Bond length alternation in unsymmetrical cyanine dyes and its influence on the vibrational structure of their electronic absorption spectra† / Heinz Mustroph in COLORATION TECHNOLOGY, Vol. 133, N° 6 (12/2017)  

[article]  inCOLORATION TECHNOLOGY > Vol. 133, N° 6 (12/2017) . - p. 469-475 Titre : Bond length alternation in unsymmetrical cyanine dyes and its influence on the vibrational structure of their electronic absorption spectra† Type de document : texte imprimé Auteurs : Heinz Mustroph, Auteur ; Knut Reiner, Auteur ; Bianca Senns, Auteur Année de publication : 2017 Article en page(s) : p. 469-475 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Analyse spectrale Colorants -- Analyse Cyanines Les cyanines sont le nom non systématique d'une famille de marqueurs synthétiques appartenant au groupe des polyméthines. Les cyanines ont de nombreuses utilisations comme marqueurs fluorescents, particulièrement en imagerie biomédicale. Selon la structure, elles couvrent un spectre allant de l'IR à l'UV. Spectres d'absorption Index. décimale : 667.3 Teinture et impression des tissus Résumé : Based on the assumption that the unsymmetrical cyanine dyes can be regarded as a hybrid of the two corresponding symmetrical dyes it was expected that ?max of the unsymmetrical dye would be the arithmetic mean of ?max of the two symmetrical dyes. There is, however, often a remarkable difference between the arithmetic mean and the observed ?max of the unsymmetrical dye – the Brooker deviation. To date, this effect is explained in terms of increasing electronic energy differences. With increasing difference of the electronic structure between the ground and excited state, the difference between equilibrium geometry of ground and excited state increases and the relative intensity of the higher vibronic transitions 0–v increases and that of the 0–0 transition decreases. ?max represents the intensity maximum of an absorption band and could be related to the 0–0, 0–1 or another vibronic transition. We discuss the origin of the Brooker deviation on the vibrational structure of the spectra. Note de contenu : - Stationary electronic absorption spectra - The origin of vibrational structure in electronic absorption spectra DOI : 10.1111/cote.12303 En ligne : https://drive.google.com/file/d/13MxemrgVtdrVJqNmN64S4M3BfbdPUS-S/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=29493 [article]

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Molecular electronic spectroscopy : from often neglected fundamental principles to limitations of state-of-the-art computational methods / Heinz Mustroph in COLORATION TECHNOLOGY, Vol. 131, N° 1 (02/2015)  

[article]  inCOLORATION TECHNOLOGY > Vol. 131, N° 1 (02/2015) . - p. 9-26 Titre : Molecular electronic spectroscopy : from often neglected fundamental principles to limitations of state-of-the-art computational methods Type de document : texte imprimé Auteurs : Heinz Mustroph, Auteur ; Steffen Ernst, Auteur ; Bianca Senns, Auteur ; Andrew D. Towns, Auteur Année de publication : 2015 Article en page(s) : p. 9-26 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Analyse spectrale Calcul Colorants Logiciels Spectroscopie moléculaire Index. décimale : 667.3 Teinture et impression des tissus Résumé : The creation of the first synthetic dyes not only stimulated the hunt for new colorants but also drove the search for rules correlating the constitution of organic compounds with their colour. Dye chemistry additionally facilitated the development of molecular electronic spectroscopy as well as theories of molecular electronic structure and electronic transitions. Powerful quantum chemical computational tools are now available for the prediction of the electronic structure and spectroscopic characteristics of organic compounds. Such methods are thus useful in designing new functional colorants and aiding interpretation of their properties. However, without a deep appreciation of the principles and assumptions behind the calculations, one runs the risk of misunderstanding what can be achieved as well as becoming confused about how the outputted electronic and vibronic transition data correspond to observed absorption spectra. This review therefore aims to cover fundamentals of electronic spectroscopy that are often overlooked and enable the dye chemist using modern computational methods to comprehend the subtle differences in the types of transition energy value that such software can generate. In addition, the limitations of these methods in predicting absorption maxima and intensities of real-world colorants will be discussed in the context of physical influences on absorption band position and shape, for example from the perspective of different forms of the Franck–Condon principle. In essence, the goal of this review is to clarify, in terms that practical dye chemists will understand, what computational methods can predict and how valid these predictions are compared with reality. Note de contenu : - MOLECULAR ELECTRONIC SPECTROSCOPY : Electronic transition energy in atoms and molecules - some fundamentals - Calculation of electronic transition energies in molecules - Sources of disparity between calculated transition energies and experimental data - Intensity of electronic transitions in molecules - Absorption band shapes - the Franck-Condon principle DOI : 10.1111/cote.12120 En ligne : https://onlinelibrary.wiley.com/doi/epdf/10.1111/cote.12120 Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=22968 [article]

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