Synthesis, characterization, and oxidation catalysis studies of a monofunctionalized copper pyridine-aza macrocycle

Abstract

A copper-containing pyridine-aza macrocycle (PyMAC) with a propionic acid functionality was synthesized and characterized using X-ray crystallography and various spectroscopic techniques. The complex was then screened for peroxidase, olefin epoxidation, and phenol oxidation properties, using an ABTS assay, GC-MS, and UV–Vis spectrophotometry, respectively. The control copper (II) perchlorate salts were superior oxidation catalysts to the pentadentate carboxylic acid complex, CuLCOOH, and the unfunctionalized amine PyMAC, CuCRH. This might indicate that free copper ions facilitate the one-electron oxidations necessary for the reactions better than complexed copper. It also indicates that the copper PyMACs are far less effective than the analogous nickel and iron systems. We did, however, obtain valuable insights on the chemistry governing this family of PyMACs by probing the CuLCOOH’s solution and solid-phase protonation equilibria, which will be useful for isolating and studying the analogous iron complex, FeLCOOH.