Synthesis, crystal structures and magnetic properties of trinuclear oxo-centered homo- and mixed-valence manganese pivalate complexes with imidazole (Im) and 1-methylimidazole (1-MeIm): [Mn3IIIO(O2CCMe3)6(Im)3](Me3CCO2)·0.5Me3CCO2H and [Mn2IIIMnIIO(O2CCMe

Two new μ3-oxo-centered trinuclear manganese complexes, one of them a homo-valence [Mn3IIIO(O2CCMe3)6(Im)3](Me3CCO2)·0.5Me3CCO2H (1) pivalate complex and the other a mixed-valence [Mn2IIIMnIIO(O2CCMe3)6(1-MeIm)3] (2) pivalate complex (where Im = imidazole, 1-MeIm = 1-methylimidazole), have been synthesized and characterized by IR spectroscopy, thermogravimetric analysis, X-ray crystallography and magnetochemistry. Complexes 1 and 2 are μ3-oxo-trinuclear compounds with the three manganese atoms bridged by six pivalate groups. At each axial position there is an Im (1) or 1-MeIm (2) molecule. In both compounds, the manganese coordination geometry is slightly distorted octahedral, consisting of the oxygen of the central triangle, four oxygen atoms from bridging pivalate ligands, and a terminal Im or 1-MeIm nitrogen atom. The crystal packing of 1 involves hydrogen bonding between complex cations [Mn3O(Piv)6(Im)3]+ and outersphere pivalate ions, whereas in compound 2 interactions of the C–H⋯π type, formed by both the aromatic and methyl C–H groups of 1-MeIm molecules, are present. Magnetic studies reveal that both compounds represent antiferromagnetically coupled, spin-frustrated triangular systems exhibiting weak to moderate exchange coupling constants.

Graphical abstractTwo new μ3-oxo-centered trinuclear manganese complexes, one of them a homo-valence [Mn3IIIO(O2CCMe3)6(Im)3](Me3CCO2)·0.5Me3CCO2H (1) pivalate complex and the other a mixed-valence [Mn2IIIMnIIO(O2CCMe3)6(1-MeIm)3] (2) pivalate complex (where Im = imidazole, 1-MeIm = 1-methylimidazole), have been synthesized and characterized by IR spectroscopy, thermogravimetric analysis, X-ray crystallography. Magnetic studies reveal that both compounds represent antiferromagnetically coupled, spin-frustrated triangular systems exhibiting weak to moderate exchange coupling constants.Figure optionsDownload full-size imageDownload as PowerPoint slide