From PASS 1 to YES to AND logic: building parallel processing into molecular logic gates by sequential addition of receptors

Abstract

The synthesis and photophysical characterization of a novel molecular logic gate 4, operating in water, is demonstrated based on the competition between fluorescence and photoinduced electron transfer (PET). It is constructed according to a ‘fluorophore–spacer–receptor₁–spacer–receptor₂’ format where anthracene is the fluorophore, receptor₁ is a tertiary amine and receptor₂ is a phenyliminodiacetate ligand. Using only protons and zinc cations as the chemical inputs and fluorescence as the output, 4 is demonstrated to be both a two-input AND and INH logic gate. When 4 is examined in context to the YES logic gates 1 and 2, and the two-input AND logic gate 3 and three-input AND logic gate 5, each with one or more of the following receptors including a tertiary amine, phenyliminodiacetate or benzo-15-crown-5 ether, logic gate 4 is the missing link in the homologous series. Collectively, the molecular logic gates 1–5 corroborate the PET ‘fluorophore–spacer–receptor’ model using chemical inputs and a light-signal output and provide insight into controlling the fluorescence quantum yield of future PET-based molecular logic gates.