La(OCOCF₃)₃·<i>n</i>H₂O@SiO₂ Lewis Acid as a Versatile and Highly Efficient Recyclable Catalyst for 5-Aryl-1,2,4-triazolidine-3-thione Synthesis in Green Solvent Water and Density Functional Theory Studies

An economic and environment-sustainable room-temperature-assisted [La-(OCOCF₃)₃·<i>n</i>H₂O@SiO₂] green Lewis acid catalyst promoted highly efficient and rapid synthesis of 5-aryl-1,2,4-triazolidine-3-thiones was achieved via the straightforward reaction of thiosemicarbazide and aromatic aldehydes in universal green solvent water. A broad substrate scope, rapid reaction at RT, excellent product yield, mild reaction medium, easy recovery and reusability of catalyst with consistent and efficient performance for more than four consecutive cycles are the prominent features of the current green synthetic approach. This water-compatible green Lewis acid catalyst was introduced for the first time in this environment-friendly greener protocol, which has been validated using established green chemistry metrics. Furthermore, the DFT quantum calculations method with the B3LYP/6-31G (d,p) basis set was utilized to analyze reactivities and substituent effects for electron-donating groups and electron-withdrawing groups by calculating the HOMO-LUMO energy gap. DFT study was also used to compute the optimized geometries, molecular electrostatic potential, density of states, and global reactivity parameter of the synthesized product (<b>3a</b>-<b>l</b>). As a result, the integration of computational chemistry with experimental methods emerges as a formidable asset in advancing the existing synthetic protocol.