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Dangling and Hydrolyzed Ligand Arms in [Mn3] and [Mn6] Coordination Assemblies: Synthesis, Characterization, and Functional Activity

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journal contribution
posted on 15.02.2017, 14:06 authored by Krishna Chattopadhyay, Gavin A. Craig, María José Heras Ojea, Moumita Pait, Animesh Kundu, Junseong Lee, Mark Murrie, Antonio Frontera, Debashis Ray
Two flexible, branched, and sterically constrained di- and tripodal side arms around a phenol backbone were utilized in ligands H3L1 and H5L2 to isolate {Mn6} and {Mn3} coordination aggregates. 2,6-Bis­{(1-hydroxy-2-methylpropan-2-ylimino)­methyl}-4-methylphenol (H3L1) gave trinuclear complex [Mn3(μ-H2L1)21,3-O2CCH3)4­(CH3OH)2]­(ClO4)2·4CH3OH (1), whereas 2,6-bis­[{1-hydroxy-2-(hydroxymethyl)­butan-2-ylimino}­methyl]-4-methylphenol (H5L2) provided hexanuclear complex [Mn64-H2L2)2(μ-HL3)23-OH)2­(μ1,3-O2CC2H5)4]­(ClO4)2·2H2O (2). Binding of acetates and coordination of {H2L1} provided a linear MnIIIMnIIMnIII arrangement in 1. A MnIII6 fused diadamantane-type assembly was obtained in 2 from propionate bridges, coordination of {H2L2}3–, and in situ generated {HL3}2–. The magnetic characterization of 1 and 2 revealed the properties dominated by intramolecular anti-ferromagnetic exchange interactions, and this was confirmed using density functional theory calculations. Complex 1 exhibited field-induced slow magnetic relaxation at 2 K due to the axial anisotropy of MnIII centers. Both the complexes show effective solvent-dependent catechol oxidation toward 3,5-di-tert-butylcatechol in air. The catechol oxidation abilities are comparable from two complexes of different nuclearity and structure.