Tetramer compound of manganese ions with mixed valence [Mn₂^IIMn₂^IV] and its spatial, electronic and magnetic studies.

In this work we report the synthesis, structural, electronic and magnetic characterization of [Mn^IV₂Mn^II₂(HL)₂(H₂L)₂(H₂O)₄](NO₃)₂  1. This novel compound was obtained from (E)-2-((2-hydroxybenzylidene)amine)-2-(hydroximethyl-propane-1,3-diol, (H₄L) and Mn(NO₃)₂. The UV-Vis and IR spectrophotometry showed the typical d-d transitions of Mn^IV in and octahedral geometry compounds ¹ and vibrational transitions in 477 cm^-1, which is assigned to the Mn-O group ². The c_M vs T gave J = 164 cm^{-1 3}. The ESR (g = 11.03, 4.87, 1.78, and g = 3.23, 2.03) analysis of 1 showed the presence of Mn^II (s = 5/2) and Mn^IV (s = 3/2) ions within the molecule. The hyperfine interaction is observed in ESR spectrum which showed two species of Mn ions⁴. An x ray diffraction suitable monocristal of 1 was obtained and its structure was possible to describe as a tetramer of [Mn^IV Mn^II Mn^II Mn^IV] building a 2D stepped supramolecular structure with a step of [Mn^IV–O-O-Mn^II] and a second step with [Mn^II–O-O-Mn^IV]. The structural study informed us that each magnetic box of [Mn^IV-O-O-Mn^II] have a superexchange antiferromagnetic interaction by the d_x2_-y2-sp³ (with more contribution of p orbitals) orbitals; however, among the boxes or steps there is a super-exchange ferromagnetic interaction, by oxo bonds Mn^II-O-Mn^II.

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