A new use for an old molecule: N-phenyl-2-(2-hydroxynaphthalen-1- ylmethylene)hydrazinecarbothioamide as a ratiometric 'Off-On' fluorescent probe for iron

N-Phenyl-2-(2-hydroxynaphthalen-1-ylmethylene)hydrazinecarbothioamide has been investigated as a fluorescent sensor for the determination of Fe(III) in aqueous solutions. The probe was prepared by the facile Schiff base condensation of 2-hydroxy-1-napthaldehyde with N-phenylhydrazinecarbothioamide. The sensor displayed good selectivity for Fe(III) when tested against a range of biologically and environmentally important cations. A concentration dependent increase in the emission of two fluorescent bands at 425 and 495 nm was observed upon increasing Fe(III) addition resulting in a linear ratiometric response in the 17-37 μM range. The binding stoichiometry was confirmed as 1:1 (host/guest) with the binding constant (log β) calculated as 4.56.