Infrared spectral studies

Although cytosine was assigned structure 109 on the basis of early infrared spectral studies,and other infrared and ultraviolet spectral... 

Infrared spectral studies of polymeric sulfur are scarce and mainly the overtone region was studied [142, 180]. In the range of the stretching vibrations, two bands at ca. 460 cm (strong) and ca. 423 cm (medium) were reported for Crystex after extraction of the soluble ring fraction by CS2 [180]. The results of the literature are summarized in Table 12. 

Several ESR studies of various cobalt(II) isocyanide complexes have been carried out (77,81,88). A Raman and infrared spectral study on [Co(CNR)5]-... 

Iron(III) complexes of 2-acetylpyridine Af-oxide iV-methyl- and 3-azabicyclo[3.2.2.]nonylthiosemicarbazone, 24 and 25, respectively, have been isolated from both iron(III) perchlorate and chloride [117], The perchlorate salt yields low spin, octahedral, monovalent, cationic complexes involving two deprotonated, tridentate thiosemicarbazone ligands coordinated via the N-oxide oxygen, azomethine nitrogen and thiol sulfur based on infrared spectral studies. Their powder ESR g-values are included in Table 1 and indicate that bonding is less covalent than for the analogous thiosemicarbazones prepared from 2-acetylpyridine, 3a and 4. Starting with iron (III) chloride, compounds with the same cations, but with tetrachloroferrate(III) anions, were isolated. 

Ethanol-dimethoxypropane solutions of either 1-formylisoquinoline or 2-formylquinoline thiosemicarbazone and cobalt(II) salts yield [Co(L)A2] complexes where A = Cl, Br, I, NO3, NCS, or NCSe [147]. All are non-electrolytes, have magnetic moments of 4.30-4.70 B.M. and are five coordinate with approximate trigonal bipyramidal stereochemistry involving NNS coordination based on electronic and infrared spectra. [Co(21-H)2] 2H2O was isolated from a cold methanolic solution of cobalt(II) chloride and 1-formylisoquinoline thiosemicarbazone [187]. Infrared spectral studies show NNS coordination the electronic spectral bands fit a distorted octahedral symmetry, and the magnetic moment is 4.48 B.M. 

Chemical analysis of the investigated samples has been carried out using standard methods [4]. The combined water content was determined by DTA and Infrared spectral studies in the range of 200 - 4000 cm 1. X - ray diffraction analysis was carried out with Dron - 3 using MoK radiation. 

Zwierzak, A., Cyclic organophosphorus compounds. 1. Synthesis and infrared spectral studies of cyclic hydrogen phosphites and thiophosphites, Can. 

Vibrational spectra, especially infrared spectra, have been obtained for a wide variety of lanthanide complexes. The main conclusions that emerge from infrared spectral studies concern the site of coordination of the ligand, the nature of anion coordination and the relative strength of metal-ligand interactions. 

Infrared spectral studies have shown that cis- and tram-olefins are not isomerized by coordination to, or displacement from, platinum salts 127). ras-4-Methylpent-2-ene forms a more stable complex than do trans-4-methylpent-2-ene or cis-pent-2-ene it is suggested 132) that the electron-donating nature of the methyl group is responsible for the latter result by strengthening the v-component of the metal-olefin bond. 

Infrared spectral studies have been made for a large number of octahedral metal-carbonyl systems of the types LM(CO)5 (L = pyridine and quinoline), L2M(CO)4 [L2 = ethylene diamine, (pyridine)2, and bipyridyl], [LM(CO)4]2 (L = dimethylarsine or dimethylphosphine M = Cr, Mo, and W), and [LFe(CO)3]2 (L = SMe, PMe2) before and after electrochemical reduction. The force constants for the carbonyl groups... 

