Herein, a novel N-(4-(tert-butyl)-phenyl)-2-chloroacetamide functionalized thiacalix [4]arene architecture, viz TCAN2PA has been synthesized and the sensing behaviour towards metal ions was explored. The probe, TCAN2PA displayed a "Turn-ON" uorescence response towards Hg(II) ions in acetonitrile over a series of competing common metal ions. A bathochromic shift in absorption band along with a signi cant "Turn-ON" uorescence behaviour of TCAN2PA was observed upon interaction with Hg(II) ions. The lower rim modi cation of thiacalixarene with N-(4-(tert-butyl)-phenyl)-2-chloroacetamide actively contributes toward the uorescence property due to the presence of strong electron-donating aryl amido substituent. Fluorescence titration experiments were conducted to nd out the limit of detection and to understand binding stoichiometry as well. The electron transfer interactions between the electron-rich TCAN2PA host with Hg(II) ions have been postulated which is also supported by computational modelling insights.