Search results for "Paramagnetic"
showing 10 items of 600 documents
Magnetism and EPR spectra of the two‐sublattice manganese chain Mn2(EDTA)⋅9H2O
1990
We report on the magnetic behavior and single‐crystal EPR spectra of the chain complex Mn2(EDTA)⋅9H2O characterized by two different alternating sites for the manganese ions. Magnetic susceptibility data are indicative of weak antiferromagnetic exchange interactions between the manganese ions, showing a maximum of about 3 K. This behavior can be accurately described on the basis of a Heisenberg chain model that assumes classical spins, giving J/k=−0.72 K and g=2.0. The EPR spectra are typically low dimensional, with an angular dependence of the linewidth of the type (3 cos2 θ−1)n (n=4/3 or 2). Nevertheless, such a behavior cannot be reproduced from a one‐dimensional model with dipolar broad…
Synthesis, spectral and magnetic properties of two different 2-nitrobenzoatocopper(II) complexes containing N,N-diethylnicotinamide
2008
Abstract Two structurally different complexes, [Cu2(2-NO2Bz)4(denia)1]n (1) and [Cu(2-NO2Bz)2(denia)2(H2O)2] (2), were prepared from the same reaction (where 2-NO2Bz = 2-nitrobenzoate, denia = N,N-diethylnicotinamide) and they are reported together with [Cu2(2-NO2Bz)4(DMF)2] (3) (DMF = N,N-dimethylformamide). The compounds under study were characterized by elemental analysis, electronic, IR and EPR spectra, magnetic measurements over the temperature range of 1.8–300 K and X-ray analysis. The molecular structure of (1) is polymeric, (2) is monomeric and (3) is dimeric. In the polymeric chain of (1), the denia molecules serve as bridges between dimeric Cu2(2-NO2bz)4 units. Each Cu(II) atom ha…
Polymeric Nanocarriers for Magnetic Targeted Drug Delivery: Preparation, Characterization, and in Vitro and in Vivo Evaluation
2013
In this paper the preparation of magnetic nano- carriers (MNCs), containing superparamagnetic domains, is reported, useful as potential magnetically targeted drug delivery systems. The preparation of MNCs was performed by using the PHEA-IB-p(BMA) graft copolymer as coating material through the homogenization−solvent evaporation method. Magnetic and nonmagnetic nanocarriers containing flutamide (FLU-MNCs) were prepared. The prepared nanocarriers have been exhaustively characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM), and magnetic measurements. Biological evaluation was performed by in vitro cytotoxicity and cell uptake tests and in vivo biodistribution …
Light-Induced Formation of Pb3+Paramagnetic Species in Lead Halide Perovskites
2018
Hybrid halide perovskites are soft materials processed at room temperature, revolutionary players in the photovoltaic field. Nowadays, investigation of the nature and role of defects is seen as one of the key challenges toward full comprehension of their behavior and achievement of high device stability under working conditions. We reveal the reversible generation, under illumination, of paramagnetic Pb3+ defects in CH3NH3PbI3, synthesized in ambient conditions, induced by the presence of Pb-O defects in the perovskite structure that may trap photogenerated holes, possibly mediated by the concomitant oxidation and migration of ions. According to the mechanism that we hypothesize, one charge…
Field-induced slow magnetic relaxation in pseudooctahedral cobalt(ii) complexes with positive axial and large rhombic anisotropy
2019
The preparation, X-ray crystal structure, spectroscopic and variable-temperature dc and ac magnetic properties of two six-coordinate cobalt(ii) complexes of formula [Co(bim)4(tcm)2] (1) and [Co(bmim)4(tcm)2] (2) (bim = 1-benzylimidazole, bmim = 1-benzyl-2-methylbenzimidazole and tcm- = tricyanomethanide ion) are reported. 1 and 2 crystallize in the monoclinic P21/n and C2/c space groups with the asymmetric units composed of one tcm- ion and half the [Co(bim)4]2+ and [Co(bmim)4]2+ complex cations, respectively. Their cobalt atoms are in compressed (1)/rhombic (2) CoN6 octahedral environments, the axial positions being occupied by monodentate tricyanomethanide anions. The neutral molecules in…
Insertion of single-ion magnets based on mononuclear Co(II) complexes into ferromagnetic oxalate-based networks
2021
The 1 : 2 and 1 : 1 Co(ii) complexes of the L ligand (L = 6-(3,5-diamino-2,4,6-triazinyl)2,2'-bipyridine) with formulas [CoII(L)2](ClO4)2·0.5MeCN·Et2O (1) and [CoII(L)(CH3CN)2(H2O)](ClO4)2·MeCN (2) have been prepared. The structural and magnetic characterization of the two compounds shows that they contain octahedral high-spin Co(ii) and present a field-induced slow relaxation of the magnetization. 1 has been inserted into a bimetallic oxalate-based network leading to a novel achiral 3D compound of formula [CoII(L)2][MnIICrIII(ox)3]2·(solvate) (3) exhibiting ferromagnetic ordering below 4.6 K. EPR measurements suggest a weak magnetic coupling between the two sublattices.
