2-((E)-(2-aminophenylimino)methyl)-6-isopropyl-3-methylphenol based fluorescent receptor for dual Ni2+ and Cu2+ recognition: Nanomolar detection

Abstract

The well-known benzene-1,2-diamine structure is considered to be a good model for the development of fluorescence-quenching chemosensors through simple and convenient syntheses. Herein, an original and simple chemosensor molecule, 2-((E)-(-2-aminophenylimino)methyl)-6-isopropyl-3-methylphenol (3), has been designed by combining a benzene-1,2-diamine and 2-hydroxy-3-isopropyl-6-methyl benzaldehyde, and its structure has been confirmed by the single crystal X-ray method. Further it has shown selectivity and sensitivity for Ni2+ and Cu2+ ions in a dual-channel mode (fluorescence emission and UV–Vis). The results indicate that 3 could be applied in multianalyte detection. The mechanism of Cdouble bond; length as m-dashN isomerization, coupled with photoinduced energy transfer, is proposed to explain the observed spectral response. The binding constant values for Ni2+ and Cu2+ were calculated to be 25 000 and 30 000 M−1 respectively by the Benesi–Hildebrand method. The detection limits of Ni2+ and Cu2+ were 100 and 50 nM, which are below the World Health Organisation (WHO) acceptable limits for drinking water.