A fluorescent combinatorial logic gate with Na+, H+-enabled OR and H+-driven low-medium-high ternary logic functions

Abstract

A novel fluorescent molecular logic gate with a 'fluorophore-spacer₁-receptor₁-spacer₂-receptor₂' format is demonstrated in 1 : 1 (v/v) methanol/water. The molecule consists of an anthracene fluorophore, and tertiary alkyl amine and N-(2-methoxyphenyl)aza-15-crown-5 ether receptors. In the presence of threshold concentrations of H⁺ and Na⁺, the molecule switches 'on' as an AND logic gate with a fluorescence quantum yield of 0.21 with proton and sodium binding constants of log β_H+ = 9.0 and log β_Na+ = 3.2, respectively. At higher proton levels, protonation also occurs at the anilinic nitrogen atom ether with a log β_H+ = 4.2, which allows for Na⁺, H⁺-enabled OR (OR + AND circuit) and H⁺-driven ternary logic functions. The reported molecule is compared and contrasted to classic anthracene-based Na⁺ and H⁺ logic gates. We propose that such logic-based molecules could be useful tools for probing the vicinity of Na⁺, H⁺ antiporters in biological systems.