Investigation of ultrafast photoinduced processes for salicylidene aniline in solution and gas phase: toward a general photo-dynamical scheme

• DOI: 10.1039/b9pp00207c
• Publication Date: 2010-03-04T09:30:33Z
• Authors: Michel Sliwa; Nicolas Mouton; Cyril Ruckebusch; Lionel Poisson; Abdenacer Idrissi; Stéphane Aloïse; Ludovic Potier; Julien Dubois; Olivier Poizat; Guy Buntinx
• Keywords: [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry; [CHIM.THEO] Chemical Sciences/Theoretical and/or physical chemistry; 01 natural sciences; 7. Clean energy; 0104 chemical sciences

Photodynamics of 2-hydroxybenzylideneaniline (photochromic salicylidene aniline SAOH) and N-(2-methoxybenzylidene)aniline (SAOMe) are studied by steady state and transient optical spectroscopy in solution and gas phase at different excitation wavelengths (266, 355 and 390 nm). Two competitive processes are observed from the enol* excited state: on one hand a rotation to get a twisted-enol, and on the other hand an excited state intramolecular proton transfer (ESIPT) followed by a cis-trans isomerisation to get the trans-keto photochromic product. For the first time both processes are characterized at an ultrashort time scale for salicylidene aniline. Resolution of the spectrokinetic data is achieved by multivariate curve resolution and attribution of the intermediate species recovered is performed in comparison with the results obtained for SAOMe, which can only undergo enol rotational isomerisation. It shows that ESIPT and rotation to the twisted-enol for SAOH occur within 100 fs, as predicted by recent quantum dynamical simulations, with an efficiency ratio dependent on the excitation wavelength. Therefore a general photoinduced mechanism for salicylidene aniline is drawn.