Conformational Control of the Photodynamics of a Bilirubin Dipyrrinone Subunit: Femtosecond Spectroscopy Combined with Nonadiabatic Simulations
| Autor: | Petr Slavíček, Jakub Švenda, Jiří Janoš, Sadegh Mahvidi, Petr Klán, Jiří Suchan, Dominik Madea, Taufiqueahmed Pirsaheb Mujawar |
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| Rok vydání: | 2020 |
| Předmět: |
Models
Molecular 010304 chemical physics Photoisomerization Chemistry Spectrum Analysis Molecular Conformation Bilirubin Surface hopping Photochemical Processes 010402 general chemistry 01 natural sciences 0104 chemical sciences Chemical physics Picosecond Excited state 0103 physical sciences Ultrafast laser spectroscopy Vibrational energy relaxation Quantum Theory Thermodynamics Physical and Theoretical Chemistry Conformational isomerism Femtochemistry |
| Zdroj: | The Journal of Physical Chemistry A. 124:10457-10471 |
| ISSN: | 1520-5215 1089-5639 |
| Popis: | The photochemistry of bilirubin has been extensively studied due to its importance in the phototherapy of hyperbilirubinemia. In the present work, we investigated the ultrafast photodynamics of a bilirubin dipyrrinone subunit, vinylneoxanthobilirubic acid methyl ester. The photoisomerization and photocyclization reactions of its (E) and (Z) isomers were studied using femtosecond transient absorption spectroscopy and by multireference electronic structure theory, where the nonadiabatic dynamics was modeled with a Landau-Zener surface hopping technique. The following picture has emerged from the combined theoretical and experimental approach. Upon excitation, dipyrrinone undergoes a very fast vibrational relaxation, followed by an internal conversion on a picosecond time scale. The internal conversion leads either to photoisomerization or regeneration of the starting material. Further relaxation dynamics on the order of tens of picoseconds was observed in the ground state. The nonadiabatic simulations revealed a strong conformational control of the photodynamics. The ultrafast formation of a cyclic photochemical product from a less-populated conformer of the studied subunit was predicted by our calculations. We discuss the relevance of the present finding for the photochemistry of native bilirubin. The work has also pointed to the limits of semiclassical nonadiabatic simulations for simulating longer photochemical processes, probably due to the zero-point leakage issue. |
| Databáze: | OpenAIRE |
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