Ho-Hsiang Wei

Structure and magnetic properties of dinuclear [Mn(III)(salen)(H2O)]2(ClO4)2 and polynuclear [Mn(III)(salen)(NO3)]n

Abstract The synthesis, crystal structure and magnetic properties of dinuclear [Mn(III)(salen)(H2O)]2(ClO4)2 (1) and polynuclear [Mn(III)(salen)(NO3)]n (2) (salen=N,N′-bis(salicylideneaminato)ethylene) are reported. Compound 1 consists of a structurally dinuclear system in which two Mn ions are bridged by the oxygen atom of μ-phenoxo of the salen ligands. Compound 2 is a linear polymeric chain in which the Mn ions are linked by NO3− groups. Cryomagnetic measurements show ferromagnetic interaction with J=6.30 cm−1 and D=−1.70 cm−1 for 1 and antiferromagnetic interaction with J=−0.55 cm−1 and D=−0.43 cm−1 for 2.

Structure, magnetic properties and catecholase activity study of oxo-bridged dinuclear copper(II) complexes

Abstract Six alkoxy-bridged dinuclear copper(II) complexes with catecholase-like sites, [Cu(L1)(NCS)]2 (1), [Cu(L2)(CH3CO2)]2·2H2O (2), [Cu(L3)(NCO)]2 (3), [Cu(L4)(NCS)]2 (4), [Cu(L5)(NCS)]2 (5), and [Cu(L4)(Cl)]2 (6), where HL1=2-(hydroxymethyl)-pyridine, HL2=6-methyl-2-pyridine-methanol, HL3=2-(2-hydroxyethyl)-pyridine, HL4=1-dimethylamino-2-methyl-1-propanol, and HL5=1-dimethylamino-2-propanol, respectively), have been prepared and characterized. The single crystal X-ray analysis show that the structures of complexes 1–6 are dimeric with two adjacent copper(II) atoms bridged by pairs of μ-oxy atoms from the alkoxyl group of the ligands. Magnetic susceptibility measurements in the temperature range 2–300 K for complexes 1–6 indicate significant antiferromagnetic coupling between the copper(II) atoms. The kinetic studies on catecholase activity of complexes for the oxidation of 3,5-di-tert-butylcatechol by O2 was studied and it found that the complexes with the bond distance of Cu(II)⋯Cu(II) located near 2.98 to ∼2.99 A show high catecholase activity. The reaction rate constant for the catecholase activity was obtained by Michaelis–Menten model.

A two-dimensional Cu II Gd III compound self-assembled by H-bonding and intermolecular weak coordinate bonding between the dinuclear cores: structure and magnetic properties

Abstract A heteronuclear CuIIGdIII complex [CuIILGdIII(NO3)3] with the hexadentate Shiff-base compartmental ligand N,N′-ethylenebis(3-ethoxysalicylaldiimine) (H2L) has been synthesized and structurally characterized. The intermolecular semicoordination of nitrate oxygen to copper(II) results a one-dimensional zigzag chain, which are linked by H-bonding to form a two-dimensional sheet. Magnetic studies reveal ferromagnetic interaction within the dinuclear core and antiferromagnetic interaction propagated through the extended network ( J=4.04 cm −1 , zJ ′ =−0.027 cm −1 , g Cu =2.109, g Gd =2.001 , where H=−2JSCu·SGd+β(gCu·SCu+gGd·SGd)H−zJ′〈S4Z〉S4Z).

Structure and magnetic properties of copper(II) carboxylate with pyridyl-substituted nitronyl nitroxides

