Spin crossover trapping

Gutlich P, Goodwin HA (2004) Spin Crossover - An Overall Perspective. 233 1-47 Giitlich P (2004) Nuclear Decay Induced Excited Spin State Trapping (NIESST). 234 231—... 

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... 

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... 

Spin crossover (SC) was observed for the first time by Cambi and Cagnasso [1]. This phenomenon was reviewed in a number of excellent reviews [2-7]. Because of its possible technological utilisation [8,9], spin crossover is widely studied at present. The usual induction of spin crossover is based on temperature variation but pressure and concentration variations may lead to the same effect. Recently, optical induction has been involved and such experiments were termed the LIESST (Light Induced Excited Spin State Trapping) and the reverse LIESST effects [7]. 

For complexes with a somewhat lower ligand-field strength such as in Co-labeled [Fe(phen)2(NCS)2], in which the thermal LS HS transition occurs at a temperature of Ti/2 175 K, the Mossbauer emission spectrum consists of the typical Fe -HS doublet at all temperatures down to 4.2 K." " A similar behavior was observed in the Mossbauer emission spectra of a whole series of Co-doped Fe spin-crossover compounds and their Co analogs. In all the spin-crossover systems, metastable Fe -HS states originating from the Co nuclear decay are trapped at temperatures below the thermal transition temperature with an efficiency of nearly 100% with respect to the decay events. 

Perhaps one of the most interesting recent applications of Mossbauer spectroscopy has been to the study of the absorption of radiation and the resultant spin state trapping in a compound exhibiting spin state crossover. 

S. Decurtins, P. Gutlich, C.P. Kohler, H. Spiering, A. Hauser, Light-induced excited spin state trapping in a transition-metal complex the hexa-l-propyltetrazole-iron(II) tetrafluoroborate spin crossover system. Chem. Phys. Lett. 105, 1 (1984)... 

A. Hauser, Reversibility of light-induced excited spin state trapping in the [Fe(ptz)6](BF4)2, and the [Zni xFcx(ptz)6](BF4)2 spin crossover systems. Chem. Phys. Lett. 124, 543-548 (1986)... 

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