INTERSYSTEM CROSSING AND LIGHT-INDUCED BISTABILITY IN IRON(II) SPIN-CROSSOVER COMPOUNDS

The dynamics of the high-spin-->low-spin intersystem crossing process in iron(II) spin-crossover compounds are strongly influenced by cooper ative effects of elastic origin which are due to the large difference in volume between high-spin and low-spin complexes. The deviation from first order kinetics is attributed to a build-up of an internal press ure as the relaxation proceeds, leading to a characteristic self-accel eration. The elastic interactions may lead to a light-induced bistabil ity for systems which otherwise remain in the high-spin state down to cryogenic temperatures.