1 / 57

Electron Driven Reactions in Free and Bound Molecules Eugen Illenberger and coworkers

Electron Driven Reactions in Free and Bound Molecules Eugen Illenberger and coworkers Institut fuer Chemie und Biochemie Physikalische und Theoretische Chemie. Coupled to something. Electron driven reactions in molecules. Free. e - / hv. • Ionisation • Electronic Excitation.

trina
Télécharger la présentation

Electron Driven Reactions in Free and Bound Molecules Eugen Illenberger and coworkers

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Electron Driven Reactions in Free and Bound Molecules Eugen Illenberger and coworkers Institut fuer Chemie und Biochemie Physikalische und Theoretische Chemie

  2. Coupled to something Electron driven reactions in molecules Free e- / hv • Ionisation • Electronic Excitation • Electron capture

  3. Dissociative Electron Attachment (DEA) Resonant Capture Autodetachment Dissociation

  4. Isolated molecules (effusive molecular beam) e- (0 - 10 eV) X- M- R e- Molecular clusters (supersonic molecular beam) e- Adsorbed and condensed molecules (UHV) M- 20 K

  5. Electron Driven Processes Subexcitation Energies • Single molecules (effusive beam) • Molecular aggregates (supersonic beam expansion) • Molecular nanofilm (UHV) • Biomolecular systems

  6. Laser (IR, UV) Stagnation Chamber Detector Molecular Beam Quadrupole Electron Monochromator Faraday Cup Skimmer Nozzle Computer e- + M  M-#  R + X-

  7. e- + SF5NCO SF5NCO-# (103) F-+ SF4NCO F + SF4NCO- (2.5x103) (2.5x103) NCO- + SF5 NCO + SF5- (1) Tania Oster, EI Int. J. Mass Spectrom. 85 (1988) 125

  8. F3C-CF2I selective C-I bond cleavage at 0 eV s ≈ 10-14 cm2 10 5 0 Direct electronic dissociation along a repulsive surface Judith Langer et al. Phys. Chem. Chem. Phys. 4 (2002) 5105

  9. C2F5I- CF3I- LUMO: s*(C-I)

  10. CF3-CF2-I Etrans: 66% Evib: 19% Erot: 15%  Judith Langer, Stefan Matejcik, EI PCCP 4 (2002) 5105

  11. (CF3)2C=N-N=C(CF3)2) HFFA

  12. HFFA Excision of CN-: Multiple bond cleavages and rearrangement Ilko Bald, Iwona Dabkowska, Oddur Ingólfsson & EI JCP (2007) 2983

  13. STM Selective bond cleavage K.-H. Rieder et al. R. Palmer et al. M Selective vibrational excitation J. I. Pascual et al. e- Single Molecule Engineering

  14. Scientists from the 's Nanoscale Science Facility have made a breakthrough in manipulating the smallest single molecules and atoms by devising a new technique of molecular dissection which induces the "birth" of a daughter atom from the parent molecule. This breakthrough, which is highlighted in a paper published in the journal, Nature, today (Thursday 17 March). The new method, devised by Professor Richard Palmer and Dr Peter Sloan, uses the tip of a Scanning Tunnelling Microscope (STM) to inject two electrons into the parent chlorobenzine molecule to induce a dissociation event - the first electron sets the molecule into vibration and the second electron breaks the bond between the parent molecule and daughter chlorine atom.

  15. Substrate Induced Photochemistry X- Photoabsorption M e- hn  h Fragment ion desorption (John Polanyi et al.) Desorption of neutral molecules (Martin Wolf, Gerhard Ertl. et al.

  16. Desorption of Neutrals via Resonances P. Antoniewicz, Phys. Rev. B21(1980) 388 V(z) M M- Distance Molecule-Surface (z) G. Ertl, M. Wolf et al.

