SPIN-CROSSOVER IN BIS(2,6-BIS(BENZIMIDAZOL-2YL)PYRIDINE)IRON(II) TETRAPHENYLBORATE

The complex [Fe(bzimpy)(2)]( BPh4)(2). nH(2)O exists with n = 4 (1), n = 2 (2) and n = 0 (3). The tetrahydrate is a spin crossover system wi th the transition centred at room temperature. The dihydrate, prepared from a solution with reduced water content, is a high-spin complex ov er the entire temperature region. The anhydrous complex, prepared by o verheating of 1, remains high-spin. Unlike that in the sulphate (4) an d perchlorate (5) analogues, the spin crossover in 1 is complete. The magnetic data fitting procedure yields the set of magnetic parameters describing the spin crossover quantitatively: g = 2.54, J/k = - 226 K, Delta H = 14.9 kJ mol(-1) and Delta S = 45 J K-1 mol(-1). (C) 1998 El sevier Science S.A. All rights reserved.