Chen-Xi Zhang

In Situ Synthesis, Characterization and Crystal Structure of a Novel Cobalt(III) Complex with Tridentate Schiff Base

The synthesis, structure and property characterization of a novel cobalt(III) complex of formula [Co(L) 2 ] (ClO 4 ) (1) is reported, where HL is the tridentate Schiff base obtained from the condensation of 2-pyridinecarboxaldehyde with pyridine-2-amine. Complex 1 crystallizes in the Orthorhombic crystal system, space group Pca2(1) with a = 14.925(2), b = 8.6786(11), c = 17.993(2)Å and Z = 4. The structure consists of [Co(L) 2 ]+ moiety and one perchloric ion. The central Co(III) ion lie in slightly distorted octahedral geometry in which the metal ion binds to two Sciff base ligand.

Synthesis, crystal structure and magnetic properties of a novel complex containing a diamagnetic metal ion and thiazole-substituted nitronyl nitroxide radicals

The synthesis, crystal structure and magnetic properties of a novel diamagnetic metal complex containing thiazole-substituted nitronyl nitroxide radicals, [HgCl2(NIT2-thz)2] (NIT2-thz = 2-(2′-thiazole)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide), is reported. The mercury(II) ion has distorted tetrahedral coordination involving two chloride atoms and two thiazole nitrogen atoms. Magnetic susceptibility data show that there are intramolecular antiferromagnetic interactions between the radicals in the complex.

Synthesis, characterization and crystal structure of a novel three-dimensional supramolecular architecture formed by manganese(II) and pyridine-2,5-dicarboxylic acid

A novel three-dimensional supramolecular compound formed by Mn(II) and pyridine-2,5-dicarboxylic acid of formula [Mn(Pydc)2(H2O)2] (Pydc = pyridine-2,5-dicarboxylic acid) has been synthesized and characterized by elemental analyses, IR, electronic spectra, thermogravimetric analysis and X-ray diffraction techniques. The X-ray structure shows that the central Mn(II) ion is coordinated by two water molecules and two chelated Pydc ligands. Water molecules coordinate with Mn(II) ions in the cis mode. Intermolecular hydrogen bonds play an important role in stabilization of the lattice and construction of the supramolecular network.

Synthesis, structure, and properties of a 1-D copper(II) complex with nitronyl nitroxide radicals

A 1-D chain complex [Cu(NIT4Py)(IDA)]∞ (NIT4Py = 2-(4′-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide and IDA = iminodiacetate) has been prepared and characterized by single-crystal X-ray diffraction, IR, TGA, and magnetic analysis. Each Cu(II) is five-coordinate with distorted square pyramidal geometry. Each IDA bridges two Cu(II) ions via one carboxylate which occupies the axial site of Cu(II), leading to a chain structure composed of Cu(II)-radical cations and IDA anions. In the complex, there exist three magnetic exchange pathways, (i) interaction between units of (Cu(II)-NIT4Py) through IDA, (ii) Cu(II)-NIT4Py interaction, and (iii) NIT4Py-NIT4Py interaction through space. Compared with the first two magnetic interactions, the last magnetic exchange interaction should be too weak to be counted because of the large distance of the neighboring NIT4Py molecules (4.993 Å). Analysis of the magnetic properties was performed using the Bleany–Bowers (dimer) model, showing that the complex exhibited both weak antiferromagnetic interaction between the Cu(II) and NIT4Py, and between the units of (Cu(II)-NIT4Py) through IDA with exchange coupling parameters J = −7.28 cm−1 and zJ′ = −0.40 cm−1.

High proton conduction behavior in 12-connected 3D porous lanthanide–organic frameworks and their polymer composites

Two novel lanthanide–organic frameworks, {[Ln3(bpydb)3(HCOO)(OH)2(DMF)]·3DMF·xH2O}n (Ln = Eu3+ (1) and x = 2; Tb3+ (2) and x = 1; bpydbH2 is 4,4′-(4,4′-bipyridine-2,6-diyl) dibenzoic acid; DMF denotes N,N′-dimethylformamide), have been synthesized and structurally characterized. Topological analysis reveals that 1 and 2 are 12-connected frameworks with an fcu topology, which are based on rod-shaped {Ln6} as 12-connected nodes. AC impedance analysis shows that the proton conductivity of 1 and 2 reaches up to 1.7 × 10−4 S cm−1 at 325 K and 1.1 × 10−4 S cm−1 at 334 K, respectively, under 98% RH. Furthermore, the polymer composite membranes of poly(vinyl alcohol) (PVA) and 1 or 2 as fillers with different mass percentages (X%, with the composite membrane denoted as 1@PVA-X or 2@PVA-X) were fabricated. The proton conductivities of both 1@PVA-10 and 2@PVA-10 are higher than those of 1 and 2 under the same conditions, which can be interpreted that the PVA polymer can provide a continuous proton transfer pathway for 1 and 2. To the best of our knowledge, it is the first composite based on Ln–MOFs and a polymer as proton exchange membranes. This research may contribute to the further development of Ln–MOFs in the field of proton exchange membranes in fuel cells.

