Chromogenic amide and CHEF-based emissive receptors for Cu 2+ & Co 2+ , as well as biological anions including the notorious CN - : The impact of a molecular chameleon, enticing early career beginners

Abstract

A rich-in-amide receptors, acrylamide-N’phenylhydrazine carbothioamide-based fluorescent probe (MA) was synthesized via a simple and one-step procedure of Schiff base condensation reaction. The structure was characterized via spectroscopic methods of 1H NMR, UV-Vis and fluorescence methods. In addition, the bench-top applications on the detection of cations and anions, in DMSO, were carried out visually and spectroscopically. As a result, MA displayed colorimetric activities once anions or cations were added, observable by naked eye detectable colour changes. The probe turned out to discriminate cations such as Cu2+, Co2+, Fe3+ and Fe2+ via colour changes, which was complemented by the changes in UV-Vis titration spectra for each individual titration. Moreover, the addition of anions (F-, AcO-, CN- and OH-) to MA had colorimetric impacts observable by naked eyes, and complemented by spectral changes upon UV-Vis analysis. The probe was fluorometrically responsive to the addition of cations (Co2+, Cu2+, Ni2+ and Fe2+) and anions (F-, AcO-, CN- and OH-), both in DMSO, which have all resulted in chelation-based fluorescence enhancement (CHEF), with Co2+ and AcO- complexes exhibiting high affinity of the host-guest species. Thus, MA proved to be a potential chromogenic-fluorogenic probe, which could be used in monitoring the presence of specific cations and anions, in aqueous soluble solvent of DMSO.