Book ChapterDOI
Nature and dynamics of the spin-state interconversion in metal complexes
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TLDR
In this article, the Bragg and Williams approximation of the Ising model is used to describe spin-state transitions in metal complexes which are driven by a change of temperature T or pressure p are always associated with a considerable reorganization of molecular geometry, the change involves metal-ligand bond lengths R, bond angles and a variation of ligand orientation.Abstract:
Spin-state transitions in metal complexes which are driven by a change of temperature T or pressure p are always associated with a considerable reorganization of molecular geometry. The change involves metal-ligand bond lengths R, bond angles, and a variation of ligand orientation. In particular, the elongation 4R by up to ∼ 10% occurring in the course of the LS → HS conversion produces an expansion of molecular volume ΔV ≌ 25 A3 per metal atom. The average crystal structure for given values of T and p is reproduced by the fractional occupancy of the individual structures of the high-spin (HS) and low-spin (LS) isomer. The transitions are reasonably well described by a number of theoretical models which are equivalent to the Bragg and Williams approximation of the Ising model. The dynamics of the spin-state transitions in solution, based on measurements by ultrasonic and photo-perturbation techniques, is in general rapid with rate constants between 4 × 105 and 3 × 108 s−1. Similar results are obtained for the spin conversion in solid complexes where the line shape analysis of Mossbauer spectra based on the theory of Blume and Tjon is applied. The dynamics may be rationalized employing one-dimensional cross sections through Gibbs free-energy surfaces G = G(R), an alternative being the comparison of the results with quantum-mechanical calculations for a radiationless non-adiabatic multiphonon process.read more
Citations
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Spin state switching in iron coordination compounds
TL;DR: The article deals with coordination compounds of iron(II) that may exhibit thermally induced spin transition, known as spin crossover, depending on the nature of the coordinating ligand sphere, and the variety of physical techniques usually applied for their characterization.
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Spin crossover in a catenane supramolecular system.
José Antonio Real,Enrique Andrés,M. Carmen Muñoz,Miguel Julve,Thierry Granier,Azzedine Bousseksou,François Varret +6 more
TL;DR: Variable-temperature magnetic susceptibility measurements and M�ssbauer studies reveal that this compound shows low-spin to high-spin crossover behavior in the temperature range from 100 to 250 kelvin, fundamental for the interpretation of the mechanism leading to the spin crossover.
References
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Journal ArticleDOI
High-spin .dblharw. low-spin transition in hexacoordinate complexes of iron(II) with monodentate 1-alkyltetrazole ligands: a variable-temperature Moessbauer, magnetic susceptibility, and far-infrared study
Journal ArticleDOI
Iron(III) chelates with hexadentate ligands from triethylenetetramine and .beta.-diketones or salicylaldehyde. Spin state dependent crystal and molecular structures of [Fe(acac)2trien]PF6(S = 5/2), [Fe(acacCl)2trien]PF6(S = 5/2), [Fe(sal)2trien]Cl.2H2O(S = 1/2), and [Fe(sal)2trien]NO3.H2O(S = 1/2)
Journal ArticleDOI
Theory of high‐spin?low‐spin transitions in transition metal compounds induced by the Jahn–Teller effect
TL;DR: In this paper, a model for high-spin?low-spin transition in transition metal compounds is presented, where the Jahn-Teller coupling between the d electrons and local distortion is considered as the driving force for the transition.
Journal ArticleDOI
Spin-state differences and spin crossover in five-coordinate Lewis base adducts of cobalt(II) Schiff base complexes. Structure of the high-spin (N,N'-o-phenylenebis(salicylaldiminato))cobalt(II)-2-methylimidazole adduct
TL;DR: C 24 H 20 CoN 4 O 2 cristallise dans P2 1 /n avec Z=4; affinement jusqu'a R=0,062.
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