Dong-Zhao Gao

Ferromagnetic interactions in a Zn(II)–nitronyl nitroxide complex with dicyanoaurate(I) bridges

A two-dimensional Zn(II)-nitronyl nitroxide radical complex, Zn(NIT4Py)2[Au(CN)2]2 (NIT4Py = 2-(4′-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) was synthesized and characterized by elemental analyses, IR spectroscopy and single-crystal X-ray diffraction methods. The complex is monoclinic, space group C2/c, with a = 26.294(9), b = 7.167(2), c = 18.532(6) Å, β = 111.758(5)°, V = 3243.6(18) Å3, Z = 4, and R 1 [I > 2σ (I)] = 0.0348, and has an infinite two-dimensional network motif. Magnetic studies showed ferromagnetic coupling between two radicals through Zn(II).

Synthesis, structure and magnetic properties of a Pr(III) complex with chelating nitronyl nitroxide radicals

The synthesis and structure of Pr(III) complex with chelating nitronyl nitroxide radicals of formula [Pr(III)(NIT2Py)2(NO3)3] (NIT2Py = 2-(2′-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) is reported. Pr(III) is ten-coordinate with three bidentate nitrate anions and two radicals. The radical behaves as a bidentate chelating ligand through one oxygen atom of the nitronyl nitroxide group and one nitrogen atom of a pyridine ring. The electronic spectrum for the complex in THF and magnetic susceptibilities from 77–300 K are reported.

A one-dimensional zigzag chain involving a cadmium(II)-imino nitroxide: structure and magnetic properties

A novel one-dimensional complex salt with the formula [Cd(IM2py)2][Au(CN)2]2 (IM2py = 2-(2′-pyridinyl)-4,4,5,5-tetramethylimidazoline-1-oxyl), has been synthesized and its structure was determined by single-crystal X-ray diffraction methods. The coordination geometry around Cd(II) ion is a distorted octahedral. IM2py coordinates to Cd(II) via pyridyl- and imino-N atoms to form a planar, five-membered chelate ring. [Cd(IM2py)2][Au(CN)2]2 units are linked through weak Au ··· Au interactions, generating an infinite 1D zigzag chain. Magnetic studies show weak antiferromagnetic coupling between two radicals through the diamagnetic Cd(II) ion.

Synthesis and crystal structures of copper and manganese complexes withN,N′-dibenzyl-1,10-phenanthroline-2,9-dimethylamine

The new ligand, N,N′-dibenzyl-1,10-phenanthroline-2,9-dimethylamine trihydrochloric acid monohydrate (L · 3HCl·H2O), has been synthesized and characterized. Complexes of the ligand (L) with CuII and MnII were prepared and their crystal structures were determined. The copper ion is five-coordinated via three nitrogen atoms of the ligand and two chloride ions, while the manganese ion is six-coordinated by three nitrogens of the ligand, two chloride ions and one water molecule. In both complexes, the ligand behaves in a tri-dentate fashion and the uncoordinated nitrogen of the other arm is protonated.

Reactions of chromium(III) complexes with ferricyanide. Magnetism of K2[Cr(salen)(H2O)][Fe(CN)6]·H2O and the crystal structure of [trans-Cr(tn)2Cl2]3[Fe(CN)6]·6H2O [salen2− = N,N′-ethylenebis(salicylideneaminato) dianion, tn = 1,3-diaminopropane]

Two CrIII–FeIII complexes, K2[Cr(salen)(H2O)][Fe(CN)6]·H2O (1) and [trans-Cr(tn)2Cl2]3[Fe(CN)6]·6H2O (2), have been prepared. Crystal structure determination shows that complex (2) possesses an ionic salt structure. General physical measurements and magnetic studies indicate that (1) assumes a cyanide-bridged dinuclear structure, and that the CrIII–FeIII magnetic coupling through the cyanide bridge is antiferromagnetic, which can be rationalized by the overlap of magnetic orbitals of the same symmetry.

