I2 catalyzed access of spiro[indoline-3,4′-pyridine] appended amine dyad: new ON–OFF chemosensors for Cu2+ and imaging in living cells

Abstract

An easy access to an amine-appended spiro[indoline-3,4′-pyridine] ON–OFF chemosensor by a one-pot four-component reaction using commercially available and an environmentally benign catalytic amount of molecular I₂ (10 mol%) in aqueous ethanol at ambient temperature is described. The generated system could be utilized for the selective detection of Cu²⁺ as it demonstrated a colorimetric naked eye change along with an ON–OFF fluorescence response towards Cu²⁺ at physiological pH. The sensors exhibited high selectivity for Cu²⁺ over other common cations with detection limit in the range of 10⁻⁷ (M). Notably, this is the first report of a spiro[indoline-3,4′-pyridine] moiety acting as a sensor for Cu²⁺via a on–off fluorescence response. In addition, the probe system was successfully applied for imaging Cu²⁺ in human hepatocellular liver carcinoma cells (HepG2), demonstrating a new avenue for molecular imaging and biomedical applications.