Synthesis, Crystal Structure, and Magnetic Properties of a Mn(III)-radical Complex

Abstract

The design and synthesis of metal-radical complexes has attracted much attention in several filed of chemistry, optics, physics and material science for the purpose of exploiting new molecule-based magnetic materials. Among these metal-radical complexes, much attraction has been paid to the research of nitronyl nitroxide radicals since they are used as spin labels or paramagnetic building blocks in the construction of multidimensional magnetic materials. Moreover, they are usually stable in the open-shell organic molecule and exhibit coordination versatility in the structure in which they can act as bridging ligands or terminal ligands. A larger number of complexes based on the nitronyl nitroxide radical and transition metal ions, such as Mn(II), Co(II), Ni(II) and Cu(II), or rare earth metals assembly have been reported. 2-(4-Pyridyl)-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3oxide (pPyNN) radical as one of the most attractive radicals has been widely used to assemble metal-radical complexes such as [M(II)(acac)2(pPyNN)] (M = Co, Ni, Mn). The Mn(III) ion has a large spin state (S = 2.0) and a strong axial magnetic anisotropy and has attracted much more interest in the design of molecular magnets especially single-molecule magnets (SMMs) and single-chain magnets (SCMs). However, to the best of our knowledge, magnetic complexes based on Mn(III) and nitronyl nitroxide radicals have not yet been reported. In the paper, we report the synthesis, crystal structure and magnetic properties of a new Mn(III)-radical complex [Mn(acacen)(pPyNN)(H2O)]ClO4 (1) (acacen = dianion of N,N'-ethylenebis(acetylacetonyl)-ideneaminato).