Selectivity through an asymmetric pathway in the degradation of non-steroidal anti-inflammatory drugs (NSAIDs) using mixed-ligand cobalt(II) complexes: experimental and theoretical insights

Understanding the asymmetric catalytic mechanism involving organometallic species provides exceptional insight into the strategies for the degradation of emerging organic contaminants. The present work demonstrates such insights on the oxidation of commonly used non-steroidal anti-inflammatory drugs (NSAIDs) such as diclofenac, paracetamol, ibuprofen, and aspirin using optically active novel Schiff base Co(II) complexes derived from salicylaldehyde containing five different amino acids (L-methionine, L-leucine, L-asparagine, L-tryptophan, and L-glutamic acid). Among the studied chiral catalysts, asymmetric degradation in the presence of a Co(II) complex containing glutamic acid mixed ligand showed an elevated rate of oxidation of non-amine NSAIDs such as ibuprofen (3.86 × 10^–2 s⁻¹) and aspirin (3.70 × 10^–3 s⁻¹) using H₂O₂ oxidant under visible light conditions at neutral pH. The formation of chiral intermediate species in both drugs has been detected and characterized by FTIR and Raman analysis. On the other hand, NSAIDs containing secondary amine groups (–NH–), such as diclofenac and paracetamol, generate effective coordination between the complex catalyst and the nitrogen atom. This explains the high activity of the Co(II) complex with glutamic acid mixed salicylaldehyde with 100% selectivity in the degradation of ibuprofen and aspirin. The thermodynamical feasibility of the proposed degradation route for ibuprofen and aspirin was analyzed with theoretically calculated total energy values of all the intermediates formed in each step of the proposed mechanism.

Graphical abstract