Abstract
A novel in situ Mn-promoted double-aldol reaction is reported. Using a unique synthetic strategy Mn4, Ni4 and Co4 complexes are isolated and their magnetic properties are studied. The Mn4 complex exhibits rare spin frustration effects which leads to an intermediate spin ground state of S=6. [Display omitted]
► Manganese(III) promoted double-aldol addition. ► New polydentate ligand via in situ double-aldol addition. ► New Mn4, Ni4 and Co4 complexes with different structural moieties. ► Spin frustration effect in a defect dicubane Mn4 core.
A novel in situ Mnn+-promoted double-aldol reaction is reported. Single crystal X-ray measurements confirm the addition of acetone to two o-vanillin molecules in an original in situα,α double aldol reaction promoted by Mn ions in the presence of base. The newly formed ligands coordinate to four MnIII ions forming a defect-dicubane core structure (1) bridged exclusively by oxygen-based ligands. Other 3d metals were employed under the same reaction conditions, however no aldol addition occurred and tetranuclear cubane-like structures formed using CoII (2) and NiII (3) ions. Magnetic measurements were carried out on all complexes using SQUID magnetometry. Dominant ferromagnetic interactions were observed for complexes 1 and 3 with J=1.8cm−1, J′=−2.5cm−1, g=1.95 for 1 and J=3.1cm−1, g=2.17 for 3 while complex 2 exhibited antiferromagnetic exchange interactions. Notably, complex 1 was shown to exhibit spin frustration rarely seen in {MnIII}4 systems resulting in an intermediate spin ground state of ST=6.