Novel 1,4-naphthoquinone N-aroylthioureas: Syntheses, crystal structure, anion recognition properties, DFT studies and determination of acid dissociation constants

Abstract In this paper, five novel 1,4-naphthoquinone N -aroylthiourea derivatives were synthesized, by the reaction of 2,3-diaminonaphthalene-1,4-dione and aroylisothiocyanates, in excellent yield (88–96%) and characterized by using FT-IR, 1 H/ 13 C NMR and HRMS. In addition, the molecular structure of one of the 1,4-naphthoquinone N -aroylthiourea compounds was characterized by single crystal X-ray diffraction studies. The absorption spectra of the compounds were determined in DMSO and the dyes have absorption in visible region in the range of 464–477 nm. The chemosensing ability of each of the prepared dyes was assessed by titrating them towards the anions; F − , Cl − , Br − , I − , AcO − , CN − , ClO 4 − , H 2 PO 4 − , HSO 4 − , and NO 3 − , using spectrophotometric and 1 H NMR titration techniques in DMSO, experimentally. The results obtained from the experimental investigation were explained by employing theoretical calculations. The molecular structure and absorption spectra of the compounds and their deprotonation forms were obtained using Density Functional Theory (DFT) and time-dependent DFT (TD-DFT) at B3LYP/6311 g(d) level of theory. The computed results are in good agreement with the experimental. Finally, the acid dissociation constants of the 1,4-naphthoquinone N -aroylthioureas were determined potentiometrically in 50% (v/v) DMSO-H 2 O hydro-organic solution at 25 ± 0.1 °C, at an ionic background of 0.1 mol/L of NaCl using the HYPERQUAD computer program.