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Porphyrin Protonation Studied by Magnetic Circular Dichroism
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SYSNO ASEP 0376366 Document Type J - Journal Article R&D Document Type Journal Article Subsidiary J Článek ve WOS Title Porphyrin Protonation Studied by Magnetic Circular Dichroism Author(s) Štěpánek, Petr (UOCHB-X) RID
Andrushchenko, Valery (UOCHB-X) RID, ORCID
Ruud, K. (NO)
Bouř, Petr (UOCHB-X) RID, ORCIDNumber of authors 4 Source Title Journal of Physical Chemistry A. - : American Chemical Society - ISSN 1089-5639
Roč. 116, č. 1 (2012), s. 778-783Number of pages 6 s. Language eng - English Country US - United States Keywords magnetic circular dichroism (MCD) ; TPPS ; spectra simulations ; porphyrin protonation Subject RIV CF - Physical ; Theoretical Chemistry R&D Projects GAP208/11/0105 GA ČR - Czech Science Foundation (CSF) GA203/09/2037 GA ČR - Czech Science Foundation (CSF) GAP208/10/0559 GA ČR - Czech Science Foundation (CSF) LH11033 GA MŠMT - Ministry of Education, Youth and Sports (MEYS) CEZ AV0Z40550506 - UOCHB-X (2005-2011) UT WOS 000298978000083 DOI 10.1021/jp2105192 Annotation Magnetic circular dichroism (MCD) spectroscopy provides valuable information about electronic excited states : in molecules. The interpretation of spectra is however difficult, often requiring additional theoretical calculations to rationalize the observed signal Recent developments in time dependent density functional theory (TDDFT) bring hope that the applicability of MCD spectroscopy for chemical problems may be significantly extended. In this study, two modern analytical TDDFT implementations are compared and used to understand experimental MCD spectra of a model porphyrin system upon protonation. Changes in porphyrin geometry and electronic structure are related to MCD intensities by comparing the spectra of 5,10,15,20-tetraphenyl-21H;23H-porphyrintetrasulfonic acid (TPPS) measured at different pH values with the TDDFT calculations. Although the theoretical results slightly dependent on the chosen exchange-correlation functional, the computations provided MCD,curves that could well rationalize the experimental data The protonation of the porphyrin core causes marked changes in the MCD spectrum, whereas the role of the substituents is limited. Also, different conformations of the porphyrin substituents cause relatively minor changes of the MCD pattern, mostly in : the Soret region, where the porphine and phenyl electronic transitions start to mix. The solvent environment simulated by the dielectric model caused a shift (similar to 20 nm) of the absorption bands but only minor variations in the absorption and MCD spectral shapes. The study thus demonstrates that the recently available first principles interpretations of MCD spectra significantly enhance the applicability of the technique for molecular structural studies Workplace Institute of Organic Chemistry and Biochemistry Contact asep@uochb.cas.cz ; Kateřina Šperková, Tel.: 232 002 584 ; Jana Procházková, Tel.: 220 183 418 Year of Publishing 2013
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