HIGHLY LUMINESCENT AU(I)-THIOLATE COORDINATION POLYMERS
Résumé
Polynuclear hybrid Au(I) compounds exhibit a very large domain of applications such as electronic devices, contrast agents, sensors or photocatalysts. All these applications are related to the ability of gold(I) to form aurophilic interactions which give luminescent materials.[1] Among hybrid gold species, gold(I) thiolate compounds are an important class of materials due to the high affinity of gold for sulfur atoms that can generate molecular complexes, extended polymers, stabilized gold nanoparticles or self-assembled monolayers. Thus in nanoscience, gold(I) thiolate polymers are a key step in the Brust-Schiffrin synthesis of functionalized gold nanoparticles.[2] However relatively little is known about the relationship between the structure of the Au(I)-SR intermediate and the formation of the nanoparticles. In addition, the luminescence of gold thiolate nanoclusters, with gold core diameter less than 2 nm, is highly dependent of the structure, the arrangement and the length of Au(I)-thiolate motifs at the surface.[3] So to understand the formation of gold thiolate nanoparticles and clusters and also to explain the luminescence of gold thiolate coordination polymers and clusters, we will present the syntheses and the first structure resolutions, by powder X-Ray diffraction, of series of [Au(I)-SR]n compounds. We will demonstrate that depending on the substituent (R = Ph, PhCOOH, PhNH2) different structures are obtained: lamellar, helicoidal or cyclic. The photophysical properties governed by aurophilic inetractions and Ligand-to-Metal Charge Transfer are studied by room temperature and solid-state emission and lifetime decay experiments, and are explained by DFT calculations. Among those coordination polymers, two exhibit dynamic OFF/ON emission switching, one associated with an irreversible solid-state thermal crystallization and the other one from a reversible esterification. In addition we will show, from those preformed coordination polymers, that exchange reactions of thiol ligands involve dissolution/recrystallization mechanism, pointing out that each thiolate ligand induces its own polymeric structure.
REFERENCES
[1]Schmidbaur H., Schier A., Chem. Soc. Rev., 41, (2012), 370.
[2]Lavenn, C.; Albrieux, F.; Tuel, A.; Demessence, A., J. Colloid Interface Sci., 418, (2014), 234.
[3]Luo Z., Yuan X., Yu Y., Zhang Q., Tai Leong D., Yang Lee J., Xie J., J.Amer. Chem. Soc., 134, (2012), 16662. Das A., Li T., Li G., Nobusada K., Zeng C., Rosi N. L., Jin R., Nanoscale, 6, (2014), 6458.