Structure, magnetic properties, catalase activity and DFT studies of [Mn2(μ-RCOO)2(μ-OR)2]2+ type dinuclear manganese(III,III) complexes

Three Mn(III,III) complexes containing dibenzoylmethane (dbm), Mn2(OMe)2(dbm)2(ClH2CCOO)2 (1), Mn2(OMe)2(dbm)2(Cl2HCCOO)2 (2) and Mn2(OMe)2(dbm)2(Cl3CCOO)2 (3) were synthesized. Crystal structure determination and magnetic characterization were done for 2. The Mn⋯Mn distance in complex 2 is 2.865 Å. It exhibits antiferromagnetic coupling with exchange parameter |J| = 20.4 cm−1 (H = −2JSASB). All three complexes, though insoluble in common solvents, catalyse the disproportionation of hydrogen peroxide when dispersed on silica gel with turnover numbers ∼150–300. DFT simulations showed that bridging moieties have remarkable effect on intermetallic distances in dimanganese(III,III) complexes.

The antiferromagnetic coupling in a dimanganese(III) complex having (μ-RCOO)2(μ-OR)2 bridge is found to be greater than in similar complexes having only the dialkoxy bridge but much lesser than in dioxo bridged complexes.Figure optionsDownload as PowerPoint slideHighlights
► Three new Mn(III,III) complexes containing dibenzoylmethane.
► Dicarboxylato–dialkoxy bridged dinuclear core, moderately antiferromagnetic.
► Insoluble complexes, show catalase activity when dispersed on silica gel.
► DFT results – bridging moieties have remarkable effect on Mn···Mn distance.