Key points are not available for this paper at this time.
Boradiazaindacenes 1 and 2 bearing phenolic subunits show deprotonation/protonation dependent fluorescence off/on-switching; the lack of emission of the phenolate forms is attributed to photoinduced electron transfer (PET) between the phenolate and indacene subunits.
Gareis et al. (1997) studied this question.