Free energy of spin-crossover complexes calculated with density functional methods

A set of iron(II) complexes that exhibit a temperature-dependent spin-crossover between the low-spin and the high-spin state were studied by density functional methods. The total electronic energy, the zero-point vibrational energy, and the entropy were calculated in order to determine the free energy. While the calculated total energy differences between the two spin states have significant errors, qualitative agreement is achieved for the zero-point vibrational energy differences and the entropy differences.