The role of symmetry breaking in the structural trapping of light-induced excited spin states

Light-Induced Excited Spin State Trapping (LIESST) data are reported for seven isostructural solvate salts from the iron(ii)/2,6-di(pyrazol-1-yl)pyridine family. A complicated relationship between their spin-crossover T_1/2 and T(LIESST) values may reflect low-temperature thermal and light-induced symmetry breaking, which is shown by one of the compounds but not by two others.