Institut de Chimie Moléculaire et des Matériaux d'Orsay

Laboratoire de Chimie Inorganique - LCI

Photochromism and photoswitchable systems

Pei Yu, Anne Léaustic
Juliette Guérin

Projects :

We are interested in organic photochromism and its use as photo-switching element for the design of novel molecular, supramolecular or hybrid systems with photoresponsive behaviors. These multifunctional and photoswitchable systems are of interest for their potential applications in various fields such as display, imaging, optical storage and processing. Among different kinds of organic photochromes, we are particularly interested in photochromic diarylethenes as they are known to undergo fast, low fatigue and thermally irreversible photochromic reactions between two isomeric states with different geometries and electronic structures.

i) Integrated diarylethene:

The fluorescence and non linear optical properties of the dithiazolylethene in its open form, which are mainly ascribed to the D-π-A motif in each side arm, are efficiently and reversibly photo-modulated by the photochromic reaction that interrupts or restores the π conjugaison linkting the electron donnor and acceptor.




Ref :Dithiazolylethene-based molecular switches for non linear optical properties and fluorescence: synthesis, crystal structures and ligating properties
J. Mater. Chem., 2007, 14, 4414-4425.


ii) Diarylethene-fluorophore dyad  

FRET (Fluorescence Resonance Energy Transfer) is used to photoswitch the fluorescence of the dyad. The open form of the diarylethene does not interfere with the DCM- based fluorophore moiety, while its closed form acts as energy acceptor of the fluorophore’s emission, thus switching its fluorescence. Using the same approach, we are working on the way the luminescence of certains rare earth metal ions can be photoswitched by the photochromic reaction of appropriate diarylethenes.



Ref : Fluorescence photoswitching and photoreversible two-way energy transfer in a photochrome-fluorophore dyad 
Photochem. Photobiol. Sci., sous presse.


Photomodulation of magnetic coupling



The idea was that the magnetic coupling between the two copper ions could be photomodulated by the reversible structure changes of the photochromic bridge. Surprisingly, Solution EPR studies revealed an interesting photo-controlled release and uptake of the two Cu(hfac)2 moieties during the interconversion between the open and closed form of the photochromic bridge. Others systems are currently under study in order to achieve photomodulation of magnetic interactions and other photoresponsive magnetic systems.

Ref :Photo-controlled release and uptake of Cu(hfac)2  in solution for a binuclear copper complex with a photochromic dithiazolylehene bridging ligand
New J. Chem., 2009, 33, 1380-1385.


Photomodulation of redox properties



The redox properties of the diarylethene can be photomodulated in a spectacular way: almost 1 volt between the open and closed forms of diarylethene. Such a redox difference allows to envisage systems in which the electron transfer or redox reaction could be triggered by light. Its association with different substrates, that may be oxidized by the closed form of the diarylethene, is underway.

Ref : Photochromic and Reductive Electrochemical Switching of a Dithiazolylethene with LargeRedox Modulation.

Novel photochromes



Design of new photochromes of original structure is a permanent challenge in the field of photochromism. With their octatetraene structures, tetraarylenes offer not only new prospects for the design of multifunctional photoswitches, but also new way of making biphotochromes.

Always in search of novel multifunctional photoswitches, we are also working on the design and spectroscopic investigations (steady- and time-resolved absorption, emission etc.) of diarylethenes associating within the same molecule ESIPT (Excited State Intramolecular Proton Transfer) process, another valuable photochemical reaction for various applications.


Ref : 4,4’-Bithiazole-based tetraarylenes: new photochromes with unique photoreactive patterns.
Chem.Commun.,2012,48, 10111-10113.




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