M. Fadouach, A. Kadiri, C. Cazeau-Dubroca, G. Nouch, M. Pesquer, D. Gorse
{"title":"Simulation théorique de la torsion par liaison hydrogène de la 2,2-biquinoléine à l'état fondamental","authors":"M. Fadouach, A. Kadiri, C. Cazeau-Dubroca, G. Nouch, M. Pesquer, D. Gorse","doi":"10.1016/0584-8539(94)80106-1","DOIUrl":"10.1016/0584-8539(94)80106-1","url":null,"abstract":"<div><p>Application of the semi-empirical AMI method gives significant evidence of the conformation of the isolated 2,2′-biquinoline (2,2′-BQ) in its ground state. The results obtained on the one hand by Fraga's method in which the molecule is simulated by the hydrogen bonding between a water molecule and the 2,2′-BQ, and on the other hand by CNDO calculations using Mataga's model, are in good agreement with the experimental results. They indicate that the spectral changes of 2,2′-BQ in its ground state in protonic media are caused by a <em>trans-cis</em> transformation resulting from a rotation around the single CC bond which links the two quinoline rings of the molecule</p></div>","PeriodicalId":82782,"journal":{"name":"Spectrochimica acta. Part A: Molecular spectroscopy","volume":"50 12","pages":"Pages 2117-2124"},"PeriodicalIF":0.0,"publicationDate":"1994-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0584-8539(94)80106-1","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82027270","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Grignon-Dubois , M. Petraud , M. Laguerre , I. Pianet
{"title":"Structural study of arylsilanes using 29Si NMR","authors":"M. Grignon-Dubois , M. Petraud , M. Laguerre , I. Pianet","doi":"10.1016/0584-8539(93)E0023-P","DOIUrl":"10.1016/0584-8539(93)E0023-P","url":null,"abstract":"<div><p><sup>29</sup>Si NMR data (σ and <sup>1</sup>H, <sup>29</sup>Si coupling constants) of a series of arylsilanes were studied in relation to their molecular structure. It is shown that silicon chemical shift variation is too weak to allow empirical attribution. In contrast, <sup>29</sup>Si, <sup>1</sup>H coupling constants across the aromatic ring, especially the <sup>3</sup><em>J</em>, allow structural assignment. Generally, SPT experiments are sufficient to obtain these values. However, full attribution of polysilylated derivatives sometimes needs other experiments to identify all the silicons. A 2D <em>J</em>-resolved INEPT experiment is described and has proven to be an efficient method for <sup>29</sup>Si NMR signal identification. The usefulness of this approach is demonstrated by the complete analysis of all the <sup>29</sup>Si lines in a trisilyl derivative. An easy-to-use INEPT decoupled-type sequence is also proposed for a rapid characterization of polysilylated derivatives or mixture of isomers.</p></div>","PeriodicalId":82782,"journal":{"name":"Spectrochimica acta. Part A: Molecular spectroscopy","volume":"50 12","pages":"Pages 2059-2068"},"PeriodicalIF":0.0,"publicationDate":"1994-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0584-8539(93)E0023-P","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80580813","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"II-utility of fluorine-19 NMR spectroscopy for investigation of charge transfer complexes","authors":"Sobhy El-Adl","doi":"10.1016/0584-8539(93)E0008-K","DOIUrl":"10.1016/0584-8539(93)E0008-K","url":null,"abstract":"<div><p>Fluorine and proton chemical shifts for the griseofulvin oxime—fluoranil complex are reported. <sup>1</sup>H, <sup>19</sup>F-NMR spectra prove the course of the charge transfer complex formation. Due to redistribution of the electron density, the protons of the donor are slightly shifted towards a lower field where deshielding has occurred. Signals of the <sup>19</sup>F-NMR spectra of fluoranil complex showed a positive value for the upfield shift of the fluorine resonance due to a shielding effect. Fluoranil (tetrafluoro-2,5-cyclohexadiene-1,4-dione) has a high electron-accepting ability with respect to the functional groups containing heteroatoms. The complete qualitative and quantitative chemical characterization of the resulting complex has been studied.