Condensation Product of 4-Methoxybenzaldehyde and Ethylenediamine: "Off-On" Fluorescent Sensor for Cerium(III)

The condensation product (L) of 4-methoxybenzaldehyde and ethylenediamine has been synthesised and characterised. L showed a 21 times enhancement in fluorescence intensity on interaction with Ce³⁺ in CH₃OH at λ_max = 360 nm when excited with 270 nm photons. Metal ions K⁺, Na⁺, Al³⁺, Co²⁺, Hg²⁺, Cd²⁺, Ni²⁺, Zn²⁺, Mn²⁺, Mg²⁺ and Ca²⁺ do not interfere. The stoichiometry of binding and the binding constants were determined from spectroscopic data and found to be 1:1 and 10^4.8 M respectively. The detection limit was found to be 10^-5.2 M. The protonation/de-protonation of water molecules coordinated to Ce³⁺ was found to show interesting behaviour on the fluorescence of L:Ce³⁺.