6533b860fe1ef96bd12c38a4

RESEARCH PRODUCT

Spin transition in iron complexes induced by heat, pressure, light and nuclear decay

subject

description

The phenomenon of temperature-dependent spin transition will be introduced and the numerous chemical and physical influences affecting the spin transition characteristics will be discussed. We shall mainly concentrate on the spin crossover system [Fe(2-pic)3]X2·Sol (2-pic=2-aminomethylpyridine; X=Cl, Br; Sol=C2H5OH, CH3OH) and demonstrate how the behaviour of the spin transition5T2g(Oh)⇌1A1g(Oh) is influenced by substituting the metalion, the non-coordinating anions X, the crystal solvent molecules Sol and by isotopic exchange with H/D and14N/15N. It will also be shown that the spin transition is very susceptible to pressure. A quantitative spin state conversion from low spin to high spin can also be achieved by illuminating the crystals of a spin crossover system at sufficiently low temperatures. The metastable quintet state can be trapped with practically infinite lifetimes. Several examples for this “Light-Induced Excited Spin State Trapping” (LIESST) will be given. Finally, the occurrence of short-lived anomalous spin quintet states following the57Co(EC)57Fe nuclear decay, which have been observed in the Mossbauer emission spectra of57Co-doped complex compounds, will be discussed with particular references to the LIESST effect.