</p></div>","PeriodicalId":82782,"journal":{"name":"Spectrochimica acta. Part A: Molecular spectroscopy","volume":"50 12","pages":"Pages 2101-2103"},"PeriodicalIF":0.0,"publicationDate":"1994-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0584-8539(93)E0008-K","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79457390","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Spectroscopic study of pH and solvent effects on the structure of Congo red and its binding mechanism to amyloid-like proteins","authors":"E. Pigorsch, A. Elhaddaoui, S. Turrell","doi":"10.1016/0584-8539(94)00151-0","DOIUrl":"10.1016/0584-8539(94)00151-0","url":null,"abstract":"<div><p>The pH and solvent effects on the structure of the azo dye Congo red were investigated. The absorption, resonance Raman and NMR spectra give evidence of the existence of different protonated dye molecules in acidic solutions. There exist a red form with an azoic structure and at least three blue forms with quinoid structures. The position of the equilibrium between the azoic and quinoid structures depends on the solvent and the pH and is related to the capability of the solvent to form three and two dimensional solvation structures, respectively.</p><p>Spectral variations similar to those observed for Congo red dissolved in organic solvents accompany binding of the dye to amyloid-like proteins. This observation leads to the suggestion that the dye molecules must experience similar changes in environment in both cases.</p></div>","PeriodicalId":82782,"journal":{"name":"Spectrochimica acta. Part A: Molecular spectroscopy","volume":"50 12","pages":"Pages 2145-2152"},"PeriodicalIF":0.0,"publicationDate":"1994-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0584-8539(94)00151-0","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78450888","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Fluorescence quantum yields of α, ω-diphenylpolyenes","authors":"Takao Itoh, Bryan E. Kohler, Charles W. Spangler","doi":"10.1016/0584-8539(94)E0007-W","DOIUrl":"10.1016/0584-8539(94)E0007-W","url":null,"abstract":"<div><p>Absolute fluorescence quantum yields of <em>trans</em>-stilbene and all-<em>trans</em> α, ω-diphenylpolyenes with the polyene double-bond number (<em>n</em>) from two to six have been determined in a room-temperature solvent. The 1<sup>1</sup>Bu-fluorescence yield measured as a function of the polyene chain length shows a maximum for <em>n</em> = 2, while the 2<sup>1</sup>Ag-fluorescence yield shows a maximum for <em>n</em> = 3, and both yields decrease with further increase of <em>n</em>. The observed quantum yield behavior is discussed briefly.</p></div>","PeriodicalId":82782,"journal":{"name":"Spectrochimica acta. Part A: Molecular spectroscopy","volume":"50 13","pages":"Pages 2261-2263"},"PeriodicalIF":0.0,"publicationDate":"1994-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0584-8539(94)E0007-W","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86234692","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Elizabeth A. Carter, Peter M. Fredericks, Jeffrey S. Church, Ronald J. Denning
{"title":"FT-Raman spectroscopy of wool—I. Preliminary studies","authors":"Elizabeth A. Carter, Peter M. Fredericks, Jeffrey S. Church, Ronald J. Denning","doi":"10.1016/0584-8539(94)80205-X","DOIUrl":"10.1016/0584-8539(94)80205-X","url":null,"abstract":"<div><p>The FT-Raman spectrum of wool has been obtained using near-IR excitation. No significant fluorescence was observed and the spectra could be obtained routinely. No sample damage was observed for laser powers up to 400 mW. Several methods of sample presentation for both wet and dry wool were investigated and the optimum data collection conditions were determined for each. Dry dense plugs of wool fibers (∼0.16 g cm<sup>−3</sup>) were found to provide the best spectra. Due to improvements in band resolution and signal-to-noise ratio, several previously unobserved spectral features in the wool spectrum have become apparent. The assignment of the Raman-active vibrational modes of wool are reviewed and updated to include these features. Raman spectra obtained from chlorinated and untreated wool samples did not exhibit any significant differences. In contrast, the ATR spectra obtained from these samples exhibited significant differences in the SO stretching region.</p></div>","PeriodicalId":82782,"journal":{"name":"Spectrochimica acta. Part A: Molecular spectroscopy","volume":"50 11","pages":"Pages 1927-1936"},"PeriodicalIF":0.0,"publicationDate":"1994-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0584-8539(94)80205-X","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85887942","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
