Dinuclear cobalt(III) and mixed valence trinuclear Mn^III-Mn^II-Mn^III complexes with a tripodal bridging pyridylaminophenol ligand

A dinuclear cobalt(ii), [Co₂(κ⁴-O,O′,N,N′-L)₂(μ-O,O′-HCOO)](ClO₄)·(C₂H₅)₂O (1) and a linear mixed valence trinuclear manganese, [Mn₃(κ⁴-O,O′,N,N′-L)₂(μ-CH₃O)₂(μ-O,O′-CH₃COO)₂]·2(C₂H₅)₂O (2) complexes with the ligand N-(2-pyridyl-methyl)-N,N-bis-[2′-hydroxy-5′-methyl-benzyl]-amine (H₂L) are reported. For both complexes the ligand is present in the deprotonated form. The coordination sphere of the cobalt centres can be described as slightly distorted octahedral with two bridging O-phenoxo, one N-pyridine, one N-amine, one terminal O-phenoxo and one bridging O-formate donor atoms. Interestingly, the bridging formate resulted from the aerial oxidation of methanol. The manganese complex (2) has a linear mixed valence Mn^III-Mn^II-Mn^III, with the Mn^II and Mn^III centres bridged by alkoxo, carboxylate and phenoxo groups. Cyclic voltammetry studies show both metal and ligand centred redox processes consistent with the structure of the complexes. Complex (2) has an S = 3/2 ground state; magnetic susceptibility measurements indicate a weak antiferromagnetic interaction. The best fit of the magnetic susceptibility data as a function of temperature was obtained using a conventional trinuclear linear model [H = -2J(S₁S₂ + S₁S₃)] with J = -0.79 cm^-1 and g = 1.99.