Determination of the nuclear structure and spin density distribution in the cyano-bridged molecular based magnet K2Mn3(H2O)6[Mo(CN)7]2-6 H2O

This article derails the local spin density determination in the cyano-bridged, two-dimensional, molecular based magnet K2Mn3(H2O)(6)[Mo(CN)-](2). 6H(2)O (T-2 = 39 K). The crystal structure. determined at room temperature by X-ray diffraction. nas redetermined at 50 K using unpolarised neutron diffraction. The importance of intermolecular hydrogen bonding interactions is clearly demonstrated in this study. previously characterised with X-rays. The local spin density was determined from polarised neutron diffraction data at 4 K with an applied field of 3 T. Positive spin densities were observed on the manganese sites, consistent with high-spin d(5) ions in octahedral fields. whilst a negative spin density was found on the molybdenum sites. signifying delocalisation onto the cyano ligands. The alternating sign of the spin populations on the metal sites. suggests that the primary Mo-III-Mn-II interactions are antiferromagnetic in nature and rile delocalisation onto the cyano-bridges clearly demonstrates the role of the ligand bridges in the magnetic exchange pathway. (C) 2001 Academic des sciences/Editions scientifiques et medicales Elsevier SAS.