Spin crossover in iron(II) tris(2-(2′-pyridyl)benzimidazole) complex monitored by variable temperature methods: synchrotron powder diffraction, DSC, IR spectra, Mössbauer spectra, and magnetic susceptibility

Abstract The thermal expansion of the spin crossover system [Fe(pybzim) 3 ](ClO 4 ) 2  · H 2 O (pybzim=2-(2 ′ -pyridyl)benzimidazole) has been determined from powder X-ray data between 50 and 250 K; the wavelength of the synchrotron source was 1.21888(1) A. The unit cell parameters of the triclinic crystal system were a =12.091 A, b =12.225 A, c =14.083 A, α =77.70°, β =80.35°, γ =74.35°, and V =1944.9 A 3 at 250 K. In addition to the linear thermal expansion of the unit cell volume, an extra expansion due to the low-spin (LS) to high-spin (HS) transition is observed. The V ( T ) function shows a sudden increase comparable with the step in the effective magnetic moment at the transition reg…