Novel pH probes based on 2-(6-methoxynaphthalen-2-yl)-3,3-dimethyl3H-indole have been synthesized and characterized. These compounds display excellent
“off−on” fluorescence responses to acidic pH especially under two-photon (TP) excitation
conditions as well as strong selectivity and sensitivity toward H+
. These features are
supported by fluorescence quantum yields over 35%, TP cross sections ∼60 GM, and
good resistance to photodegradation under acidic conditions. The synthetic versatility of
this model allows subcellular targets to be tuned through minor scaffold modifications
without affecting its optical characteristics. The effectiveness of the probes’ innate
photophysical properties and the structural modifications for different pH-related
applications are demonstrated in mouse embryonic fibroblast cells
