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

[Image: see text] 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 Cu(2+) was found. The Cu(2+) 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 Cu(2+) being 1:1. The binding constant between 1 and Cu(2+) from the Benesi–Hildebrand plot was 1.49 × 10(4) M(–1). The limit of detection of 1 in Cu(2+) detection was 0.64 μM (0.040 ppm), which is much lower than the WHO and US EPA maximum allowable Cu(2+) level in drinking water (2 and 1.3 ppm, respectively). The custom-built colorimeter demonstrates a good linear relationship between Cu(2+) concentration and electrical resistance (Ω) upon 1–Cu(2+) ion binding.