Functionalize of Zn (II) complexes of thiosemicarbazones Schiff bases and tryptophan as an auxiliary ligand on HY zeolite, synthesis, characterization and catalytic activity for organic transition

Abstract

Nowadays, the number of studies about ternary complexes where metal is coordinated by two or more ligands have been increased these complexes usually use as a homogenous catalysts for organic reactions. In this way, we report the synthesis of a heterogeneous catalyst for the first time by functionalized Zn(II) thiosemicarbazones Schiff bases and tryptophan as an auxiliary ligand complex on HY zeolite (Zn-HY-L-AA). The prepared catalyst was characterized by different methods such as FT-IR, XRD, BET, FESEM, EDX, DRS, TGA, ICP-OES, and NH3-TPD. The result confirmed the complex was successfully immobilized the HY zeolite. In addition, the preparation of a micro-meso structure catalyst with strong acid sites was confirmed by BET and NH3-TPD techniques. The Zn-HY-L-AA exhibits excellent catalytic activity for two sets of important organic reactions, preparation of polyhydroquinoline derivatives, and aldol condensation at room temperature and under solvent-free conditions. Besides following the green chemistry conditions for these organic reactions, the heterogeneous catalyst is easily separated. It can be used for recyclability up to 6 times without significant loss in catalytic activity and change in the structure after consecutive cycles. In addition, a comparison of prepared catalysts showed a high yield for two sets of organic reactions under milder conditions concerning other works.