Journal of Applied Crystallography

Volume 34, Part 3 (June 2001)



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J. Appl. Cryst. (2001). 34, 229-238    [doi:10.1107/S0021889801000462]

X-ray structure study of the light-induced metastable states of the spin-crossover compound [Fe(mtz)6](BF4)2

J. Kusz, H. Spiering and P. Gütlich

Abstract: Iron(II) complexes exhibiting thermal spin-crossover may be converted from the 1A1 low-spin (LS) state to the 5T2 high-spin (HS) state by irradiation with green light (light-induced excited spin-state trapping, LIESST) and from the LS to the HS state by irradiation with red light (reverse LIESST). The lifetime of the metastable LIESST states may be sufficiently long to enable an X-ray diffraction study. The lattice parameters of a single crystal of [Fe(mtz)6](BF4)2 (mtz = methyltetrazole) (space group P21/n) were measured between 300 and 10  K. While one Fe lattice site (A) of the crystal changes from the HS to the LS state near 78  K, the other site (B) remains in the LS state. Using the green light (514  nm) of an argon ion laser the crystal was quantitatively converted to the HS state at 10  K. Irradiation of the crystal at 10  K by red light of a laser diode (820  nm) with site A in the LS and site B in the HS state converts site B almost completely to the LS state. The lattice parameters of both metastable states were measured up to 50  K, where they start to decay on a minute timescale. At 10  K, a full data set for evaluation of the crystal structure was recorded. The volume change of the crystal per complex molecule accompanying the spin transition is 31.5  Å3 at site A and close to zero [-0.21  (14)  Å3] at site B.

Online 22 May 2001


hkldisplay filedownload file

Structure factor file (CIF format) (314.8 kbytes)
fmtzb1_10K 100% HS after LIESST from 100% LS in P2(1)/n'


hkldisplay filedownload file

Structure factor file (CIF format) (315.9 kbytes)
fmtzb1_10Ks in P2(1)/n


hkldisplay filedownload file

Structure factor file (CIF format) (296.6 kbytes)
fmtzb1 LS(100%)_10K after 630nm from 50%LS in 10K in P2(1)/n


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