Ratiometric and colorimetric detection of Cu2+ via the oxidation of benzodihydroquinoline derivatives and related synthetic methodology

Abstract

As well as Cu2+ being a serious environmental contamination concern, the deposition of Cu2+ in the human body may cause metal poisoning, leading to the Wilson's disease genetic disorder. A Boc-benzodihydroquinoline derivative (BBHQ)-based oxidative probe was therefore synthesized and developed as a novel Cu2+ sensor. BBHQ was prepared in a straightforward manner from aminonaphthol and methylpropiolate via a Michael addition reaction and intramolecular cyclization. BBHQ was found to fluoresce, with a quantum yield of 0.38 in CH3CN and displayed a remarkable ratiometric fluorescence in the presence of Cu2+ via its oxidation to a benzoquinoline derivative. Based on the recognition of Cu2+, the color of the solution changed from green to blue under blacklight and from yellow to colorless under room light. The intensity of the fluorescence of BBHQ showed a linear relationship with the concentration of Cu2+ in the range of 0–5 μM, with an LOD of 45 nM (2.86 ppb). This sensing system using Cu2+ was also successfully developed into a new type of oxidation of dihydropyridine and dihydroquinoline, which can afford the corresponding pyridine and quinoline derivatives in excellent yields.