An optical pH probe is a simple and effective tool for
determining
an accurate pH value in its localized area. However, basic pH probes
with pK
BH+ values above 8 have rarely
been reported, although many components with high pK
a such as arginine play important roles in vivo. Herein,
we introduce novel colorimetric and fluorescent basic probes 1–5, which are designed using push–pull-type
aminoquinoline and aminobenzoquinoline fluorophores, with pK
BH+ values ranging from 8.4 to 9.9. After the
basicity of the remarkably sensitive basic probe 4 was
tuned, it was able to successfully distinguish between the pK
a values of MeOH (15.5) and EtOH (15.9), thus
displaying selective protonation and fluorescence enhancement in MeOH
over EtOH. Our pH probes can be used to detect MeOH poisoning in commercial
EtOH products such as hand sanitizers, providing an effective solution
to this problem observed during the COVID-19 pandemic.
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