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Issue 20, 2010
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Synthesis, magnetic and photomagnetic study of new iron(II) spin-crossover complexes with N4O2 coordination sphere

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Abstract

A new family of neutral mononuclear iron(II) spin crossover (SCO) compounds, Fe(L1–6)2 (L1–6 = N′-((pyridin-2-yl)methylene)benzohydrazide (HL1), N′-(1-(pyridin-2-yl)ethylidene)-benzohydrazide (HL2), N′-(phenyl(pyridin-2-yl)methylene)benzohydrazide (HL3), 2-hydroxy-N′-((pyridin-2-yl)methylene)benzohydrazide (HL4), 2-hydroxy-N′-(1-(pyridin-2-yl)ethylidene)benzohydrazide (HL5), 2-hydroxy-N′-(phenyl(pyridin-2-yl)methylene)benzohydrazide (HL6)) with N4O2 donor sets have been synthesized from series tridentate Schiff base ligands with N,N,O donor sets. The investigation of magnetic properties of these compounds reveal that in the measured temperature range, compound 1 is in the high-spin (HS) state, and compound 3 and 6 are mainly in the low-spin (LS) state, whereas the other compounds exhibit various SCO properties: compound 2 undergoes a gradual incomplete SCO with characteristic temperature T1/2 higher than 350 K; compound 4 exhibits a special stepwise thermally induced SCO occurring at ∼150 K (smooth) and 200 K (two-steps, with TS1↑/↓ = 204/202 K and TS2↑/↓ = 227/219 K) with a mixture of the HS and LS states yielded below 100 K; compound 5 shows a gradual and complete LS ↔ HS SCO with characteristic temperature T1/2 = 273 K. All the three SCO compounds show the LIESST (light induced exited spin state trapping) effect with different levels of photoconversion. To thoroughly analyze these behaviours, Mössbauer spectra and DSC of 4 and 5, crystal structures of all the compounds at 290 K and 5 in the LS state at 110 K were carried out, which confirmed the structural changes accompanying the spin transition. In addition, alkyl substitution effect on the ligand field was suggested for this system.

Graphical abstract: Synthesis, magnetic and photomagnetic study of new iron(ii) spin-crossover complexes with N4O2 coordination sphere

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Publication details

The article was received on 03 Dec 2009, accepted on 01 Mar 2010 and first published on 18 Mar 2010


Article type: Paper
DOI: 10.1039/B925482J
Citation: Dalton Trans., 2010,39, 4856-4868
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    Synthesis, magnetic and photomagnetic study of new iron(II) spin-crossover complexes with N4O2 coordination sphere

    L. Zhang, G. Xu, H. Xu, V. Mereacre, Z. Wang, A. K. Powell and S. Gao, Dalton Trans., 2010, 39, 4856
    DOI: 10.1039/B925482J

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