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61.
62.
Kuepper K Bondino F Prince KC Zangrando M Zacchigna M Takás AF Crainic T Matteucci M Parmigiani F Winiarski A Galakhov VR Mukovskii YM Neumann M 《The journal of physical chemistry. B》2005,109(33):15667-15670
We have investigated for the first time the orbital ordering in a three-dimensional colossal magnetoresistance manganite, namely La(7/8)Sr(1/8)MnO3, by applying soft X-ray linear dichroism (XLD) to the Mn L edge. We found that the cooperative Jahn-Teller distorted orthorhombic phase, which is present at a temperature of 240 K, is probably accompanied by a predominantly cross type (x2 - z2)/(y2 - z2) orbital ordering. This result is discussed in the light of different exchange interaction models. 相似文献
63.
Renata Dreos Lassaad Mechi Lucio Randaccio Ennio Zangrando Rached Ben Hassen 《Journal of organometallic chemistry》2006,691(15):3305-3309
The reduction of [Co(III)(tmsalen)(py)2]+ with NaBH4/PdCl2 and the successive oxidative addition of CH2ClI, carried out in neutral methanolic solution and followed by the addition of NaOH, afford a new dinuclear complex. The molecular structure reveals that it is formed by an octahedral [Co(tmsalen)(py)(OH)] unit connected to a β-folded [Co(tmsalenCH2)]+ fragment, in such a way that the latter metal completes the coordination sphere with the hydroxo group and a tmsalen oxygen from the former unit. 相似文献
64.
Giuliana Pitacco Orazio A. Attanasi Lucia De Crescentini Gianfranco Favi Fulvia Felluga Cristina Forzato Fabio Mantellini Patrizia Nitti Ennio Valentin Ennio Zangrando 《Tetrahedron: Asymmetry》2010,21(5):617-622
Chiral non-racemic 1,4-dihydropyridazines were prepared by the reaction of 1,2-diaza-1,3-dienes with arylacetaldehydes under organocatalytic conditions. l-Proline and (S)-(+)-1-(2-pyrrolidinylmethyl)pyrrolidine coupled with trifluoroacetic acid were used as organocatalysts. Enantiomeric excesses ranged from 25% to 78%. 相似文献
65.
J. Szade W. Burian Z. Celiski T. OKeevan M. Zangrando F. Bondino E. Magnano 《Surface science》2005,580(1-3):163-166
Resonant photoemission was used to investigate the EuF3 ultrathin layer for the photon energies within the Eu 4d → 4f excitation region. Photoemission from the valence band in resonance showed the lines which can be attributed to two Eu valence states (Eu+3 and Eu+2) whereas the off resonance spectra of EuF3 ultrathin layer do not exhibit divalent states of Eu. An explanation of that effect is proposed which is based on the charge transfer from the ligand. 相似文献
66.
Animesh PatraSandipan Sarkar Titas MukherjeeEnnio Zangrando Pabitra Chattopadhyay 《Polyhedron》2011,30(17):2783-2789
Zinc(II) complexes of the formula [Zn(L)(X)2] (where X = Cl−, N3−, NCO− and SCN− (1a-d, respectively)) and {[Zn(L)(ClO4)(H2O)](ClO4)}n (2), were isolated in the pure form on the reaction of 1,3-bis(2-pyridylmethylthio)propane (L) with different zinc(II) salts. All the complexes were characterized by physicochemical and spectroscopic tools. The X-ray crystallographic analyses of the complexes 1d and 2 showed that the former is mononuclear while complex 2 is a 1D coordination polymer, {[Zn(L)(ClO4)(H2O)](ClO4)}n, due to a different coordination mode of the tetradentate ligand L. The zinc(II) ions present an octahedral coordination geometry in both compounds, which is more distorted in the mononuclear complex 1d. The study indicates that the counter anion of the zinc(II) salt used as reactant leads to a different type of complex when isolated as a crystalline material. A spectroscopic study of the interaction of complex, 2 with calf thymus-DNA (CT-DNA) in Tris-HCl buffer showed a significant non-intercalative interaction with a binding constant (Kb) of 4.7 × 104 M−1, and the linear Stern-Volmer quenching constant (Ksv) and the binding sites (n) were found to be 1.3 × 103 and 0.92 respectively, calculated from ethidium bromide (EB) fluorescence displacement experiments. 相似文献
67.
M. T. H. Tarafder M. A. A. A. A. Islam M. B. H. Howlader N. Guidolin E. Zangrando 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(12):m363-m365
In the title compound, [Pd(C23H29N2OS2)2], the PdII atom displays the expected square‐planar coordination geometry. However, the trans configuration, which allows the PdII atom to be located on a crystallographic inversion centre, is unusual with respect to the cis arrangement found in analogous Pd complexes comprising similar N,S‐chelating ligands. 相似文献
68.
