On/Off Fluorescent Chemosensor for Selective Detection of Divalent Iron and Copper Ions: Molecular Logic Operation and Protein Binding

Abstract

Here, naphthalene diamine-based β-diketone derivative (compound LH) was successfully used as a dual signaling probe for divalent cations, Fe²⁺ and Cu²⁺ ions, in bimodal methods (colorimetric and fluorometric). It showed fluorescent enhancement for Fe²⁺ ion by photoinduced electron transfer mechanism and fluorescence quenching for Cu²⁺ ion by charge-transfer process. Binding stoichiometry for [LH-(Fe²⁺)₂] and [LH-(Cu²⁺)₂] was found to be 1:2 by Job's plot method and, the binding constants were calculated as 1.6638 × 10¹⁰ and 9.22929 × 10⁸ M^-1, respectively. Compound LH exhibited OR and XOR logic gate behavior with H⁺, Fe²⁺, and Cu²⁺ as inputs. Further, the compound LH and bovine serum albumin binding interaction showed quenching of fluorescence by Förster resonance energy-transfer mechanism.