The catalytic performance of Schiff base complexes is found to be influenced by the choice of metal ions and ligands. For instance, methyltrioxorhenium (MTO) forms complexes with Schiff bases derived from 2-pyridinecarboxaldehyde and amines, showing high catalytic activity and selectivity in epoxidation reactions . However, these complexes are sensitive to water and large excesses of ligands, which can lead to catalyst decomposition. The design of Schiff base catalysts for hydrogen evolution requires careful consideration of the ligand structure, metal ion selection, and reaction conditions. The ability to fine-tune the electronic and steric properties of Schiff bases through the selection of suitable aldehydes or ketones and primary amines offers a versatile platform for catalyst design . Future research in this area may focus on developing more stable and efficient Schiff base catalysts for HER, potentially incorporating elements such as crown ether rings to enhance catalytic performance .