1. 1 Ultrafast processes in molecules Mario Barbatti barbatti@kofo.mpg.de Introduction

2. 2 settling the bases: photochemistry, excited states, and conical intersections

3. 3 Stating the problem: What does happen to a molecule when it is electronically excited? How does it relax and get rid of the energy excess? How long does this process take? What products are formed? How does the relaxation affect or is affected by the environment? Is it possible to interfere and to control the outputs?

4. 4 Basic sciencesInteraction photon/matter Coeherence/decoherence Nature of transition states Nonadiabatic phenomena BiologyLight and UV detection Photosynthesis Genetic code degradation Cellular proton pump Atmospheric sciencesUV induced chemistry Greenhouse effect AstrophysicsInterstellar molecular synthesis TechnologyControl of chemical reactions Molecular photo-switches

5. 5 Pump-probe experiments based on ultra-fast laser pulses have increased the resolution of the chemical measurements to the femtosecond (10 -15 s) time scale.

6. 6 Theory is necessary to map the ground and excited state surfaces and to model the mechanisms taking place upon the photoexcitation. Theory is indispensable to deconvolute the raw time- resolved experimental information and to reveal the nature of the transition species. In particular, excited-state dynamics simulations can shed light on time dependent properties such as lifetimes and reaction yields.

7. 7

8. 8 P ~ |  j|  |i  | 2  ~ ns

9. 9 P ~ v  j| |ij| |i N  ~ fs

10. 10 1.How are the excited state surfaces? 2. For which geometries does the molecule have conical intersections? 3. Can the molecule reach them?

11. 11 Antol et al. JCP 127, 234303 (2007) Barbatti et al., Chem. Phys. 349, 278 (2008) pyridone formamide

12. 12 Conical intersectionStructureExamples TwistedPolar substituted ethylenes (CH 2 NH 2 + ) PSB3, PSB4 HBT Twisted-pyramidalizedEthylene 6-membered rings (aminopyrimidine) 4MCF Stilbene Stretched- bipyramidalized Polar substituted ethylenes Formamide 5-membered rings (pyrrole, imidazole) H-migration/carbeneEthylidene Cyclohexene Out-of-plane OFormamide Rings with carbonyl groups (pyridone, cytosine, thymine) Bond breakingHeteroaromatic rings (pyrrole, adenine, thiophene, furan, imidazole) Proton transferWatson-Crick base pairs

13. 13 Barbatti et al. PCCP 10, 482 (2008)

14. 14

15. 15 At a certain excitation energy: 1. Which reaction path is the most important for the excited-state relaxation? 2. How long does this relaxation take?

16. 16 about methods & programs

17. 17 SubjectApproachMethods Vertical excitation spectra Conventional adiabatic quantum chemistry MRCI, CC2, TDDFT Stationary points in excited states Conventional adiabatic quantum chemistry MRCI, CC2, TDDFT Conical intersectionsNonadiabatic quantum chemistry MRCI, MCSCF Reaction pathsConvent. adiabatic quantum chemistry (multireference) MRCI, CASPT2, MCSCF Lifetime and yieldsMixed quantum-classical dynamics methods MRCI, MCSCF (+ MM)

18. 18 Wave packet propagation Surface hopping propagation

19. 19 Q   Boat Chair Envelope Twisted-chair Screw-boat Ex.: 1 S 6 = Screw-boat with atoms 1 above the plane and 6 below Cremer and Pople, JACS 97, 1358 (1975)

20. 20 dynamics: adenine

21. 21

22. 22

23. 23 PCCP 12, 4959 (2010)

24. 24Base  1 (ps)  2 (ps)Ade1.00 Gua0.36 Thy0.496.4 Ura0.532.4 Cyt0.823.2 Ullrich, Schultz, Zgierski, Stolow, PCCP 6, 2796 (2004) Short lifetimes together with the low fluorescence quantum yields indicate internal conversion through conical intersections Purines: single step Pyrimidines: multiple steps Purines: single step Pyrimidines: multiple steps

25. 25 A short lifetime can enhance the photostability because the molecule does not stay too long in reactive excited states This effect might have constituted an evolutionary advantage for the five nucleobases forming DNA and RNA Indeed, there are experimental evidences that purine precursors in the prebiotic world were photostable

26. 26 1 ps 30 ps 9H-Adenine 2-aminopurine

27. 27 N9 H N1 C2 H  */cs  NH */cs 9 6 2 Many conical intersections available. Which of them are used for internal conversion? Why? On which time scale?

