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Studium biologicky relevantních systémů v elektronicky excitovaných stavech
Zámečníková, Martina ; Soldán, Pavel (advisor) ; Bludský, Ota (referee) ; Nachtigallová, Dana (referee)
Very short lifetimes of excited states of isolated bases in nucleic acids, on the picosec- ond order, are believed to contribute to photostability of the genetic code. When embedded in DNA this behavior becomes more complex, mainly due to their inter- actions via stacking and hydrogen bonding. The DNA photophysiscs is not fully understood yet. It depends e.g. on the conformation and the character of excited states. The studies on smaller systems can help to improve the understanding of these phenomena. The aim of this work was to examine the dynamics of the excited states of the n → π∗ character of the complex of N-methylformamide dimer and two waters. The study was performed using non-adiabatic dynamics simulations with on-the-fly Surface Hopping algorithm based on the potential energy surfaces and non-adiabatic couplings obtained with multi-reference approach. The results show that after the vertical excitation into delocalized S2 state the system relaxes into S1 state within several tens femtoseconds. For majority of the population, the charac- ter of the state then oscillates between localized and delocalized during the whole course of the dynamics. Comparison with calculations with the waters removed in- dicates that the delocalization is caused by waters serving as a bridge between the two chromophores. 1
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Theoretical study of spin-orbit coupling on spectra and photophysics of rhenium complexes
Heydová, Radka ; Záliš, Stanislav (advisor) ; Slavíček, Petr (referee) ; Srnec, Martin (referee)
Title: Theoretical study of spin-orbit coupling on spectra and photophysics of rhenium complexes Author: RNDr. Radka Heydová Department: Physical and Macromolecular Chemistry Supervisor: Ing. Stanislav Záliš, CSc., JHI AS CR, v.v.i. Supervisor's e-mail address: stanislav.zalis@jh.inst-cas.cz Abstract: Relativistic effects, especially spin-orbit coupling (SOC), play an essential role in transition metal chemistry and SOC treatment is indispensable for a correct theoretical description. To demonstrate the importance of SOC, the energies and oscillator strengths of vertical transitions for a series of [ReX(CO)3(2,2'-bipyridine)] (X = Cl, Br, I) and [Re(imidazole)(CO)3(1,10-phenanthroline)]+ complexes were calculated in the spin-free (SF) and spin-orbit (SO) conceptual frameworks. Two different computational approaches were adopted: SO-MS-CASPT2 where SOC was added a posteriori using a configuration interaction model (SO-RASSI), and the approximate perturbative SO-TD-DFT method. Relativistic effects were included via the two-component Douglas-Kroll-Hess transformation and the zeroth-order regular approximation in the former and the latter technique, respectively. The SF (i.e. accounting only for the scalar relativistic effects) and SO results from both methods were compared with each other and to available...
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Studium biologicky relevantních systémů v elektronicky excitovaných stavech
Zámečníková, Martina ; Soldán, Pavel (advisor) ; Bludský, Ota (referee) ; Nachtigallová, Dana (referee)
Very short lifetimes of excited states of isolated bases in nucleic acids, on the picosec- ond order, are believed to contribute to photostability of the genetic code. When embedded in DNA this behavior becomes more complex, mainly due to their inter- actions via stacking and hydrogen bonding. The DNA photophysiscs is not fully understood yet. It depends e.g. on the conformation and the character of excited states. The studies on smaller systems can help to improve the understanding of these phenomena. The aim of this work was to examine the dynamics of the excited states of the n → π∗ character of the complex of N-methylformamide dimer and two waters. The study was performed using non-adiabatic dynamics simulations with on-the-fly Surface Hopping algorithm based on the potential energy surfaces and non-adiabatic couplings obtained with multi-reference approach. The results show that after the vertical excitation into delocalized S2 state the system relaxes into S1 state within several tens femtoseconds. For majority of the population, the charac- ter of the state then oscillates between localized and delocalized during the whole course of the dynamics. Comparison with calculations with the waters removed in- dicates that the delocalization is caused by waters serving as a bridge between the two chromophores. 1
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