Synthesis, Characterization and Combined Superoxide Dismutase and Catalase Activities of Manganese Complexes of 1,4‐Bis(salicylidenamino)butan‐2‐ol

Two Mn IV complexes of general formula [Mn(salbutO)X] [H 3 salbutO = 1,4‐bis(salicylidenamino)butan‐2‐ol, 1 : X = N 3 , 2 : X = SCN] have been prepared and structurally characterized. The crystal structure of 1 shows that salbutO 3– acts as a pentadentate ligand through the two phenolato‐ O , two imino‐ N , and one alcoholato‐ O atoms, and the sixth coordination position is occupied by the azido‐ N atom, resulting in a slightly distorted N 3 O 3 donor set around the Mn IV ion. ESI‐MS, UV/Vis, and 1 H NMR spectroscopy were used for solution studies. In methanol and dmf, the starting complexes are converted into [Mn III (salbutO)] and its dimeric form. The E 1/2 of Mn III /Mn IV (ca. 0.4 V vs. Ag/AgCl) allows this couple to efficiently catalyze the dismutation of O 2 · – with catalytic rate constant and IC 50 values of 1.91 × 10 6 M –1  s –1 and 1.43 μ M , respectively, which were obtained through the nitro blue tetrazolium photoreduction inhibition SOD assay, in aqueous solution of pH 7.8. The Mn‐salbutO complexes also show catalase activity in methanol and dmf, with k cat = 1.6 M –2  s –1 and 5.6 M –1  s –1 , respectively, an advantageous property for acting as scavenger of reactive oxygen species (ROS). This valuable conjunction of properties results from the conversion of [Mn IV (salbutO)X] into [Mn III (salbutO)] 2 in equilibrium with its monomer [Mn III (salbutO)].