CHEF-Affected Fluorogenic Nanomolar Detection of Al3+ by an Anthranilic Acid–Naphthalene Hybrid: Cell Imaging and Crystal Structure

We report the synthesis of a novel hydrazine-bridged anthranilic acid–naphthalene conjugate (E)-2-(benzamido)-N′-((2-hydroxynaphthalen-1-yl) methylene) benzohydrazide (BBHAN) and its crystal structure. BBHAN can detect Al3+ by a sharp increment in fluorescence intensity (∼40 times) in aqueous methanolic medium. The limit of detection of BBHAN towards Al3+ is 1.68 × 10–9 M, and the former undergoes a 2:1 binding with Al3+ with a high binding constant of ∼1.15 × 1011 M2–. BBHAN detects Al3+ by the well-known mechanism of chelation-enhanced fluorescence (CHEF), established by fluorescence time-resolved measurement. The mode of interaction between BBHAN and Al3+ has been explored by 1H NMR and electrospray ionization mass spectrometry techniques. Paper strips coated with BBHAN can detect Al3+ under UV light observed through the naked eye. Lastly, BBHAN can detect Al3+ in MDA-MB-468 cells.