8‐(4‐aminophenyl)BODIPYs as fluorescent pH probes: facile synthesis, computational study and lysosome imaging

Abstract

AbstractFive novel BODIPY‐based dyes (3 a‐e) were facilely synthesized via Buchwald‐Hartwig cross coupling reaction. The 8‐(4‐aminophenyl)BODIPYs can be used as fluorescent pH probes with broad response ranges. Low fluorescence intensities of 3a–e were observed under neutral or weak acidic conditions, whereas, the fluorescence signals significantly increased with further decreasing pH values, indicating that they are highly sensitive to acidic pH alterations. Fluorescence response mechanism of the probes to pH is based on the photo‐induced electron transfer (PET), which was investigated by density functional theory (DFT) and time dependent‐density functional theory (TD‐DFT) calculations. Cell imaging experiments demonstrated 3 b (pKa 3.59) was a novel lysosome‐targeting probe with excellent membrane permeability, high sensitivity and selectivity, as well as low cytotoxicity. In addition, probes 3 a and 3 d with pKa 2.66, 2.51 could be potential for detecting extremely acidic conditions in bacteria.