Search results for "Paramagnetic"
showing 10 items of 600 documents
126. Dosimetric analysis of phenolic solid state pellets exposed to radio-therapeutic photon and electron beams through electron spin resonance techn…
2018
Abstract Purpose Among the various dosimetric techniques used for characterizing the radiation beams used in radiation therapy, the electron spin resonance (ESR) arouses increasing interest for applications in various therapy procedures. In this work we report the ESR investigation of particular phenol compounds exposed to clinical photon and electron beams [1] . Materials and methods Pellets were produced by mixing Phenol (IRGANOX 1076® Sigma Aldrich) and paraffin (10% by weight). The irradiations of dosimeters were performed with photon and electron beams with absorbed doses ranging from 0 to 13 Gy. Basic dosimetric properties of phenolic dosimeters, such as reproducibility, dose-response…
Double azido/cyanato bridged copper(II) dimers incorporating tridentate nitrogen donors Schiff base: Structure, EPR and magnetic studies
2015
Abstract A neutral tridentate nitrogen donor Schiff base ligand L (L = (E)-N-(phenyl(pyridin-2-yl)methylene)-2-(pyridin-2-yl)ethanamine) has been synthesized and characterized by spectroscopic techniques, and employed to synthesize two new μ1,1-azido/cyanato bridged dinuclear copper(II) complexes, [Cu(L)(μ1,1-N3)(ClO4)]2 (1) and [Cu(L)(μ1,1-NCO)(ClO4)]2 (2). Both compounds have been spectroscopically and structurally characterized. Structural investigation reveals centro-symmetric nature of the complexes in which the center of inversion lies at the midpoint of the two copper(II) ions. The metal ions display distorted octahedral geometry. The tridentate neutral ligand L coordinates the metal…
A new linear double phenoxide-bridged trinuclear Cu(II) Schiff base complex: Synthesis, crystallographic elucidation, magneto-structural correlation …
2014
Abstract The tetradentate (ONNO) donor Schiff base ligand LH2, derived from the condensation of salicylaldehyde and 1,3-diaminopropane, has been synthesized and reacted with CuBr2 to yield a trinuclear complex with the molecular formula [Cu3L2Br2]. Single crystal X-ray diffraction study reveals that the two terminal copper atoms adopt a square pyramidal geometry, whereas the central copper atom, situated at the inversion centre, is surrounded by four phenoxide oxygen atoms in a square planar fashion. Variable temperature magnetic susceptibility measurement study shows strong antiferromagnetic intra-trimer interactions between the copper centers with a J value of −302 cm−1. EPR study of the …
Synthesis and spectral studies on metal complexes with the neutral O,N,O-tridentate Schiff base 6-amino-5-formyl-1,3-dimethyluracil-benzoylhydrazone
1999
Abstract From the reaction between different Co(II), Cu(II), Zn(II) and Pd(II) salts and the Schiff base 6-amino-5-formyl-1,3-dimethyluracil-benzoylhydrazone (H 2 BEZDO), in ethanol and acetone media, five complexes with M/L stoichiometry 1/1, containing the neutral organic ligand, have been obtained. These compounds have been studied by IR, 13 C and 1 H-NMR, UV-VIS-NIR and EPR spectroscopies and magnetic measurements. A single crystal X-ray diffraction study has been carried out on the compound [Cu(ClO 4 )(H 2 BEZDO)(H 2 O)]ClO 4 . The structure consists of mononuclear cations [Cu(ClO 4 )(H 2 BEZDO)(H 2 O)] + and uncoordinated perchlorate anions. The coordination environment around the Cu(…
Ferromagnetic exchange coupling in a new bis(μ-chloro)-bridged copper(II) Schiff base complex: Synthesis, structure, magnetic properties and catalyti…
2009
Abstract A new (μ-chloro)-bridged complex [Cu(HL)Cl]2 · H2O (1) with the Schiff base ligand H2L, [2-((E)-(2-hydroxyethylimino)methyl)-4-bromophenol], has been synthesized and characterized by elemental analysis, IR, UV–Vis and EPR spectroscopic studies. X-ray diffraction studies show that 1 is a binuclear CuII complex with a pair of chlorine atoms bridging the copper atoms in a central Cu2Cl2 core. Each copper atom in 1 adopts a distorted square-pyramidal geometry with the imine nitrogen atom, alkoxy and phenoxy oxygen atoms from the Schiff base ligand and a bridging chlorine atom constructing the basal plane, while the apical position of the pyramid is occupied by the other bridging chlori…
