860401-20-3Relevant academic research and scientific papers
Tuning tetranuclear manganese-oxo core electronic properties: Adamantane-shaped complexes synthesized by ligand exchange
Dube, Christopher E.,Mukhopadhyay, Sumitra,Bonitatebus Jr., Peter J.,Staples, Richard J.,Armstrong, William H.
, p. 5161 - 5175 (2005)
A series of adamantane-shaped [Mn4O6]4+ aggregates has been prepared. Ligand substitution reactions of [Mn 4O6-(bpea)4](ClO4)4 (1) with tridentate amine and iminodicarboxylate ligands in acetonitrile affords derivative clusters [Mn4O6(tacn)4](ClO 4)4 (4), [Mn4O6(bpea) 2(dien)2](ClO4)4 (5), [Mn 4O6(Medien)4](ClO4)4 (6), [Mn4O6(tach)4](ClO4)4 (7), [Mn4O6(bpea)2(me-ida)2] (8), [Mn4O6(bpea)2(bz-ida)2] (9), [Mn4O6(bpea)2(tbu-ida)2] (10), and [Mn4O6(bpea)2(cpent-ida) 2] (11) generally on the order of 10 min with retention of core nuclearity and oxidation state. Of these complexes, only 4 had been synthesized previously. Characterization of two members of this series by X-ray crystallography reveals that compound 7 crystallizes as [Mn4O 6(tach)4](ClO4)4·3CH 3CN·4.5H2O in the cubic space group Fm3m and compound 11 crystallizes as [Mn4O6(bpea)2( cpent-ida)2]-7MeOH in the monoclinic space group C2/c. The unique substitution chemistry of 1 with iminodicarboxylate ligands afforded asymmetrically ligated complexes 8-11, the mixed ligand nature of which is most likely unachievable using self-assembly synthetic methods. A special feature of the iminodicarboxylate ligand complexes 8-11 is the substantial site differentiation of the oxo bridges of the [Mn4O6] 4+ cores. While there are four site-differentiated oxo bridges in 8, the solution structural symmetry of 8H+ reveals essentially a single protonation isomer, in contrast to the observation of two protonation isomers for 1H+, one for each of the site-differentiated oxo bridges in 1. Magnetic susceptibility measurements on 4, 7, 8, and 9 indicate that each complex is overall ferromagnetically coupled, and variable-field magnetization data for 7 and 9 are consistent with an S = 6 ground state. Electrochemical analysis demonstrates that ligand substitution of bpea affords accessibility to the MnV(MnIV)3 oxidation state.
