FT-IR spectroscopic investigations

Fourier transform-infrared (FT-IR) spectroscopic studies on SO-SA complexation provides information that may be complementary to that of NMR and other techniques, namely, in particular, on the involvement of functional groups in intermolecular and intramolecular interactions. Attenuated total reflectance (ATR) IR spectroscopy has been used for the study of binding modes of cinchona alkaloid selectors either in solution [95] or in solid state [94], or directly on the CSP [96]. 

The same set of measurements for DNP-Leu as selectand and 0-9-allylcarbamoyl-10,11-dihydroquinidine as selector displayed a considerably different picture. While no indication for H-bond formation between the aromatic a-amino group and the carbamate of the selector could be deduced, the IR spectra of free and respective complexed forms suggested the occurrence of K-K-interactions of the DNP group as evidenced by a shifted C=C stretching vibration from 1594 to 1588 cm in the stronger bound 5-complex (force constant weakened due to delocalized electrons). This type of shift was not found in the weak TJ-complex, but in the corresponding 5-complex of DNP-N-methyl-Leu as well. The spectral data nicely reflect the binding relationships in HPLC where both DNP-Leu and DNP-N-methyl-Leu are well separated with comparable separation factors, but with an elution order that is opposite compared to DNB-Leu. 

Self-association of the selector and stereoselective yet intercomplex H-bond formation could be identified in an ATR FT-IR study of Akasaka et al. [94] in which 

FIGURE 1.18 Demodulated spectra of (a) DNB-(i )-Leu vs. solvent, (b) DNB-(5)-Leu vs. solvent, (c) DNB-(i )-Leu vs. (DNB-(5)-Leu with modulation period of 299 s, and (d) DNB-(i )-Leu vs. (DNB-(5)-Leu with modulation period of 523 s on 0-9-(fert-butylcarbamoyl)quinine-based CSP. The boldface spectra are the so-called in-phase spectra. (Reprinted from R. Wirz et ah. Anal. Chem., 76 5319 (2004). With permission.) 

Also control experiments were performed in which the transmission spectra of free selector and in complex with 5- and R-enantiomers were measured in solution and the difference spectra confirmed similar binding states in solution and on the surface of the CSR 

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Nijhuis et al. proposed a different reaction route, in which the role of the periphery around Au NPs is not expUcitly described [35, 36]. Based on a detailed FT-IR spectroscopic investigation, they indicate that C3H6 reacts with the Ti02 surfaces to form a bidentate propoxy species with the help of Au NPs. Over the Au surfaces, the peroxide species are formed by the reaction of O2 with H2, which is the ratedetermining step. The bidentate propoxy species desorb with the assistance of the peroxide species to produce PO and water. This hypothesis is based on the theoretical prediction that gold is active to produce H2O2 from H2 and O2 [37] and on some recent experimental results for direct H2O2 synthesis [38, 39]. 

P. Lasch, M. Boese, A. Pacifico and M. Diem, FT-IR spectroscopic investigations of single cells on the subcellular level, Vib. Spectrosc., 2002, 28, 147-157. 

Zscherp, C., Schlesinger, R., and Heberle, J., Time-resolved FT-IR spectroscopic investigation of the pH-dependent proton transfer reactions in the E194Q mutant of bacteriorhodopsin, Biochem. Biophys. Res. Commun., 283, 57-63, 2001. 

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... 

The tautomerism of DMTD (31a, 31b), as well as those of 5-amino-l,3,4-thiadiazole-2-thiol (AMTD) (32a, 32b) and 5-methyl-l,3,4-thiadiazole-2-thiol (MMTD) (33a, 33b), were investigated by means of FT-Raman and FT-IR spectroscopic techniques by Edwards and coworkers136. 

This work gives results about the characterisation of Sn02 materials, pure and W -added, prepared via a sol-gel route. The materials were characterised as powders or thick films using a variety of techniques. The powder and thick film morphology was analysed by TEM, HRTEM and SEM, the powder texture by volumetric measurements. Powders and films made by regularly shaped and nano-sized particles, even after thermal treatments at 850 °C were obtained. Electrical and FT-IR spectroscopic measurements were employed on films and powders, respectively. Electrical and FT-IR measurements show that W lowers the response of the tin oxide towards CO, but enhances its ability to sense NO2. The surface species formed by CO and NO2 interaction were carefiilly investigated by FT-IR spectroscopy. 

In a recent literature report we could publish only part of our results, mainly because of space constrains. Therefore, in the present contribution we wish to give an exhaustive presentation of the results obtained during the detailed parameter investigation and FT-IR spectroscopic monitoring of the methanol carbonylation over supported rhodium catalysts. 

It was demonstrated that concentration profiles of different components can be obtained utilizing the partial least squares method. With concentration profiles readily measurable, it is possible to obtain other quantities such as diffusion type, that is, Fickian versus non-Fickian mechanism of diffusion. The application of in situ ATR FT-IR spectroscopic imaging has been employed to investigate polymer interdiffusion of PVP and polyfethylene glycol) (PEG) under high pressure CO2 [74]. The diffusion mechanism of the system was described based on the spectroscopic imaging data, and it was found that CO2 molecules dissolved in the polymeric system greatly enhanced the interdiffusion process. 

Akasaka K, Gyimesi-Forras K, Lammerhofer M, Fujita T, Watanabe M, Harada N, Lindner W. Investigations of molecular recognition aspects related to the enantiomer separation of 2-methoxy-2-(l-naphthyl)propionic acid using quinine carbamate as chiral selector an NMR and FT-IR spectroscopic as well as X-ray crystallographic study. Chirality 2005 17 544-555. 

Recently we investigated ferromagnetic properties of CoPt bimetallic nanoparticles [232,233]. CoPt3 nanoparticles can be prepared by a two-step reduction using NaBH4 as a reductant. The bimetallic nanoparticles were characterized by thermogravimetry (TG) and differential thermal analysis (DTA), FT-IR, TEM) and XRD. Structural and spectroscopic studies showed that the bimetallic nanoparticles adopt an fee crystalline structure with an average particle size of 2.6 nm. SQUID studies revealed... 

Aurbach and co-workers performed a series of ex situ as well as in situ spectroscopic analyses on the surface of the working electrode upon which the cyclic voltammetry of electrolytes was carried out. On the basis of the functionalities detected in FT-IR, X-ray microanalysis, and nuclear magnetic resonance (NMR) studies, they were able to investigate the mechanisms involved in the reduction process of carbonate solvents and proposed that, upon reduction, these solvents mainly form lithium alkyl carbonates (RCOsLi), which are sensitive to various contaminants in the electrolyte system. For example, the presence of CO2 or trace moisture would cause the formation of Li2COs. This peculiar reduction product has been observed on all occasions when cyclic carbonates are present, and it seems to be independent of the nature of the working electrodes. A single electron mechanism has been shown for PC reduction in Scheme 1, while those of EC and linear carbonates are shown in Scheme 7. ... 

A variety of surface-sensitive spectroscopic and microscopic methods were critical in the investigation of these systems. In the work by Advincula et al, the composition, thickness, physical and thermal properties, and morphology of the tethered polymer brushes were carefully analyzed [72]. A variety of surface-sensitive techniques such as ellipsometry, contact angle measurements, AFM, quartz crystal microbalance (QCM), FT-IR grazing incidence... 

FT-IR and Si NMR spectroscopic investigations reveal an invasive silicon oxide network structure that becomes less interconnected or coordinated with increasing solids uptake according to procedure A. However, incorporated networks of greater connectivity can be affected using the slow, incremental, TEOS addition method of procedure B. 

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