Search results for "MÖSSBAUER SPECTROSCOPY"

Synthesis and spectroscopic characterization of organotin derivatives ofN-benzoylglycylglycine

1991

Di- and tri-organotin derivatives of N-benzoylglycylglycine (HBzGlyGly) were synthesized and characterized by infrared, 1H, 13C NMR and 119Sn Mossbauer spectroscopy. Diorganotin derivatives appear to be dimer distannoxanes ([R2SnBzGlyGly]2O)2 (R = CH3, n-C4H9, n-C8H17) with a ladder-type structure where tin atoms are five-coordinated and N-benzoylglycylglycine alternatively acts as a unidentate or bridging bidentate ligand through the carboxylate group. For triorganotin derivatives R3SnBzGlyGly (R= CH3, n-C4Hg) we propose a polymeric structure where N-benzoylglycylglycine bridges planar SnC3 units through the carboxylate group.

PREDICTION OF MOESSBAUER PARAMETERS IN A DOUGLAS–KROLL–HESS FRAMEWORK

2008

Dielectric relaxation models applied of the dynamics of myoglobin as determined by Mössbauer spectroscopy

1996

Abstract Protein specific modes of motions are found in myoglobin crystals above 180 K. In this contribution we show that this type of motions can be analyzed by a Davidson-Cole, a Cole-Cole or a Havriliak-Negami distribution in analogy to dielectric relaxation. However, the temperature dependence of the obtained parameters is quite unusual indicating a broadening of the distributions with temperature instead of motional narrowing. This can be understood from the picture of conformational substates if one assumes that more and more substates become accessible with increasing temperature. The result shows that the analogy between glass forming organic liquids and proteins should not be exagg…

Electric relaxation and Mn3+/Mn4+ charge transfer in Fe-doped Bi12MnO20–BiMn2O5 structural self-composite

2016

Fe-doped Bi12MnO20–BiMn2O5 ceramics was sintered at 1130 K for 6 h in ambient air. Two centro-symmetric phases formed thermodynamically stable self-composite material that was deduced from X-ray pattern analysis. The lattice parameters were a = 10.147(8) Å—for the cubic I23 Bi12MnO20 phase; and a = 7.545(4) Å, b = 8.538(1) Å, c = 5.758(3) Å—for the orthorhombic Pbam BiMn2O5 phase. The 57Fe Mössbauer spectrum, recorded at room temperature, has shown pure electronic quadrupolar split. The major doublets reflected the occurrence of Fe3+ ions distributed in two sites, i.e., octahedral Fe4+O6 and square pyramidal Fe3+O5, with preferential occupation of the pyramidal sites, that was consistent wi…

119Sn M�ssbauer studies of bis[cysteinato(1?)-S]- and bis[penicillaminato(1?)-S]-diorganotin(IV) species in the crystalline state and in frozen aqueo…

1988

The bonding and the configuration of the tin environment in the title compounds {R2Sn[SCH2CH(NH3+)COO−]2 and R2Sn[SC(CH3)2CH(NH3+)COO−]2, indicated in the following as R2Sn(cysH)2 and R2Sn(penH)2 respectively} has been investigated through the determination of the Mossbauer-Zeeman spectra of Ph2Sn(cysH)2 and Ph2Sn(penH)2 in the solid state, and through conventional Mossbauer spectroscopy of Me2Sn(penH)2 in the solid state as well as of Me2Sn(cysH)2 and Me2Sn(penH)2 in aqueous solution (frozen). The treatment of the data by the pointcharge model approach suggested the general occurrence of a tetrahedral C2SnS2 core. In aqueous Hepes buffer, a tertiary amino nitrogen atom has been observed to…

119Sn mössbauer, IR, 1H NMR spectroscopic and thermal decomposition studies on organotin(IV) adducts with glycylglycine

1985

Abstract The complexes R2SnCl2·(H2glygly), (H2glygly = glycylglycine) (R = Me, Bun, Octn, Ph) and RSnCl3·(H2glygly)

Atmospheric Corrosion Investigation in Industrial, Marine and Rural Environments in South-East Brazil

2002

ASTM 283-C, AISI 304 and 316-L steel specimens (called coupons) were exposed in marine, industrial and rural area(s) for different periods ranging between 1–12 months, in four different season campaigns. The corrosion rate was determined by chemical loss measurements. Rust characterization was performed by XRD, SEM, optical, and Mossbauer spectroscopy (in transmission and backscattering geometry). Superparamagnetic maghemite and goethite were found as corrosion products. Magnetic goethite and feroxyhite decrease with time of exposure. Lepidochrosite is detected and its intensity increase with the atmospheric exposure time. The results obtained from XRD and Mossbauer are in good agreement.

Abiotic versus biotic iron mineral transformation studied by a miniaturized backscattering Mössbauer spectrometer (MIMOS II), X-ray diffraction and R…

2017

Abstract Searching for biomarkers or signatures of microbial transformations of minerals is a critical aspect for determining how life evolved on Earth, and whether or not life may have existed in other planets, including Mars. In order to solve such questions, several missions to Mars have sought to determine the geochemistry and mineralogy on the Martian surface. This research includes the two miniaturized Mossbauer spectrometers (MIMOS II) on board the Mars Exploration Rovers Spirit and Opportunity, which have detected a variety of iron minerals on Mars, including magnetite (Fe2+Fe3+2O4) and goethite (α-FeO(OH)). On Earth, both minerals can derive from microbiological activity (e.g. thro…

Characterisation of the magnetic iron phases in Clovis Class rocks in Gusev crater from the MER Spirit Mössbauer spectrometer

2007

Abstract Mossbauer backscattering spectra of eight Martian rocks, acquired by the MIMOS II spectrometer of Rover Spirit (MER-A) and containing goethite in addition to other iron minerals, have been selected for in-depth numerical analysis. Where feasible, different temperature windows for a given rock were considered. A novel calibration/folding procedure, exclusively based on the fitted positions of the eight prominent absorption lines in the transmission spectra of the reference target and not relying on the error signal of the MIMOS II spectrometer, has been developed. It is demonstrated that this procedure yields reliable and reasonably accurate values for the adjusted Mossbauer paramet…

A119Sn Mössbauer spectroscopic study on complexes of di-and tri-organotin(IV) moieties with 2-mercaptoethanesulfonates, in the solid state and in aqu…

1988

The configuration of the bonding environment of tin in the complexes [R2Sn(SCH2CH2SO3)2]2− (R = Me, Ph) and [Me3Sn(SCH2CH2SO3)]− has been determined to be tetrahedral both in the solid state and in aqueous solution (for the methyl derivatives). The coordination number of tin increases to five in aqueous solutions for the Me2Sn(IV) complexes in Hepes buffer (N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid; at least in fivefold excess, at pH 7.4) due to coordination by the tertiary amino nitrogen atom. No effect is detected due to the surfactant 2-hydroxypropylcellulose concerning both coordination to tin and influence on the Mossbauer parameters. The stoichiometry of mixed complex format…