An imidazolyl-pyreno-imidazole conjugate as a cyanide sensor and a set–reset memorized sequential logic device

Abstract

In this work a pyrenyl-bisimidazole receptor has been synthesized and fully characterized by standard analytical tools and spectroscopic techniques including single crystal X-ray crystallography. Crystal structure analysis shows the occurrence of strong π–π and CH–π interactions among the adjacent Py-BiimzH₂ units. Moreover, each NH proton on the imidazole ring is involved in strong intermolecular hydrogen bonding interactions with N atoms of the neighboring unit forming infinite chains. The absorption and both steady state and time-resolved emission properties of the compound were found to be modulated to a significant extent by selective inorganic anions and transition metal cations in solution. Theoretical calculations employing density functional theory (DFT) and time-dependent density functional theory (TD-DFT) were carried out and good correlation between the experimental and the TD-DFT calculated results led to the accurate assignment of the main absorption and emission bands of the original compound as well as its anionic and metal complexes. More importantly, the compound can act as an efficient ratiometric optical chemosensor for CN⁻ in H₂O–DMSO (9 : 1) media. The anion sensing properties of the receptor was thoroughly investigated in both neat DMSO as well as mixed H₂O–DMSO (9 : 1) media through different channels. From the response profiles in terms of absorption or emission intensity and wavelength towards inorganic ions (Cu²⁺ and CN⁻), we developed a molecular system which can mimic sequential Boolean logic functions of XOR, OR, XNOR and NOR logic gates. Moreover, we were able to construct a memory device which nicely demonstrates the “Write–Read–Erase–Read” behavior.