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Title: Unraveling the Fluorescence Features of Individual Corrole NH Tautomers
Authors: Kruk, Mikalai
Ngo, Thien H.
Starukhin, Aleksander
Hofkens, Johan
Dehaen, Wim
MAES, Wouter 
Issue Date: 2012
Source: JOURNAL OF PHYSICAL CHEMISTRY A, 116 (44), p. 10695-10703
Abstract: The fluorescence spectra of 10-(4,6-dichloropyrimidin-5-yl)-5,15-dimesitylcorrole have been studied in the temperature range from 4.2 to 332 K. For the first time, the individual fluorescence profiles of the two corrole NH tautomers have been assigned over the whole temperature range. The pronounced temperature dependence of the fluorescence spectra of the meso-pyrimidinylcorrole under study was found to originate from switching between the fluorescence emissions of the two tautomers due to a reduced NH tautomerization rate with decreasing temperature. As a result, the long wavelength tautomer dominates the total emission spectrum at room temperature, whereas at low temperatures, the majority of the emission comes from the short wavelength tautomer. Energy level diagrams (involving the two NH tautomers) explaining the excitation energy deactivation channels in the meso-pyrimidinylcorrole at room temperature and below are presented. A significant H/D isotope effect on the NH tautomerization rate has been observed, resulting in an enhanced contribution of the short wavelength tautomer to the total fluorescence spectrum at the expense of that of the long wavelength tautomer. Substantially different fluorescence quantum yields have been determined for the individual NH tautomers, leading to a pronounced temperature dependence of the overall fluorescence quantum yield. The obtained results allow the unambiguous statement that the two NH tautomers of corroles coexist in fluid and solid solutions in a wide range of temperatures, with the proportion depending on the corrole substitution pattern. Moreover, this study shows that the (future) interpretation of the fluorescence properties of meso-pyrimidinylcorroles and all other corrole materials should be done (more) carefully, taking into account the coexistence of NH tautomers with individual spectral signatures.
Notes: Kruk, M (reprint author), Natl Acad Sci, BI Stepanov Inst Phys, Pr Nezavisimosti 68, Minsk 220072, Byelarus.[Kruk, Mikalai; Starukhin, Aleksander] Natl Acad Sci, BI Stepanov Inst Phys, Minsk 220072, Byelarus. [Ngo, Thien H.; Hofkens, Johan; Dehaen, Wim; Maes, Wouter] Katholieke Univ Leuven, Dept Chem, B-3001 Louvain, Belgium. [Ngo, Thien H.] Free Univ Berlin, Inst Chem & Biochem Organ Chem, D-14195 Berlin, Germany. [Verstappen, Pieter; Maes, Wouter] Hasselt Univ, Inst Mat Res IMO IMOMEC, B-3590 Diepenbeek, Belgium. kruk@imaph.bas-net;
Keywords: Chemistry, Physical; Physics, Atomic, Molecular & Chemical; free-base corroles; core-modified corroles; photophysical properties; substituted corroles; electron-transfer; energy-transfer; metal-free; dyads; chemistry; porphyrins
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ISSN: 1089-5639
e-ISSN: 1520-5215
DOI: 10.1021/jp305326x
ISI #: 000310769100006
Category: A1
Type: Journal Contribution
Validations: ecoom 2013
Appears in Collections:Research publications

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