HIGH ACTIVITIES OF HYDROGEN-PEROXIDE DECOMPOSITION CATALYZED BY DINUCLEAR SCHIFF-BASE MN(III)-CU(II) COMPLEXES ACCOMPANYING METAL SUBSTITUTION IN N,N-DIMETHYLFORMAMIDE AND THE CRYSTAL-STRUCTURE OF A SUBSTITUTED SCHIFF-BASE CU(II) COMPLEX

The effects of divalent metal ions (M2+ = Mn2+, Co2+, Ni2+, Cu2+, and Zn2+ ions) an the catalase-like activities of mononuclear Schiff base Mn(III) complexes, such as [Mn(salen)CI] (H(2)salen: N,N'-ethylenebis( salicylideneamine)), [Mn(saltn)Cl] (H(2)saltn: N,N'-propane-1,3-diylbi s(salicylideneamine)), [Mn(saltnOH)Cl] (H(2)saltnOH: 2-hydroxypropane- 1,3-diyl)bis(salicylideneamine)), and [Mn(saltnOCOPh)Cl] (H(2)saltnOCO Ph: enzoyloxypropane-1,3-diyl)bis(salicylideneamine)), in N,N-dimethyl formamide (DMF) have been reported. Except for the Cu2+ ion, H2O2 deco mposition was depressed in the presence of M2+ = Mn2+, Co2+, Ni2+, and Zn2+ ions because [Mn(salen)](+) reacted with M2+ to give dinuclear M n(III)-M(II) and trinuclear Mn(III)2-M(II) complexes inactive toward H 2O2 in DMF. For the Cu2+ ion, the dinuclear complexes with the salen a nd saltnOCOPh ligands showed high activities, although the trinuclear complexes were inactive toward H2O2. The ESR spectra suggested that th e intramolecular electron transfer from Cu(II) to Mn(III) on the dinuc lear Mn(III)-Cu(II) complex partly occurs to produce a dinuclear Mn(II )-Cu(III) complex active toward H2O2. During H2O2 decomposition includ ing the radical reaction path, [Cu(salR)] (R = en, tnOCOPh) and Mn2+ w ere produced accompanying metal substitution by Cu2+ on the dinuclear complex. To clarify the substituted product, the preparation and an X- ray crystal structure analysis of [Cu(saltnOCOPh)] were carried out. T hree independent [Cu(saltnOCOPh)] complexes (CuA, CuB, and CuC) were p resent along with an intermolecular pi-pi stacking interaction between benzene rings on the salicylidenediamine moiety and benzene ring on t he benzoyloxy group in the crystal. The geometries around the coppers in both CuA and CuC are more distorted toward tetrahedral from square plane than that in CuB. No stacking interaction between benzene rings on [Cu(saltnOCOPh)] occurs in DMF solution.