Mononuclear manganese(III) catechol compounds as substrate adduct complexes for manganese-substituted intradiol cleaving catechol dioxygenases

The complexes [Mn(L1)(tcc)] (1), [Mn(L2)(tcc)] · H2O · 0.5CH3OH (2), [Mn(L3)(tcc)] · CH2Cl2 (3), [Mn(L4)(tcc)] · 1.5CH2Cl2 (4), [Mn(L5)(tcc)] (5), and (HN(C2H5)3)[Mn(L6)(tcc)] · CH2Cl2 (6) have been synthesized using the ligands HL1 (2-[(bis(pyridin-2-ylmethyl)amino)methyl]phenol), HL2 (2-[[((6-methylpyridin-2-yl)methyl)(pyridin-2-ylmethyl)amino]methyl] phenol), HL3 (2-[[((6-methylpyridin-2-yl)methyl)(pyridin-2-ylmethyl)amino]methyl]-4-nitrophenol), HL4 (2-[(bis(pyridin-2-ylmethyl)amino)methyl]-4-bromophenol), HL5 (2-[(bis(pyridin-2-ylmethyl)amino)methyl]-6-methoxyphenol) and H2L6 ([(bis(2-hydroxy-5-nitrobenzyl))(pyridin-2-ylmethyl)]amine) and characterized by X-ray crystallography, mass spectrometry, IR, UV–Vis spectroscopy, cyclic voltammetry, and elemental analysis. Compounds 1 and 6 crystallize in the monoclinic space groups P21/n and P21/c, respectively, whereas the crystal structures of complexes 2, 3, and 4 were solved in the triclinic space group . Complex 5 crystallizes in the orthorhombic space group P212121. Complexes 1–6 are structural related to the proposed active site of intradiol cleaving catechol dioxygenase exhibiting a distorted octahedral N3O3 (1–5) and N2O4 (6) donor set, respectively. Complexes 1–6 can be regarded as structural manganese analogous for substituted forms of iron-containing intradiol cleaving catechol dioxygenases, where the substrate tetrachlorocatechol (tcc) is asymmetrically bound to the metal center.