The optical properties (UV-Visible and fluorescence spectra) of PTE-EA (10 µM) remained unaltered upon the addition of various metal ions as their perchlorate salts including Zn 2+ , Ni 2+ , Mg 2+ , Pb 2+ , Hg 2+ , Li + , K + , Fe 2+ , Ba 2+ , Co 2+ , Ca 2+ , Sr 2+ and Cd 2+ in HEPES:CH3CN (3:7, v/v, pH 7.3). However, the addition of Cu 2+ resulted in exceptional changes appeared as vanishing of the absorption band at 536 nm with increase at 460 nm and increase in the fluorescence intensity at 520 nm (Figure ). 536 nm and concomitant escalation of absorption intensity of blue shifted peak at 460 nm with a stokes shift of 76 nm and a clear isosbestic point at 480 nm, revealing the termination of ICT phenomena after binding with the recognition group (donor) resulting in PTE-EAꓵCu 2+ complex.