I.R. Lewis, N.W. Daniel Jr, N.C. Chaffin, P.R. Griffiths
{"title":"Raman spectrometry and neural networks for the classification of wood types—1","authors":"I.R. Lewis, N.W. Daniel Jr, N.C. Chaffin, P.R. Griffiths","doi":"10.1016/0584-8539(94)80207-6","DOIUrl":"10.1016/0584-8539(94)80207-6","url":null,"abstract":"<div><p>In this work the coupling of near infrared (NIR) Fourier-transform (FT) Raman spectroscopy and neural computing for spectral feature extraction and classification of woods is reported. A NIR FT-Raman spectrometer operating at 1064 nm was used for all measurements; particular attention was paid to the effects of sample fluorescence and heating. It was demonstrated that fluorescence rejection is accomplished only for the lighter colored woods and that fluorescence was found to be severe for 10 of the 71 woods studied in this work even using excitation at 1064 nm. It was further found that hardwoods were no more or less susceptible to sample heating than softwoods. Feed-forward neural networks were used to extract the principal features of wood spectra at resolutions of 4, 8 and 16 cm<sup>−1</sup> and to classify spectra as either temperate hardwoods or temperate softwoods. Neural networks were constructed using zero and two processing elements in the hidden layer. It was shown that neural networks with two hidden processing elements perform near optimally, since each hidden layer processing element may function as either a hardwood or softwood feature detector. This work represents the first time that FT-Raman spectroscopy and neural network technology have been coupled for spectral feature extraction and classification.</p></div>","PeriodicalId":82782,"journal":{"name":"Spectrochimica acta. Part A: Molecular spectroscopy","volume":"50 11","pages":"Pages 1943-1958"},"PeriodicalIF":0.0,"publicationDate":"1994-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0584-8539(94)80207-6","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80286919","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"The application of Fourier-transform Raman spectroscopy to the determination of conformation in poly(ε-caprolactam) chains","authors":"P. Schmidt, P.J. Hendra","doi":"10.1016/0584-8539(94)80211-4","DOIUrl":"10.1016/0584-8539(94)80211-4","url":null,"abstract":"<div><p>The Fourier-transform Raman spectra of various structural forms of poly(ε-caprolactam) have been obtained and the Raman bands characterizing planar and nonplanar conformation of the ε-caprolactam units have been defined. These bands have been used for the investigation of the conformational composition of ε-caprolactam sequences in several ε-caprolactam-butadiene block copolymers.</p></div>","PeriodicalId":82782,"journal":{"name":"Spectrochimica acta. Part A: Molecular spectroscopy","volume":"50 11","pages":"Pages 1999-2004"},"PeriodicalIF":0.0,"publicationDate":"1994-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0584-8539(94)80211-4","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87815242","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"FT Raman spectroscopic study of the diimide hydrogenation of cis-polybutadiene: Some evidence of cis—trans isomerization","authors":"Saran Poshyachinda, Vivat Kanitthanon","doi":"10.1016/0584-8539(94)80213-0","DOIUrl":"10.1016/0584-8539(94)80213-0","url":null,"abstract":"<div><p>The diimide hydrogenation of <em>cis</em>-polybutadiene is studied. <em>p</em>-Toluenesulfonylhydrazide is used to fully and partially hydrogenate <em>cis</em>-polybutadiene. The microstructure and hydrogenation of the samples obtained are subsequently studied by FT Raman spectroscopy. <em>Cis—trans</em> isomerization is found to take place during the reaction. A mechanism of isomerization and hydrogenation is also proposed.</p></div>","PeriodicalId":82782,"journal":{"name":"Spectrochimica acta. Part A: Molecular spectroscopy","volume":"50 11","pages":"Pages 2011-2017"},"PeriodicalIF":0.0,"publicationDate":"1994-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0584-8539(94)80213-0","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73323109","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}