Molecular logic circuits and a security keypad lock based on a novel colorimetric azo receptor with dual detection ability for copper(II) and fluoride ions

A novel azoimine dye-based colorimetric chemosensor (1) has been designed and synthesised for dual recognition of copper(II) and fluoride ions in aqueous media. Significantly, the outstanding dual-ion recognition properties along with the excellent reversibility prompted us to consider 1 as an ideal candidate for fabrication of multiple logic circuits. According to the response profile of 1 towards Cu²⁺ and F^? inputs, we developed a unique tunable system integrated with one INHIBIT logic gate as well as one OR gate. Also, 1 behaved as a molecular keypad lock with sequential addition of Cu²⁺ and F^? inputs. In accession, a reversible ‘Write–Read–Erase–Read’ function with complementary ‘IMP/INH’ logic gate has been demonstrated through a feedback loop using F^? and trifluoroacetic acid as two chemical inputs. To the best of our knowledge, this is the first report where the symmetrical bis azo-azomethine dye has been exploited as a molecular keypad lock.