On the dielectric properties of the spin crossover complex [Fe(bpp)2] [BF4]2

The thermal variation of the dielectric constant in the spin crossover complex [Fe(bpp)2] [BF4]2 displays a 16 K large hysteresis loop centered around 178 K corresponding to the spin transition temperatures. Unexpectedly, the dielectric constant has a higher value in the low‐spin state. DFT calculations were carried out to determine the microscopic electronic polarizabilities, but these latter could not be correlated with the macroscopic permittivity changes pointing the importance of the effect of the counter‐anions which must be necessarily taken into account in future DFT calculations. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)