Influence of solvation on 1 aminonaphthalene photophysics ultrafast

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) 65 th Ohio Spectroscopy Meeting

Motivation q To understand the photophysics of 1 -aminonaphthalene (AMN), in particular the dynamics of the La/Lb state coupling. q 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 q From H-bonded clusters to bulk. AMN in methanol solutions. 65 th Ohio Spectroscopy Meeting

Experimental Methods Transient Multi-Photon Ionization AMN Δt Δt Pump+Probe 65 th Ohio Spectroscopy Meeting

Experimental Methods Fluorescence Up-Conversion 65 th Ohio Spectroscopy Meeting

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

AMN Electronic Spectroscopy Fluorescence Spectroscopy Theoretical Calculations: CASSCF/CASPT 2 * M. Merchán and L. Serrano-Andrés. University of Valencia LIF Excitation Spectrum Dispersed Emission * S. Jiang and D. H. Levy. J. Phys. Chem. A, 106 (2002) 8590 -8598. 65 th Ohio Spectroscopy Meeting

AMN Short Time Dynamics 65 th Ohio Spectroscopy Meeting

AMN Long Time Dynamics Excitation (nm) τ2 (ps) Probe 800 nm 311 940± 138 308 710± 100 304 513± 70 298 348± 30 294 290± 35 286 120± 10 280 84± 6 267 35± 5 245 16± 2 235 14± 2 q A lifetime τ2 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. 65 th Ohio Spectroscopy Meeting

AMN-Water Clusters Aniline-Water Cluster Aniline-Methanol Cluster * G. Piania et al, Chem. Phys, 330 (2006) 138 -145. Aniline AMN-Water Clusters Wavenumbers (cm -1) 65 th Ohio Spectroscopy Meeting

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

AMN-Water Clusters Dynamics Short Time Dynamics Long Time Dynamics τ3= 350 ps τ1= 150 -200 fs; τ2= 5 -10 ps 65 th Ohio Spectroscopy Meeting

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

AMN in Methanol Solutions Time Resolved Fluorescence τ1=500 fs τ2=11 ps Time (fs) Time (ps) 65 th Ohio Spectroscopy Meeting

Effect of Solvation on AMN Photophysics Dynamic Stokes Shift Lb→La Internal Conversion La La Lb Lb τ1=500 fs τ2=11 ps S 0 Solute Coordinate Solvent Coordinate 65 th Ohio Spectroscopy Meeting

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

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

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