New naphthoquinone-imidazole hybrids: Synthesis, anion recognition properties, DFT studies and acid dissociation constants

Abstract

The two new naphthoquinone-imidazole based dyes containing indole and pyrene moiety were synthesized and their molecular structures were confirmed by FT-IR, 1H/13C NMR, and HRMS. The anion selectivity and sensitivity of dyes were studied with selected TBA salts in DMSO and binary mixture DMSO:Water (1:1, v/v). These interaction mechanisms were verified by spectrophotometric, spectrofluorometric, and 1H NMR titration methods. While the both dyes interact with F−, AcO−, CN−, and H2PO4− in DMSO, only CN− interact with dyes in the aqueous solution. In addition, the experimental results were explained by DFT calculations. The acid dissociation constants of the dyes were determined in 25.0 ± 0.1 °C, 0.1 M NaCl ionic strength in 40% (v/v) DMSO-Water aqueous solution, and acid dissociation constants relating protonated carbonyl group and nitrogen atoms were determined for each dye.