Spin crossover behaviour in the iron(II)-2,2-dipyridilamine system:: Synthesis, X-ray structure and magnetic

The monomeric compounds [Fe(dpa)(2)(X)(2)] (.) solv [X = NCS- (solv = 0.5H(2)O) (1), N(CN)(2)(-) (2) and dpa = 2,2-dipyridilamine] have been synthesised and characterised. They crystallise in the P2(1)/n and in the Cc monoclinic systems, respectively. Four of six nitrogen atoms coordinated to the Fe(11) ions belong to two dpa ligands which lie in cis conformation. The remaining positions are occupied by two nitrogen atoms of the pseudo-halide ligands. The magnetic susceptibility measurements at ambient pressure have revealed that compound I exhibits an incomplete spin crossover behaviour (T-1/2 88 K), whereas compound 2 remains in the high-spin configuration. Pressure studies performed on compound 1 have shown virtually complete spin crossover behaviour as pressure attains 6.5 kbar. (c) 2005 Published by Elsevier B.V.