystallizes in the monoclinic system, space group P21/c in contrast to MOF 2 in the tetragonal system, space group I. MOF 1 contains an elongated [CoO6] octahedron with two bound methoxy groups in the trans position, whereas MOF 2 has a compressed [MnO6] octahedron with two coordinated methoxy groups in the cis arrangement. The ligand L shows a novel bis(tridentate) bridging coordination mode. MOF 1 exhibits a 3D framework with CdSO4 (cds) topology consisting of two different nodes and good thermal stability (313 °C). MOF 2 is a doubly interpenetrated 3D α-Po framework with a higher thermal stability (368 °C). The study of magnetic properties in the temperature range of 1.8–300 K shows the occurrence of weak ferromagnetic interactions (J = 0.15 K) between the high-spin Co(II) ions in 1, but a weak antiferromagnetic coupling (J = −0.15 cm−1) between Mn(II) ions in 2 due to the syn-anti carboxylate bridge.

Facile synthesis of a water stable 3D Eu-MOF showing high proton conductivity and its application as a sensitive luminescent sensor for Cu2+ ions

The development of cost-effective proton-conducting materials with high conductivity and water stability is currently of great interest in fuel-cell technology. By using a simple aqueous solution method, a water stable 3D Eu-MOF material, [Me2NH2][Eu(ox)2(H2O)]·3H2O (1), can be easily synthesized from oxalic acid (H2ox) and Eu(NO3)3·6H2O on a large scale. 1 possesses a dia net topology and an extensive hydrogen-bonded network consisting of dimethyl ammonium and water molecules in 1D channels. 1 shows a high proton conductivity of 2.73 × 10−3 S cm−1 at 55 °C and 95% relative humidity, and it is used as a sensitive luminescent sensor for Cu2+ ions in aqueous solutions.

Three 3D lanthanide–organic frameworks with sra topology: syntheses, structures, luminescence and magnetic properties

Three 3D lanthanide–organic frameworks (LOFs), [Ln(HL)(DMF)]·2DMF (Ln = Eu (1), Gd (2), Dy (3); H4L = 3,3′-dihydroxy-4,4′-biphenyldicarboxylic acid), have been prepared by solvothermal reaction of Ln(NO3)3·6H2O and H4L in DMF–H2O mixed solvent. Crystallographic data show that 1–3 are isomorphous and crystallize in the monoclinic space group P21/c. Each Ln(III) is eight-coordinated to seven O atoms from five (HL)3− ligands and one O atom from a DMF molecule in a dodecahedron geometry. The adjacent Ln(III) ions are linked by the carboxylate groups of the (HL)3− ligands to form a 1D inorganic rod-shaped [Ln(CO2)3]n chain as a secondary building unit (SBU). The infinite 1D chains are interconnected by the biphenyl groups, giving rise to a 3D sra framework containing 1D open rhombic channels with dimensions of 18.4 × 11.6 A along the a axis. The present LOF is the first sra-net built from Ln–O–C rods with only one ligand. The ligand (HL)3− shows an unusual septadentate coordination mode with one bound hydroxy group. Furthermore, 1 exhibits characteristic luminescence of Eu3+ upon 394 nm excitation. The investigation of magnetic properties reveals the weak antiferromagnetic interactions (J1 = −0.018(14) and J2 = −0.021(13) cm−1) between Gd(III) ions in 2 and θ = −1.62(2) K in 3 due to thermal depopulation of the Stark levels of Dy(III) ions and/or the possible antiferromagnetic interactions between Dy(III) ions.

Syntheses, crystal structures, and spectral characterization of an asymmetrically substituted 1,2,4-triazole and its iron(II) complex

One new asymmetrically substituted 1,2,4-triazole, 4-amino-3-(p-bromophenyl)-5-(2-pyridyl)-1,2,4-triazole (L), and its iron(II) complex, trans-[FeL2(NCS)2] (1), have been synthesized and characterized by elemental analyses, FT-IR, 1H NMR, ESI mass spectra, and single-crystal X-ray crystallography. Crystallographic studies revealed that 1 contains a distorted octahedral [FeN6] core with two trans NCS−. Each L adopts a chelating bidentate coordination via N of pyridyl and one N of the triazole ring. Magnetic susceptibility measurements indicated that 1 remained in a high-spin state between 1.8 and 300 K.

Synthesis, crystal structures, and magnetic properties of three iron(II) complexes with 3-(p-bromophenyl)-4-phenyl-5-(2-pyridyl)-1,2,4-triazole

Three iron(II) complexes with 3-(p-bromophenyl)-4-phenyl-5-(2-pyridyl)-1,2,4-triazole (L), trans-[FeL2(NCS)2] (1), trans-[FeL2(NCS)2]·2MeOH (1·2MeOH), and trans-[FeL2(NCSe)2] (2), have been synthesized and characterized by elemental analysis, FT-IR, ESI-MS, and single crystal X-ray crystallography. Crystallographic studies reveal that all the complexes contain a distorted octahedral [FeN6] core with two trans NCS(Se)− ions. Each L adopts a chelating bidentate coordination via one N of pyridyl and one N of triazole. Magnetic susceptibility measurement indicated that both 1 and 1·2MeOH are in a high-spin state from 2 to 300 K. Three iron(II) complexes with an asymmetrically 3,4,5-triarylsubstituted 1,2,4-triazole, [FeL2(NCS)2] (1), [FeL2(NCS)2]·2MeOH (1·2MeOH) and [FeL2(NCSe)2] (2), have been synthesized and characterized by single crystal X-ray crystallography.

Syntheses, crystal structures, and spectral characterization of two new Cu(II) and Co(II) complexes with an asymmetrical substituted triaryltriazole

Two new complexes, trans-[CuL2(ClO4)2] (1) and cis-[CoL2(H2O)2](ClO4)2 · 2H2O (2) with 3-(p-methoxyphenyl)-4-(p-chlorophenyl)-5-(2-pyridyl)-1,2,4-triazole (L), have been synthesized and characterized by elemental analysis, FT-IR, ESI-MS, TGA/DSC, powder XRD, and single crystal X-ray crystallography. Each L in the complexes is chelating bidentate via one N of pyridyl and one N of triazole. Both complexes have similar distorted octahedral [MN4O2] cores (M = Cu2+ and Co2+) with two in trans-positions in 1 but two H2O molecules cis in 2.

[Ln4@Ln4] matryoshka tetrahedron: a novel secondary building unit

A novel secondary building unit, a Russian nesting doll [Ln4@Ln4] tetrahedron, was developed for building metal–organic frameworks with an unprecedented binodal (3,20)-connected 3D network by using a linear bridge-linking ligand.