Influence of solvation on 1-aminonaphthalene photophysics: ultrafast relaxation in the isolated molecule, molecular clusters and solution by Raúl Montero, Alvaro Peralta Conde, Fernando Castaño and Asier Longarte Departamento de Química Física Universidad del País Vasco (UPV/EHU) 65th Ohio Spectroscopy Meeting

Motivation  To understand the photophysics of 1-aminonaphthalene (AMN), in particular the dynamics of the L a /L b state coupling.  Influence of solvation on the photophysics of the molecule. The interaction of polar solvents with the amino group. AMN(H 2 O) 1-3 clusters  From H-bonded clusters to bulk. AMN in methanol solutions.

65th Ohio Spectroscopy Meeting Experimental Methods AMN ΔtΔt Pump+Probe ΔtΔt Transient Multi-Photon Ionization S0S0 Ion Pump ΔtΔt S2S2 S1S1 Probe

65th Ohio Spectroscopy Meeting Experimental Methods Fluorescence Up-Conversion

65th Ohio Spectroscopy Meeting Oscillator Amplifier OPA 1 OPA 2 3 ω Experimental Methods Femtosecond Pulses

65th Ohio Spectroscopy Meeting AMN Electronic Spectroscopy Theoretical Calculations:CASSCF/CASPT2 * M. Merchán and L. Serrano-Andrés. University of Valencia Fluorescence Spectroscopy LIF Excitation Spectrum Dispersed Emission * S. Jiang and D. H. Levy. J. Phys. Chem. A, 106 (2002)

65th Ohio Spectroscopy Meeting AMN Short Time Dynamics

65th Ohio Spectroscopy Meeting AMN Long Time Dynamics Excitation (nm)τ 2 (ps) Probe 800 nm ± ± ± ± ± ± ± ± ± ±2  A lifetime τ 2 is found at longer time scales, which shortens from 1 ns to 14 picoseconds with the excitation energy. This component is attributed internal conversion to the ground state and intersystem crossing.

65th Ohio Spectroscopy Meeting AMN-Water Clusters Aniline-Water Cluster Aniline-Methanol Cluster Aniline AMN-Water Clusters Wavenumbers (cm -1 ) * G. Piania et al, Chem. Phys, 330 (2006)

65th Ohio Spectroscopy Meeting AMN-Water Clusters Mass Spectrum Broadband REMPI Spectrum Theoretical Calculations (B3LYP/6-31+G*) AMN(H 2 O) 1 AMN(H 2 O) 2 AMN(H 2 O) 3

65th Ohio Spectroscopy Meeting AMN-Water Clusters Dynamics τ 1 = fs; τ 2 = 5-10 ps τ 3 = 350 ps τ 2 = 5-10 ps Short Time DynamicsLong Time Dynamics

65th Ohio Spectroscopy Meeting AMN in Methanol Solutions Fluorescence Spectra Water Cyclohexane Absorption Emission

Time (fs) Time (ps) Time Resolved Fluorescence AMN in Methanol Solutions 65th Ohio Spectroscopy Meeting τ 1 =500 fs τ 2 =11 ps

65th Ohio Spectroscopy Meeting Effect of Solvation on AMN Photophysics S0S0 τ 1 =500 fs LbLb LaLa Solute Coordinate L b →L a Internal Conversion S0S0 Solvent Coordinate τ 2 =11 ps LbLb LaLa Dynamic Stokes Shift

65th Ohio Spectroscopy Meeting Dynamic Stokes Shift * J. L. Perez Lustres, et al. Angew. Chem. Int. Ed. 2005, 44, 5635 –5639.

65th Ohio Spectroscopy Meeting Remarks On the way…  AMN solvated by two or three water molecules reproduces the behavior found in solution.  The observed photophysics can be explained in terms of the different time-scale response of the solute and solvent coordinates.  The reorganization of the solvent molecules can explained the anomalous electronic spectroscopy of the amino-water complexes.  Ab initio calculations of the L a /L b potential energy surfaces of the AMN-Water clusters.  Time resolved measurements on deuterated methanol and solvents with similar polarity.  …probing the dynamical shift response directly on the solvent coordinates.

65th Ohio Spectroscopy Meeting Acknowledgments Grupo de Química Teórica (UV) Prof. Luis Serrano-Andrés Prof. Manuela Merchán Israel González-Ramírez Angelo Giussani Raúl Montero Dr. Álvaro Peralta Conde Prof. Fernando Castaño Grupo de Espectroscopía (UPV/EHU) Financial Support Spanish Ministry of Science and Innovation CONSOLIDER Program Basque Goverment UPV/EHU