Journal ArticleDOI
Slow magnetic relaxation and electron delocalization in an S = 9/2 iron(II∕III) complex with two crystallographically inequivalent iron sites.
Susanta Hazra,Sujit Sasmal,Michel Fleck,Fernande Grandjean,Moulay Tahar Sougrati,Meenakshi Ghosh,T. David Harris,Pierre Bonville,Gary J. Long,Sasankasekhar Mohanta +9 more
TLDR
The magnetic, electronic, and Mössbauer spectral properties of [Fe(2)L(μ-OAc)(2)]ClO(4), 1, where L is the dianion of the tetraimino-diphenolate macrocyclic ligand, indicate that 1 is a class III mixed valence iron(II∕III) complex with an electron that is fully delocalized between two crystallographically inequivalent iron sites.Abstract:
The magnetic, electronic, and Mossbauer spectral properties of [Fe(2)L(μ-OAc)(2)]ClO(4), 1, where L is the dianion of the tetraimino-diphenolate macrocyclic ligand, H(2)L, indicate that 1 is a class III mixed valence iron(II∕III) complex with an electron that is fully delocalized between two crystallographically inequivalent iron sites to yield a [Fe(2)](V) cationic configuration with a S(t) = 9∕2 ground state. Fits of the dc magnetic susceptibility between 2 and 300 K and of the isofield variable-temperature magnetization of 1 yield an isotropic magnetic exchange parameter, J, of -32(2) cm(-1) for an electron transfer parameter, B, of 950 cm(-1), a zero-field uniaxial D(9∕2) parameter of -0.9(1) cm(-1), and g = 1.95(5). In agreement with the presence of uniaxial magnetic anisotropy, ac susceptibility measurements reveal that 1 is a single-molecule magnet at low temperature with a single molecule magnetic effective relaxation barrier, U(eff), of 9.8 cm(-1). At 5.25 K the Mossbauer spectra of 1 exhibit two spectral components, assigned to the two crystallographically inequivalent iron sites with a static effective hyperfine field; as the temperature increases from 7 to 310 K, the spectra exhibit increasingly rapid relaxation of the hyperfine field on the iron-57 Larmor precession time of 5 × 10(-8) s. A fit of the temperature dependence of the average effective hyperfine field yields |D(9∕2)| = 0.9 cm(-1). An Arrhenius plot of the logarithm of the relaxation frequency between 5 and 85 K yields a relaxation barrier of 17 cm(-1).read more
Citations
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A Polynuclear Lanthanide Single-Molecule Magnet with a Record
Po-Heng Lin,Tara J. Burchell,Liviu Ungur,Liviu F. Chibotaru,Wolfgang Wernsdorfer,Muralee Murugesu +5 more
TL;DR: The magnet-like behavior can be observed by slow relaxation of the magnetization below the blocking temperature as mentioned in this paper, and this assumption has formed the basis for the understanding of the origin of the anisotropic barrier.
Journal ArticleDOI
An azophenine radical-bridged Fe2 single-molecule magnet with record magnetic exchange coupling
TL;DR: To the authors' knowledge, this complex exhibits by far the strongest magnetic exchange coupling ever to be observed in a single-molecule magnet.
Journal ArticleDOI
Mössbauer spectroscopy as a probe of magnetization dynamics in the linear iron(I) and iron(II) complexes [Fe(C(SiMe3)3)2](1-/0.).
Joseph M. Zadrozny,Dianne J. Xiao,Jeffrey R. Long,Mihail Atanasov,Mihail Atanasov,Frank Neese,Fernande Grandjean,Gary J. Long +7 more
TL;DR: Two distinct high-temperature regimes of magnetic relaxation are observed with mechanisms that correspond to two distinct single-excitation Orbach processes within the ground-state spin-orbit coupled manifold of the iron(I) ion.
Journal ArticleDOI
Dinuclear mixed-valence CoIIICoII complexes derived from a macrocyclic ligand: unique example of a CoIIICoII complex showing catecholase activity
TL;DR: The work in this paper presents the syntheses, characterization, catecholase activity, and electrospray ionization mass spectroscopic (ESI-MS positive) study of three mixed-valence dinuclear Co(III)Co(II) complexes of composition.
Journal ArticleDOI
Structures, magnetochemistry, spectroscopy, theoretical study, and catechol oxidase activity of dinuclear and dimer-of-dinuclear mixed-valence Mn(III)Mn(II) complexes derived from a macrocyclic ligand.
TL;DR: A magneto-structural correlation based on Mn-O bridging distances has been proposed to explain the different sign of the exchange coupling constants of two mixed-valence dinuclear Mn(III)Mn(II) complexes.
References
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Book ChapterDOI
Mixed Valence Chemistry-A Survey and Classification
Melvin B. Robin,Peter Day +1 more
TL;DR: In this article, a review is concerned with the neglected class of inorganic compounds, which contain ions of the same element in two different formal states of oxidation, and a number of references cite that many individual examples of this class have been studied, yet they have very rarely been treated as a class, and there has never before, to our knowledge, been a systematic attempt to classify their properties in terms of their electronic and molecular structures.
Journal ArticleDOI
Considerations on Double Exchange
TL;DR: In this paper, it was shown that while the states of large total spin have both the highest and lowest energies, their average energy is the same as those of low total spin.
Journal ArticleDOI
Optical transitions of symmetrical mixed-valence systems in the Class II–III transition regime
TL;DR: Spectral band shapes and intensities are calculated utilizing increasingly complex models including two to four states for borderline mixed-valence systems using free-energy surfaces constructed for harmonic diabetic surfaces and characterized as a function of increasing electronic coupling to simulate the Class II to III transition.
Journal ArticleDOI
A record anisotropy barrier for a single-molecule magnet.
Constantinos J. Milios,Alina Vinslava,Wolfgang Wernsdorfer,Stephen A. Moggach,Simon Parsons,Spyros P. Perlepes,George Christou,Euan K. Brechin +7 more
TL;DR: Structural distortion in a [Mn6] complex switches the magnetic exchange from antiferro- to ferromagnetic, resulting in a single-molecule magnet with a record anisotropy barrier.
Journal ArticleDOI
A polynuclear lanthanide single-molecule magnet with a record anisotropic barrier.
Po-Heng Lin,Tara J. Burchell,Liviu Ungur,Liviu F. Chibotaru,Wolfgang Wernsdorfer,Muralee Murugesu +5 more
TL;DR: The synthesis, structure, and magnetism of a tetranuclear dysprosium(III) SMM that exhibits the largest relaxation barrier seen for any polynuclear SMM to date is reported.