Structural elucidation of N-amidothiourea derived from nicotinic acid hydrazide: A detailed study of its application as selective anion sensor

[Display omitted] •Synthesis of nicotinic acid hydrazide-based thiourea receptor.•Structural analysis of the synthesized thiourea receptor by X-ray crystallography.•Application of the thiourea receptor as a chemosensor for selective anions.•Real-time application of the thiourea receptor as a chemosensor for F− ions.•The experimental findings were supported by theoretical calculation. A novelN-amidothiourea receptor (1), synthesized by the reaction of nicotinic acid hydrazide with phenyl isothiocyanate, was evaluated for the detection of fluoride, acetate, and hydroxide ions selectively over other anions. Receptor1was characterized by various spectroscopic methods, and further structural elucidation of it was done by Single Crystal X-ray diffraction analysis. The efficacy of receptor1as a colorimetric sensor for fluoride ions was observed by an instant colour change from colourless to light yellow, which can be attributed to the H-bonding complex formation between receptor1and anion. The binding characteristics of the thiourea receptor with fluoride ion (F−) showed 1:1 binding stoichiometry at a lower concentration, whereas at a higher concentration, the binding stoichiometry increased to 1:2. The receptor, when treated with acetate and hydroxide ion, showed 1:2 and 1:1 binding stoichiometry, respectively. The binding affinity of receptor1was found to be following the Brønsted acidity order, i.e., OH− > AcO− > F−. Detailed quantum chemical calculations also supported the experimental findings.