Ligand-dependent modulation of ROS response in soybean by Cu(II)–amino acid complexes

exhibited the most consistent behavior, combining high chemical reactivity with effective ROS reduction in planta and moderate copper accumulation in leaf tissues. These findings demonstrate that ligand coordination strongly influences copper behavior, decoupling in vitro reactivity from biological outcome under stress conditions. Overall, the results establish a structure-reactivity-biological response relationship for Cu(II)-amino acid complexes and highlight the importance of copper speciation in the design of safer redox-active compounds for biological applications.