Synthesis and multipurpose assessment of Cu(II) and Pd(II) Schiff base complexes as catalysts and antimicrobial agents

Schiff base derivatives of isatin were synthesized with tryptamine in excellent yields to explore their broad applications as ligand precursors. Further, the ligand was reacted with Cu(OAc)2.H2O and PdCl2(CH3CN)2 to form the corresponding complexes with a 1:2 metal-to-ligand stoichiometry. The ligand and its complexes were analyzed with various techniques, including UV, FTIR, ESI-MS spectroscopy, and some physicochemical methods. Thermal analysis displayed high stability, with the Cu(II) complex remaining stable upto 250 °C and the Pd(II) complex showed no major decomposition until 340 °C. The molecular composition was examined with the help of XRD and CHN techniques. The antimicrobial evaluations revealed that complexation significantly enhanced bioactivity compared to the free ligand. The complexes exhibited moderate to strong growth inhibition against bacterial (E. coli, P. syringae, S. aureus, and S. epidermidis) and fungal strains (A. flavus and C. albicans). Additionally, the synthesized complexes were utilized as catalysts in the Suzuki-Miyaura coupling reaction of bromobenzene and phenylboronic acid. Another catalytic proficiency in reductive degradation of common dyes, like methylene blue (MEB), Rhodamine-B (Rh-B), Congo red (CR), and methyl orange (MO), was investigated for copper and palladium complexes. Both metal complexes facilitated the reductive degradation of hazardous organic dyes, in aqueous media.