Water inclusion mediated structural diversity and the role of H-bonds in molecular assemblies of manganese(III) bicompartmental Schiff-base complexes

• Structural diversity in Mn(III)-MeOsalen derivatives determined by hydrogen bonds.
• The structural unit is a dinuclear species formed by coordinated water insertion.
• Examples of polymorphism, solvent chains and cocrystallization are reported.
• A dinuclear Mn/K derivative allows the oxidation of ethanol to ethylenglycol.

Six new manganese(III) derivatives using the ligand H2MeOsalen: N,N′-ethylenebis(3-methoxysalicylaldiimine), have been synthesized and structurally characterized. In all cases the manganese ion is six-coordinated and occupies the internal cavity of the bicompartmental salen ligand. The manganese ion completes its coordination environment with one axial water molecule and one additional ligand, either water, ethanol or one acetate anion. The molecular unit is dimerized by the insertion of the coordinated water molecule into the external MeOsalen cavity of one neighbouring complex. This supramolecular dimer constitutes the structural basis for these compounds, the differences arising from the intermolecular hydrogen bonds involving the counter anions and crystallization solvent molecules. In this way, examples of pseudopolymorphism, cocrystallization and water/anion tapes held by the interaction with the complex dimers are described. The compound [{Mn(MeOsalen)K(H2O)0.5}2(μ-OOCMe)](PF6)3·HOCH2CH2OH is a heterometallic Mn/K derivative where the potassium ion occupies the external cavity, while the coordination of the manganese ion is completed by bridging acetate and ethyleneglycol ligands. The formation of ethyleneglycol is attributed to a stoichiometric oxidation of the ethanol solvent, attributed to the presence of the potassium ion in the complex.

The [Mn(MeOsalen)(H2O)L]22+ moiety shows a high structural versatility due to its ability in the formation of hydrogen bonds, resulting in examples of polymorphism, cocrystallization, water/anion tapes and one heterobinuclear Mn:K derivative active in the ethanol oxidation to ethylenglycol.Figure optionsDownload as PowerPoint slide