The synthesis, crystal structure and magnetic properties of four new copper(II) carboxylate complexes with pyridyl-substituted nitronyl nitroxides, [Cu2(-ClCH2CO2)2(ClCH2CO2)2(NITpPy)2(H2O)2]CH3OH (1), [Cu(Cl2CHCO2)2(NITpPy)2(H2O)] (2), [Cu(Cl3CCO2)2(NITpPy)2(H2O)] (3) and [Cu(Cl2CHCO2)2(NITmPy)2(H2O)2 ]( 4) (NITpPy= 4,4,5,5-tetramethyl-2-(4-pyridyl)-2imidazoline-N 1 -oxy N 3 -oxide, NITmPy=4,4,5,5-tetramethyl-2-(3-pyridyl)-2-imidazoline-N 1 -oxy N 3 -oxide) are reported. Complex 1 has a dimeric structure where two copper ions are doubly bridged by four oxygen atoms from two -ClCH2CO2 − ions. Complexes 2 and 3 are mononuclear, the copper(II) ion has five coordination with square-pyramidal symmetry. In complex 4, the copper(II) ion has distorted-octahedral six coordination. Temperature dependence studies of the mT values of complexes 1 – 4 revealed that 1 exhibits a strong intramolecular metal–metal antiferromagnetic interaction and a weak intramolecular metal–nitroxide antiferromagnetic coupling, 2 and 3 exhibit a weak intramolecular metal–nitroxide antiferromagnetic coupling, while 4 possesses weak ferromagnetic exchange interactions between metal and NITmPy. A simple spin polarization model has been used to justify the observed magnetic exchange interactions between Cu(II) and radical ligands.

Synthesis, crystal structure and magnetic properties of zinc(II)-hexafluoro-acetylacetonate complexes with pyridyl-substituted nitronyl and imino nitroxide radicals

The reactions of zinc hexafluoroacetylacetonate (hfac) hydrate with pyridyl-substituted imidazolin-1-oxyl 3-oxide radicals in n-heptane obtained three new complexes, [Zn(hfac)2(NIT-mPy)2 ]( 1) (NIT-mPy 2-(3-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro1H-imidazolyl-1-oxy 3-oxide), [Zn(hfac)2(NIT-pPy)2]2 (2) (NIT-pPy 2-(4-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-1-oxy 3-oxide), and [Zn(hfac)2(IM-oPy)] (3) (IM-oPy 2(2-pyridyl)-4,4,5,5,-tetramethyl-4,5-dihydro-1H-imidazolyl-1-oxy). Crystal structures and magnetic properties have been studied. In complexes 1 and 2, each zinc ion is six-coordinated with four oxygen atoms from two hfac ligands and two nitrogen atoms of pyridyl groups. In 3, each zinc ion is coordinated with a bidentate imino nitroxide and two hfac ligands. EPR and magnetic susceptibility data support that between the radicals in complexes 1 ‐ 3 are intra- and intermolecular antiferromagnetic interactions. The magnetic behaviors are discussed in connection with the crystal structure.

STRUCTURE AND MAGNETIC PROPERTIES OF A NOVEL CHLORO-BRIDGED POLYMERIC CADMIUM(II) COMPLEX WITH PYRIDYL-SUBSTITUTED NITRONYL NITROXIDE

Abstract A complex of 2(2-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-1-oxy-3-N-oxide (NIToPy) with Cd(II)Cl2, [(CdCl2)3-(NIToPy)2(C2H5)2], has been structurally and cryomagnetically characterized. The structure is based on a layered zigzagging polymeric chain along the (101) plane; the Cd(II) ions are linked into infinite chains by double chlorine bridges alternating between one CdCl4O2 and two CdCl4NO octahedral coordination units. The temperature-dependence of the magnetic susceptibility reveals the presence of a Heisenberg antiferromagnetic exchange interaction of a two spin S = 1 2 system, with J = −0.25 cm−1 associated with the intermolecular interaction between the NO groups of two neighboring NIToPy radicals.

A novel chloro-bridged tetranuclear cadmium(II) cluster with pyridyl-substituted nitronyl nitroxide: structure and magnetic properties

Abstract A tetranuclear cadmium(II) complex of 2(2-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1 H-imidazol-1-oxy 3-N-oxide (NIToPy) with CdCl2,[Cd4Cl8(NIToPy)4], has been structurally and magnetically characterized. The structure is based on a novel chloro-bridged tetranuclear cadmium quasi-cubane cluster, in which each cadmium atom is chelated by one NIToPy radical, and coordinated with four bridging chlorine atoms. The temperature dependence of the magnetic susceptibility measurements shows a weak ferromagnetic coupling between the radicals. An excellent simulation of the experimental data with the prism type four spins Hamiltonian H=−2J1(S1S2+S2S3+S3S4+S1S4)−2J2S2S4 obtained the parameters: J 1 =1.12 cm −1 , J 2 =−0.20 cm −1 , and g=2.04.

