LIESST

Under LIESST (light induced excited spin state trapping ) or LIESST effect refers to the transition of a complex compound by the low-spin state to a metastable high-spin state under the action of light of a certain wavelength.

This metastable high-spin state at sufficiently low temperatures can have an almost infinite durability. ( Trapping! ) the excitation of the low-spin compound [ FeIIL6 ] 2 [ BF4 ] 2 → high-spin [ FeIIL6 ] 2 [ BF4 ] can as an example of such an operation 2 (with L = Propyltetrazol ) by means of a green argon laser ( 514.5 nm). The reverse reaction in the more stable low-spin state is thermally 40K or possible red light.