Fluorescent molecular logic gates for the early detection of corrosion

Abstract

Four novel molecules for sensing pH and redox potential (pE) were designed and synthesised based on the asymmetrical 1,8-naphthalimide fluorophore. Attachment of the proton receptor and electron donor at either the N-imide or 4-position produced two pairs of positional isomers. Two of the molecules are designed based on an 'electron donor-spacen- fluorophore-spacer-recepton' modular format with dimethylamine or morpholine as the proton receptors and ferrocene as the electron donor. The two other molecules consist of the same chemical units, but adopt a 'recepton-spaceri-fluorophore -spacer-electron-donor' arrangement. The ferrocene and proton receptors are connected to the fluorophore via a methylene and ethylene spacers, respectively. Furthennore, a three-input logic gate for Na+, pH and pE was synthesised based on 'electron donor-spacen-fluorophore-spacer-recepton- space-recepton' design. A piperazine unit was employed as recepton for protons and a benzo-15-crown-5 as receptor2 for Na+ separated by a methylene group.