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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
2
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.
Kinetic Mechanism of the nitronaphthalenes1
Absorption
Internal Conversion
Vibrational Cooling
ConformationalRelaxationISC
63%2
Dissociation
ISC
Absorption
0
10
20
0
10
20
30
400 500 6000
5
Time delay (ps) 0.00to 0.77
2NNAcetonitrile
Time delay (ps) 0.00to 0.80
2M1NN
1NN
A (10
-3)
Wavelength (nm)
Time delay (ps) 0.00to 0.87
Fast UV rise - nitronaphthalenes
0
5
10
0
20
40
400 500 6000
5
Time delay (ps) 0.00 to 0.80
2NN
Cyclohexane
Time delay (ps) 0.00 to 0.80
2M1NN
1NN
A (
10-3
)
Wavelength (nm)
Time delay (ps) 0.00 to 0.90
Cyclohexane Acetonitrile
Molecule τ1 (fs) τ1 (fs)
2NN 110 ± 10 140 ± 101NN 110 ± 50 140 ± 502M1NN 370 ± 70 210 ± 30
S0
Ground State
S1* Excited State
T3
Excited State
S1
Dissociative State
7
• *1 fs = 1 femtosecond = 10-15 s (= 0.000000000000001 s)• Fast rise occurs in wide variety of solvents• Lifetime of ~150 fs*
8
01020
30
0
10
20
30
400 500 6000
3
6
Time delay (ps) 0.8 to 14 31
2NNAcetonitrile
Time delay (ps) 0.8 to 37 75
2M1NN
1NN
A (10
-3)
Wavelength (nm)
Time delay (ps) 0.9 to 12 24
Internal Conversion and Vibrational Cooling
0
10
20
0
20
40
400 500 6000
4
8
Time delay (ps) 0.8 to 11 35
2NNCyclohexane
Time delay (ps) 0.8 to 30 85
2M1NN
1NN
A (10
-3)
Wavelength (nm)
Time delay (ps) 0.9 to 25 49
Cyclohexane AcetonitrileMolecule τ2 (ps) τ2 (ps)
2NN 2.1 ± 0.1 2.0 ± 0.11NN 2.3 ± 0.2 2.8 ± 0.22M1NN 1.4 ± 0.3 0.6 ± 0.1
T3
Excited State
T1*
Vibrationally-Excited State
T1
Relaxed State
IC
VC
Cyclohexane AcetonitrileMolecule τ3 (ps) τ3 (ps)
2NN 10 ± 1 12.3 ± 0.21NN 10.3 ± 0.3 11.2 ± 0.42M1NN 7.1 ± 0.9 5.9 ± 0.3
9
τ3: Vibrational Cooling-Evidence
350 400 450 5000.0
0.5
1.0
500 550 600 6500.0
0.5
1.0
500 550 600 6500.0
0.5
1.0
Wavelength (nm)
Time delay (ps) 20 27 36 62
2NN
Wavelength (nm)
Time Delay (ps) 4 9 24
1NN
A (10
-3)
A (10
-3)
A (10
-3)
Wavelength (nm)
Time delay (ps) 1.8 4.4 12 25
2M1NN
Normalized triplet spectra for molecules in cyclohexane
T1*
Vibrationally-Excited State
T1
Relaxed State
Vibrational Cooling
Cyclohexane AcetonitrileMolecule τ3 (ps) τ3 (ps)
2NN 10 ± 1 12.3 ± 0.21NN 10.3 ± 0.3 11.2 ± 0.42M1NN 7.1 ± 0.9 5.9 ± 0.3
10
Au naphthalenes
Mono
C2h
11
hν
ISC
IC
VC
S0
S1
Tn
T1
τ1: Fast rise-Au naphthalenes
0
2
4
6
8
350 400 450 500 550 600 650
0
2
4
6
Time delay (ps) 0.00 to 0.87
Mono
A (
10-3)
Wavelength (nm)
Time delay (ps) 0.00 to 0.80C2h
τ1 (fs)
Mono 300 ± 50
C2h 180 ± 50
12
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
13
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
14
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)
15
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)
16
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
17
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.
1NN 2NN
18
DFT Calculations
hν
ISC
IC
VC
S0
S1
Tn
T1
Mono (eV) C2h (eV)S1 4.32 (0.089) 4.13 (0.292)Tn 4.27 4.11
TD-PBE0/IEFPCM/(TZVP, Stuttgart on Au)
Mono
C2h
19
hν
ISC~10-110 ps
Fast IC
S0
S1
T3
T1
S2 IC~200 fs
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
20
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
21
Acknowledgements
• ACS Petroleum Research Fund• Case Western Reserve University• Crespo Group• Gray group
22
23
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
24
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
25
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
26
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.
1NN 2NN
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