A phthalimide scaffold smart molecule for visualization of acid-base equilibrium and determination of acid dissociation constants in the non-aqueous medium

Abstract

A phthalimide decorated novel acid-responsive probe Z1 is designed and synthesized based on a conjugated donor-acceptor (D-A) subunit. The synthesized probe shows a colorimetric visual change through protonation and deprotonation processes with the addition of acid and base in the non-aqueous medium. A ratiometric UV–vis absorption spectral change is observed with the addition of acid, and the density functional theory investigation supports the experimental findings. A colorimetric paper strip-based experiment has been demonstrated to detect trace amounts of acid and bases in non-aqueous solvents. Furthermore, the overlapping indicator method is explored to estimate acid dissociation constants in the non-aqueous medium. The acid-responsive colorimetric behavior of this probe is fully reversible with the addition of bases, and using this reversible colorimetric response, we have constructed the INHIBIT (INH) and IMPLICATION (IMP) molecular logic gate. The present report invokes a new avenue for synthesizing several acid-base sensors and estimating the acid dissociation constants of diverse acid-base compounds in the non-aqueous medium.