Basic Fluorescent Protonation-Type pH Probe Sensitive to Small ΔpKa of Methanol and Ethanol

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 pKBH+ values above 8 have rarely
been reported, although many components with high pKa 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 pKBH+ 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 pKa 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.

光学pH探头是一种简便而有效的工具，用于精确测定其局部区域的pH值。然而，尽管许多具有高pKa值（如精氨酸）的成分在体内发挥着重要作用，但基本pH探头中pKBH+值超过8的报道却极为罕见。在此，我们介绍了新型比色和荧光碱性探头1-5，这些探头采用推-拉式氨基喹啉和氨基苯并喹啉荧光团设计，其pKBH+值介于8.4至9.9之间。经过对灵敏度极高的碱性探头4的碱性调整后，它能够成功区分甲醇（pKa值为15.5）和乙醇（pKa值为15.9）的pKa值，从而在甲醇中表现出选择性质子化和荧光增强，相对于乙醇。我们的pH探头可用于检测商业乙醇产品（如洗手液）中的甲醇中毒，为COVID-19大流行期间观察到的这一问题的解决提供了有效方案。