Colorimetric Cu2+Detection of (1 E,2 E)-1,2-Bis((1 H-pyrrol-2-yl)methylene)hydrazine Using a Custom-Built Colorimeter

Abstract

The compound (1E,2E)-1,2-bis((1H-pyrrol-2-yl)methylene)hydrazine (1) was investigated for its chemosensor application. The colorimetric response of 1 with various ions was investigated, and the selective optical change upon mixing with Cu2+ was found. The Cu2+ binding stoichiometry of 1 derived from Job's plot and the in silico study give us the tentative structural detail of the binding mode of 1 and Cu2+ being 1:1. The binding constant between 1 and Cu2+ from the Benesi-Hildebrand plot was 1.49 × 104 M-1. The limit of detection of 1 in Cu2+ detection was 0.64 μM (0.040 ppm), which is much lower than the WHO and US EPA maximum allowable Cu2+ level in drinking water (2 and 1.3 ppm, respectively). The custom-built colorimeter demonstrates a good linear relationship between Cu2+ concentration and electrical resistance (ω) upon 1-Cu2+ ion binding.