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Blue species

Yoshimura et al. [193] carried out microdeterminations of phosphate by gel-phase colorimetry with molybdenum blue. In this method phosphate reacted with molybdate in acidic conditions to produce 12-phosphomolybdate. The blue species of phosphomolybdate were reduced by ascorbic acid in the presence of antimonyl ions and adsorbed on to Sephadex G-25 gel beads. Attenuation at 836 and 416 nm (adsorption maximum and minimum wavelengths) was measured, and the difference was used to determine trace levels of phosphate. The effect of nitrate, sulfate, silicic acid, arsenate, aluminium, titanium, iron, manganese, copper, and humic acid on the determination were examined. [Pg.100]

As mentioned above, the Pt(2.25+)4 species (B1 and B2) possesses one unpaired electron of Pt(III) (S = 1/2) and is the only species which exhibits paramagnetism among the four oxidation states. The ESR spectrum of the ce-pyridonate-blue species shown in Fig. 7 exhibits an axial signal characteristic of the platinum-blues (g = —2.4 and g = —2.0) (48, 49, 70, 96). Similar signal patterns are also observed for several other blue compounds (34, 47, 57, 86, 88, 89), and these common features show that the unpaired electron resides on the dz2 orbital located along the Pt chain. The g values observed for the para-... [Pg.388]

An intense purple-blue species forms within a few seconds when Cr +, in excess, is added to 4,4 -bipyridinium ion, bpyH. The color fades slowly over many minutes. The formation and disappearance of the intermediate, kf and respectively, are assigned to k2 and Atj respectively from considerations of the assessed spectrum of the intermediate. The reactions involved are... [Pg.21]

Methods of preparation of the Fe nitroprussides, Fe2 Fe(CN)5NO 3,-9H2O and Fe Fe(CN)5NO Cl,0.5H2O have been described.Examination of the physical and chemical properties of [Fe(CN)5NO] shows the anion to formally contain Fe " and should be formulated as Fe —NO not Fe " — + ggj3 suggested that a blue species, formed when nitro-... [Pg.213]

Blue copper proteins, 36 323, 377-378, see also Azurin Plastocyanin active site protonations, 36 396-398 charge, 36 398-401 classification, 36 378-379 comparison with rubredoxin, 36 404 coordinated amino acid spacing, 36 399 cucumber basic protein, 36 390 electron transfer routes, 36 403-404 electron transport, 36 378 EXAFS studies, 36 390-391 functional role, 36 382-383 occurrence, 36 379-382 properties, 36 380 pseudoazurin, 36 389-390 reduction potentials, 36 393-396 self-exchange rate constants, 36 401-403 UV-VIS spectra, 36 391-393 Blue species... [Pg.28]

IVCT). The second e value corresponds to the abundance of 28 Mo centers (see Ref. 5). Using an excitation line within the contour of the 1070-nm band gives rise to a resonance-Raman spectrum showing hve bands in the region between 900 and 200 cm very characteristic for all molybdenum blue species [802 (s), 535 (m), 462 (s), 326 (s), 215 (s) cm ]. [Pg.199]

Sulfur forms a series of homoatomic dianions catena-S (x = 2-8), which, without exception, have unbranched chain structures in the solid state.The electrochemical reduction of cyclo-Sg in aprotic solvents occurs via an initial two-electron process to produce catenaS P In solution, catena- and other long-chain polysulfides, e.g. catena- and catenaSi, dissociate via an entropy-driven process to give radical anions S (x = 2-4), including the ubiquitous trisulfur radical anion (x = 3). This intensely blue species is the chromophore in the mineral lapis lazuli, which is used in the manufacture of jewellery. [Pg.295]

Reduction of ZrIV in ZrX4-Al2X6 (X = Cl, Br or I) melts, with either zirconium or aluminum metal, yields soluble blue species. These species were not isolated, but they have been formulated as Zr(X2AlX2)3 complexes on the basis of their electronic spectra. Absorption bands at 17 400 (X = C1), 16 000 (X = Br) and 14 000 cm-1 (X = I) may be assigned to the 2t -2es transition of Zr111 in an octahedral environment of halide ions. The solid zirconium(III) halides exhibit ligand-field bands at closely similar frequencies.32... [Pg.370]

