Raman scattering in the spin-crossover system [Fe(pmd)(H2O){Au(CN)2}2]*H2O reveals a complex three-phase spin-state transition in contrast to earlier observations in magnetization measurements. We observe different spin state phases as function of te
mperature and electromagnetic radiation in the visible spectral range. There exists a fluctuating spin state phase with an unexpected wipeout of the low frequency phonon scattering intensity. Furthermore we observe one phase with reduced symmetry that is attributed to a cooperative Jahn-Teller effect. Pronounced electron-phonon interaction manifests itself as a strong Fano-resonance of phonons related to {FeN6} and {FeN4O2} coordination octahedra. Density functional theory supports this interpretation.
