1. 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

2. Jablonski Diagram S0S0 S1S1 SnSn TnTn ISC IC 2 Fluorescence Phosphorescence IC ISC VC IC = Internal Conversion ISC = Intersystem Crossing

3. 3 Transient Absorbance: Pump Probe S0S0 S1S1 SnSn Pump Probe k ic

4. 4 Transient Absorbance: Pump Probe S0S0 S1S1 SnSn Pump Probe k ic

5. 5 Transient Absorbance: Pump Probe S0S0 S1S1 SnSn Pump Probe k ic

6. 6 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 nitronaphthalenes 1 Absorption Internal Conversion Vibrational Cooling Conformational Relaxation ISC 63% 2 Dissociation

7. ISC Absorption Fast UV rise - nitronaphthalenes CyclohexaneAcetonitrile Molecule τ 1 (fs) 2NN110 ± 10140 ± 10 1NN110 ± 50140 ± 50 2M1NN370 ± 70210 ± 30 7 *1 fs = 1 femtosecond = 10 -15 s (= 0.000000000000001 s) Fast rise occurs in wide variety of solvents Lifetime of ~150 fs*

8. Internal Conversion and Vibrational Cooling CyclohexaneAcetonitrile Molecule τ 2 (ps) 2NN2.1 ± 0.12.0 ± 0.1 1NN2.3 ± 0.22.8 ± 0.2 2M1NN1.4 ± 0.30.6 ± 0.1 8 IC VC CyclohexaneAcetonitrile Molecule τ 3 (ps) 2NN10 ± 112.3 ± 0.2 1NN10.3 ± 0.311.2 ± 0.4 2M1NN 7.1 ± 0.95.9 ± 0.3

9. τ 3 : Vibrational Cooling-Evidence Normalized triplet spectra for molecules in cyclohexane 9 Vibrational Cooling CyclohexaneAcetonitrile Molecule τ 3 (ps) 2NN10 ± 112.3 ± 0.2 1NN10.3 ± 0.311.2 ± 0.4 2M1NN7.1 ± 0.95.9 ± 0.3

10. 10 Au naphthalenes Mono C2h

11. 11 τ 1 : Fast rise-Au naphthalenes τ 1 (fs) Mono 300 ± 50 C2h180 ± 50

12. 12 Internal Conversion and Vibrational Cooling Au naphthalenes τ 2 (ps) τ 3 (ps) Mono 0.98 ± 0.058.7 ± 0.5 C2h1.9 ± 0.25.1 ± 0.8

13. 13 τ 3 : Vibrational Cooling-Evidence τ 3 (ps) Mono 8.7 ± 0.5 C2h5.1 ± 0.8 VC spectra features Blue shift Narrowing

14. ISC 14 Kinetic Mechanism of 1-Nitronaphthalene: Supporting Calculations Absorption Internal Conversion Vibrational Cooling Conformational Relaxation 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 15 Kinetic Mechanism of 1-Nitronaphthalene: Supporting Calculations Absorption Internal Conversion Vibrational Cooling Conformational Relaxation 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) 16 1NN2NN

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. 17 1NN2NN

18. 18 DFT Calculations Mono (eV)C2h (eV) S1S1 4.32 (0.089)4.13 (0.292) TnTn 4.274.11 TD-PBE0/IEFPCM/(TZVP, Stuttgart on Au) Mono C2h

19. 19 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.

20. Conclusions 20 Nitronaphthalenes General Mechanism

21. Acknowledgements ACS Petroleum Research Fund Case Western Reserve University Crespo Group Gray group 21

22. 22

23. 23 Comparison between naphthalene and pyrene derivatives 1-nitropyrene mechanism proposed by Crespo-Hernández and coworkers Refs

24. Experimental Setup Helios and Eos are from Ultrafast Systems, LLC Integra is from Quantronix TOPAS is from Quantronix/Light Conversion 24

25. Background and Significance Chapman’s Orientation-Photoreactivity Relationship 1 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. 26 1NN2NN