The influence of pseudohalide ligands on the SIM behaviour of four-coordinate benzylimidazole-containing cobalt(ii) complexes.
2018
Three, mononuclear complexes of the formula [Co(bmim)2(SCN)2] (1), [Co(bmim)2(NCO)2] (2) and [Co(bmim)2(N3)2] (3) [bmim = 1-benzyl-2-methylimidazole] were prepared and structurally analyzed by single-crystal X-ray crystallography. The cobalt(ii) ions in 1-3 are tetrahedrally coordinated with two bmim molecules and two pseudohalide anions. The angular distortion parameter δ was calculated and the SHAPE program (based on the CShM concept) was used for 1-3 to estimate the angular distortion from an ideal tetrahedron. The molecules of 1-3 are effectively separated, and the values of the shortest distance of cobalt-cobalt are 8.442(6) and 6.774(8) A for 1, 10.349(8) and 10.716(8) A for 2 and 6.7…
Changes in Surface Free Energy and Surface Conductivity of Carbon Nanotube/Polyimide Nanocomposite Films Induced by UV Irradiation.
2021
Changes in surface energy and electrical conductivity of polyimide (PI)-based nanocomposite films filled with carbon nanotubes (CNTs) induced by UV exposure are gaining considerable interest in microelectronic, aeronautical, and aerospace applications. However, the underlying mechanism of PI photochemistry and oxidation reactions induced by UV irradiation upon the surface in the presence of CNTs is still not clear. Here, we probed the interplay between CNTs and PIs under UV exposure in the surface properties of CNT/PI nanocomposite films. Changes in contact angles and surface electrical conductivity at the surface of CNT/PI nanocomposite films after UV exposure were measured. The unpaired e…
Dinuclear manganese(iii) complexes with bioinspired coordination and variable linkers showing weak exchange effects: a synthetic, structural, spectro…
2019
Three dimanganese(iii) complexes have been synthesised and fully characterised by standard spectroscopic methods and spectroelectrochemistry. Each MnIII ion is chelated by a salen type ligand (H2L), but there is variation in the bridging group: LMn(OOCCH[double bond, length as m-dash]CHCOO)MnL, LMn(OOCC6H4COO)MnL, and LMn(OOCC6H4C6H4COO)MnL. X-ray diffraction revealed an axial compression of each six-coordinate high-spin d4 MnIII ion, which is a Jahn-Teller-active ion. Temperature dependent magnetic susceptibility and variable temperature-variable field (VTVH) magnetisation measurements, as well as high-frequency and -field EPR (HFEPR) spectroscopy were used to accurately describe the magne…
Using the methods of radiospectroscopy (EPR, NMR) to study the nature of the defect structure of solid solutions based on lead zirconate titanate (PZ…
2014
The nature of intrinsic and impurity point defects in lead zirconate titanate (PZT) ceramics has been explored. Using electron paramagnetic resonance (EPR), nuclear magnetic resonance (NMR), and X-ray photoelectron spectroscopy (XPS) methods, several impurity sites have been identified in the materials, including the Fe 3+ -oxygen vacancy (VO) complex and Pb ions. Both of these centers are incorporated into the PZT lattice. The Fe 3+ -V paramagnetic complex serves as a sensitive probe of the local crystal field in the ceramic; the symmetry of this defect roughly correlates with PZT phase diagram as the composition is varied from PbTiO 3 to PbZrO 3 . NMR spectra 207 Pb in PbTiO 3 , PbZrO 3 ,…