Kai Jiang

Constructing porous lanthanide coordination polymers of 4,4′-bipyridine- N , N ′-dioxide templated by single- and double-Keggin anions

Three porous coordination polymers, {[Nd(dpdo)2(H2O)5(CH3OH)2](PMo12O40)(CH3OH)-(H2O)5} n (1), {[Tb(dpdo)4(H2O)3](PMo12O40)(H2O)2CH3CN} n (2) and {[Tb(dpdo)4(H2O)3]H(SiMo12O40)(dpdo)0.5(CH3CN)0.5(H2O)4} n (3) (where dpdo is 4,4′-bipyridine-N,N′-dioxide), templated by single- or double-Keggin polyanions were synthesized and characterized by single crystal X-ray diffraction. The compounds exhibit three different 3D non-interwoven frameworks with large cavities occupied by the single- or double-Keggin-type anions. Thermogravimetric analyses suggest different stability for the three metal-organic frameworks. The SHG (second harmonic generation) efficiency of 1 confirms its noncentric framework.

Syntheses, crystal structures and magnetic properties of a new thienyl-substituted nitronyl nitroxide and its copper(II) complex

A new building block for molecule-based magnetic materials − thiophene-substituted nitronyl nitroxide, NIT2-thp, [1, NIT2-thp = 4,4,5,5-tetramethyl-2-(thiophenal-2-yl)imidazoline-1-oxyl-3-oxide] and its copper(II) complex [Cu(hfac)2]3(NIT2-thp)2 (2) (hfac = hexafluoroacetylacetonate) have been synthesized and characterized structurally and magnetically. For 1, dimers were formed and arranged through intermolecular interactions, the shortest contact between nitroxide groups is 4.115 Å among adjacent dimers. In 2 two types of copper interaction with 1 give three colinear Cu(II) ions linked by two μ − 1,4 bridging nitroxide ligands. The central metal ion is in a distorted octahedron, axially coordinated by two nitroxide oxygen atoms, while the two external metal ions are in distorted square-pyramidal environments with the nitroxide oxygen atom coordinated in the basal plane. Magnetic susceptibility data for 1 and 2 have been measured in the range 3–300 K. There are antiferromagnetic interactions (J = −3.89 cm−1) between the dimers of 1 and also ferromagnetic interactions in 2. The magnetic properties of 1 and 2 are discussed in connection with their crystal structures.

4,4,5,5-Tetramethyl-2-(4-pyridinio)imidazoline-1-oxyl-3-oxide chloride

The title compound C12H17N3O2 +·Cl− consists of a discrete [NITpPyH]+ cation [NITpPy = 2-(4′-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide] and a chloride anion. The NITpPy molecule is protonated at the N atom of the pyridyl ring. The anions and cations are connected via N—H⋯Cl hydrogen bonds.

4,4,5,5-Tetra­methyl-2-(4-pyridinio)-2-imidazoline-1-oxyl-3-oxide perchlorate

The crystal structure of the title compound, C12H17N3O2 +·ClO4 −, consists of 4,4,5,5-tetramethyl-2-(4-pyridinio)imidazoline-1-oxyl-3-oxide radical cations and perchlorate anions. Both the cation and the Cl atom of the anion are located on the same twofold rotation axis, and the crystal structure shows the average structure for the radical cation. The five-membered ring assumes a half-chair conformation. The cation links with the anion via N—H⋯O hydrogen bonding.

Double-Keggin-type Anion-templated Synthesis of a 3D Porous Coordination Polymer of Eu(III) Ions and dpdo Ligands

A porous coordination polymer, {[Eu(dpdo)4(H2O)3]H(SiMo12O40)(dpdo)0.5(CH3CN)0.5(H2O)4}n (1), (where dpdo is 4,4′-bipyridine-N,N′-dioxide) templated by double-Keggin-type polyanions has been synthesized through the self-assembly of Eu(III) ions and dpdo in acetonitrile/water solution and structurally characterized by elemental analysis, IR spectra and single crystal X-ray diffraction. The X-ray structure analysis reveals that compound 1 exhibits a 3D non-interwoven framework with large cavities housing centro-symmetrically related shoulder-by-shoulder double-Keggin anions as guests. The result of a thermogravimetric analysis suggests that the metal-organic framework has high thermal stability.

Synthesis, crystal structure and ferromagnetic interactions of a silver(I) complex with imizadolyl-substituted nitroxide radicals

A silver(I) complex with nitronyl nitroxide, [Ag2(NIT-R)4(NO3)2] · CH3OH [NIT-R = 2-(5-methylimidazol-4-yl)-4,4,5,5-tetramethyl-2-imidazoline-1-oxyl-3-oxide], has been prepared and characterized by magnetic and single-crystal X-ray diffraction studies. In the complex, the silver(I) ion is coordinated with two monodentate nitronyl nitroxide radicals by the nitrogen of the imizadole ring. The silver(I) ion is two-coordinate and forms a dimer through Ag ··· Ag weak metal bonding interactions. The magnetic properties for the title complex have been investigated in the temperature range 2 ∼ 300 K showing ferromagnetic interactions between the coordinated nitronyl nitroxides (J = 3.64 cm−1) and intermolecular antiferromagnetic interactions.

Synthesis, crystal structure and magnetic properties of a one-dimensional chain polymer, [Ni(IM2-Py)2(NO3)](NO3)

A novel complex [Ni(IM2-Py)2(NO3)](NO3), where IM2-Py is 2-(2′-pyridyl)-4,4,5,5-tetramethyl-2-imidazoline-1-oxyl, has been synthesized and characterized structurally and magnetically. The structure consists of [Ni(IM2-Py)2(NO3)]+ and a anion. The nickel(II) is in a distorted octahedral environment with four nitrogen atoms from two IM2-Py units and two oxygen atoms from a anion. The units of [Ni(IM2-Py)2(NO3)]+ were connected as a one-dimensional polymer by intermolecular interactions. Variable temperature magnetic susceptibility data show antiferromagnetic interactions between the nickel(II) and imino nitroxide radicals.