Angewandte Chemie International Edition
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Cover Picture (Angew. Chem. Int. Ed. Engl. 20/1994)
The Cover picture shows the structure of the complex cation [Fe(1-methyltetrazole)6]2+, the electron distribution in the low-spin (blue ion) and high-spin (red ion) states, and the corresponding oscillator potentials of the totally symmetric mode of the complex. In spin crossover compounds the energy difference ΔE ≈ kBT between the lowest vibrational levels and the much higher density of high-spin states lead to a reversible spin transition well below the decomposition temperature. Also light of different wavelengths switches between the low-spin and the metastable high-spin state at low temperatures. The results of research on the spin crossover phenomenon are summarized by P. Gütlich et al. on p. 2024 ff.