Light-induced excited spin-state trapping LIESST

In the same line, [Fe(qsal)2][Ni(dmit)2].2CH3CN has also been proven to show a cooperative spin transition based on n-n interactions between ligands [105]. Moreover, this compound is also one of the rare Fenl complex to exhibit the light-induced excited spin state trapping (LIESST) effect. 

In 1984, Decurtins et al. discovered that the compound [Fe(ptz)6](BF4)2 (ptz=l-propyltetrazole) can be converted from the stable LS state to the metastable HS state by irradiation with green light at sufficiently low temperatures [14]. This phenomenon has become known as light-induced excited spin state trapping (LIESST) and is dealt with in detail by A. Hauser in a separate chapter in this series. Later, Hauser reported the reverse-LIESST effect, whereby red light is used to convert the compound back into the LS state [15]. 

Photoinduced spin-related phenomena are a particularly important field of the solid-state photophysics, because fast spin switching is a prospective basis for applications in the field of spintronics. An illustrative example is the production of the metastable state of the iron propyltetrazole (ptz) complex [Fe(ptz)6](BF4)2 by laser light-induced excited spin-state trapping (LIESST) and the determination of the resulting structure by steady-state X-ray photodiffraction [68]. In another example, steady-state X-ray photodiffraction at cryogenic temperatures was successfully utilized to study photoinduced phase transition due to spin crossover in the tris(a-picolylamine)iron(II) complex [69]. The phase transition is accompanied by... 

Both photoinduced LS —> HS and HS > LS transitions involve transition through a 3Ti state, from which the system can relax into the LS and HS ground states via intersystem crossing processes. This reversible state switching has been summarized as light-induced excited spin state trapping (LIESST) effect,29 and especially for Fe-based compounds it can be conveniently traced by Mossbauer spectroscopy. 

Optical excitation of the LS( Aig) ground state at very low temperature in some thermally driven spin-crossover compounds may result in the formation of a trapped HS( T2g) metastable state. This effect, termed light-induced excited spin-state trapping (LIESST), has been discovered and described by Giitlich and co-workers... 

LIGHT-INDUCED EXCITED SPIN STATE TRAPPING (LIESST) 427... 

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