MAGNETO-STRUCTURAL CORRELATION OF DIMERIC COPPER(II) CARBOXYLATES WITH PYRIDYL-SUBSTITUTED NITRONYL NITROXIDES

Abstract The synthesis, crystal structure and magneto–structural correlations of three new paddle-wheel type dicopper(II) carboxylate complexes with pyridyl-substituted nitronyl nitroxides, [Cu2(μ-Me3CCO2)4(NITpPy)2](C6H6) (1), [Cu2(μ-CH3CO2)4(NITpPy)2] (2), and [Cu2(μ-C6H6CH2CO2)4(NITmPy)2] (3) (NITpPy=4,4,5,5-tetramethyl-2-(4-pyridyl)-2-imidazoline-N1-oxyl N3-oxide, NITmPy=4,4,5,5-tetramethyl-2-(3-pyridyl)-2-imidazoline-N1-oxyl N3-oxide) are reported. Structures of complexes 1–3 consist of a symmetrical dimeric Cu(II) carboxylate paddle-wheel core and pyridyl nitrogen atoms of radical ligands at the apical position. Cryomagnetic susceptibilities were measured in the temperature range 4–300 K. According to the structural results, the magnetic data are discussed in terms of four S=1/2 spin units involving one strong coupled dicopper(II) unit plus two monomer nitroxyl radicals. It is found that two paddle-wheel copper(II) ions are strongly coupled antiferromagnetically with J=−192, −172, and −160 cm−1 for complexes 1, 2, and 3, respectively, while the interactions between copper(II) and the radicals are very weak. The magneto–structural correlations for complexes 1, 2, and 3 are discussed on the basis of the structural parameters and magnetic data for the complexes

Dimeric iron(III) complexes with salicylaldimine ligands: structures, magnetic properties, and activity of H2O2 disproportionation

Abstract The preparations, characterizations, structures, magnetic properties and catalase-like activities of four new alkoxy bridged dimeric five-coordinate iron(III) salicylaldimine complexes, [FeL1Cl]2 (1) (H2L1=N-(3-hydroxypropyl)(5-bromosalicylaldimine)), [FeL2Cl]2 (2) (H2L2=N-(3-hydroxypropyl)(3-methoxysalicylaldimine)), [FeL3Cl]2 (3) (H2L3=N-(3-hydroxypropyl)(4-diethylaminosalicylaldimine)), and [FeL4Cl]2 (4) (H2L4=N-(3-hydroxypropyl)(3,5-diiodosalicyaldimine)) are reported. The crystal structure of complexes 1–3 show an alkoxy bridged dimeric iron(III) complex, which occupies a site of inversion symmetry, and each iron atom is five-coordinate with square-pyramidal arrangements. Mossbauer spectra reveal the presence of high-spin iron(III) ions in complexes 1–4. The magnetic susceptibility (300–2 K) indicate an antiferromagnetic interaction between the two oxygen-bridged iron(III) ions with J=−17.5, −12.40, −19.0 and −21.0 cm−1 for the complexes of 1–4, respectively. The H2O2 disproportionation of complexes 1–4 in acetonitrile at 25°C show the rate law of kobs[H2O2]2[complex].

Structure and magnetic properties of (μ-oxo)bis[meso-tetrakis(p-tolyl-porphyrinato)iron(III)] and (μ-oxo)bis[N,N′-ethylenebis(2-acetylphenoliminato)iron(III)]

Abstract Synthesis, structure and magnetic properties of (μ-oxo)bis[meso-tetrakis(p-tolyl-porphyrinato)iron(III)] (1), [(TTP)Fe]2O, and (μ-oxo)bis[N,N′-ethylenebis(2-acetylphenoliminato)iron(III)] (2), [(aceten)Fe]2O, are reported. X-ray crystallographic studies reveal the structure in which two iron(III) atoms are bridged by the oxo groups in compounds 1 and 2. The bridging angle of 178.2(3)° for 1 is larger than that of 156.5(3)° for 2. The average Fe–O(μ) bond lengths are 1.74(3) and 1.7723(17) A for 1 and 2, respectively. The average displacements of the iron(III) atoms from the mean N4 plane in 1 and the N2O2 coordinated plane in 2 are 0.53 and 0.59 A, respectively. The average N–Fe(1)–Fe(2)–N′ twist dihedral angle is 24.70° for 1. Antiferromagnetic coupling shows an increase as the bridging angle Fe–O–Fe increases and the average Fe–O(μ) bond length decreases: J=−142 cm−1 for 1 and −104 cm−1 for 2.