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- Meghdadi, S., et al.
(författare)
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Synthesis, X-ray crystal structure, and electrochemistry of copper(II) complexes of a new tridentate unsymmetrical Schiff base ligand and its hydrolytically rearranged isomer
- 2012
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Ingår i: Inorganica Chimica Acta. - : Elsevier BV. - 0020-1693. ; 385, s. 31-38
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Tidskriftsartikel (refereegranskat)abstract
- A new unsymmetrical Schiff base ligand HL1, HBacabza, and its copper(II) complexes [Cu2L21(OAc)(2)] (1) and [Cu2L22(N-3)(2)]center dot 2H(2)O (2) with HBacabza = 3-(2- aminobenzylimino)-1-phenylbutan-1-one as HL1 and its hydrolytically rearranged isomer 3-(2-aminomethylphenyleneimino)-1-phenylbutan-1-one as HL2, have been synthesized and characterized by elemental analyses and spectroscopic methods. The rearrangement of HL1 to HL2 occurs in a hydrolysis-recondensation process in the reaction of HL1 with Cu(ClO4)(2)center dot 6H(2)O and NaN3. The crystal structures of the ligand and its complexes have been determined by single crystal X-ray diffraction. The deprotonated Bacabza coordinates to the metal center as a tridentate ligand. The acetate anion coordinates through one oxygen atom in complex 1 leading to a mono-atomic acetate oxygen-bridging dimeric copper(II) complex. Similarly, the azide anion coordinates through one nitrogen atom in complex 2 leading to a mono-atomic azide nitrogen-bridging dimeric copper(II) complex. The copper(II) ions adopt a distorted square pyramidal (4 + 1) coordination in these two complexes. The cyclic voltammetric studies of these complexes in N, N-dimethylformamide indicate that the reduction process corresponding to Cu-II/Cu-I is electrochemically irreversible in complex 1, presumably due to the structural changes during the course of redox reaction, and quasi-reversible in complex 2.
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| 2. |
- Leal-Ferreira, M., et al.
(författare)
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Magnetic fields around evolved stars
- 2014
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Ingår i: Asymmetrical Planetary Nebulae VI conference, Proceedings of the conference held 4-8 November, 2013. ; , s. 49-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A number of mechanisms, such as magnetic fields, (binary) companions and circumstellar disks have been suggested to be the cause of non-spherical PNe and in particular collimated outflows. This work investigates one of these mechanisms: the magnetic fields. While MHD simulations show that the fields can indeed be important, few observations of magnetic fields have been done so far. We used the VLBA to observe five evolved stars, with the goal of detecting the magnetic field by means of water maser polarization. The sample consists in four AGB stars (IK Tau, RT Vir, IRC+60370 and AP Lyn) and one pPN (OH231.8+4.2). In four of the five sources, several strong maser features were detected allowing us to measure the linear and/or circular polarization. Based on the circular polarization detections, we infer the strength of the component of the field along the line of sight to be between ~30 mG and ~330 mG in the water maser regions of these four sources. When extrapolated to the surface of the stars, the magnetic field strength would be between a few hundred mG and a few Gauss when assuming a toroidal field geometry and higher when assuming more complex magnetic fields. We conclude that the magnetic energy we derived in the water maser regions is higher than the thermal and kinetic energy, leading to the conclusion that, indeed, magnetic fields probably play an important role in shaping Planetary Nebulae.
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