Spectroscopic investigation

Several spectroscopic techniques are used for investigating the surface speciation/structure of the deposited precursor species [39-46]. The X-ray absorption fine structure (EXAFS) related techniques are very useful. These allows identification of the kind of atoms surrounding a transition element deposited on the support surface as well as the number of each kind of these atoms and the distances of the transition element from the surrounding atoms. The first and the second coordination sphere can be rather safely probed. Deposition studies on polycrystalline oxidic supports or on monocrystals exposing a certain crystal face have been reported (e.g. the deposition of the 

Co(II) aqua complexes on the (1 1 0) rutile termination). In the first case we mainly examine whether a surface inner-sphere complex is actually formed and investigate the general characteristics of its structure. In the second case we try to approach the exact structure of this complex. 

ATR (FTIR), DR (UV-Vis-near-IR), NMR, EPR, and RAMAN spectroscopies have been also used to examine whether inner-sphere complexes are formed upon the deposition of TMIS on the surface of an oxidic support and, in some cases, to find the interface speciation. The structure of a deposited TMIS could be changed upon drying. Thus, the apphcation of a spectroscopic technique before drying is in some cases critical. In this respect ATR is very useful because it allows the strong IR absorption of the water molecules to be overcome and interfacial species to be identified. 

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Our studies also included IR spectroscopic investigation of the observed ions (Fig. 6.2). John Evans, who was at the time a spectroscopist at the Midland Dow laboratories, offered his cooperation and was able to obtain and analyze the vibrational spectra of our alkyl cations. It is rewarding that, some 30 years later, FT-IR spectra obtained by Denis Sunko and his colleagues in Zagreb with low-temperature matrix-deposition techniques and Schleyer s calculations of the spectra showed good agreement with our early work, considering that our work was... 

It seems now established by NMR spectroscopic investigations that a change can take place in electronic structures and atomic configuration of the dyes depending on the polarity of the solvent. Parameters describing the transition from one single bond to more double bond character vary according to the nature of the solvent (107). 

From 1960 onwards, fhe increasing availabilify of intense, monochromatic laser sources provided a fremendous impetus to a wide range of spectroscopic investigations. The most immediately obvious application of early, essentially non-tunable, lasers was to all types of Raman spectroscopy in the gas, liquid or solid phase. The experimental techniques. 

It has been shown by IR-spectroscopic investigations which evidence on the appearance of new absorption bands after chitosan introducing, elementary analyses data. (N, occurrence in the samples, which quantity depends on chitosan nature and isolation conditions) It leads to significant increase of sorption capacity and specific surface of sorbents, which contain chitosan from silk waren chrysalises. Where as these parameters decrease for sorbents with chitosan from crabs. Evidently it is connected to more dense structure of the last one. It has been shown, that yield of sorbent on the base of PES and chitosan obtained by sol-gel method has depended significantly on such factors as components ratio, temperature, catalyst quantity etc. 

Spectroscopic investigation of enamines conjugated with ketone, ester and nitrile groups established the prevalence of enamine rather than imine-enol tautomers in examples of secondary amines (206-212). Similar studies have been made with enamines of acylpyridines and acetophenones (213,214). 

Ultraviolet and infrared spectroscopic investigations and also chemical behavior show unambiguously that the compounds which result from the last-rnentioned type of nucleophilic reagent and cotarnine possess the cyclic form. " Examples of these are cotar-nine anil (20a), cotarnine oxime (20b), cotarnine phenylhydra-zone (20c), anhydrocotarnine carbamide (20d), hydrocotarnyl-acetic acid (20e), anhydrocotarnine acetone (20f), and also the compound (21) obtained from two molecules of cotarnine and one molecule of acetone by the elimination of two molecules of water. The cyclic form had ben demonstrated earlier for anhydrocotarnine-nitromethane (20g) and anhydrocotarnine-acetophenone (20h). ... 

The combination of positive and negative charges within the same molecule causes a more complicated situation, which obviously has not been well-defined to date. A quite large number of pyrrolizidine alkaloids are related to Otonecine (8) (Scheme 3). Spectroscopic investigations show that these alkaloids exist in the nonionized form in CDCI3, and in the zwitterionic form in D2O (00JNP857, 71TL3421). The dipolar structure is the result of an intramolecular interaction between a nucleophilic and an electrophilic center. 

Italian investigators have recently shown by infrared spectroscopy that 3-hydroxy-5-phenylisoxazole exists as such and not in the isoxazolone form. This conclusion is supported by a spectroscopic investigation of the 4,5-dimethyl and other dialkyl analogs. ... 

Diradical species 4 is more stable than diradical 5, and the oxetane 6 is thus formed preferentially oxetane 7 is obtained as minor product only. Evidence for diradical intermediates came from trapping experiments, as well as spectroscopic investigations. ... 

NMR SPECTROSCOPIC INVESTIGATIONS OF SURFACE AND INTERLAYER SPECIES ON MINERALS, CLAYS AND OTHER OXIDES... 

Kulinski, T., Visser, A. J. W. G., O Kane, D. J., and Lee, J. (1987). Spectroscopic investigations of the single tryptophan residue and of riboflavin and 7-oxolumazine bound to lumazine apoprotein from Photobacterium leiognathi. Biochemistry 26 540-549. 

The anti diastereoselectivity is improved to a 6 1 ratio by the addition of triethylborane to the reaction mixture83. NMR-spectroscopic investigations indicate that a boronate complex is the decisive intermediate84, since it can also be prepared by the addition of alkyllithium to the dialkyl(2-butenyl)borane (path ). 

Spectroscopic investigations of excited states of transition metal complexes. G. A. Crosby, Acc. Chem. Res., 1975, 8,231-238 (53). 

Debye s theory, considered in Chapter 2, applies only to dense media, whereas spectroscopic investigations of orientational relaxation are possible for both gas and liquid. These data provide a clear presentation of the transformation of spectra during condensation of the medium (see Fig. 0.1 and Fig. 0.2). In order to describe this phenomenon, at least qualitatively, one should employ impact theory. The first reason for this is that it is able to describe correctly the shape of static spectra, corresponding to free rotation, and their impact broadening at low pressures. The second (and main) reason is that impact theory can reproduce spectral collapse and subsequent pressure narrowing while proceeding to the Debye limit. 

Bulanin M. O., Orlova N. D. Spectroscopical investigations of molecular rotational motion in condensed media, In Spectroscopy of Interacting Molecules, ed. M. O. Bulanin, Leningrad State University, Leningrad, pp. 55-97 (1970). 

The outer configurations of the transition metals in Table 1-1 imply, and detailed spectroscopic investigations confirm, that the 3d orbitals lie at higher energies than the 45 orbitals. On the other hand, the configurations of the ions listed, in... 

As previously mentioned, there have been no detailed spectroscopic investigations of Na2Ga2(C6H3-2,6-Trip2)2- It is possible that studies as basic as UV-visible spectrum could provide information. Raman spectroscopy could also allow an estimate of the approximate strength of the Ga—Ga bond. 

The molecule S12, like Se, is of Dsd symmetry but in the soHd state it occupies sites of the much lower C211 symmetry [163]. Due to the low solubihty and the thermal decomposition on melting only solid state vibrational spectra have been recorded [2,79]. However, from carbon disulfide the compound Si2-CS2 crystallizes in which the S12 molecules occupy sites of the high Sg symmetry which is close to 03a [163]. The spectroscopic investigation of this adduct has resulted in a revision [79] of the earher vibrational assignment [2] and therefore also of the earlier force constants calculation [164]. In Fig. 24 the low-temperature Raman spectra of S12 and Si2-CS2 are shown. 

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