Employment of a naphthalene-based tetraol ligand in Mn chemistry: Mononuclear and linear trinuclear clusters

The reaction of MnBr2·4H2O with 2-(hydroxymethyl)-2-((3-hydroxynaphthalen-2-yl)methyleneamino)propane-1,3-diol (LH4) in MeOH, afforded the complex [MnIV(LH2)2]·MeOH (1·MeOH) in very good yield. Repeating the same reaction and replacing MnBr2 4H2O with Mn(OAc)2·4H2O gave the complex [MnIII2MnII(LH2)2(OAc)4(MeOH)2]·4MeOH (2·4MeOH) in good yield. Finally, the reaction of Mn(OAc)2·4H2O, with LH4 and PhCOONa in the presence of NEt3 in MeOH, afforded the complex [MnIII2MnII(LH2)2(OAc)2(O2CPh)2(MeOH)2]·MeOH (3·MeOH) in moderate yield. The crystal structures of 1–3 have been determined by single-crystal X-ray crystallography. Complex 1 is a mononuclear MnIV complex, in which the metal ion is found in a trans-O4N2 octahedral environment. Complex 2 is a mixed-valent linear [MnIII2MnII] cluster in which the central MnII ion is connected via carboxylates and monoatomic bridges from the tetraol ligands to the two terminal MnIII ions, while cluster 3 can be regarded as the “incomplete” benzoate analogue of complex 2. DC magnetic susceptibility studies were performed on a polycrystalline samples of 2 and 3, revealing the presence of antiferromagnetic interactions within the clusters leading to an S = 1/2 ground-state for both complexes.

Employment of 2-(hydroxymethyl)-2-((3-hydroxynaphthalen-2-yl)methyleneamino) propane-1,3-diol in manganese cluster chemistry afforded three complexes: Complex 1 is a mononuclear MnIV complex, while 2 and 3 are linear [MnIIIMnIIMnIII] clusters.Figure optionsDownload as PowerPoint slideHighlights
► Linear clusters.
► Mixed-valent manganese clusters.
► Long intramolecular magnetic interaction.