Hexacyanometalate molecular chemistry:: trinuclear CrNi2 complexes;: micro-SQUID magnetisation studies of intermolecular interactions

Three different CrNi2 complexes were synthesised. They differ from each other by the nature of the terminal ligand and of the counter anion: [Cr(CN)(4){CN-Ni(tetren)}(2)]Cl, that crystallises in two different crystallographic systems and [Cr(CN)(4){CN-Ni(dienpy2) 21(004). The ground state spin value is 7/2 for the three systems (ferromagnetic interaction between chromium(III) and nickel(II) ions). The magnetisation of the three CrNi2 complexes was measured using an array of micro-SQUIDs in a temperature range between 0.04 and 7 K, under a magnetic field up to +/- 1 T. The three samples present a three-dimensional magnetic ordering. The correlation between the structure and the inter-molecular coupling is analysed in terms of steric hindrances of the terminal ligand, orientation of the molecules in the unit cell (canted structure) and crystal symmetry. (C) 2003 Elsevier Science Ltd. All rights reserved.