X-Nico

3 unusual facts about Spin crossover


Spin crossover

X-ray crystallography is used to measure the bond distances between the metal and the ligands, which give insight into the spin state of the complex.

Due to the changes in magnetic properties that occur from a spin transition - the complex being more diamagnetic in a LS state and more paramagnetic in a HS state - magnetic susceptibility measurements as a function of temperature are most commonly used in addition to optical spectroscopy and X-ray crystallography.

Typically, bond lengths determined by X-ray crystallography show a small decrease at increasing temperatures due to an increase in the amplitude of atom vibrations, which is the case seen here above 110 K for the average Co-N bond lengths (1.90 Å at 200 K and 1.89 Å at 298 K for the top axial CoIII ion and 1.88 Å at 200 K and 1.84 Å at 298 K for the bottom axial CoIII ion, Figure 11).



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