Thermodynamic properties of spin crossover 3d-metal coordination compounds

Berezovskii, G. A.; Лавренова, Л. Г.

doi:10.1007/s10973-010-1043-y

Cited by 11 publications

(6 citation statements)

References 40 publications

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“…The temperature dependence of the HS molar fraction (γ) could be fitted with the domain SCO model to give the thermodynamic parameters n ·Δ H = 37.2 kJ mol –1 and n ·Δ S = 119 J mol –1 K –1 , where n is the domain size and represents the number of molecules per domain. Taking into account that typical Δ S values for Fe(II) SCO complexes lie in the range of 40–65 J mol –1 K –1 , ,, the n parameter appears to be ∼2 or 3. The substantial domain size is also reflected by the relative abruptness of the SCO conversion curve (Figure ); the transition is clearly more abrupt than expected for a simple two-state Boltzmann distribution.…”

Section: Resultsmentioning

confidence: 99%

Spin Crossover in Fe(II) and Co(II) Complexes with the Same Click-Derived Tripodal Ligand

Schweinfurth¹,

Demeshko

Hohloch³

et al. 2014

Inorg. Chem.

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The complexes [Fe(tbta)2](BF4)2·2EtOH (1), [Fe(tbta)2](BF4)2·2CH3CN (2), [Fe(tbta)2](BF4)2·2CHCl3 (3), and [Fe(tbta)2](BF4)2 (4) were synthesized from the respective metal salts and the click-derived tripodal ligand tris[(1-benzyl-1H-1,2,3-triazol-4-yl)methyl]amine (tbta). Structural characterization of these complexes (at 100 or 133 K) revealed Fe-N bond lengths for the solvent containing compounds 1-3 that are typical of a high spin (HS) Fe(II) complex. In contrast, the solvent-free compound 4 show Fe-N bond lengths that are characteristic of a low spin (LS) Fe(II) state. The Fe center in all complexes is bound to two triazole and one amine N atom from each tbta ligand, with the third triazole arm remaining uncoordinated. The benzyl substituents of the uncoordinated triazole arms and the triazole rings engage in strong intermolecular and intramolecular noncovalent interactions. These interactions are missing in the solvent containing molecules 1, 2, and 3, where the solvent molecules occupy positions that hinder these noncovalent interactions. The solvent-free complex (4) displays spin crossover (SCO) with a spin transition temperature T1/2 near room temperature, as revealed by superconducting quantum interference device (SQUID) magnetometric and Mössbauer spectroscopic measurements. The complexes 1, 2, and 3 remain HS throughout the investigated temperature range. Different torsion angles at the metal centers, which are influenced by the noncovalent interactions, are likely responsible for the differences in the magnetic behavior of these complexes. The corresponding solvent-free Co(II) complex (6) is also LS at lower temperatures and displays SCO with a temperature T1/2 near room temperature. Theoretical calculations at molecular and periodic DFT-D3 levels for 1-4 qualitatively reproduce the experimental findings, and corroborate the importance of intermolecular and intramolecular noncovalent interactions for the magnetic properties of these complexes. The present work thus represents rare examples of SCO complexes where the use of identical ligand sets produces SCO in Fe(II) as well as Co(II) complexes.

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Section: Resultsmentioning

confidence: 99%

Spin Crossover in Fe(II) and Co(II) Complexes with the Same Click-Derived Tripodal Ligand

Schweinfurth¹,

Demeshko

Hohloch³

et al. 2014

Inorg. Chem.

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“…Thermodynamic data for trinuclear and polynuclear iron(II) spin crossover complexes are compared with those for mononuclear complexes by Berezovskii and Lavrenova. 13…”

Section: Spin Crossover Phenomenamentioning

confidence: 99%

“…In this system, Kato et al 569 made it possible to study physical properties in the phase diagram systematically by preparing high-quality single crystals using partial deuterated or 13 C substituted molecules so as to tune material in the phase diagram by chemical pressure precisely. The isotope-substituted molecules can make high-quality single crystals free from disorders inevitably produced by a solid solution of molecules with slightly different size.…”

Section: π−D Interacting Systemsmentioning

confidence: 99%

“…The electronic properties are dominated by strong magnetic interactions |J|/k B larger than 200 K . In these salts, the spin-liquid nature has been unveiled by 13 C NMR, 582−584 heat capacity, 585,586 and thermal transport 587,588 measurements. A possible relation between the superconductivity of conductive π-electrons and coupling with charge degrees of freedom in the dimer unit is stimulating extensive interests in frustration problems and electron correlations.…”

Section: Organic Spin Liquid Systemsmentioning

confidence: 99%

“…However, descriptions about how to interpret experimental results are scarce or limited to very classical examples, if any. Therefore, a brief description will be made, at first, about what kinds of microscopic and macroscopic information are derived from actual calorimetry. − …”

Section: Introductionmentioning

confidence: 99%

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