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A study of the thermal and light induced spin transition in FeL2 (BF4)(2) and FeL2 (ClO4)(2) L=2,6-di(3-methylpyrazol-1-yl)pyrazine

Money, V.A.; Elhaik, J.; Evans, I.R.; Halcrow, M.A.; Howard, J.A.K.


V.A. Money

J. Elhaik

M.A. Halcrow

J.A.K. Howard


The spin crossover compounds [FeL2](BF4)(2), L = 2,6-di(3-methylpyrazol-1-yl) pyrazine and [FeL2](ClO4)(2) have very unusual two stage spin transitions which are initially steep and then become more gradual. A detailed variable temperature single crystal X-ray diffraction study has shown that the course of the spin transition is controlled by an order - disorder transition in the counter anions. The high and low spin states both crystallise in the tetragonal space group I (4) over bar, the structures of the high and low spin states are presented at 290 and 30 K, respectively. The title compounds are shown to undergo LIESST ( Light Induced Excited Spin State Trapping) under irradiation with either red or green laser light with wavelengths of 632.8 and 532.06 nm, respectively, at 30 K. The cell parameters for the tetragonal photo-induced metastable high spin state at this temperature are a = 9.169(6), c = 17.77(1) Angstrom for [FeL2](ClO4)(2) with an increase in unit cell volume of 21 Angstrom(3), and a = 9.11(1), c = 17.75(2) Angstrom and an increase in volume of 42.8 Angstrom(3) for [FeL2](BF4)(2).


Money, V., Elhaik, J., Evans, I., Halcrow, M., & Howard, J. (2004). A study of the thermal and light induced spin transition in FeL2 (BF4)(2) and FeL2 (ClO4)(2) L=2,6-di(3-methylpyrazol-1-yl)pyrazine. Dalton Transactions, 43(1), 65-69.

Journal Article Type Article
Publication Date 2004
Journal Dalton Transactions
Print ISSN 1477-9226
Publisher Royal Society of Chemistry
Peer Reviewed Peer Reviewed
Volume 43
Issue 1
Pages 65-69