Figure 10.

Predicted entropy increase on crossover to the high-spin state of [Fe(TPP)(CN)]⁻ includes electronic and vibrational contributions. The blue trace indicates the entropy calculated by excluding the predicted frequencies of four torsional oscillations about the C_m-phenyl bonds, which increase significantly in the quintet state, while the red trace includes all vibrations. The dashed line indicates the temperature-independent electronic contribution ΔS = k_B ln 5 due to the increased spin multiplicity in the high-spin state. The difference between quintet and singlet vibrational entropies calculated from Eq. 2 using DFT-computed frequencies determines the additional vibrational contribution.