COMPLETE SPIN-CROSSOVER IN THE [FE(PYBZIM)(3)](CLO4)(2)CENTER-DOT-H2OCOMPLEX

The magnetic properties of a hexacoordinated Fe(II) complex with the b identate ligand 2-(2-pyridyl) benzimidazole (pybzim) - [Fe(pybzim)(3)] (ClO4)(2) . H2O have been investigated by AC susceptometer measurement s, The temperature dependence of the AC magnetic susceptibility for a powder sample showed Essentially diamagnetic behaviour below 85 K and paramagnetism (mu(eff)/mu(B) = 4.5-5.3, S = 2) above 160 K, obeying th e Curie-Weiss law. Spin crossover behaviour can be found within the te mperature range of 90 to 160 K; it is centred at 141 K. The complex is ESR silent in X-band made: neither Che powder sample (77 K and 300 K) nor a methanol solution exhibit an ESR. signal, The spin-crossover tr ansition of a freshly prepared pou der sample is complete. However, ti me evolution causes (within months) an increasing admixture of iron(II I), which was proved by magnetic susceptibility measurement, ESR, and electron spectra of the complex.