title: Temperature-dependent exchange interaction in molecular magnets Cu(hfac)2L(R) studied by EPR: methodology and interpretations.
abstract: Exchange-coupled spin triads nitroxide-copper(II)-nitroxide are the key building blocks of molecular magnets Cu(hfac)(2)L(R). These compounds exhibit thermally induced structural rearrangements and spin transitions, where the exchange interaction between spins of copper(II) ion and nitroxide radicals changes typically by 1 order of magnitude. We have shown previously that electron paramagnetic resonance (EPR) spectroscopy is sensitive to the observed magnetic anomalies and provides information on both inter- and intracluster exchange interactions. The value of intracluster exchange interaction is temperature-dependent (J(T)), that can be accessed by monitoring the effective g-factor of the spin triad as a function of temperature (g(eff)(T)). This paper describes approaches for studying the g(eff)(T) and J(T) dependences and establishes correlations between them. The experimentally obtained g(eff)(T) dependences are interpreted using three different models for the mechanism of structural rearrangements on the molecular level leading to different meanings of the J(T) function. The contributions from these mechanisms and their manifestations in X-ray, magnetic susceptibility and EPR data are discussed.
authors.affiliation: International Tomography Center SB RAS, 630090 Novosibirsk, Russia. sergey.veber@tomo.nsc.ru
authors.forename: Sergey L
authors.initials: SL
authors.lastname: Veber
authors.forename: Matvey V
authors.initials: MV
authors.lastname: Fedin
authors.forename: Ksenia Yu
authors.initials: KY
authors.lastname: Maryunina
authors.forename: Alexey
authors.initials: A
authors.lastname: Potapov
authors.forename: Daniella
authors.initials: D
authors.lastname: Goldfarb
authors.forename: Edward
authors.initials: E
authors.lastname: Reijerse
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Lubitz
authors.forename: Renad Z
authors.initials: RZ
authors.lastname: Sagdeev
authors.forename: Victor I
authors.initials: VI
authors.lastname: Ovcharenko
authors.forename: Elena G
authors.initials: EG
authors.lastname: Bagryanskaya
mesh_terms: D003300:Copper / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D006845:Hydrocarbons, Fluorinated / Q000737:chemistry*; D059346:Magnets / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000737:chemistry*; D010422:Pentanones / Q000737:chemistry*; D013696:Temperature
chemical_list: D006845:Hydrocarbons, Fluorinated; D009942:Organometallic Compounds; D010422:Pentanones; C518705:hexafluoroacetylacetonate; D003300:Copper