Search results for "MOSSBAUER"

Mineralogy at Gusev Crater from the Mössbauer spectrometer on the Spirit Rover.

2004

Mössbauer spectra measured on Mars by the Spirit rover during the primary mission are characterized by two ferrous iron doublets (olivine and probably pyroxene) and a ferric iron doublet (tentatively associated to nanophase ferric iron oxide). Two sextets resulting from nonstoichiometric magnetite are also present, except for a coating on the rock Mazatzal, where a hematite-like sextet is present. Greater proportions of ferric-bearing phases are associated with undisturbed soils and rock surfaces as compared to fresh rock surfaces exposed by grinding. The ubiquitous presence of olivine in soil suggests that physical rather than chemical weathering processes currently dominate at Gusev crat…

Structure and physical properties of [mu-tris(1,4-bis(tetrazol-1-yl)butane-N4,N4 ')iron(II)] bis(hexafluorophosphate), a new Fe(II) spin-crossover co…

2004

[mu-Tris(1,4-bis(tetrazol-1-yl)butane-N4,N4')iron(II)] bis(hexafluorophosphate), [Fe(btzb)(3)](PF6)(2), crystallizes in a three-dimensional 3-fold interlocked structure featuring a sharp two-step spin-crossover behavior. The spin conversion takes place between 164 and 182 K showing a discontinuity at about T-1/2 = 174 K and a hysteresis of about 4 K between T-1/2 and the low-spin state. The spin transition has been independently followed by magnetic susceptibility measurements, Fe-57-Mossbauer spectroscopy, and variable temperature far and midrange FIR spectroscopy. The title compound crystallizes in the trigonal space group P (3) over bar (No. 147) with a unit cell content of one formula u…

Application of 61Ni Mössbauer spectroscopy to chemical problems

1996

Using the possibility to produce 61Co sources at the MAinz MIcrotron, 61Ni Mossbauer spectroscopy was applied to different kinds of chemical problems. Measurements of isomer shifts and V zz values in some common compounds and compounds with unusual chemical bonding for comparison with band structure calculations, measurement of 61Ni Mossbauer parameters in model compounds for hydrogenase and dehydrogenase with an active [NiS4] centre, and study of novel binary NiF3 compounds at helium temperature are presented.

Complexes of diorganotin(IV) dihalides with diphosphoryl compounds and their Mössbauer spectra

1993

Synthese und Strukturen neuer Eisen-Sauerstoff-Alkoxid-Cluster

2004

Der Eisen-Sauerstoff-Alkoxy-Cluster [Fe9O3(OC2H5)21]·C2H5OH kann unter unterschiedlichen Bedingungen zu Molekulen umgesetzt werden, denen alle die allgemeine Formel [Fe5O(OR)8(OR′)5] gemeinsam ist. Erwarmt man [Fe9O3(OC2H5)21]·C2H5OH in Toluol, so entsteht [Fe5O(OC2H5)13], das durch Kristallisation abgetrennt werden kann, wohingegen ein Auflosen von [Fe9O3(OC2H5)21]·C2H5OH in tert-Butylamin zum 1 : 2-Addukt [Fe5O(OC2H5)13]·2 t-Bu-NH2 fuhrt. Mit Triethyl- oder Triphenylsilanol entsteht aus [Fe9O3(OC2H5)21]·C2H5OH wieder ein Sauerstoff-Eisencluster des gleichen Motivs: [Fe5O(OC2H5)8{OSi(C2H5)3}5] bzw. [Fe5O(OC2H5)8{OSi(C6H5)3}5]. Die Molekulstruktur [Fe5O(OC2H5)8{OSi(C2H5)3}5], die uber Rontg…

A heptanuclear Fe(II)–Fe(III)6 system with twelve unpaired electrons

2000

Abstract The pentadentate ligand 5 LH2 = saldptn = N,N′-bis(1-hydroxy-2-benzyliden)-1,7-diamino-4-azaheptane has been prepared by a Schiff base condensation between 1,7-diamino-4-azaheptane and the corresponding salicyaldehyde. Its complexation with Fe(III) gave the high-spin (S=5/2) complex of [Fe III ( 5 L)Cl]. This precursor was combined with [Fe(CN)6]4− and a blue heptanuclear complex [FeII{(CN)Fe III ( 5 L)}6]Cl2 resulted. This system belongs to the class of high-spin molecules possessing twelve unpaired electrons (S=6) as proven by the magnetic susceptibility measurements and Mossbauer spectra.

