A selective fluorescent receptor for the determination of nickel (II) in semi-aqueous media

The malonohydrazide based fluorescent probe (7E,8E)–N1′,N3′-bis(1-(2-hydroxyphenyl)ethylidene) malonohydrazide (receptor 5) was designed and synthesized. It was confirmed by spectroscopic methods and the single crystal X-ray method. The receptors 5 show strong intramolecular hydrogen bonding which is useful in host–guest complexation. The fluorescence spectra of receptor 5 have shown distinct enhancement with the addition of Ni2+ ion over other surveyed cations. The stability constant was obtained by Benesi–Hildebrand, Scatchard and Connorʹs fitting methodologies. The 1:1 stoichiometry of the host–guest complexation was confirmed by Jobʹs continuous variation method.