Untersuchungen der Quantendynamik und Kontrolle von elementaren Prozessen und DNA-Bausteinen und in Photosensitizern

• Antragstellerin: Professorin Dr. Leticia González
• Fachliche Zuordnung: Theoretische Chemie: Elektronenstruktur, Dynamik, Simulation
• Förderung: Förderung von 2008 bis 2013
• Projektkennung: Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 82552438

• Erstellungsjahr: 2013

Zusammenfassung der Projektergebnisse

The study of the both DNA nucleobases and endoperoxides shows that the description of non-adiabatic processes is vital to understand UV-photoinitiated deactivation mechanisms. In both cases, conical intersections involving more than two states where found and interestingly in both cases, triplet states were found to play a fundamental role. Since the associated dynamics involves a large number of degrees of freedom, a general ab initio molecular dynamics method which includes non-adiabatic as well as spin-orbit couplings (and dipole couplings for explicit laser interaction) on the same footing, was developed. The advantage of this method, termed SHARC (Surface hopping in the adiabatic representation including arbitrary couplings), is that allows then to consider both internal conversion and intersystem crossing processes into account. The application to this method to keto-cytosine illustrated that, contrary to what is generally believed, ISC can be an ultrafast process taking place in a similar scale as internal conversion. Moreover, it is shown that several relaxation pathways are responsible for the fs transient observed experimentally in cytosine, including deactivation via three-state conical intersections. Moreover, we also showed that the enol form of cytosine also seems to be responsible for the slower, ps, transient observed experimentally. Due to the role of ISC played in these systems, it seems very plausible that the much longer time scale (ns) is due to the deactivation from the lowest triplet to the ground state. An eight-state degeneracy including four singlets and four triplet states was found in a model oxygen carrier endoperoxide. Using both quantum dynamical simulations in up to nine degrees of freedom as well as molecular dynamics in full dimensionality with SHARC it was shown that this high-order degeneracy plays a key role in providing an efficient deactivation to the ground state while generate oxygen homolysis products. Due to the time invested in developing new methods not foreseen in the proposal, no time could be allocated to treat DNA mispairs.

Projektbezogene Publikationen (Auswahl)

• Identifying the low-lying electronic states of anthracene-9,10-endoperoxide. Chem. Phys. Lett. 452, 67-71, (2008)
  I. Corral, L. González, A. Lauer, W. Freyer, H. Fidder, and K. Heyne
  
• On the puzzling deactivation mechanism of thymine after light irradiation. AIP Conf. Proc. 180, 169-175, (2008)
  L. González, J. González-Vázquez, E. Samoylova, and T. Schultz
  
• Theoretical investigation of anthracene-9,10-endoperoxide vertical singlet and triplet excitation spectra. J. Comput. Chem. 29, 1982-1991, (2008)
  I. Corral and L. González
  
• Thymine relaxation after UV irradiation: the role of tautomerization and πσ* states. Phys. Chem. Chem. Phys. 11, 3927-3934, (2009)
  J. González-Vázquez, L. González, E. Samoylova, and T. Schultz
  
• A time-dependent picture of the ultrafast deactivation of keto-Cytosine including three-state conical intersections. Chem. Phys. Chem. 11, 3617-3624, (2010)
  J. González-Vázquez and L. González
  
• Four plus four state degeneracies in the O-O photolysis of aromatic endoperoxides. J. Phys. Chem. Lett. 1, 1036-1040, (2010)
  D. Mollenhauer, I. Corral, and L. González
  
• Four-state conical intersections: The nonradiative deactivation funnel connected to O-O homolysis in benzene endoperoxide. Chem. Phys. Lett. 499, 21-25, (2010)
  I. Corral and L. González
  
• Can TD-DFT predict excited states in endoperoxides? Comp. Theo. Chem. 975, 13-19, (2011)
  L. Martinez-Fernandez, L. González, and I. Corral
  
• Nonadiabatic ab initio molecular dynamics including spin-orbit coupling and laser fields Faraday Discuss. 153, 261-273, (2011)
  P. Marquetand, M. Richter, J. González-Vázquez, I. Sola, and L. González
  
• SHARC - ab initio molecular dynamics with surface hopping in the adiabatic representation including arbitrary couplings. J. Chem. Theory Comput. 7, 1253-1258, (2011). Corrigendum: 8, 374-374, (2012)
  M. Richter, P. Marquetand, J. González-Vázquez, I. Sola, and L. González
  
• 9D nonadiabatic quantum dynamics through a four-state degeneracy: Investigating the homolysis of the O-O bond in anthracene-9,10-endoperoxide. J. Chem. Phys. 137, 22A524, (2012)
  M. Assmann, G. Worth, and L. González
  
• Femtosecond intersystem crossing in the DNA nucleobase cytosine. J. Phys. Chem. Lett. 3, 3090-3095, (2012)
  M. Richter, P. Marquetand, J. González-Vázquez, I. Solá, and L. González
  
• Mixed quantum-classical dynamics in the adiabatic representation to simulate molecules driven by strong laser pulses. J. Phys. Chem. A 116, 2800-2807, (2012)
  J. J. Bajo, J. González-Vázquez, I. Sola, J. Santamaria, M. Richter, P. Marquetand, and L. González
  
• Singlet oxygen generation versus O--O homolysis in phenyl-substituted anthracene endoperoxides investigated by RASPT2, CASPT2, CC2 and TD-DFT methods Theor. Chem. Acc. 131, 1295, (2012)
  S. Kupfer, G. Pérez-Hernández, and L. González