Environmental effects in nitroquinoline derivatives solutions: Solvatochromism, acid-base effect and ion-sensor investigation

Abstract

Since the first chemical fluorescent sensor reported in 1867, it has often been sought to find intelligent organic molecules that act as chemical sensors of high selectivity and sensitivity. In this process, the colorimetric and fluorescence methods have more advantages, as they are generally very sensitive, low cost, easily executable, versatile and of quick result. Colorimetric receptors containing several chromophores with azo-compounds have been developed since the discovery of chemosensors. Quinoline derivatives attract the interest of the scientific community in this regard. Thus, the present study using a facile synthesis aimed to help in development and behavioural study of new nitroquinolinic compounds against different solvents, pHs and organic/inorganic salts to observe potential recognition of anionic or cationic species. In four compounds a good non-linear fitting between the absorption intensity and amount of acid/base were established. The structural characterization of each of the prepared compounds was carried out with different spectroscopic and spectrometric techniques. UV–Vis and fluorescence measurements were also essential to confirm the binding/interaction process of ionic species and helped to find molecules with potential use in the identification of Co2+ and U2+ species, in addition to showing the sensitivity of species to pH and different solvents. The combination of theory and experiment is able to give a better understanding of the behavior in acidic, basic and neutral medium, DFT calculations were employed for this purpose.