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, F, CF 3 , MeO, t Bu): Effect of the R Group on the Magnetic Properties and the Catalase Activity

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 t Bu ( 5 ); bpy = 2,2′‐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 2.85 and 0.7 cm –1 , respectively. The coordination octahedron around the Mn III ions shows a rhombic distortion due to the coordination of a water molecule. This kind of distortion and the R group of the benzoato–derivative bridge in a para position favour ferromagnetic behaviour. Moreover, the presence of an electron‐withdrawing substituent increases this magnetic character. All compounds show catalase activity with a conversion range between 20 and 55 % of the initial H 2 O 2 within 10 min. Compounds 4 , 5 and 3 with an electron‐donating R group are more efficient than 2 , 3 with electron‐withdrawing groups.