A highly selective fluorescent chemosensor based on thio-β-enaminone analog with a turn-on response for Cu(II) in aqueous media

Abstract

Novel chemosensor, 1,1,2-trimethyl-1H-benzo[e]indoline based thio-β-enaminone (TBE) was developed with excellent sensitivity and selectivity for Cu2+ ions. In comparison with different cations (Na+, Mg2+, Al3+, K+, Ca2+, Mn2+, Co2+, Ni2+, Zn2+, Cd2+, Ba2+, La3+, Hg2+, Pb2+), TBE gave pronounced 20-fold fluorescence enhancement for Cu2+ ions, which remained unaffected in presence of other interfering metal ions. The ratiometric binding of TBE–Cu2+ complex determined from Job's plot gave 1:1 interaction, which was confirmed by ESI-MS. Binding of Cu2+ ions to TBE was studied over the wide pH range and the result demonstrated maximum fluorescence enhancement in the pH range of 3.0–10. The binding association constant (Ka) value determined from Benesi–Hildebrand equation was 1.10×104M−1. The high detection limit in micromolar range (8.2×10−7M) for Cu2+ ions makes TBE a suitable candidate for the development of a potential probe. Applicability of TBE to detect Cu2+ ions in human serum and tap water has been demonstrated.