Spin crossover principles

The cooperative mechanism of the spin-crossover phenomenon is well imderstood in some aspects. For instance, theoretical models account for the thermal evolution of the system. However, due to their phenomenologic character, the key parameters accounting for intermolecular interactions do not reflect the relevance of the microscopic details which could orientate us in designing molecules that can recognize each other and combine to produce systems with prescribed characteristics. Consequently, very general principles guide the syntiietic chemistry in the search for suitable spin-crossover compounds often trial and error or serendipity are the sole strategies. 

Figure 33 Scheme of the addressing principle of a spin-crossover compound where the starting state is LS. The APAT operation addresses the HS state, and the — AT -f AT operation addreses the LS state (adapted fom ref. 102). 

The principle of laser photoperturbation of A T spin crossover in an Fe(II) complex in solution, coupled with fast (nanosecond) optical probe... 

Apply the crossover theorem, with reference to the figure in Example 14.5. The proportions of the iron-sulfur proteins in complexes I, II, and III with iron atoms in the Fe3+ and Fe2+ states can, in principle, be estimated from the electron spin resonance signals of the preparation of mitochondria. In the case of mitochondria oxidizing NADH in the presence of rotenone, application of the crossover theorem reveals that the iron atoms in the iron-sulfur proteins in complex I will become more reduced, while those in complex III will become more oxidized, in comparison to their states in the absence of rotenone. In the case of KCN-treated mitochondria, both sets of iron-sulfur proteins will become more... 

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