Structural Variation and Magneto-Structural Correlation in Two New Dinuclear Bis(µ2-Phenoxo)-Bridged CuII Schiff-Base Complexes: Catalytic Potential …
2010
Two new dinuclear bis(μ2-phenoxo)-bridged copper(ii) complexes [Cu(NCS)L1]2 (1) and [Cu(NCS)L2]2 (2) have been synthesized using two tridentate NNO-donor Schiff-base ligands, L1H (Me2N(CH2)3N=CHC6H3(OMe)(OH)) and L2H (Me2N(CH2)3N=C(CH3)C6H4(OH)), respectively. They have been characterized by elemental analyses, IR, UV-visible, and electron paramagnetic resonance (EPR) spectroscopy, cyclic voltammetry, and magnetic susceptibility measurements. X-Ray single-crystal structures reveal a central Cu2O2 core in each complex with an isothiocyanate ligand coordinated terminally to each metal centre. The coordination environments around the CuII ions in 1 and 2 are a distorted trigonal bipyramid and…
Sterically-controlled nuclearity in new copper(II) complexes with di-compartmental ligands: Formation of antiferromagnetically coupled angular trimer…
2010
Abstract Two new copper(II) complexes, [Cu3(L1)2(H2O)2](ClO4)2 (1) and [CuL2 ⊂ (H2O)] (2) have been derived from two di-compartmental Schiff base ligands H2L1 and H2L2, respectively. Depending on slight modification of the substituent group of the potentially N2O4 donor ligands, tri- and mononuclear structures are obtained, which have been confirmed by single-crystal X-ray diffraction studies. Both complexes have been characterized by elemental analysis, IR, UV–vis and EPR spectroscopy. Complex 1 consists of an angular trinuclear array of copper ions, while complex 2 consists of a mononuclear copper center. Variable temperature magnetic susceptibility measurements have been performed to inv…
Synthesis, structural aspects and magnetic properties of an unusual 2D thiocyanato-bridged cobalt(II)–Schiff base network
2010
Abstract A new two-dimensional (2D) thiocyanato-bridged cobalt(II) network formulated as [LCo2(NCS)2]n (1), has been synthesized with the Schiff base ligand N,N′-bis(3-methoxysalicylidenimino)-1,3-diaminopropane (H2L) and thiocyanate anions. This novel layered compound has been completely characterized by elemental analysis, FT-IR, UV–Vis spectroscopy and the structure has been established by single crystal X-ray diffraction studies. The structure of 1 consists of a doubly phenoxo-bridged dimer comprising two different cobalt(II) centers with different coordination geometries (octahedral and tetrahedral). The 2D network is accomplished by bridging thiocyanate ligands, connecting the dimeric…
ESR, ENDOR and TRIPLE resonance studies on radical reactions of 1,4-benzoquinone and 1,4-hydroquinone in alkaline methanol and liquid ammonia
1990
The relative signs and absolute values of the hyperfine coupling constants of different methoxy-1,4-benzoquinones were measured by ESR, ENDOR and TRIPLE resonance spectroscopy. Reactions of 1,4-benzoquinone and 1,4-hydroquinone with methanol took place in alkaline methanol, giving rise to methoxy-substituted 1,4-benzoquinones. The same substitution reaction occurred in a mixture of ammonia and methanol. The reactions depended on temperature and the alkali concentration. Coupling constants were assigned by the modified additivity relationship method. An extremely small line width of 0.014 G was measured in the ESR spectrum of deuterated 2,5-dimethoxy-1,4-benzoquinone.
Syntheses, Structures, and Magnetic Properties of Copper( II ) Complexes with 1,3‐[Bis(2‐pyridylmethyl)amino]benzene (1,3‐tpbd) as Ligand
2004
The dinuclear copper(II) complexes {[Cu2(1,3-tpbd)(H2O)(OAc)2](ClO4)2}0.23{[Cu2(1,3-tpbd)(H2O)2(OAc)](ClO4)3}0.77·0.77H2O (1), [Cu2(1,3-tpbd)(H2O)2(OAc)2](ClO4)2·2H2O (2), and the tetranuclear copper(II) complex [Cu4(1,3-tpbd)2(H2O)2(SO4)4]·8H2O (3) {1,3-tpbd = 1,3-bis[bis(2-pyridylmethyl)amino]benzene} were synthesised and structurally characterised by X-ray diffraction. Variable-temperature (2.0−290 K) magnetic susceptibility measurements on these complexes as well as on the dinuclear copper(II) complex [Cu2(1,3-tpbd)(H2O)2(ClO4)3]ClO4 (4) (whose structure was published earlier) were performed. In contrast to 2 and 3, significant ferromagnetic coupling with J = +9.3 cm−1 was observed for …