  17. Molecular Aggregates

  18. Van der Waals clusters Dissociation (DEA) relaxation e- + Electron induced intra- cluster chemistry Collisional stabilization new anionic products

  19. Dissociative  Associative Attachment Petra Tegeder, Oddur Ingólfsson et al., Z. Phys. Chem. 195 (1996) 217. C6F5X X=Cl, Br, I

  20. C6F5X Qc Reaction Coordinate Q

  21. Intracluster Ion-Molecule Reactions X- + RY  [XRY]#-  XR + Y- Nucleophilic Displacement (SN2) Reaction e.g. : F- + CH3Cl  CH3F + Cl- (Judith Langer)

  22. Binary Clusters (NF3)n• (CH3Cl)m

  23. SN2 Reaction DEA to NF3 Judith Langer, Stefan Matejcik & EI Phys. Chem. Chem. Phys. 2 (2000) 1001

  24. H C Electron attachment to CH3COCH3 (A) Single molecules [CH3COCH2]¯ = [M¯H]¯ Ion yield / s-1 Electron energy / eV

  25. CH3COCH3 (58 amu) Judith Langer, Isabel Martin & EI (2007) Clusters Mass spectrum • New dissociative channel at ≈ 0 eV: • Loss of 2 molecules H2 • from acetone dimer anion (112 amu) • from dimer or trimer anions forming ion-molecules-complexes (170-286 amu) Ion intensity / arbitrary units no M¯ Mass / amu p = 0.25 bar, ε = 0 eV, M: Ar 1:50 with M = CH3COCH3

  26. Condensed Phase Reactions • Electron stimulated desorption via DEA (the effect of the medium) • Slow Electrons as a Soft Tool for Surface Modifications • Substrate Mediated Processes

  27. F2C=CF2 p* No fragment ion desorption via DEA Fritz Weik and EI, J. Chem. Phys. 103 (1995) 1406

  28. CF3I Gas 6 ML CPL 296 (1998) 208 Surf. Sci. 528 (2003) 67 Condensed Phase Strong enhancement

  29. CF3- E M*- M* M* M*- M M 0 (ET = 1.5 eV) Bound molecule Free molecule

  30. Biomolecular Systems

  31. Radiation Damage Electron driven rections

  32. DNA Bases Thymine: e-+TT-#  (T-H)-+ H EA(T-H) ≈ 3 - 4 eV H. A-Carime, S. Gohlke, EI PRL 92 (2004) 168103

  33. PRL 92 (2004) 168103 Thymine 1.8 eV 3 1 6 1.0 eV

  34. 12 10 8 6 4 2 0 0 1 2 3 4 DB state 3 1 Cross section (Å2) p* Electron energy (eV)

  35. Deoxyribose in DNA TAR Ribose Tetrahydrofuran (THF) as model for the sugar unit in DNA ?

  36. Ilko Bald, Janina Kopyra, Iwona Dabkowska Egill Antonsson & EI, JCP 126 (2007) 074308 p* Resonance

  37. Electron attachment to the phosphate group

  38. Constanze König, Janina Kopyra, Ilko Bald & EI Phys. Rev. Letters 97 (2006) 018105 EIPAM fellow DEA to dibutyl phosphate (DBP) Strand break by single bond cleavage

  39. EA(PO3) = 4.95 eV EA(PO2) = 3.42 eV Constanze König, Janina Kopyra, IlkoBald & EI Phys. Rev. Letters 97 (2006) 018105 DEA to dibutyl phosphate (DBP) SSB via excision of P-containing units

  40. R. Barrios, P Skurski and J. Simons, JPC B 106 (2002) 7991 Simons et al. JACS 126 (2004) 6441.

  41. 1.8 eV No transfer of excess charge initially localised on T • H. A.Carime et al., Chem. Phys. Letters 387 (2004) 267. • S. Ptasinska et al., Angew. Chem. Int. Ed. 45 (2006) 183.

  42. T-A Pairing 1 eV 1.8 eV

  43. Cluster Experiments (Supersonic beam) HCOOH formic acid CF3COOH / CF3COOD

  44. + H CF3COOH single molecules +HF Bratislava/Berlin + FCOOH Isabel Martin et al., CPL 419 (2005) 228

  45. CF3COOH clusters in the molecular beam Judith Langer et al., Int. J. Mass Spectrom 249/250 (2006) 477

  46. • strong enhancement of electron capture cross section • chemical reactions induced at very low energy

  47. • NBs act as antennas for low energy electrons eventually transfer to the backbone (SSB) • Sugar unit is sensitive • Phosphate group is sensitive  Different mechanisms contribute to SSBs

More Related