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-brid ged, 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 diffr action. The importance of intermolecular hydrogen bonding interactions is c learly demonstrated in this study. previously characterised with X-rays. Th e 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. s ignifying delocalisation onto the cyano ligands. The alternating sign of th e spin populations on the metal sites. suggests that the primary Mo-III-Mn- II interactions are antiferromagnetic in nature and rile delocalisation ont o the cyano-bridges clearly demonstrates the role of the ligand bridges in the magnetic exchange pathway. (C) 2001 Academic des sciences/Editions scie ntifiques et medicales Elsevier SAS.