Naphthalene based highly selective OFF–ON–OFF type fluorescent probe for Al3+ and NO2− ions for living cell imaging at physiological pH

A naphthalene based fluorescent probe, 1-((Z)-(naphthalene-4-ylimino)methyl)naphthalene-2-ol (L) has been synthesized by condensing 1-naphthyl amine with 2-hydroxy naphthaldehyde. The structure of L has been established by single crystal X-ray structure. It selectively binds Al3+ with a binding constant (Ka) of 1.83 × 105 M−1/2 and detection limit of 1.0 × 10−7 M. Moreover, [L–Al3+] complex can detect NO2− ion as low as 5.7 × 10−8 M. Binding of L to Al3+ and [L–Al3+] complex to NO2− ion has been established by different spectroscopic studies. The probe is very effective for detection of intracellular Al3+ through fluorescence microscopic imaging.