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.