Cyclic Solid‐State Multiple Phase Changes with Tuned Photoemission in a Gold Thiolate Coordination Polymer

Abstract

The discovery of a universal memory that exhibits fast access speed, high-density storage, and nonvolatility has fuelled research into phase-change materials over the past decades. In spite of the efficiency of the inorganic chalcogenides for phase-change random access memory (PCRAM), they still have some inherent drawbacks, such as high temperature required for phase change and difficulty to control the domain size of the phase change, because of their brittleness. Here we present a Au I -thiolate coordination polymer which undergoes two successive phase changes on application of mild heating (< 200 °C) from amorphous-to-crystal-line1-to-crystalline2 phases. These transitions are reversible upon soft hand grinding. More importantly, each phase exhibits different photoluminescent properties for an efficient optical read-out. We believe that the ability of the Au I -thiolate coordination polymer to have reversible phase changes under soft conditions and at the same time to display distinct optical signals, can pave the way for the next generation of PCRAM.

Gold(I)–Thiolate Coordination Polymers as Multifunctional Materials: The Case of Au(I)–p-Fluorothiophenolate

“…This long lifetime with the large Stokes supports that the emission is phosphorescent involving a triplet ligand to metal charge transfer ( 3 LMCT) state. 19,39 The emission peak position and shape remain unchanged upon variation of the excitation wavelength (Figure S9). Additionally, the excitation spectra (monitored at the emission peak) match closely with the absorption peak, confirming that there is only one emissive state that is also directly coupled to the absorbing ligandcentered state.…”

“…As it has been mentioned in part c and already observed for some 1D gold−thiolate CPs, amorphous [Au(p-SPhF)] n exhibits a phase change from amorphous to crystalline upon heating at 173 °C (see DSC on Figure 5a). 12,19 Thus, the reversible phase change of 2 was studied. The crystalline and red emissive 1 was ground for 30 min in an agate mortar and pestle.…”

“…The energy emissions vary from the yellow region of the visible spectrum to the near-infrared region, with possible multiple emission bands for ratiometric thermometry. 12,13,19,22 The softness of these gold−thiolate CPs allows shaping and has been a fruitful strategy to get flexible (nano)fibers, 23,24 transparent glasses, 25 and phase-change materials of pure [Au(SR)] n CPs. 19 Thus, red-emissive and flexible fibers of crystalline [Au(SPh)] n CP have been reported.…”

“…17,18 Structure resolution of some gold(I)−thiolate CPs shows that they adopt a 1D or 2D structure with common Au(I)−S−Au(I) chains that form double-interpenetrated helices or are parallel, respectively. 12,17,19 In addition, Au(I) is a d 10 metal that exhibits strong photoluminescent properties and can exhibit aurophillic interactions. 20,21 Thus, gold(I)− thiolate CPs can display wide photoemission properties in the solid state and at room temperature (RT) with quantum yields up to 70%.…”

One-Dimensional Heterobimetallic Au/Ag Coordination Polymer Showing a Selective, Reversible, and Visible Vapor-Chromic Photoluminescent Response toward Methanol

“…Photoluminescent (PL) chemical sensing methods have the advantage of simplicity, portability, and sensitivity; − thus they have been widely developed for the detection of environmental pollutants. A group of poly-nucleated gold and silver complexes have attracted interest in this respect because their emissions are related to metal–metal–ligand charge transfer (MMLCT) , or ligand-to-metal–metal charge transfer , processes that are sensitive to external stimuli, resulting in vapor-chromic, − solvato-chromic, mechano-chromic, , pressure-chromic, and thermo-chromic − responses. Some inorganic complexes and coordination polymers have been employed to detect organic solvent or volatile organic vapors (VOCs). ,, For example, Yao and Yam reported a gold­(I)-sulfido complex [(L H ) 4 Au 10 S 4 ]­Cl 2 exhibiting reversible yellow to green emission when immersed in cyclohexane and benzene .…”