case studies ii: diverse examples in photochemistry · 2015. 12. 14. · case studies ii: diverse...
TRANSCRIPT
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CasestudiesII: DiverseexamplesinphotochemistryMario BarbattiA*Midex Chair Professormario.barbatti@univ‐amu.fr
Aix Marseille Université, Institut de Chimie Radicalaire
L7
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L I G H T A N DM O L E C U L E S
When environment matters: Formamide dissociation
case study
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L I G H T A N DM O L E C U L E S
• Lundell, Krajewska, Rasanen, J Phys Chem A 102, 6643 (1998)
O
NH2
193 nmGas phase
193 nmAr matrix
193 nmXe matrix
NH3 ••• CO
NH2 + COH
H2 + NCOH
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L I G H T A N DM O L E C U L E S
• Eckert‐Maksic, Vazdar, Ruckenbauer, Barbatti, Muller, Lischka, PCCP 12, 12719 (2010)
QM: formamide• CASSCF(10,8)/6‐31G*
MM: Ar matrix• 661 atoms• 18 K• OPLSAA force field
Dynamics• 100 trajectories• 2 ps• 0.5 fs step
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L I G H T A N DM O L E C U L E S
• Eckert‐Maksic, Vazdar, Ruckenbauer, Barbatti, Muller, Lischka, PCCP 12, 12719 (2010)
O
NH2
H2
O
NH
0.5 ps O
CHNH2…. (47%)
0.5 psO
NH2
(22%)
O
NH2
*
(16%)
2 ps
O
CNH3 ..... (15%)
1 ps
+> 2ps
O
CNH3 .....> 2ps
> 2ps?
?
?
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L I G H T A N DM O L E C U L E S
• Eckert‐Maksic, Vazdar, Ruckenbauer, Barbatti, Muller, Lischka, PCCP 12, 12719 (2010)
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L I G H T A N DM O L E C U L E S
• Crespo‐Otero, Mardyukov, Sanchez‐Garcia, Barbatti, Sander, ChemPhysChem 14, 827 (2013)
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L I G H T A N DM O L E C U L E S
UV in prebiotic reactions
case study
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L I G H T A N DM O L E C U L E S
9• Powner, Sutherland, Szostak, JACS 132, 16677 (2010)
• Ferris, Orgel, JACS 88, 1074 (1966)
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L I G H T A N DM O L E C U L E S
10
Dynamics and Chemical Kinetics revealed the only possible route
QM/MM: hot 4HCN in water
RRKM
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L I G H T A N DM O L E C U L E S
11• Boulanger, Anoop, Nachtigallova, Thiel, MB, ACIE 52, 8000 (2013)
4HCN
purinenucleotides
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L I G H T A N DM O L E C U L E S
Photodynamics of Isolated Nucleobases
case study
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L I G H T A N DM O L E C U L E S
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Base F 1 (ps) 2 (ps)Ade 0.0003 1.0Gua 0.0003 0.4Thy 0.0001 0.5 6.4Ura 0.0001 0.5 2.4Cyt 0.0001 0.8 3.2
• Ullrich, Schultz, Zgierski, Stolow, PCCP 6, 2796 (2004)
Low fluorescence quantum yieldsand short excited‐state lifetimes
indicate conversion through conical intersections
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L I G H T A N DM O L E C U L E S
14
N9 H
N1
C2
H
*/cs
*/cs
NH*/cs
9
6
2
Many conicalintersections: whichof them are used for IC? Why? On which time scale?
• Marian, J Chem Phys 122, 104314 (2005)• Perun, Sobolewski, Domcke, JACS 127, 6257 (2005)
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L I G H T A N DM O L E C U L E S
15
youtube.com/user/mbarbatti
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L I G H T A N DM O L E C U L E S
16• Plasser, Crespo‐Otero, Pederzoli, Pittner, Lischka, Barbatti, JCTC 10, 1395 (2014)
Expe
rimen
talAD
C(2)
0
20
40
60
80
S 0 p
opul
atio
n at
1 p
s (%
)
682
5712 N9 H
N1
C2
H
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L I G H T A N DM O L E C U L E S
Tautomers and Solvents
case study
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L I G H T A N DM O L E C U L E S
18
Experimental
• Cohen, Hare, Kohler, JACS 125, 13594 (2003)
Short time constant (0.18 ps):
Long time constant (8.8 ps):
N
N NH
N
NH2
7H-adenine
N
N N
NH
NH2
9H-adenine
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L I G H T A N DM O L E C U L E S
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0 200 400 600 800 10000.0
0.2
0.4
0.6
0.8
1.0
0 200 400 600 800 10000.0
0.2
0.4
0.6
0.8
1.0
9H-Ade
7H-Ade
Exci
ted
stat
e po
pula
tion
T im e (fs)
SimulationsExperimental
short
longExperimental assignment must be reviewed based on the computational data
N
N NH
N
NH2
N
N N
NH
NH2
• Barbatti, JACS 136, 10246 (2014) ADC(2)/aug‐cc‐pVDZ
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L I G H T A N DM O L E C U L E S
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9H‐Ade + water: C2 puckering
similar to Gas Phase
7H‐Ade + water: Planar
completely different from GP
ADC(2)/aug‐cc‐pVDZ
youtube.com/user/mbarbatti
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L I G H T A N DM O L E C U L E S
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Microsolvated 7H‐Ade
• Barbatti, JACS 136, 10246 (2014)
nN+nO *
Water is not only disturbing the system; it plays an active
role in the deactivation
e
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L I G H T A N DM O L E C U L E S
Why does 2-Aminopurine Fluoresce in Water but not in Vapor?
case study
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L I G H T A N DM O L E C U L E S
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Adenine 2‐Aminopurine
• Canuel, Mons, Piuzzi, Tardivel, Dimicoli, Elhanine, J Chem Phys 122, 074316 (2005)
Adenine 2‐Aminopurine
Vapor 1 30
Water 0.18 18000
Excited‐State Lifetime in ps
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L I G H T A N DM O L E C U L E S
24• Lobsiger, Blaser, Sinha, Frey, Leutwyler, Nat Chem 6, 989 (2014)
There is a correlation between the lifetime and the number/position of
water molecules
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L I G H T A N DM O L E C U L E S
25
2AP‐1W
2AP‐1WT
2AP‐2W
2AP‐2WT 2AP‐3WT 2AP‐4WT
2AP (0W)
2AP‐3W
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L I G H T A N DM O L E C U L E S
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ADC(2)/aug‐cc‐pVDZ
0.1 0.2 0.3 0.4
0
5
10
15
20
3WT2WT
1WT
3W
2W1W
Life
time
(ns)
S1 Energy Barrier (eV)
W
0W
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L I G H T A N DM O L E C U L E S
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• Water far from NH2: adiabatic path to X
• Water near NH2:nonadiabatic path to X
• Barbatti and Lischka, PCCP 17, 15452 (2015)
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L I G H T A N DM O L E C U L E S
• A combination of static properties and dynamics allows to get many physical chemical insights.• Use the imagination to go beyond routine.