A PAS domain with an oxygen labile [4Fe-4S](2+) cluster in the oxygen sensor kinase NreB of Staphylococcus carnosus.

2008

The cytoplasmic histidine sensor kinase NreB of Staphylococcus carnosus responds to O(2) and controls together with the response regulator NreC the expression of genes of nitrate/nitrite respiration. nreBC homologous genes were found in Staphylococcus strains and Bacillus clausii, and a modified form was found in some Lactobacillus strains. NreB contains a sensory domain with similarity to heme B binding PAS domains. Anaerobically prepared NreB of S. carnosus exhibited a (diamagnetic) [4Fe-4S](2+) cluster when assessed by Mossbauer spectroscopy. Upon reaction with air, the cluster was degraded with a half-life of approximately 2.5 min. No significant amounts of Mossbauer or EPR detectable i…

Structural investigations on diorganotin and triorganotin(IV) phosphomycin derivatives.

2008

Abstract Four new diorganotin(IV), (R = Me, Bu), and triorganotin(IV), (R = Me, Ph), derivatives of the phosphomycin disodium salt antibiotic[(1R,2S)-1,2-epoxypropylphosphonate]Na2 have been synthesized and their solid state configuration studied by X-ray crystallography, FT-IR, Mossbauer, UV–Vis spectroscopies. The X-ray diffraction investigation, performed on the bis[trimethyltin(IV)]phosphomycin, showed that the coordination geometry at all the Sn atoms is trigonal bipyramidal. The structure of the complex forms an unusual polymeric zig-zag planar network. The FT-IR and the 119Sn Mossbauer studies supported the formation of trigonal bipyramidal (Tbp) molecular structures, both in the dio…

Hexanuclear iron(III) salicylaldoximato complexes presenting the [Fe6(mu3-O)2(mu2-OR)2]12+ core: syntheses, crystal structures, and spectroscopic and…

2006

The use of salicylaldehyde oxime (H2salox) in iron(III) carboxylate chemistry has yielded two new hexanuclear compounds [Fe6(mu3-O)2(O2CPh)10(salox)2(L)2].xMeCN.yH2O [L = MeCONH2, x = 6, y = 0 (1); L = H2O, x = 2, y = 3 (2)]. Compound 1 crystallizes in the triclinic space group P with (at 25 degrees C) a = 13.210(8) A, b = 13.87(1) A, c = 17.04(1) A, alpha = 105.79(2) degrees , beta = 96.72(2) degrees , gamma = 116.69(2) degrees , V = 2578.17(2) A(3), and Z = 1. Compound 2 crystallizes in the monoclinic space group C2/c with (at 25 degrees C) a = 21.81(1) A, b = 17.93(1) A, c = 27.72(1) A, beta = 111.70(2) degrees , V = 10070(10) A(3), and Z = 4. Complexes 1 and 2 contain the [Fe6(mu3-O)2(m…

The interaction of Fe(III), adriamycin and daunomycin with nucleotides and DNA and their effects on cell growth of fibroblasts (NIH-3T3)

1996

The interactions of the iron complexes of the anthracycline antitumour drugs daunomycin (DN) and adriamycin (ADM) with the mononucleotide AMP, herring sperm DNA, plasmic pBR322 and immortalized 3T3 fibroblasts were studied. By means of Mössbauer spectroscopy it was demonstrated that DNA is a powerful ferric iron chelator as compared with AMP, which is not able to compete with DN or acetohydroxamic acid for ferric iron. The difference between AMP and DNA is postulated to be based on the chelate effect. The Mössbauer spectra of the ternary Fe-anthracycline-DNA systems differ from Fe-anthracycline binary complexes, indicating rearrangement reactions. Dialysis experiments clearly disclose the f…