Visible spectra data

Visible Spectra Data for Acid Phosphatases and Model Complexes... 

Titration in a mixture with resolution of difference UV-visible spectra Data analysis for up to nine components with TITAN program Bjerrum plots for determinationn of systematic cone, errors Evaluation of digital potentiometric titns. by the Tubbs method... 

Brown and Lin reported a quantitative method for methanol based on its effect on the visible spectrum of methylene blue. In the absence of methanol, the visible spectrum for methylene blue shows two prominent absorption bands centered at approximately 610 nm and 660 nm, corresponding to the monomer and dimer, respectively. In the presence of methanol, the intensity of the dimer s absorption band decreases, and that of the monomer increases. For concentrations of methanol between 0 and 30% v/v, the ratio of the absorbance at 663 nm, Asss, to that at 610 nm, Asio, is a linear function of the amount of methanol. Using the following standardization data, determine the %v/v methanol in a sample for which Agio is 0.75 and Ag63 is 1.07. 

Photomultipliers are used as detectors in the single-channel instruments. GaAs cathode tubes give a flat frequency response over the visible spectrum to 800 nm in the near IR. Contemporary Raman spectrometers use computers for instrument control, and data collection and storage, and permit versatile displays. 

The addition of sulfite to APS reductase results in changes of the flavin visible spectrum that are explained by the formation of an adduct between the sulfite and the FAD group (135). Addition of AMP to the as-isolated enzyme causes no change in the spectroscopic properties. Addition of AMP to the sulfite-reacted enzyme causes the reduction of center I. However, the formation of a semiquinone signal has never been observed either by EPR or visible spectroscopies. Also, Mossbauer and EPR data indicate that AMP closely interacts with center I (139). 

The most recent report of -coordination to a ruthenium porphyrin fragment details the reaction of [Ru(OEP)j2 with C o in benzene/THF (100 1) solution. The UV-visible spectrum of the complex showed a new band at 780 nm, not observed in the spectrum of either Ru(OEP) 2 or C(,o, and H and C NMR data also indicated the presence of a new complex. This has been formulated on the basis of the spectroscopic data as the fullerene complex Ru(OEP)(... 

UV/visible spectroscopy of organometallic transients has been extremely important for kinetic measurements on previously identified species, but the spectra are less valuable for structural identification since most spectra show broad and featureless bands. One way round this problem has been to utilise matrix IR spectroscopy for characterisation and to use the data obtained from the matrix UV/visible spectrum to monitor the room-temperature kinetics. A more satisfactory method is to record the IR spectra of transients directly and there has been much activity in both gas phase and solution organometallic chemistry this field has been recently reviewed ( 35). In our laboratory,... 

It must be sensitive at least over the spectral range 400-600 nm, and ideally over the complete range of the visible spectrum (i.e., 380-750 nm) and even over the UV and IR regions. When its sensitivity varies with wavelength, as is usually the case, it must be possible to correct the data in this respect. 

Spectroscopy has not proven to be very conclusive in solving this problem. Similarities between the visible spectrum of the calcined catalyst and that of bulk dichromates have been noted (5,12-14). In the end, however, there is always doubt about the interpretation of spectra because no adequate reference data exist for these surface bound species (76). Krauss and coworkers have carefully studied the luminescence of Cr/silica and concluded that at least a portion of the chromium is present as chromate (75). 

The available evidence supports the demethylation scheme and the identity of the initial red product as that of the basic tautomer of trimethylthionine (Azure B), as shown in eqs. 33 and 34. Addition of acid or other weak proton donor protonates the red dye to give the blue form. We have reexamined the reaction of MB or New methylene blue (NMB) in dry acetonitrile with tri-ethylamine (TEA). We have also found that a comparable reaction of NMB occurs with trimethylbenzylstannane (TMBS). Figure 8 shows changes in the visible spectrum of NMB which occur in addition of TEA. Table 12 lists quantitative data. The spectra... 

The He(l) photoelectron spectrum of trithiadiazepin 5 was assigned by Koopmans correlation with PM3 eigenvalues based on the structural data, and by the 7i-perfluoro effect observed. The 7i-system can be rationalized by heteroatom first-order perturbation, which reduces the cyclic Jt-delocalization. Replacement of the four F substituents by FI affected neither the long-wavelength absorption band in the UV/Vis (Vis = visible) spectrum nor the S1SN shift in the 15N NMR <1997CBR247>. 

Reaction of Cytochrome cIinn with Bis(ferrozine)copper(II) Knowledge of the redox properties of cytochrome c was an encouragement to initiate a kinetics investigation of the reduction of an unusual copper(II) complex species by cyt c11. Ferrozine (5,6-bis(4-sulphonatophenyl)-3-(2-pyridyl)-1,2.4-triazine)286 (see Scheme 7.1), a ligand that had come to prominence as a sensitive spectrophotometric probe for the presence of aqua-Fe(II),19c,287 forms a bis complex with Cu(II) that is square pyramidal, with a water molecule in a fifth axial position, whereas the bis-ferrozine complex of Cu(I) is tetrahedral.286 These geometries are based primarily upon analysis of the UV/visible spectrum. Both complexes are anionic, as for the tris-oxalato complex of cobalt in reaction with cytochrome c (Section 7.3.3.4), the expectation is that the two partners will bind sufficiently strongly in the precursor complex to allow separation of the precursor formation constant from the electron transfer rate constant, from the empirical kinetic data. 

Landt and Witte,29 using data collected by Brodowski30 for samples of molasses, pointed out that a plot of log a against log X gives a reasonably straight line over the visible spectrum. 

Lovenberg, Buchanan, and Rabinowitz (65) tested the response of ferredoxin to mercury compounds. Two mercurial reagents used, p-mer-curibenzoate (PCMB) and o-((3-hydroxymercuri-2-methoxypropyl)car-bamyl)phenoxyacetate (sodium mersalyl) reacted rapidly with ferredoxin and caused a bleaching of the visible spectrum and a concomitant loss of biological activity. C. pasteurianum ferredoxin was titrated with PCMB as described by Boyer (24) and the results showed that 20 moles of PCMB reacted with 1 mole of ferredoxin. In another determination, 2 moles of PCMB reacted with 1 mole of sodium sulfide. Since ferredoxin contained 7 moles of inorganic sulfide and 8 moles of half-cystine residues, 22 (7 x 2 = 14 14 + 8 = 22) moles of PCMB would be expected to react with 1 mole of ferredoxin. These data, summarized in Table 8, are consistent with the existence of two types of sulfur in ferredoxin. This conclusion was supported by the presence of half-cystine residues in ferredoxin after inorganic sulfide had been removed by acid hydrolysis, as well as results of sulfur analyses, which showed an amount of sulfur greater than could be attributed to half-cystine residues. 

The nature of the coordinated dioxygen within the Ru porphyrins remains uncertain. Some data (lack of an ESR signal, visible spectrum) support a Ru(III)—02 formulation, while the other data (comparison of visible spectral data with the corresponding carbonyl, binding constant for 02, and binding of ethylene) imply a Ru(IV)—022- formulation (8, 135). We have reconstituted apomyoglobin with Ru porphyrins, and characterized in solution the Ru(II) species RuMb and the oxidized met-form RuMb+ (142) as well as the carbonyl RuMb(CO), which has been reported previously (143). Unlike myoglobin itself, RuMb is hexacoordinate and low-spin treatment with 02 leads to the met-form via an outer-sphere oxidation (cf. Reaction 35). Our hopes of... 

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