Sensing Activity of a New Generation of Thiourea-based Receptors; A Theoretical Study on the Anion Sensing

A theoretical density functional theory (DFT) study was performed on a series of the neutral N-phenylthiourea substituents (p-OC2H5, p-CH3, m-CH3, H, p-Cl, p-Br, m-Cl, and p-NO2) as the sensor of acetate and fluoride anions. The hydrogen bond character was analyzed as a scale of the sensing activity. It was confirmed that hydrogen bond between the p-NO2 derivatives of N-phenylthiourea and fluoride anion is stronger than acetate in CH3CN as a solvent. Therefore, N-(p-nitrophenyl) thiourea acts as a better chemical sensor in fluoride detection. For the investigation of the N-H bond properties, donor-acceptor interaction energy through the natural bond orbital analysis was obtained. Topology analysis by estimation of the kinetic and potential energy densities of the hydrogen bonds was done. Finally, some correlations between the quantum chemistry descriptors and sensing characters of the studied compounds were obtained and analyzed.