Dinuclear Mn^III Compounds [{Mn(bpy)(H₂O)}₂(μ‐4‐RC₆H₄COO)₂(μ‐O)](NO₃)₂ (R = Me, F, CF₃, MeO, tBu): Effect of the R Group on the Magnetic Properties and the Catalase Activity

Abstract

Five new dinuclear Mn III compounds [{Mn(bpy)(H 2 O)} 2 (μ-4-RC 6 H 4 COO) 2 (μ-O)](NO 3 ) 2 [R = Me (1), F (2), CF 3 (3), MeO (4) and tBu (5); bpy = 2,2Ј-bipyridine] have been synthesized; compounds 1-3 have been characterized by X-ray diffraction. Moreover, a few crystals of the Mn III compound [{Mn(bpy)(H 2 O)}(μ-4-FC 6 H 4 COO)(μ-O){Mn(NO 3 )(bpy)(H 2 O)}]-(NO 3 ) 2 (6) have been obtained. Variable-temperature magnetic susceptibility data of 1-5 were recorded; all compounds show ferromagnetic behaviour with J = 1.48 cm -1 for 1, 1.44 cm -1 for 2, 5.66 cm -1 for 3, 3.22 cm -1 for 4 and 2.68 cm -1 for 5 (H = -JS 1 ·S 2 ); and |D Mn | = 1.5 cm -1 and |E Mn | = 0.5 cm -1 for all compounds except for 2, for which these values are [c]

Catalase Activity of Dinuclear MnIII Compounds with Chlorobenzoato Bridges

“…[9] For compounds with the formula [{Mn(bpy)(H 2 O)} 2 (μ-O)(μ-RC 6 H 4 COO) 2 ](NO 3 ) 2 , a quite good correlation between the catalase activity and the Hammett parameter of the R group in the RC 6 H 4 COO ligands was observed. [9] For compounds with the formula [{Mn(bpy)(H 2 O)} 2 (μ-O)(μ-RC 6 H 4 COO) 2 ](NO 3 ) 2 , a quite good correlation between the catalase activity and the Hammett parameter of the R group in the RC 6 H 4 COO ligands was observed.…”

“…[5][6][7][8][9][10][11][12]15] Recently, a magneto-structural study was carried out for analogous compounds with different benzoato ligands to analyze the effect of three structural parameters: The distortion of the coordination octahedron of the manganese ions (λ), the torsion angle between the carboxylate group and the phenyl ring (ω), and the relative orientation of the coordination octahedra (τ). [5][6][7][8][9][10][11][12]15] Recently, a magneto-structural study was carried out for analogous compounds with different benzoato ligands to analyze the effect of three structural parameters: The distortion of the coordination octahedron of the manganese ions (λ), the torsion angle between the carboxylate group and the phenyl ring (ω), and the relative orientation of the coordination octahedra (τ).…”

“…20 The catalase activity of Mn(NO 3 ) 2 has been studied previously; [9] around 1 % of H 2 O 2 decomposed in the experiment with 0.60 mL of hydrogen peroxide. To analyze the catalytic activity and effect of substrate concentration on the reaction rate and efficiency, five experiments were carried out with different initial amounts of 30 % hydrogen peroxide (0.…”

“…The active site in Mn catalases, the enzymes responsible for the disproportionation reaction of H 2 O 2 , consists of two manganese ions with glutamate and histidine ligands with a Mn 2 (μ-O/OH/H 2 O) 2 (μ-RCOO) core [2] and the catalytic cycle involves a redox transformation between Mn II 2 and Mn III 2 . [5][6][7][8][9][10][11][12] Previously we have reported the catalase activity of compounds with chloroacetato and acetato bridges [8] and with benzoato de-Mn III compounds with 2-and 4-chlorobenzoato ligands has been investigated. [4] In our research group attention has been focused on the synthesis and characterization of dinuclear Mn III compounds with the general formula [{Mn(L)(NN)} 2 (μ-O)(μ-RCOO) 2 ]X 2 , in which the ligand L occupies a labile position suitable for the coordination of H 2 O 2 .…”

Redox‐State Dependent Ligand Exchange in Manganese‐Based Oxidation Catalysis

“…The exchange of the carboxylato ligand with hydroxide and hydroperoxide [144] [145] studied the reactivity of complexes 38-41 to explore the influence of the number of carboxylato moieties in the tripodal ligands on electronic prop-erties and activity towards H 2 O 2 disproportionation, mimicking the carboxylato-rich active site of the manganese catalase enzymes (see above) ( Figure 11). The corresponding Mn III Mn III (μ-O) 2 complexes were generated by one-electron reduction.…”