Triphenylamine, carbazole or tetraphenylethylene-based gold(I) complexes: Tunable solid-state room-temperature phosphorescence and various mechanochromic luminescence characteristics

Three novel gold(I) complexes based on triphenylamine, carbazole or tetraphenylethylene moiety have been successfully designed and synthesized. Meanwhile, their structures were characterized by nuclear magnetic resonance spectroscopy and elemental analysis. Their solid-state luminescence characteristics were surveyed by photoluminescence spectroscopy, and their distinct mechanical stimulus-responsive behaviors in the solid state were also investigated by photoluminescence spectroscopy. Interestingly, the solid-state phosphorescence and emission lifetimes of these mononuclear gold(I) complexes 1-3 could be tuned by introducing different fluorophores involving triphenylamine, carbazole or tetraphenylethylene. Furthermore, luminogen 1 exhibited switchable mechanochromic luminescence behavior with color change from yellow to colorless, and the solid-state luminescence on-off mechanochromism between yellow-green and colorless of luminogen 2 could also be observed. However, no mechanochromism phenomenon was observed for tetraphenylethene-containing luminogen 3. The powder X-ray diffraction results suggested that the unusual high-contrast mechanochromism characteristics of luminogens 1 and 2 could be attributed to a crystalline-to- amorphous morphology transition.