Slow relaxation: Exergonic high-spin→low-spin relaxation after photoexcitation has been found to be exceedingly slow in a class of iron(II) complexes with hexadentate imine ligands. The thermal activation barriers that arise between the quintet- and singlet-spin manifolds are the highest ever recorded for spin crossover of isolated molecules in free solution (see figure).

Special Issue: Special Issue to Honour Professor Dr. Rudi van Eldik on the occasion of his 70th birthda