A series of new Ru(II)-DMSO complexes containing dicarboxylate ligands (dicarb), namely, oxalate (ox), malonate (mal), methylmalonate (mmal), dimethylmalonate (dmmal), and succinate (suc), have been synthesized and structurally characterized. These compounds were prepared from the known Ru(II)-Cl-DMSO anticancer complexes cis,fac-[RuCl2(DMSO-S)3(DMSO-O)] (1) and trans-[RuCl2(DMSO-S)4] (2) and from the chloride-free precursor fac-[Ru(DMSO-S)3(DMSO-O)3][CF3SO3]2 (3), with the aim of assessing how the nature of the anionic ligands influences the biological activity of these species. Basically, the investigated ligands can be divided into two groups. The reaction of either 1 or 2 with K2(dicarb) (dicarb = ox, mal, mmal) yielded preferentially the mononuclear species [K]fac-[RuCl(DMSO-S)3(eta2-dicarb)] (dicarb = mal, 6; mmal, 9; ox, 14) that contains a chelating dicarboxylate unit and a residual chloride. Likewise, when 3 was used as a precursor, the neutral mononuclear species fac-[Ru(DMSO-O)(DMSO-S)3(eta2-dicarb)] (dicarb = mal, 7; mmal, 10; ox, 16), which contains a DMSO-O ligand in the place of Cl-, was obtained. On the contrary, K2(suc) and K2(dmmal) yielded preferentially the dinuclear species [fac-Ru(DMSO-S)3(H2O)(mu-dicarb)]2 (dicarb = dmmal, 11; suc, 13), with two bridging dicarboxylate moieties. The two water molecules in anti geometry have strong intramolecular H-bonding with the non-coordinated oxygen atoms of the carboxylate groups. The solid-state X-ray structural data showed that the preferential binding mode of the investigated dicarboxylates, either bridging (mu) or chelating (eta2), is dictated mainly by steric reasons. Oxalate, unlike the other dicarboxylates, has also the bridging bis-chelate (eta4,mu) coordination mode available: this was found in the dinuclear species [{fac-RuCl(DMSO-S)3}2(eta4,mu-ox)] (15) and [{fac-Ru(DMSO-O)(DMSO-S)3}2(eta4,mu-ox)][CF3SO3]2 (17). We also isolated the unprecedented neutral metallacycle, [fac-Ru(DMSO-S)3(eta3,mu-ox)]4 (18), in which each oxalate unit has one unbound oxygen atom. The new complexes were thoroughly characterized by 1-D (1H and 13C) and 2-D (H-H- COSY and HMQC) NMR spectroscopy in solution and by IR spectroscopy in the solid state. The molecular structures of 10 compounds, 6-11, 13, 15, 17, and 18, were determined by X-ray crystallography. The behavior of selected complexes in aqueous solution was investigated by 1H NMR spectroscopy. 相似文献
69.
Derossi S Casanova M Iengo E Zangrando E Stener M Alessio E 《Inorganic chemistry》2007,46(26):11243-11253
The combination of cis-protected metal fragments with linear linkers is expected to yield molecular squares. We found instead that treatment of the 90 degrees angular precursor trans-[RuCl2(dmso-S)4] (1) with an equivalent amount of the linear and rigid pyrazine (pyz) linker unexpectedly yields, in a number of different experimental conditions, the molecular triangle [{trans,cis-RuCl2(dmso-S)2(mu-pyz)}3] (3), together with polymeric material. Very similar results were also obtained from the reaction between 1 and the preformed corner fragment trans,cis,cis-[RuCl2(dmso-S)2(pyz)2] (6). In both cases, the expected molecular square [{trans,cis-RuCl2(dmso-S)2(mu-pyz)}4] (4) was observed only as a transient species. These results suggest that 3, which is the first example of a neutral molecular triangle with octahedral metal corners and pyrazine edges, is both the thermodynamic and the kinetic product of the reactions described above. The X-ray structure of 3 shows that the main distortions from ideal coordination geometry concern the N-Ru-N angles, which are narrower than 90 degrees , and the coordination bonds of pyz. The pyrazine molecules, which are basically planar, are significantly tilted from linearity. Calculations performed on 6 indicated that the N-Ru-N angle is ca. six times more rigid than the tilt angle of pyrazine. The structural and theoretical findings on 3 and 6, together with the previous examples of molecular triangles and squares with cis-protected metal corners and linear pyz edges, suggest that the entropically favored molecular triangles might be preferred over the expected molecular squares with metal corner fragments that spontaneously favor Npyz-M-Npyz angles narrower than 90 degrees because of the presence of ancillary ligands with significant steric demand on the coordination plane. The rather-flexible coordination geometry of pyrazine can accommodate the moderate distortions from linearity required to close the small metallacycle with modest additional strain. 相似文献
70.
Subal Chandra Manna Sanjit Konar Ennio Zangrando Joan Ribas Nirmalendu Ray Chaudhuri 《Polyhedron》2007
Four 3d–4f heterometallic coordination polymers, [Cu3(IDA)6Ln2] · n(H2O) [IDA = iminodiacetate dianion; Ln = Gd, n = 3 (1); Ln = Nd, n = 6 (2); Ln = Sm, n = 6 (3)] and [Cu(Cl)(NTA)Sm(H2O)6] · (ClO4) · (H2O) (4) [NTA = nitrilotriacetate trianion], have heen synthesized and characterized by single crystal X-ray diffraction analysis. Complexes 1–3 are isomorphous, showing a 3D coordination framework having tubular channels filled by lattice water molecules running parallel to the c axis. Whereas complex 4 is a 1D polymer of alternating copper and samarium ions connected by NTA, and the chains get involved in H-bonding interactions resulting in a 3D network. A low temperature magnetic study reveals ferromagnetic interactions for complex 1. Thermogravimetric and X-ray powder diffraction analyses of 1, 2 and 3 show that the covalently bonded 3D network remains almost unaffected after deaquation. 相似文献