Ponente
Descripción
Thiourea derivatives have been reported as receptors or ionophores for heavy metal cations. Having hard and soft donor sites in their structure facilitates its versatility. In this work, density functional theory (DFT) method has been used to investigate the electronic and structural properties of two 1-(2-furoyl)thiourea derivatives: 3-ciclopropyl (FCP) and 3,3-diethyl (FDE) substituted. Furthermore, we have considered the molecular recognition of the cis - trans conformations with Pb2+ cation. The calculations were done at B3LYP/6-31+G(d,p) level with the Gaussian-16 program. A LANL2DZ pseudopotential was used for lead. The optimized structure, total energy, energy gap, highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO) energy, ionization potential, electron affinity, chemical potential, global hardness, softness, and electrophilicity index have been calculated for both compounds. The 3-monosubstituted FCP ligand has an intramolecular hydrogen bond between N3H and carbonyl oxygen atom, displaying smaller energy gap and larger values for both softness and electrophilicity index as compared with FDE. These results point to a larger reactivity of FCP. In particular, the remarkable difference for electrophilicity index values indicate FCP could not be suitable as ionophore towards an electrophile, e.g. Pb2+ ions. The results support the bad sensibility value (16 mV/dec vs 29,57 mV/dec for a divalent cation, according to Nerst) obtained for constructed Pb2+ selective electrodes based on FCP as receptor.