The action of H202 on acidic dichromate solutions gives an unstable blue species which can be extracted into ether (equation 128).2,518,1428 On the addition of pyridine the blue compound Crvl0(02)2py crystallizes. The molecules are distorted pentagonal pyramids with sideways-bonded peroxo groups (298) 1429 some workers with less refined data have reported rather different bond distances.1430 In water the blue species is considered to be CrO(62)2(OH2), in ether it is Cr0(02)20Et2, and amines such as aniline, bipy and phen can replace the pyridine. With bidentate bipy the coordination sphere becomes essentially a pentagonal bipyramid (299),... [Pg.945]

SiMouO ]4-.134 The structure of the heteropoly blue species (four-electron-reduced PM012O40]3-) formed in the molybdenum blue determination of phosphorus has been reported135 and a review of molybdate heteropoly blues has appeared.130 A stability index of polyanion structures has been discussed.137 The presence of two PMo, anions in aqueous solutions of molybdate and phosphate has been demonstrated by 31P NMR.138 Solid state NMR (nonspinning and MAS techniques) has been used for characterization of heteropolyanions.139 Molybdenum-95 NMR spectra of some polymolybdates have been reported.140... [Pg.1055]

In Eq. (34) the configuration may be either cis or trans and X can be, for example, OH, Cl", F, SCN", or -NH2CH2CH2NH3+ (cf. Table XV). The blue species are unstable, and one cis ammonia ligand in the basic rhodo ion and the X groups in the basic erythro ions are hydrolyzed rapidly in the basic solutions. The Ka values have therefore been determined by a rapid-flow technique in combination with potentio-metric or spectrophotometric measurements (24). [Pg.107]

Although agreement among workers in the field is not complete, it now appears that the predominant species in concentrated solution is the solvated Na2 molecule with the two 3a electrons delocalized over a number of surrounding solvent molecules, but still paired. The blue species is probably an ammoniated electron—that is, the electride ion. ... [Pg.102]

The blue species, which is one of the products at room temperature,... [Pg.754]

These are dark blue species obtained by reduction of both isopoly- and heteropoly molybdates and tungstates, and thus the class is broader than the name implies. It appears that in general, these reductions are reversible and major structural features are retained. In the case of the [M6Oi9]2 ions, reduction by one electron gives a 3-ion in which the added electron is weakly trapped at one metal atom but is thermally mobile. [Pg.932]

The Dawson [X2Mo18062]6 ions can also be reversibly reduced to blue species. In general, the question of how delocalized the added electrons are in all these blue species remains open to further investigation. [Pg.933]

Of interest in view of the antitumor properties of cw-PtCl2(NH3)2 (see below) are the cations such as ciy-[Pt(NH3)2(H20)2]2+. Exposure of phosphate containing solutions to air gives blue species that may be related to the platinum blues discussed later. There are also well-established amine complexes such as [M(am)4]2+ and [M(en)2]2+. [Pg.1070]

As expected from simple MO considerations, the radical cations of five-membered heterocycles, e.g. the blue species formed from furan, pyrrole, thiophene, and their alkyl derivatives, are n ions. The semi-occupied orbital is the n orbital with the heteroatom in the nodal plane (ai), see Scheme 2, structure 1. In radical cations of a,ca-bis-(l-pyrrolyl) alkanes the charge remains localized on a single ring, rather than being delocalized over both units [5, 10, 11]. [Pg.1004]


See other pages where Blue species is mentioned: [Pg.1436]    [Pg.70]    [Pg.71]    [Pg.547]    [Pg.389]    [Pg.393]    [Pg.218]    [Pg.30]    [Pg.487]    [Pg.171]    [Pg.190]    [Pg.628]    [Pg.198]    [Pg.628]    [Pg.1050]    [Pg.959]    [Pg.847]    [Pg.428]    [Pg.100]    [Pg.32]    [Pg.49]    [Pg.185]    [Pg.29]    [Pg.583]    [Pg.92]    [Pg.4079]    [Pg.52]    [Pg.72]    [Pg.959]    [Pg.309]    [Pg.95]   


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Blue species dinuclear

Blue species equilibria

Blue species oxidation

Heteropolymolybdate Blue Species

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