Photo-dynamics of new organic photochromic materials with fast thermal back reaction

Conférence intitulée "Photo-dynamics of new organic photochromic materials with fast thermal back reaction"

ABSTRACT

 

Photochromic materials with fast thermal back reaction (less than 100 milliseconds) are foreseen for their applications in real time dynamic imaging or ophthalmic lenses. Few photochromic molecules families can keep their fast thermal reaction within solid state and we will discuss here the design and photo-dynamics of such new materials.

The first example is based on salicylidene anilines molecules (SA). Historically the photoreaction is explained by an excited-state intramolecular proton transfer (ESIPT) from an enol form to an excited cis-keto form, followed by cis-trans isomerization that ultimately affords a trans-keto photoproduct which goes back to the enol form in few milliseconds in solution. We investigated the photodynamics of SA molecules in different environment (free in solution, encapsulated, polycrystalline powder). We showed that in addition to the classical ESIPT a rotation to a twisted-enol occurs within 100 fs. We demonstrated finally that encapsulation can be a convenient way to keep photochromic properties in the solid state with a fast thermal back reaction.

The second example is given for a new class of photochromic compounds (Fast HABI) based on a reversible C-N band cleavage of a colorless dimer upon UV light irradiation which form a colored pair of bridged imidazole radicals, and disappear generally in few hundred of millisecond. We will discuss here the synthesis of Fast HABI colloidal nanoparticles in water using nanosecond laser ablation technique and reprecipitation method. The lifetime is drastically reduced to few hundreds of microseconds for nanoparticles synthesized by laser ablation, and it was rationalized by the help of ultrafast spectroscopy and DFT calculations.

[1] Sliwa et al. J. Phys. Chem. C 2009; [2] Sliwa et al. Photochem. Photochem. Photobiol. Sci. 2010; [3] Sliwa et al. Chem. Phys. Chem., 2011; [4] Debus et al. Chemom. Intell. Lab. Syst. 2013 [5] Kishimoto et al. J. Am. Chem Soc. 2009; [6] Mutoh et al.  J. Phys. Chem. C 2013.

Contact : Benoît CHAMPAGNE - Johan WOUTERS - 4554 - 4550 - benoit.champagne@unamur.be
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