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Issue 38, 2009
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Structural, thermal and photomagnetic properties of spin crossover [Fe(bpp)2]2+ salts bearing [Cr(L)(ox)2] anions

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Abstract

This paper is divided into two parts: in the first part, the influence of solvate molecules on the magnetic properties of spin crossover salts of [Fe(bpp)2][Cr(L)(ox)2]ClO4·nS (bpp = 2,6-bis(pyrazol-3yl)pyridine; L = 2,2′-bipyridine (bpy) or 1,10-phenanthroline (phen); ox = oxalate dianion; S = solvent) is analyzed. The second part is devoted to the photomagnetic properties of the previously reported [Fe(bpp)2][Cr(L)(ox)2]2 family of compounds. The study describes the crystal structure, differential scanning calorimetry (DSC) and magnetic properties of [Fe(bpp)2][Cr(bpy)(ox)2]ClO4·EtOH·4H2O (1) and [Fe(bpp)2][Cr(phen)(ox)2]ClO4·1.5EtOH·4H2O (2). Both salts are high-spin (HS) compounds. Desolvation of 1 yields a material exhibiting a gradual spin crossover that involves 50% of the Fe2+ cations. Rehydration of this desolvated salt induces a significant increase in the low-spin (LS) population. Desolvation of 2 affords a material showing a more abrupt spin crossover with thermal hysteresis (T1/2↑ = 286 K and T1/2↓ = 273 K). This material is not very sensitive to rehydration. The anhydrous compounds [Fe(bpp)2][Cr(bpy)(ox)2]2 (3) and [Fe(bpp)2][Cr(phen)(ox)2]2 (4) display some quantitative photomagnetic conversion with T(LIESST) values of 41 and 51 K, respectively. Kinetic parameters governing the photo-induced HS–LS relaxation process have been determined and used to reproduce the T(LIESST) curves.

Graphical abstract: Structural, thermal and photomagnetic properties of spin crossover [Fe(bpp)2]2+ salts bearing [Cr(L)(ox)2]− anions

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Publication details

The article was received on 11 Feb 2009, accepted on 07 Jul 2009 and first published on 10 Aug 2009


Article type: Paper
DOI: 10.1039/B902825K
Citation: Dalton Trans., 2009,0, 8087-8095
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    Structural, thermal and photomagnetic properties of spin crossover [Fe(bpp)2]2+ salts bearing [Cr(L)(ox)2] anions

    M. Clemente-León, E. Coronado, M. C. Giménez-López, F. M. Romero, S. Asthana, C. Desplanches and J. Létard, Dalton Trans., 2009, 0, 8087
    DOI: 10.1039/B902825K

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