LIESST

In chemistry and physics, LIESST (Light-Induced Excited Spin-State Trapping) is a method of changing the electronic spin state of a compound by means of irradiation with light.

[1] Many transition metal complexes with electronic configuration d4-d7 are capable of spin crossover (and d8 when molecular symmetry is lower than Oh).

Alternatives to LIESST include using thermal changes and pressure to induce spin crossover.

The metal most commonly exhibiting spin crossover is iron, with the first known example, an iron(III) tris(dithiocarbamato) complex, reported by Cambi [3] et al. in 1931.

Two successive steps of intersystem crossing result in the high spin complex.