Electron Driven Reactionsin Free and Bound Molecules
Eugen Illenberger
and coworkers
Institut fuer Chemie und Biochemie
Physikalische und Theoretische Chemie
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Electron driven reactions in molecules
• Ionisation
• Electronic Excitation
e- / hv Free
Coupled to something
• Electron capture
DissociationAutodetachment
ResonantCapture
Dissociative Electron Attachment (DEA)
e- (0 - 10 eV)
M-
X-
RM-
e-
e-
Isolated molecules(effusive molecular beam)
Molecular clusters(supersonic molecular beam)
Adsorbed and condensed molecules (UHV)
20 K
Electron Driven Processes
Subexcitation Energies
• Single molecules (effusive beam)
• Molecular aggregates (supersonic beam expansion)
• Molecular nanofilm (UHV)
• Biomolecular systems
ElectronMonochromator
Molecular Beam
Quadrupole
Faraday CupSkimmer
Detector
Nozzle
ComputerStagnationChamber
Laser (IR, UV)
e- + M M-# R + X-
F-+ SF4NCO
F + SF4NCO-
(103)
(2.5x103)
(2.5x103)
(1)
NCO- + SF5
NCO + SF5-
Tania Oster, EIInt. J. Mass Spectrom. 85 (1988) 125
e- + SF5NCO SF5NCO-#
Judith Langer et al.Phys. Chem. Chem. Phys. 4 (2002) 5105
F3C-CF2I
selective C-I bondcleavage at 0 eV
≈ 10-14 cm2
Direct electronic dissociation
along a repulsive surface
0 105
CF3I- C2F5I-
LUMO: *(C-I)
€
Erot
E*=
1
1+θ
μR2 sin2α
CF3-CF2-IEtrans: 66%
Evib: 19%Erot: 15%
Judith Langer, Stefan Matejcik, EIPCCP 4 (2002) 5105
(CF3)2C=N-N=C(CF3)2)
HFFA
HFFA
Excision of CN-: Multiple bond
cleavages and rearrangement
Ilko Bald, Iwona Dabkowska,Oddur Ingólfsson & EI JCP (2007) 2983
STM
M
e-
Single Molecule Engineering
Selective bond cleavageK.-H. Rieder et al.R. Palmer et al.
Selective vibrational excitationJ. I. Pascual et al.
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.
e-M
X-
h
Substrate Induced Photochemistry
h
Photoabsorption
Fragment ion desorption (John Polanyi et al.)
Desorption of neutral molecules (Martin Wolf, Gerhard Ertl. et al.
V(z)
Distance Molecule-Surface (z)
M- M
Desorption of Neutrals via ResonancesP. Antoniewicz, Phys. Rev. B21(1980) 388
G. Ertl, M. Wolf et al.
Molecular Aggregates
#mm MMe −− →+
n)M(mMn −+−
Dissociation (DEA)
Collisional stabilization
Van der Waals clusters
Electron induced intra-cluster chemistry
new anionic products
e- + relaxation
Dissociative Associative Attachment
Petra Tegeder, Oddur Ingólfsson et al., Z. Phys. Chem. 195 (1996) 217.
C6F5X
X=Cl, Br, I
Reaction Coordinate Q
Qc
C6F5X
Intracluster Ion-Molecule Reactions
X- + RY [XRY]#- XR + Y-
Nucleophilic Displacement (SN2) Reaction
e.g. : F- + CH3Cl CH3F + Cl-
(Judith Langer)
Binary Clusters (NF3)n• (CH3Cl)m
Judith Langer, Stefan Matejcik & EIPhys. Chem. Chem. Phys. 2 (2000) 1001
DEA to NF3
SN2 Reaction
Electron attachment to CH3COCH3 (A)
Single molecules
[CH3COCH2]¯
= [M¯H]¯
Electron energy / eV
Ion
yiel
d /
s-1 H C
Clusters
Mass / amu
p = 0.25 bar, ε = 0 eV, M: Ar 1:50 with M = CH3COCH3
CH3COCH3 (58 amu) Judith Langer, Isabel Martin & EI
(2007)
Mass spectrum• New dissociative channel at ≈ 0 eV:
Loss of 2 molecules H2
a)from acetone dimer
anion (112 amu)
b)from dimer or trimer
anions forming ion-
molecules-complexes
(170-286 amu)
no M¯
Ion inte
nsi
ty /
arb
itra
ry u
nit
s
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
Fritz Weik and EI, J. Chem. Phys. 103 (1995) 1406
*
No fragment ion
desorption via DEA
F2C=CF2
CF3I
Gas
CondensedPhase
CPL 296 (1998) 208Surf. Sci. 528 (2003) 67
6 ML
Strong enhancement
CF3-
M
M*
M*-
E
M
M*M*-
0
Free molecule Bound molecule
(ET = 1.5 eV)
Biomolecular Systems
Radiation Damage
Electron driven rections
EA(T-H) ≈ 3 - 4 eV
H. A-Carime, S. Gohlke, EIPRL 92 (2004) 168103
Thymine:
e-+TT-# (T-H)-+ H
DNA Bases
Thymine
PRL 92 (2004) 168103
1
3
6
1.0 eV
1.8 eV
0 1 2 3 4
0
2
4
6
8
10
12
Cro
ss s
ecti
on (
Å2 )
Electron energy (eV)
*
1
3
DB state
Deoxyribose in DNA TAR Ribose
Tetrahydrofuran (THF) as model for the sugar unit in DNA ?
