1D and 2D Gold(I)-Thiophenolate-based Coordination Polymers, a Rich Palette of Photophysical Properties
Résumé
Hybrid Au(I) compounds exhibit a large domain of applications such as electronic devices, contrast agents, sensors or photocatalysts. These applications are related to the ability of gold(I) to form aurophilic interactions implying self-assembly and luminescence.1 Among them, gold(I) thiolates are an important class of materials, due to the soft-soft interaction between Au(I) and thiolates, and their potential to form self-assembled monolayers, to protect and functionalize gold clusters and nanoparticles and to generate oligomeric or polymeric species, used for a long time as antiarthritic agents. However due to the fast precipitation and the insolubility of these solids, a little is known about their structure making the origin of the photoluminescence difficult to rationalized.2 Here, we present the syntheses and the first structure resolutions, by powder X-Ray diffraction, of series of gold(I)-thiophenolate-based coordination polymers, [Au(SPhR)]n. Depending on the substituent and its position, different chain-like and lamellar structures are obtained (Fig. 1).3 The photophysical properties of these hybrid materials are analyzed in solid-state and coupled with DFT calculations. These studies show different origins of the charge transfers depending on the electrophilicity of the thiolate molecules coupled with the participation or not of the aurophilic interactions. Among those coordination polymers, some exhibit high quantum yield around 70 % at room temperature and in the solid state,3b another one shows an rare switch ON of the emission with a thermally induced solid-state phase change from amorphous to crystalline.3a When the mercaptobenzoic acids are used in ortho and para positions, the structures of the resulting [Au(SPhCO2H)]n coordination polymers are 1D and 2D, respectively. Thus their photoluminescent properties are distinct, [Au(o-SPhCO2H)]n presents thermally induced delayed fluorescence (TADF) phenomenon and in the case of the [Au(p-SPhCO2H)]n, its dual emission, associated with luminescence thermochromism was highlighted as intrinsic and ratiometric optical temperature sensor.3c These different examples shed light on the great potential of gold thiolate coordination polymers as emerging hybrid materials for diverse optical applications.