Sulfate spectroscopic studies

De Mendoza reported the first example of anion-directed helix formation in 1996 [91]. The assembly of this helical structure relies, not only on electrostatic interactions between the anionic template and the positively charged strands, but also on hydrogen bonding. The tetraguanidinium strand 69 (see Scheme 34) self-assembles around a sulfate anion via hydrogen bonding to produce a double helical structure. The formation of this assembly and its anion-dependence was proposed on the basis of NMR and CD spectroscopic studies. 

Persson, P. Lovgren, L. (1996) Potentiometric and spectroscopic studies of sulfate com-plexation at the goethite-water interface. Geo-chim. Cosmochim. Acta 60 2789-2799... 

Cation exchange, solvent extraction and Raman spectroscopic studies of highly acidic zirconium sulfate solutions suggest that these solutions contain a mixture of solution species having from one to four sulfate ligands per Zr atom.153,351 The sulfato-zirconium complexes appear to be somewhat more stable than the analogous hafnium complexes.351... 

Davydov, A. A., Kantcheva, M. and Chepotko, M. L. FTIR spectroscopic study on nickel(II)-exchanged sulfated alumina nature of the active sites in the catalytic oligomerization of ethene. Catal. Lett., 2002, 83, 97-108. 

Recent Laser Raman spectroscopic studies of sulfated zirconia indicate a monodentate structure (162). 

Sipos, R et al. Raman spectroscopic study of ion-pairing of alkali metal ions with carbonate and sulfate in aqueous solutions Aust. 7. Chem. 2000, 53, 887-890. 

Many of the important chemical reactions controlling arsenic partitioning between solid and liquid phases in aquifers occur at particle-water interfaces. Several spectroscopic methods exist to monitor the electronic, vibrational, and other properties of atoms or molecules localized in the interfacial region. These methods provide information on valence, local coordination, protonation, and other properties that is difficult to obtain by other means. This chapter synthesizes recent infrared, x-ray photoelectron, and x-ray absorption spectroscopic studies of arsenic speciation in natural and synthetic solid phases. The local coordination of arsenic in sulfide minerals, in arsenate and arsenite precipitates, in secondary sulfates and carbonates, adsorbed on iron, manganese, and aluminium hydrous oxides, and adsorbed on aluminosilicate clay minerals is summarized. The chapter concludes with a discussion of the implications of these studies (conducted primarily in model systems) for arsenic speciation in aquifer sediments. 

Elzinga, E.J., Peak, D., and Sparks, D.L., Spectroscopic studies of Pb(II)-sulfate interactions at the goethite-water interface, Geochim. Cosmochim. Acta, 65, 2219, 2001. 

The in situ vibrational spectroscopic studies have confirmed coadsorption of sulfate and bisulfate ions on polycrystalline Pt and the following adsorption structures were suggested for the different potential regions. 

Lloyd and Porter have conducted extensive mass spectroscopic studies of several cyclic sulfites and cyclic sulfates of 1,2-diols, 1,3-diols, and 1,4-diols. One important fragment of a cyclic sulfite of a 1,2-diol is extruded SO2 (77AJC569) (Scheme 2). 

The adsorption kinetics of a mixture of surfactants (sodium dodecyl sulfate and sodium laurate) onto a vacuum-deposited AI2O3 film and diphenylchlorosi-lane [322] and phthalocyanines [323] on chemically deposited silicon oxide on silicon was also studied [324], Coated ATR was also effective in the IR spectroscopic studies of adsorption on polymers (Section 7.7). 

Philipp B., Nehls 1., Wagenknecht W, Schnabelrauch M., Carbon- NMR spectroscopic study of the homogeneous sulfation of cellulose and xylan in the dinitrogen tetroxide-DMF system, Carbohyd. Res., 164, 1987, 107-116. 

F. Babou, G. Coudurier,J.C. Vedrine, Acidic properties of sulfated zirconia an infrared spectroscopic study, J. Catal. 152 (1995) 341—349. 

The FTIR spectroscopic studies were made on anions (chromates, phosphates, arsenates, sulfates, and nitrates) sorbed from their aqueous solutions on natural clinoptilolite [llMl]. Systematic changes in the spectra coimected with the anion concentration in the initial solution have been revealed. 

Frejd and coworkers then used lactam 45 as a structural H-Phe-Phe-OH mimic in peptides (116). The resulting conjugate 48 was expected to function as a structural mimic of substance P (Scheme 5.25). However, CD spectroscopic studies indicated that the constraints imposed by the l,l -ferrocenophane prohibited the peptide to adopt the characteristic a-hehcal secondary structure found for native SP in a biomimetic SDS (Sodium n-Dodecyl Sulfate) micellar environment. In another interesting paper, Frejd and coworkers prepared a [Leu ]-Enkephalin mimetic in which the H-Tyr-Gly-Gly-Phe-subunit has been replaced by a Gly-Gly-looped l,l -ferrocenyl-bis-alanine residue (49, Scheme 5.25) [117]. The ferrocene Cp rings of this constrained compound constitute a substitute for the aromatic phenol (Tyr) and phenyl (Phe) rings. NMR-spectroscopic studies revealed this... 

Gopalakrishnan S, Jungwirth P, Tobias DJ, Allen HC (2005) Air-liquid interfaces of aqueous solutions containing ammonium and sulfate spectroscopic and molecular dynamics studies. J Phys Chem 109 8861-8872... 

Sulfate anion solutions have been less abundantly studied under conditions of HTP in contrast to the great number of Raman spectroscopic studies reported at ambient or moderately high temperatures (see Sec. I). This is rather surprising because of the great im-... 

Both titania (anatase more than rutile) and, even more, zirconia (tetragonal more than monoclinic), when sulfated or covered with tungsten oxide become very active for some hydrocarbon conversion reactions such as -butane skeletal isomerization [263]. For this reason, a discussion began on whether these materials have to be considered superacidic. Spectroscopic studies showed that the sulfate ions [264] as well as the tungstate ions [265,266] on ionic oxides in dry conditions, are tetracoordinated with one short S=0 and W=0 bond (mono-oxo structure) as shown in Scheme 9.3(11). Polymeric forms of tungstate species could also be present [267]. However, in the presence of water the situation changes very much. According to the Lewis acidity of wolframyl species, it is believed that it can react with water and be converted in a hydrated form, as shown in Scheme 9.3. Residual... 

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