Copper-Induced Fluorescence Quenching in a <i>Bis</i>[2-(2′-hydroxyphenyl)benzoxazole]pyridinium Derivative for Quantification of Cu²⁺ in Solution

Abstract

Accurate determination of Cu2+ in solution is crucial for preventing several disease conditions. Spectroscopy-based techniques for metal ion detection are promising methods due to their excellent sensitivity and rapid response time. In this work, we are reporting a newly synthesized 2-(2′-Hydroxyphenyl) benzoxazole-based compound, probe 2, by incorporating a vinyl pyridinium segment into the bis(HBO) 4 system. Probe 2 exhibited excellent specificity toward Cu2+ in solution. The ratiometric absorbance (λ440/λ370) and the quenching of fluorescence at λem ≈585 nm exhibited an excellent linear correlation. The formation of the 2-Cu complex can be utilized as a highly sensitive spectroscopic method for the detection of Cu2+ in solution with a detection limit of 0.15 µM. In addition, Cu2+-induced fluorescence quenching in probe 2 occurs mainly via a static quenching mechanism by forming a 2-Cu complex, and the stability constant for the 2-Cu complex was calculated based on spectroscopic measurements.

Keywords

• fluorescent dyes
• 2-(2′-hydroxyphenyl)benzoxazole (HBO)
• excited-state intramolecular proton transfer (ESIPT)
• fluorescence quenching
• copper ion