<p>These days, optical sensors are getting considerable interest of researchers due to their portability and rapid on-site detection abilities for metal ions. In this paper, a Schiff base 2-((4-(dimethylamino)benzylidene)amino)acetic acid (DMAB-G) was studied for its optical sensing properties towards metals ions i.e. Al³⁺, Mn²⁺, Fe²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Ag⁺, Cd²⁺, Hg²⁺, Pb²⁺, AsO₂⁻ and La³⁺. This naked eye probe showed a selective color change from colorless to pale yellow only for mercuric (Hg²⁺) ions which is consistent with red shift from 342&#xa0;nm to 448&#xa0;nm having an LOD of 1.71 × 10^− 6 M in aqueous medium which make it better sensor compared to literature reported ones. Furthermore, calculations revealed a DMAB-G bound with Hg²⁺ ions in a ratio of 2:1 with an association constant of 1.7 × 10³ M^− 2. FT-IR data suggested that DMAB-G interacted with mercuric ions by coordination through nitrogen of imine group and carbonyl of carboxyl moieties which was further confirmed by DFT-Calculations.</p> Graphical abstract <p></p>