ULTRAFAST DYNAMICS IN NITRO- AND (ORGANOPHOSPHINE)GOLD(I)-POLYCYCLIC AROMATIC HYDROCARBONS R. Aaron Vogt , Christian Reichardt, Carlos E. Crespo-Hernández, Thomas G. Gray Department of Chemistry, Case Western Reserve University Molecular Spectroscopy Symposium - June 21, 2011
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ULTRAFAST DYNAMICS IN NITRO- AND (ORGANOPHOSPHINE)GOLD(I)-POLYCYCLIC AROMATIC HYDROCARBONS R. Aaron Vogt, Christian Reichardt, Carlos E. Crespo-Hernández,
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ULTRAFAST DYNAMICS IN NITRO- AND (ORGANOPHOSPHINE)GOLD(I)-POLYCYCLIC
AROMATIC HYDROCARBONSR. Aaron Vogt, Christian Reichardt, Carlos E. Crespo-Hernández,
Thomas G. Gray
Department of Chemistry, Case Western Reserve University
Molecular Spectroscopy Symposium - June 21, 2011
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Jablonski Diagram
S0
S1
Sn
Tn
ISC
IC Fluorescence
Phosphorescence
IC
ISC
VC
IC = Internal ConversionISC = Intersystem Crossing
3
Transient Absorbance: Pump Probe
S0
S1
Sn
Pump
Probe
kic
4
Transient Absorbance: Pump Probe
S0
S1
Sn
Pump
Probe
kic
5
Transient Absorbance: Pump Probe
S0
S1
Sn
Pump
Probe
kic
6
S0
Ground State
S1* Excited State S1
Dissociative State
T3
Excited State
ArO·NO·
T1*
Vibrationally-Excited State
T1
Relaxed State
1 Reichardt, C., Vogt, R.A., Crespo-Hernández, C. E., J. Chem. Phys. 2009, 131, 224518.2 Hurley, R., Testa, A.C. J. Am. Chem. Soc. 1968, 90, 1949.
Internal Conversion and Vibrational CoolingAu naphthalenes
hν
ISC
IC
VC
S0
S1
Tn
T1
0
2
4
6
8
10
350 400 450 500 550 600 6500
2
4
6
8
10
Time delay (ps) 0.87 1.03 1.4 2.3 6.2 19 200
Mono
A (
10-3)
Wavelength (nm)
Time delay (ps) 0.80 1.3 1.7 2.1 3.2 5.4 10 30
C2h
τ2 (ps) τ3 (ps)
Mono 0.98 ± 0.05 8.7 ± 0.5
C2h 1.9 ± 0.2 5.1 ± 0.8
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400 420 440 460
0.7
0.8
0.9
1.0
420 440 460 480
0.6
0.8
1.0
Wavelength (nm)
Time delay (ps) 4 7 15 40
Mono
A (
10-3)
A (
10-3)
Wavelength (nm)
Time delay (ps) 4 6 10 41
C2h
τ3: Vibrational Cooling-Evidence
τ3 (ps)
Mono 8.7 ± 0.5
C2h 5.1 ± 0.8
VC spectra features• Blue shift• Narrowing
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ISC
Kinetic Mechanism of 1-Nitronaphthalene:Supporting Calculations S0
Ground State
S1* Excited State
T3
Excited State
T1*
Vibrationally-Excited State
T1
Relaxed State
Absorption
Internal Conversion
Vibrational Cooling
S1
Dissociative State
ConformationalRelaxation
Calculated PES for nitronaphthalenes in acetonitrile. The nitro-aromatic torsion angle was fixed while all other coordinates were optimized. B3LYP/IEFPCM/6-311++G(d,p)//TD-PBE0/NE-IEFPCM(Acetonitrile)
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ISC
Kinetic Mechanism of 1-Nitronaphthalene:Supporting Calculations S0
Ground State
S1* Excited State
T3
Excited State
T1*
Vibrationally-Excited State
T1
Relaxed State
Absorption
Internal Conversion
Vibrational Cooling
S1
Dissociative State
ConformationalRelaxation
Calculated PES for nitronaphthalenes in acetonitrile. The nitro-aromatic torsion angle was fixed while all other coordinates were optimized. B3LYP/IEFPCM/6-311++G(d,p)//TD-PBE0/NE-IEFPCM(Acetonitrile)
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DFT Calculations
Calculated PES for nitronaphthalenes in acetonitrile. The nitro-aromatic torsion angle was fixed while all other coordinates were optimized. B3LYP/IEFPCM/6-311++G(d,p)//TD-PBE0/NE-IEFPCM(Acetonitrile)
1NN 2NN
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DFT Calculations
Calculated PES for nitronaphthalenes in acetonitrile. The nitro-aromatic torsion angle was fixed while all other coordinates were optimized. B3LYP/IEFPCM/6-311++G(d,p)//TD-PBE0/NE-IEFPCM level of theory.
Comparison between naphthalene and pyrene derivatives
Crespo-Hernández Carlos, E.; Burdzinski, G.; Arce, R. J. Phys. Chem. A 2008, 112, 6313.Vogt, R. A.; Peay, M. A.; Gray, T. G.; Crespo-Hernandez, C. E. J. Phys. Chem. Lett. 2010, 1, 1205.
hν
ISC~7 ps
Fast IC
S0
S1
T3
T1
CR~100 fs
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Conclusions
hν
ISC
IC
VC
S0
S1
Tn
T1
Nitronaphthalenes General Mechanism
S1Tn
VC
IC
Nitro-Aromatic Torsion Angle
En
erg
y T1
2NN
1NN
2M1NN
S0
ArO·+
NO·
Products
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Acknowledgements
• ACS Petroleum Research Fund• Case Western Reserve University• Crespo Group• Gray group
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Comparison between naphthalene and pyrene derivatives
1-nitropyrene mechanism proposed byCrespo-Hernández and coworkers
Refs
Experimental Setup
• Helios and Eos are from Ultrafast Systems, LLC• Integra is from Quantronix• TOPAS is from Quantronix/Light Conversion
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N
O
O
N
O
O
O
N O
(1)
O + NO
(3)
(2)
N
O
OX
(parallel)
(perpendicular)
Background and SignificanceChapman’s Orientation-Photoreactivity Relationship1
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Schematic representation of Chapman’s Orientation-Photoreactivity relationship in the photochemistry of nitro-PAHs
1 Chapman, O. L.; Heckert, D. C.; Reasoner, J. W.; Thackaberry, S. P.. J. Am. Chem. Soc. 1966, 88, 5550.
oxaziridine-type transition state
nitric oxide
nitrite intermediate
aryloxy radical
Carlos E. Crespo
Why this is shown here and not during the introduction? Actually, I will suggest to focus on the mechanism that we have developed and not discuss Chapman's and/or Brown's mechanisms for this talk at this level of details.
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DFT Calculations
Calculated PES for nitronaphthalenes in acetonitrile. The nitro-aromatic torsion angle was fixed while all other coordinates were optimized. B3LYP/IEFPCM/6-311++G(d,p)//TD-PBE0/NE-IEFPCM level of theory.