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Hybrid organic-inorganic materials

Photoactive Hybrid Polyoxometallates

Rémi Dessapt (MC), Hélène Serier-Brault (MC), Patricia Bolle

We are specialized in designing new photochromic and/or photoluminescent hybrid organic-inorganic materials based on polyoxometalates (POMs) which are anionic molecular transition metal-oxide clusters (Mo, W, V). These innovative smart systems exhibit remarkable photophysical properties in the solid state that are highly tunable by varying the nature of the inorganic and inorganic components, and their degree of interaction in the hybrid frameworks. These materials have potential technological and marketable applications such as ophthalmic lenses, smart pigments for paints and windows, optical switches, photoswitchable receptors, high-density optical data storage, and chemosensors.

Luminescent Coordination Polymers

Hélène Serier-Brault (Associate Professor), Rémi Dessapt (Associate Professor)

Coordination polymers are organic-inorganic hybrid materials containing metal centers or metallic clusters linked by organic molecules. The multitude of organic ligands and metal ions makes it possible to form varied mono and multidimensional networks. When the metal center is a lanthanide ion, the material exhibits luminescence properties via an antenna effect of the organic part. These emission properties are of interest for lighting applications but also as nano-thermometers since the emission of certain lanthanides may vary with temperature. Recently, we are developing new coordination polymers based on Eu3+ and Tb3+ ions as a nanoscale temperature probe.

Noncentrosymmetric Compounds

Romain Gautier (CR)

Noncentrosymmetric compounds are interesting for different properties such as second harmonic generation, piezoelectricity or optical rotation. In our group, we recently focus on racemates and the properties related to noncentrosymmetry. Racemates have been assumed to be optically inactive for the last 160 years. The cancelation of opposite optical rotations from left- and right-handed enantiomers (racemates) was discussed by Pasteur for tartaric acids and has never been dismissed. In our recent work, we showed, using single-crystal circular dichroism measurements, that specific arrangements of racemic units can lead to optical activity and that as many as one in twenty racemic compounds are potential optically active materials. Indeed, the enantiomers of opposite handedness can arrange into the 21 non-enantiomorphous point groups while optical activity can be described in the eleven enaniomorphous point-groups and four non-enantiomorphous point-groups (Figure). Thus, the “optical activity” and “Racemic compound” groups are not independent. The optical activity from racemic materials has been confirmed by the measurement of single-crystal circular dichroism on two compounds crystallizing in the point-group mm2 (Figure). In these crystal structures, the arrangement of these units is a key to breaking the centrosymmetry and leads to the presence of optical activity.

Copper(I) halide complexes

Sandrine Perruchas (CR), Romain Gautier (CR)

Luminescent materials based on transition-metal complexes have been receiving increasing attention due to their wide field of applications in detection, sensing, biological labelling, and display visualization devices. The family of copper(I) halides constitutes an interesting class of luminophors owing to its large variety of photophysical properties which is associated to an extraordinary structural diversity. In this context, our research aims at studying new copper(I) halide compounds in order to develop original functional materials.

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