Spectroscopic studies, blue

A spectroscopic study of Claus blue, with comparisons to the much better characterized (180) ion [Rh2(0H)2(H20)n(/u,-02)]3+, was thus undertaken (181). By the use of UV-vis, ESR, and IR/Raman spectroscopies, as well as magnetic susceptibility measurements and voltamme-tric studies, it was determined that Claus blue solutions actually contain superoxo-dirhodium complexes, and not RhO2- ions. The su-peroxo bridge does not, however, derive from dioxygen, but from oxidation of coordinated hydroxide. Finally, Claus blue solutions were demonstrated to be good starting materials for the preparation of superoxo-dirhodium carboxylate complexes, which could be isolated and characterized. 

Spectroscopic studies on blue electron-transfer proteins 651... 

Chem. 29 (1967), pp. 1637-1642. Spectroscopic studies of die reaction of hexa-cyanoferrate(III) in water and ethanol. 3.3x 10 4 M Fe(NC>3)3 were exposed with a cyanide excess of likewise 3.3x10 mol l"1. With pH values of approximately 10, all the Fe2[Fe(CN)6] was converted into Iron Blue within 48 hours. Cyanate, die anticipated product of die oxidation of die CN-, could not, however, be proven. Perhaps this is further oxidized directly into C02. If this mechanism is assumed, die result, purely stoichiometrically, is that an alkaline environment must be favorable. This finding is supported by die known fact that hexacyan-oferrate(III) is a strong oxidation agent in alkaline medium and is even able to oxidize divalent chrome to hexavalent, therefore, that is, CN ions must have oxidized very quickly J.C. Bailar, Comprehensive Inorganic Chemistry, Vol. 3, Pergamon Press, Oxford 1973, p. 1047. An overly alkaline environment would, however, disturb die complexing of the Fe3+- ion by cyanide, which is then displaced by OH- (Fe(OH)3 then occurs as a by-product) and/or the latter can hardly be displaced from die iron. 

Hofmeister, A. M. Rossman, G. R. (1986) A spectroscopic study of blue radiation coloring in plagioclase. Amer. Mineral, 71,95-8. 

Although blues prepared from unsubstituted uracil, thymine and related bases (e.g., 6-methyluracil, 5,6-dihydrouracil etc.) were the first to be prepared and tested, their composition is the least clear. The author suspects that there is still long way to go to fully understand the nature of these blues . It is possible that there are even blues built on different principles. A main obstacle to the elucidation of Pt blues derived from the unsubstituted pyrimidine nucleobases lies in their versatility as ligands. Not only is there the possibility that these ligands bind to metal ions, specifically Pt, via N(l) or N(3) or (only with uracil) C(5), but also many possible combinations of two or more binding sites, e.g., N(l),0(2) N(3),0(2) N(3),0(4) N(1),N(3) N(3),0(2),0(4) N(1),0(2),N(3),0(4) etc. (Scheme 6). A series of these binding patterns has been established by X-ray crystal-structure analyses [68-70], and others are likely on the basis of spectroscopic studies [71] [72] or from comparison with results obtained for N(l) substituted derivatives. The possibility of different tautomers of platinated forms being... 

Spectroscopic studies of Co (II) derivatives of stellacyanin, plastocyanin, and azurin have established that the charge transfer interpretation is preferred (10, 11). Intense bands (c 2 X 103) that appear to be analogous to the 600-nm system of blue proteins are observed between 300 and 350 nm in the Co (II) derivatives. The shift in band position of about 16 kK [Cu(II) << Co (II)] accords well with expectation for an LMCT transition. The visible and near-infrared absorption, CD, and MCD spectra of Co (II) derivatives of stellacyanin, plastocyanin, and azurin have been interpreted (12) successfully in terms of the d-d transitions expected for distorted tetrahedral metal centers (Table I). Average ligand field parameters are the same for all three Co (II) proteins (Dq = 490, B = 730 cm"1), which strongly suggests that the donor atom... 

A. The Diamagnetic Copper(I) State Spectroscopic Studies and Solution Structures of Blue Copper Proteins... 

Most interestingly, upon irradiation with UV light all members of this class of pale yellow to yellow absorbing spirocycles display a pronounced and intense blue over green to yeUow orange fluorescence with large Stokes shifts in solution (4,300-9,600 cm ) and in the solid state. UVA is and emission spectroscopic studies reveal that both absorption and emission properties are strongly affected by minute substituent variations or conformational biases. 

Additional information has been obtained from single crystal, polarized optical and ESR spectroscopic studies " on poplar plastocyanin, which have allowed a correlation of the electronic structure of the blue copper active site with its geometric structure. In summary, the three dominant absorption bands at 13 350, 16 490 and 17 870 cm were assigned to CysS Cu (d -y charge-transfer transitions. The methionine makes only a small contribution, due to the long Cu—S(Met) bond (2.9 A) and the poor overlap of the methionine sulfur orbitals with the d y orbital of copper. Histidine-Cu charge transfer contributes to the weaker absorptions at 21 390 and... 

Binding of a paramagnetic, redox-inactive [Cr(CN)6]3- anion to specific sites of a blue copper protein, amicyanin, has been used in NMR-spectroscopic studies of the protein structure in solutions.285Ab initio calculations of the ligand-field spectra of [Cr(CN)6]3 have been performed and the results compared with those for cyano complexes of the other first-row transition metals.286 The role of Cr—C—N bending vibrations in the phosphorescence spectra... 

Giustetto, R., Llabres i Xamena, RX., Ricchiardi, G., Bordiga, S., Damin, A., Gobetto, R., and Chierotti, M.R. 2005. Maya blue A computational and spectroscopic study. Journal of Physical Chemistry B 109, 19360-19368. 

Giustetto, Roberto, Llabres I Xamena Francesc X., Ricchiardi Gabriele, Bordiga Silvia, Damin Alessandro, Gobetto Roberto, and Chierotti Michele R. 2005. Maya blue a computational and spectroscopic study. Journal of Physical Chemistry. B, Condensed Matter, Materials, Surfaces, Interfaces, Biophysical Chemistry 109 19360-19368. 

The precipitates of Prussian blue analog cyanides always contain variable amounts of water, which can be removed without significant effects on the X-ray diffraction pattern. Some of these water molecules can be replaced by other molecules such as ammonia or alcohol 37). It was therefore assumed that the water is present partly as zeolitic, partly as surface water 3). Recent infrared spectroscopic studies, however, reveal that, in addition, coordinated water molecules are also present 33, 38). 

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