Studies on spin state preferences in Fe(II) complexes

Values for the enthalpy difference between high and low spin states (kJ/mol) estimated with 75 established density functionals (blue), 12 favored functionals (red), and ωB97XD (green), for a truncated model of a four-coordinate crossover system TpFe(II)NPh3 (Tp = trispyrazolylborate). Recommended functionals have a systematic error favoring the high spin state of about 25 kJ/mol. The ωB97XD functional can be recommended for such studies.42