Synthesis and crystal structure of two metal complexes involving reduced imino nitroxides

Two novel complexes, [Co(mal)(IMH2py)2]ClO4 (1) and [Mn(mal)(IMH2py)2] · H2O (2), have been synthesized and their crystal structures determined by X-ray diffraction methods. The imino nitroxide 1-oxy-2-(2′-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole (IM2py) is reduced during reaction to yield 1-hydroxy-2(2′-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole (IMH2py); mal is the malonate anion. Complexes 1 and 2 crystallize in the monoclinic space group C2 space group with a = 17.004(9), b = 10.753(5), c = 9.207(5) Å, β = 113.856(8)° and Z = 2 for 1, and a = 16.721(5), b = 10.897(5), c = 9.253(3) Å, β = 120.807(6)° and Z = 2 for 2. Each metal ion is six-coordinated by two imino nitrogen atoms of two iminohydroxylamine groups, two nitrogen atoms of two pyridyl groups and two oxygen atoms of the malonate ion.

A novel dimeric zinc(II) complex with a tripodal peptide ligand: a structure stabilized by ligand sharing

The crystal structure of a novel dimeric zinc(II) complex, [ZnL(H2O)]2(ClO4)2·4H2O (L = N-(bis(2-pyridyl)methyl)-2-pyridinecarboxamide), has been determined by X-ray diffraction. In this complex each planar Npy–Namido–Npy moiety of the ligand coordinates to one zinc ion and the pendant pyridine of one [ZnL] unit completes the coordination sphere of a [ZnL] neighbor. Units of the complex are connected in a two-dimensional network by intermolecular hydrogen bonds. The thermodynamic properties of the ligand with bivalent metal ions Co(II), Ni(II), Cu(II) and Zn(II) were studied by potentiometric titration and the order of the stability constants is in agreement with the Irving–Williams series. The dimeric complex is stabilized through ligand sharing, as confirmed by the crystal structure and thermodynamic properties.

Structures and magnetic properties of two new heterospin complexes involving nitroxide radicals and oxamido-bridged copper(II)

Two new binuclear copper(II) complexes containing four spin carriers with pyridyl-substituted nitroxide radicals have been synthesized and characterized structurally and magnetically. These complexes are formulated as [Cu2(oxap)(IM4py)2](ClO4)2 (1) and [Cu2(oxap)(NIT4py)2](ClO4)2 (2), respectively, in which oxap stands for N,N′-bis(2-aminopropyl). IM4py stands for 2-(4′-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl and NIT4py for 2-(4′-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide. The structures of the complexes consist of centro-symmetric trans oxamido-bridged copper(II) binuclear units and nitroxide radicals. In 1 and 2 the copper atoms are in a distorted square plane and radicals (IM4py and NIT4py) coordinate to copper via nitrogen atoms from pyridine rings. Magnetic analysis indicates that 1 and 2 exhibit strong metal-metal antiferromagnetic coupling through oxamido-bridged and antiferromagnetic exchange interactions between copper(II) ion and radicals, respectively. The magnetic behaviors are discussed with reference to their crystal structures.

Magnetic interactions in a new heterospin complex involving nitroxide radical and oxamido-bridged copper(II)

A new binuclear copper(II) complex [Cu2(oxpn)(IM2py)2](ClO4)2, containing four spin carriers with pyridyl-substituted nitroxide radicals has been synthesized and characterized structurally and magnetically (oxpn = N,N′-bis(3-aminopropyl)oxamido, IM2py = 2-(2′-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl). The structure of the complex consists of centrosymmetric trans oxamido-bridged copper(II) binuclear units and nitroxide radicals. The coordination geometry around each copper atom is distorted square pyramidal and the apical position is occupied by a nitrogen atom of the imidazoline ring of a radical ligand. Magnetic analysis indicates that the complex exhibits strong antiferromagnetic coupling between copper(II) ions through the oxamido bridge and a ferromagnetic interaction between copper(II) ions and radical ligands. The magnetic behaviour is discussed with reference to the crystal structure.