Syntheses and Biological Activities of Lanthanide Metal Complexes with Nitronly Nitroxide

Using compounds ErCl3·6H2O (1), TbCl3·6H2O (2), DyCl3·6H2O (3), GdCl3·6H2O (4), and radical NITPh-p-Cl (5) (2-(4/-chlorphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide), four complexes based on lanthanide ions and nitronyl nitroxide radical, Ln(hfac)3(NITPh-p-Cl)2 (Ln = Er (6), Tb (7), Dy (8), Gd (9), hfac = hexafluoroacetylacetonate) have been synthesized and characterized by elemental analysis, IR, and UV-vis methods. The filter paper scraps diffusion method was used to determine the antibacterial performance with four lanthanide ions, radical and four lanthanide-radical complexes. The results reveal that antibacterial activities of the four complexes are stronger than that of the accordance pure lanthanide ions for the testing bacterium. The antibacterial activity of the complex 9 is best in all the compounds.

Three new lanthanide compounds based on nitronyl nitroxide radical: Crystal structure, magnetic properties, and luminescence properties

Abstract Three new lanthanide compounds were obtained using 2-(3-methylthiophene)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) (NIT-3Methien). These compounds, [Gd(hfac)3(NIT-3Methien)2]∙0.5CH3(CH2)5CH3 (1: Half n-heptane trihexafluoroacetylacetonate-di-2-(3-methylthiophene)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide gadolinium(III)), [Tb(hfac)3(NIT-3Methien)2]∙0.5H2O (2: Half Hydrate trihexafluoroacetylacetonate-di-2-(3-methylthiophene)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide terbium(III)), and [Dy(hfac)3(NIT-3Methien)2]∙0.5H2O (3: Half Hydrate trihexafluoroacetylacetonate-di-2-(3-methylthiophene)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide dysprosium(III)), (CH3(CH2)5CH3 = n-heptane), (hfac = hexafluoroacetylacetonate), were characterized structurally and magnetically. The three compounds crystallize in the triclinic space group P1( - ). Ln(III) ion was eight-coordinate by six oxygens from three hfac ligands and two oxygens from two radicals. In 1, direct current (DC) magnetic studies reveal ferromagnetic interactions between the Gd(III) ion and radicals with J1 = 0.94 cm−1. In 2 and 3, there are antiferromagnetic interactions between the Tb(III), or Dy(III) ions and radicals. The luminescence characterizations show that 2 exhibits highly selective luminescent sensing of Cr2O72− ions.

A new Europium metal-organic framework with both high proton conductivity and highly sensitivity detection of ascorbic acid

A new metal–organic framework (MOF), [{(H3O)[Eu (SBDB)(H2O)2]}n] (H4SBDB = 1,5-disulfo-benzene-2,4-dicarboxylic acid) (1), was successfully synthesized under solvothermal conditions. Ten central Eu3+ ions are coordinated by the H4SBDB ligands and two coordination water molecules. The adjacent Eu3+ ions are connected by oxygen atoms from carboxyl groups, forming a 1D chain. 1D chains are linked by H4SBDB ligands to induce a 2D infinitely extensible planar structure, and then connected by hydrogen bonds to form a 3D supernetwork structure. Complex 1 exhibits excellent thermal and chemical stability. AC impedance analysis shows that the highest proton conductivity of 1 reaches up to 1.0 × 10−4 S cm−1 (338 K, 98% RH). Furthermore, complex 1 is an excellent luminescence-based sensor with high sensitivity and a low detection limit for ascorbic acid (AA) in aqueous solutions.

Two copper complexes based on nitronyl nitroxide with different halides: structures and magnetic properties

Abstract Complexes based on different halogen-substituted nitronyl nitroxide radicals and Cu(II), Cu3(hfac)6(NIT-Ph-F)2 (1) and Cu3(hfac)6(NIT-Ph-Cl)2 (2) (hfac = hexafluoroacetylacetonate; NIT-Ph-F = 2-(4′-fluorophenyl)-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide; NIT-Ph-Cl = 2-(4′-chlorphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide), were synthesized and characterized structurally and magnetically. X-ray crystal structure analyses show that 1 and 2 have similar centrosymmetric five-spin structures consisting of three Cu(II) ions bridged by two nitroxide ligands. The Cu(II) is coordinated by six oxygens to form an octahedron, while the five coordination of the terminal Cu(II) ion is square pyramidal. Magnetic measurements reveal strong antiferromagnetic interactions between Cu(II) ions and radicals in 1 (J = −38.9 cm−1) and weak antiferromagnetic interactions between Cu(II) ions and radicals in 2 (J = −1.23 cm−1), which may be explained by the bond length of the Cu–Orad (2.468(2) Å) in 1, which is shorter than that (2.514(2) Å) in 2, and the dihedral angle (73.17(1)°) of the plane O7–O8–Cu(2)–O7A–O8A with the moiety O5–N1–C11–N2–O6 in 1 is smaller than (77.82(1)°) in 2.

A Mononuclear Lanthanide Metal Compounds Based on the Nitronyl Nitroxide Radicals: Synthesis, Crystal Structure, and Magnetic Properties

A complex [Er(hfac)3[NITPh-p-Cl]2], (hfac=hexafluoroacetylacetonate; and NITPh-p-Cl=2-(4′-chlorophenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) was synthesized and characterized structurally by X-ray crystal structure and magnetic measurements. X-ray crystal structure analysis revealed that the Er(III) ions are eight-coordinated and the complex has slightly distorted dodecahedron geometry. The variable temperature magnetic susceptibility measurements studies revealed that there are antiferromagnetic interactions between the Er(III) ions and the radicals in this complex.