Publication Type Journal Article
Title Slow magnetic relaxation and electron delocalization in an S=9/2 iron(II/III) complex with two crystallographically inequivalent iron sites
Authors Susanta Hazra Sujit Sasmal Michel Fleck Fernande Grandjean Moulay T. Sougrati Meenakshi Ghosh T. David Harris Pierre Bonville Gary J. Long Sasankasekhar Mohanta
Groups
Journal JOURNAL OF CHEMICAL PHYSICS
Year 2011
Month May
Volume 134
Number 17
Pages
Abstract The magnetic, electronic, and Mossbauer spectral properties of [Fe2L(mu-OAc)(2)]ClO4, 1, where L is the dianion of the tetraimino-diphenolate macrocyclic ligand, H2L, 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 x 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). (C) 2011 American Institute of Physics. [doi:10.1063/1.3581028]
DOI http://dx.doi.org/10.1063/1.3581028
ISBN
Publisher
Book Title
ISSN 0021-9606
EISSN 1089-7690
Conference Name
Bibtex ID ISI:000290393200039
Observations
Back to Publications List