Chinese-Lantern shaped [MnII2MnIII6NaI3] cluster assembled from Schiff base and azide bridges: synthesis, magnetic study and catecholase-like activity

A multisite Schiff base, H2damp, derived from the condensation of o-vanillin and a sterically constrained amino-alcohol (2-amino-2-methylpropan-1-ol) was utilized to isolate a new mixed valence heterometallic complex [Na3MnIII6MnII2(damp)6(µ4-O)2(µ1,3-O2CCH3)2(µ1,1-N3)6(µ1,1,3-N3)(H2O)2]·5H2O·CH3OH (1). Room temperature reaction of H2damp in MeOH with Mn(II) acetate and NaN3 provided the complex having MnII2MnIII6NaI3 core. X-ray structure determination revealed the use of azide ancillary ligands for the growth of the complex on ligand-bound MnIII3O fragments. The variable temperature magnetic characterization of 1 revealed intramolecular anti-ferromagnetic exchange interactions. Complex 1 also showed catalytic property for the aerial oxidation of 3,5-di-tert-butyl catechol (3,5-DTBCH2) with a turnover number (kcat) of 392 h−1. EPR and mass spectrometric analysis established the probable mechanism of catalytic oxidase reactivity on the model substrate. In EPR study the characteristic peak at g ∼ 2 allowed us to spot the presence of an organic radical confirming the conversion of DTBCH2 to DTBQ in radical pathway.