28. 28 E (eV)  R (Å.amu 1/2 ) cs  * n*n* cs  * n*n* cs  * n*n* cs n*n* A1 A2 G1 C2 C1c P1b  * P1 P1a P1c P2 C1 A2a A1a G1a P2a P1d C1d C1b C1a G2 G2a

29. 29 E (eV)  R (Å.amu 1/2 ) cs  * n*n* cs  * n*n* cs  * n*n* cs n*n*  * A2 A2a A1 A1a JACS 130, 6831 (2008)

30. 30 E (eV)  R (Å.amu 1/2 ) cs  * n*n* cs  * n*n* cs  * n*n* cs n*n* A1 A2  * A2a A1a G1 G1a G2 G2a J Chem Phys 134, 014304 (2011)

31. G2 G2a 31 E (eV)  R (Å.amu 1/2 ) cs  * n*n* cs  * n*n* cs  * n*n* cs n*n* A1 A2 G1 P1b  * P1 P1a P1c A2a A1a G1a P2 P2a J Phys Chem A 113, 12686 (2009) J Phys Chem A 115, 5247 (2011)

32. G2 G2a 32 E (eV)  R (Å.amu 1/2 ) cs  * n*n* cs  * n*n* cs  * n*n* cs n*n* A1 A2 G1 P1b  * P1 P1a P1c P2 A2a A1a G1a P2a P1d C1c C1d C2 C1b C1 C1a PCCP 13, 6145 (2011)

33. 33 PNAS 107, 21453 (2010) E (eV)  R (Å.amu 1/2 ) cs  * n*n* cs  * n*n* cs  * n*n* cs n*n* A1 A2 G1 C2 C1c P1b  * P1 P1a P1c P2 C1 A2a A1a G1a P2a P1d C1d C1b C1a Single step Multiple steps G2 G2a

34. 34 PHOTOINDUCED PHENOMENA IN NUCLEIC ACIDS 1. Photoinduced processes in nucleic acids Mario Barbatti, Antonio Borin, Susanne Ullrich 2. UV-excitation I: frequency resolved Mattanjah S. de Vries 3. UV-excitation II: time resolved Thomas Schultz 4. Excitation of nucleobases I: reaction paths Manuela Merchán 5. Excitation of nucleobases II: dynamics Letícia Gonzalez 6. Excitation of paired and stacked nucleobases Dana Nachtigallova, Hans Lischka 7. Modified nucleobases Spiridoula Matsika 8. UV-excitation of solvated nucleobases I Carlos E. Crespo-Hernandez Mario Barbatti, Antonio C. Borin, Susanne Ullrich (Eds.) Coming soon 9. UV-excitation of solvated nucleobases II Roberto Improta 10. Excitation of single and double strands I Bern Kohler 11. Excitation of single and double strands II Zhenggang Lan, Walter Thiel 12. Synchrotron irradiation of DNA fragments Martin Schwell 13. Physiological aspects of excitation of DNA Donat-P. Häder 14. Photoynthesis in prebiotic environments Scott Sandford 15. Photoinduced charge-transfer in DNA and applications in nano-electronics Kiyohiko Kawai, Tetsuro Majima 16. Electronic energy transfer in nucleic acids Dimitra Markovitsi

35. 35 9H-adenine 2-pyridone Chem. Phys. 349, 278 (2008)

36. 36 Adenine is trapped close to 2 E conformation and because of this it has time enough to tune the coordinates of the conical intersection. Adenine is a non-fluorescent species. Pyridone does not stay close to any specific conformation long enough in order to have time to tune the coordinates of the conical intersections. Pyridone is a fluorescent species.

37. 37 conclusions

38. 38

39. 39

40. 40 MQCD simulations are not a substitute for the conventional quantum-chemistry calculations, but a complementary tool to be used carefully given their high computational costs They can be specially useful to test specific hypothesis raised either by experimental analysis or conventional calculations

41. 41 Zewail, J. Phys. Chem. A 104, 5660 (2000)

42. 42 Contact barbatti@kofo.mpg.de Next lecture Transient spectrum Excited state surfaces