Fluorescent Chemosensing Properties of New Isoindoline Based-Receptors towards F - and Cu 2+ Ions

Abstract

Two simple colorimetric and fluorescent anion chemosensors based on amide moieties, 4-nitro-N-[(1,3-dioxoisoindolin-2yl)benzamide (1), 3,5-dinitro-N-[(1,3-dioxoisoindolin-2yl)benzamide (2) have been synthesized and characterized. Comparing with other anions studied, the UV-visible absorption spectrum in DMSO shows significant response toward F- ion with high selectivity, and meanwhile color change is observed from colorless to pink and violet for 1 and 2 respectively in the presence of tetrabutylammonium fluoride (TBAF) (5 × 10-3 M). Moreover, F--induced color changes remain the same even in the large excess of Cl- , Br- and I-. In addition, the 1H NMR spectrum titration in DMSO-d6 shows deprotonation of the receptors 1 and 2 in the presence of basic F- ion. In particular, addition of F- to the receptors 1 and 2 resulted in an enhancement in fluorescence intensity at 770 nm. Both receptors 1 and 2 exhibit a fluorescent emission enhancement when addition of Zn2+, Ni2+, Co2+, Cu2+ and Mn2+ metal ions. The fluorescent enhancement values for the receptor 1 are 2.29 (Cu2+), 1.85 (Ni2+), 1.37 (Co2+), 1.27 (Mn2+), 1.25 (Zn2+) and for 2, 2.57 (Cu2+), 1.66 (Ni2+), 1.36 (Co2+), 1.15 (Mn2+), 1.09 (Zn2+). The selectivity of Cu2+ is higher for 1 and 2 than other metal ions such as Zn2+, Ni2+, Co2+ and Mn2+.