Popis: |
Substituent and temperature effects on the spin-crossover behaviour of cationic complexes of iron(II)-X-2,6-bis(benzimidazol-2′-yl)pyridine (X = H, OH, Cl and CH3) were investigated by means of UV-visible and Fourier transform infrared spectroscopy on solid-state compounds. At room temperature the low-spin isomer is predominant for X = H and Cl complexes, whereas the X = OH complex shows a spin equilibrium and the CH3-substituted complex is present in its high-spin form. The spin-crossover behaviour for the Cl-substituted species corresponds to a ΔHSC of about 0.5 kJ mol−1, which is much lower than the respective values found for the solution. Crystal water seems to favour the low-spin state of the OH complex. |