Synthesis of (<i>Z</i>)-Enediynes via Stereoinvertive Nucleophilic Substitution of (<i>E</i>)-Sulfonylethenes with Arylethynide, and Their Aggregation-Induced Optical Properties

(<i>Z</i>)-Enediynes were successfully synthesized from a trio of terminal ethynes through consecutive three-step reactions: iodosulfonylation of ethyne with I₂/PhSO₂Na, followed by ethynylations of iodo and sulfonyl moieties of the resulting iodosulfonylethene via Sonogashira-Hagihara coupling and nucleophilic addition-elimination, respectively. The molecular structure of the obtained (<i>Z</i>)-enediyne was fully characterized by X-ray crystal structure analysis, revealing that the nucleophilic substitution of (<i>E</i>)-sulfonylethene with arylethynide underwent a selective stereoinversion. The (<i>Z</i>)-enediynes exhibited photoluminescence in both the solution and solid states (crystals and powders). Ph₂N-substituted derivatives showed remarkable solvatofluorochromism, and upon replacing the solvent from toluene to acetonitrile, the emission color changed from blue to yellow.