Crystalline-Amorphous-Crystalline Transformation in a Highly Brilliant Luminescent System with Trigonal-Planar Gold(I) Centers

Abstract

Photoluminescent compounds showing emission color changes in response to external stimuli have received considerable attention because of their wide range of applications. Here, we report the unique photoluminescence behavior of a digold(I) coordination system with trigonal-planar AuI centers, [Au2(dppm)3]2+ (dppm = bis(diphenylphosphino)methane). This system shows an extremely intense phosphorescence, with a quantum yield of >95% in the solid state. Both the emission color and thermal stability vary due to changing counter ions (Cl− vs. OTf−). Of particular note is the thermal crystalline-amorphous-crystalline transformation for the chloride salt, which is accompanied by drastic emission color changes. Single-crystal and powder X-ray diffractions demonstrate that the two-step transformation is induced by the loss of water molecules of crystallization with the subsequent removal of a dppm ligand to form [Au2(dppm)2]2+, which is mechanically reverted back to [Au2(dppm)3]2+.

Fine-Tuning of Luminescence through Changes in Au–S Bond Lengths as a Function of Temperature or Solvent

“…These OH-containing solvent molecules interact with the [Au 2 (dppaptc) 2 ] 2+ and the Cl – ions via strong hydrogen-bonding interactions (N–H···O, O–H···Cl, N–H···Cl, C–H···Cl) (Figure and Figure S14). All of these interactions result in the formation of the shorter Au–S bonds. , The shorter Au–S bonds are associated with yellow crystals, while the longer Au1–S1 bonds are found in colorless crystals, which is fully consistent with the colors observed in different solvents.…”

“…All of these interactions result in the formation of the shorter Au−S bonds. 48,49 The shorter Au−S bonds are associated with yellow crystals, while the longer Au1−S1 bonds are found in colorless crystals, which is fully consistent with the colors observed in different solvents. Solid-state luminescence at 300 K was examined for all solvated complexes 1•solvent listed in Table 1.…”

A trigonal coordination of Au(I) phosphane complexes stabilized by O–H⋯X (X = Cl–, Br–, I–) interactions

“…It should be mentioned that there are also several examples of bidentate phosphane ligands which form dinuclear gold(I) complexes with short Au … Au distances. However, such phosphorescence is based on aurophilic interactions and also observable at room temperature [49].…”

Reversible Solid-State Phase Transitions between Au–P Complexes Accompanied by Switchable Fluorescence

“…5−7 Coordination compounds with defined structures are easier to investigate in this respect 8−12 and can undergo solid-state phase transitions involving metal exchange 13,14 or in situ conversion of ligands 15,16 and involving a change in the shapes of voids in porous crystals 17,18 or packing mode variations in low-dimensional structures. 19,20 Complexes of Au(I) are particularly interesting in this respect because of the labile formation of photoluminescent Au−Au interactions in response to stimuli such as pressure, 21,22 temperature, 23,24 solvent, 25,26 and light irradiation. 27 Arylphosphines have been proven to be useful stimuli-responsive ligands for Au(I) phase-transition complexes.…”

“…Solid-state phase-transition materials have potential applications in chemical/biological probes, sensors, , LEDs, and chemical switches. − Coordination compounds with defined structures are easier to investigate in this respect − and can undergo solid-state phase transitions involving metal exchange , or in situ conversion of ligands , and involving a change in the shapes of voids in porous crystals , or packing mode variations in low-dimensional structures. , Complexes of Au­(I) are particularly interesting in this respect because of the labile formation of photoluminescent Au–Au interactions in response to stimuli such as pressure, , temperature, , solvent, , and light irradiation . Arylphosphines have been proven to be useful stimuli-responsive ligands for Au­(I) phase-transition complexes. − Balch and co-workers, for example, have reported the conversion of cagelike [Au 6 (Triphos) 4 Cl]·(PF 6 ) 5 ·2­(CH 3 C 6 H 5 ) [Triphos = bis­(2-diphenylphosphinoethyl)­phenylphosphine] to [μ-Cl­{Au 3 (Triphos) 2 } 2 ]­(PF 6 ) 5 ·3CH 3 OH] upon grinding with a concomitant fluorescence shift from blue to green .…”