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E E Castellano

Publications and source records attributed to E E Castellano.

6 recordsLinked to original sources
PubMed2002

On the lability of dimethylsulfoxide (DMSO) coordinated to the [Ru(II)-NO(+)] species: X-ray structures of mer-[RuCl(3)(DMSO)(2)(NO)] and mer-[RuCl(3)(CD(3)CN)(DMSO)(NO)].

The syntheses of nitrosyl-dimethylsulfoxide-ruthenium(II) complexes with general formula mer-[RuCl(3)(L)(DMSO)(NO)] (L=DMSO or CD(3)CN) is reported. The mer-[RuCl(3)(DMSO)(2)(NO)] (1) complex was obtained from the reaction of [RuCl(3)(NO)] with the sulfoxide ligand in acetone. The mer-[RuCl(3)(CD(3)CN)(DMSO)(NO)] (2) compound was obtained from mer-[RuCl(3)(DMSO)(2)(NO)] maintained in deuterated acetonitrile. These data suggest a slow kinetic reaction due the low lability of the DMSO ligand coordinated to the [Ru(II)-NO(+)] species. The crystal and molecular structures of (1) and (2) have been determined from X-ray studies. Crystal data: for (1), monoclinic, P2(1)/c, a=8.8340(2) A, b=12.0230(3) A, c=13.7064(4) A, beta=114.546(2) degrees, Z=4, R1=0.0429; for (2), monoclinic, P21/n, a=10.0180(7) A, b=9.5070(7) A, c=13.3340(9) A, beta=102.264(4) degrees, Z=4, R1=0.0472. The spectroscopic characterization of (1), in solid state (infrared spectrum) and in solution (nuclear magnetic resonance and cyclic voltammetry) is also described.

Journal Article↗
PubMed2001

Structural transition and pair formation in Fe3O2BO3.

We observe for the first time a structural phase transition in the oxyborate Fe3O2BO3 which occurs along three leg ladders present in this material. X-ray diffraction shows that this transition at 283 K is associated with a new phase where atomic displacements occur in alternate directions perpendicular to the axis and within the plane of the ladders. Magnetic data show that these displacements lead to the formation of singlet pairs which dissociate close to the structural transition. Anomalies in the transport properties also occur close to 283 K showing that the structural transition is related to a charge ordering phenomenon in a low dimensional structure.

Journal Article↗
PubMed2001

1,2,5-Oxadiazole N-oxide derivatives as potential anti-cancer agents: synthesis and biological evaluation. Part IV.

Several new 1,2,5-oxadiazole N-oxide derivatives and some deoxygenated analogues were synthesized to be tested as potential selective hypoxic cell cytotoxins. Compounds prepared were designed in order to gain insight into the mechanism of action of this kind of cytotoxin. Compounds were tested in oxia and hypoxia and they proved to be non-selective. 3-Cyano-N(2)-oxide-4-phenyl-1,2,5-oxadiazole showed the best cytotoxic activity in oxia. The cytotoxicity observed for these derivatives could be explained in terms of the electronic characteristics of the 1,2,5-oxadiazole substituents. Electrochemical and ESR studies were performed on the more cytotoxic derivative.

Aerobiosis↗
PubMed2000

7Beta-oxygenated limonoids from Trichilia elegans ssp. elegans.

Five 7beta- and 7alpha-oxygenated obacunone-type limonoids were obtained on reinvestigation of the seeds of Trichilia elegans ssp. elegans: 7-deoxo-7beta-acetoxykihadanins A and B, 7-deoxo-7beta-hydroxykihadanins A and B and 7-deoxo-7alpha-hydroxykihadanin A, the last three being isolated after acetylation procedures as their mono- and/or diacetate derivatives. This is the first report of the natural occurrence of C-7 beta-substituted limonoids without any oxygenated function at C-6. The structures of these compounds have been established on the basis of 1D- and 2D-NMR spectral techniques, ESI-mass spectrum and X-ray crystallographic data.

Flavonoids↗
PubMed1998

Set-up and experimental parameters of the protein crystallography beamline at the Brazilian National Synchrotron Laboratory.

The Brazilian National Synchrotron Light Laboratory (LNLS) has a dedicated protein crystallography beamline. The optical elements of the beamline include an elastically bent cylindrical mirror and a triangular bent-crystal monochromator, which focus synchrotron radiation at the position of the sample in the vertical and horizontal planes, respectively. The monochromatic radiation is tunable between 2.0 and 1.2 A with the optimum wavelengths from 1.3 to 1.6 A, chosen to maximize the photon flux from the bending magnets of the storage ring (1.37 GeV). Diffraction images are recorded on a 345 mm-diameter MarResearch image-plate detector system with on-line readout. The experimental parameters of the beamline, such as the integral monochromatic flux and focus size, have been measured. The size of the beam at the position of the focal point is 0.5 x 0.5 mm(2). The flux density is between 4.4 x 10(10) and 8 x 10(10) photons s(-1) mm(-2) for wavelengths from 1.28 to 1.6 A. The energy resolution is sufficient to measure absorption edges of elements between 1.28 and 2 A. The facility, intended to serve the national and international community, has been commissioned and is available for users.

Journal Article↗