2,7-Diazatriptycene: acid-responsive ternary fluorescence switching via modulation of through-space conjugation.

An unexplored 2,7-diazatriptycene exhibits protonation-controlled ternary fluorescence switching (on/off, cyan/violet) through modulation of through-space conjugation. Theoretical calculations clarified the origin of the contrasting fluorescence quantum yields of 2,7- and 2,6-diazatriptycene. Protonation also reorganizes crystal packing from herringbone assemblies to charge-segregated layered structures.