Spin State Switching in the [FeII(HL-F)2](AsF6)2 Compound

Abstract The course of spin transformation induced by the proton transfer in the iron(II) hydrazone crystalline compound [Fe(HL-F)2](AsF6)2 has been explained through single-point DFT calculations applying the observed structural data on the titled compound in the temperature range 25–220 K. It has been revealed that the four crystallographically identical complexes present in the crystal structure at temperatures 25 K and 123 K contain iron(II) ions only in the low-spin 1A1-state. From eight iron(II) complexes present in the crystal unit at 153 K, only a half of complexes passed to the high-spin state. From the performed calculations, it also follows that at 220 K all iron(II) ions in the four types of complexes experimentally detected in the crystal structure have reached the high-spin state. The undertaken study has also revealed the difference in the magnitudes and type of alignment of the dipole moments of the complexes present in the crystal structure at temperatures 25, 123, 153, and 220 K. On the basis of the obtained results, a qualitative interpretation of the observed magnetic susceptibility data of the [Fe(HL-F)2](AsF6)2 compound has been given.