* Resonance Ilko Bald, Janina Kopyra, Iwona DabkowskaEgill Antonsson & EI, JCP 126 (2007) 074308
Electron attachment to the phosphate group
DEA to dibutyl phosphate (DBP)
Constanze König, Janina Kopyra, Ilko Bald & EI Phys. Rev. Letters 97 (2006) 018105
Strand break by single bond cleavage
EIPAM fellow
DEA to dibutyl phosphate (DBP)
EA(PO3) = 4.95 eVEA(PO2) = 3.42 eV
Constanze König, Janina Kopyra, IlkoBald & EI Phys. Rev. Letters 97 (2006) 018105
SSB via excision of P-containing units
R. Barrios, P Skurski and J. Simons, JPC B 106 (2002) 7991
Simons et al. JACS 126 (2004) 6441.
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.
1.8 eV
T-A Pairing
1 eV
1.8 eV
HCOOH formic acid
Cluster Experiments(Supersonic beam)
CF3COOH / CF3COOD
+ H
+ HF
+ FCOOH
Isabel Martin et al., CPL 419 (2005) 228
CF3COOH single molecules
Bratislava/Berlin
CF3COOH clusters in themolecular beam
Judith Langer et al., Int. J. Mass Spectrom 249/250 (2006) 477
• strong enhancement of electron capture cross section
• chemical reactions induced at very low energy
• 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
Future Directions:
Model DA immobilised on microarrays
Transfer of larger units into the gas phase
Hybridization
Tihomir Solomun et al. Eur. J. Physics D 35 (2005) 437.
Laser induced acoustic desorption (LIAD)(Ilko Bald)
m foil
Pulsed laser (Nd Yag)
Desorbing neutrals
Electrons
Paul Scheier, Tilmann Märk, Universität InnsbruckRoger Azria, Anne Lafossse, Robert Abouaf, Université Paris Sud, Orsay Nigel Mason, UCL London/ Open U. Milton Keynes Stefan Matejcik, Michal Stano, Jan D. Skalny, Comenius University, BratislavaMichael Huels, Léon Sanche, Université de Sherbrooke, QuébecHartmut Hotop, Kaiserslautern /Chris Mayhew, BirminghamE. Krishnakumar, S.V. K. Kumar, Tata Institute, BombayGregorsz Karwasz, Torun/TrentoFranco Gianturco, RomeOddur Ingólfsson, Reykjavik
Sascha Gohlke Janina KopyraRichard Balog Andrzej RosaJudith Langer Iwona DabkowskaEsther Fischbach Constanze KönigIlko Bald Tomas SkalickyIsabel Martin Michal StanoHassan Abdoul-Carime Tihomir SolomunWerner F. Schmidt Jessica ScheikeMario Orzol Marie Perot
FU Berlin
Deutsche Forschungsgemeinschaft (DFG)European Union, ESF (EPIC, COST, EIPAM)
Volkswagen Stiftung
Bundesministerium für Wirtschaft und Arbeit (BMWA)INNOVENT Jena
Alexander-von-Humboldt-StiftungDeutscher Akademischer Austausch Dienst (DAAD)
Freie Universität Berlin
NATO Research Council