Hydrogen sulfide reacts with molten sulfur and depresses the viscosity of the latter, particulady at 130-180°C infrared spectral studies show that polysulfanes, 11, S, form. The average chain length of these polysulfanes is shorter than the equilibrium chain length of molten sulfur alone at the same temperature consequently, the viscosity of the molten sulfur is markedly reduced (99,100). 

An exhaustive review of infrared spectral studies of sulfur compounds appeared in 1963.168... 

Infrared spectral studies of pyridine adsorbed on alkali metal ion-exchanged faujasites have demonstrated the absence of Brpnsted acidity, as reported by Eberly (151), Ignat eva et al. (208), and Ward (156, 209-211). Pyridine is adsorbed weakly by coordination to the alkali metal ions (151, 156). Addition of small amounts of water does not result in formation of Br0nsted acid sites, indicating that the coordinate bound pyridine is not associated with Lewis acid sites in the zeolite framework (210). 

Infrared spectral studies of rare earth (RE) ion-exchanged faujasites have been reported by Rabo et al. (214), Christner et al. (217), Ward (211, 212), and Bolton (218). Distinct hydroxyl absorption bands are observed at 3740, 3640, and 3522 cm-1 after calcination at temperatures in the range of 340° to 450°C. As previously discussed, the hydroxyl groups at 3740 cm-1 are attributed to silanol groups either located at lattice termination sites or arising from amorphous silica associated with the structure. The hydroxyl groups that form the 3522 cm-1 band are nonacidic to pyridine or piperidine and are thought to be associated with the rare earth cations. 

Infrared spectral studies on molybdenum hexacarbonyl-alumina were reported by Davie, Whan, and Kemball 78). Without any activation procedure they obtained a sharp carbonyl frequency corresponding to unchanged hexacarbon-yl on the support. This material was not active for disproportionation. After treatment for one hour under vacuum at 373 °K the catalyst had lost the sharp carbonyl band but showed two wider and broader bands and was active for dis-proportionating propylene. The authors stated that the active catalyst clearly had a lower symmetry than the hexacarbonyl and must have lost one or more of the carbonyl groups. After exposure of the activated catalyst to air, the catalyst was inactive and showed no absorption in the carbonyl region. 

D.J. McGarvey, J.R. Stuff, B.R. Williams and H.D. Durst, Vapor-phase infrared spectral study of analogs of the nerve agent sarin, Spectrosc. Lett., 33, 795-819 (2000) Erratum D.J. McGarvey, J.R. Stuff, B.R. Williams and H.D. Durst, Spectrosc. Lett., 34, 253 (2001). 

Indeed the correct structure, shown in Fig. 1, was predicted by Dilthey10 in 1921. It seems that this structure was not considered seriously until the early 1940 s when the infrared spectral studies on diborane(6) by Bell and Longuet-Higgins11 and also by Price12 indicated that the bridge structure was probably correct. This... 

Maeda, A., Sasaki, J., Pfefferle, J. M., Shichida, Y, and Yoshizawa, T. (1991). Fourier transform infrared spectral studies on the Schiff base mode of aW-trans bacteriorhodopsin and its photointermediates, K and L. Photochem. Photobiol. 54, 911-921. 

Infrared spectral studies of a number of these systems have shown that adduct formation is accompanied by a fall in the carbonyl stretching frequency to a value close to that associated with the corresponding metal carbonylate anion (Table XIV). Thus bands assigned to the carbonyl stretching frequencies KCO) in HsSiCo(CO)4 occur between 2105 and 2025 cm in the adduct HsSiCo(CO)4 2NMes there is only one broad strong band at 1882 cm , close to those observed with Co(CO)4 at 1883 and 1861 cm . The adduct is therefore formulated as [HaSi 2NMe3] [Co(CO)4] . Indeed, it is believed that in all the cases shown in Table XIII except entry 17, the Lewis base molecules are... 

Moore MH, Hudson RL. (1992) Far-infrared spectral studies of phase changes in water ice induced by proton irradiation. Astrophys/401 353-360. 

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