title: Tuning of Charge Transfer Assisted Phase Transition and Slow Magnetic Relaxation Functionalities in {Fe(9-x)Co(x)[W(CN)8]6} (x = 0-9) Molecular Solid Solution.
abstract: Precisely controlled stoichiometric mixtures of Co(2+) and Fe(2+) metal ions were combined with the [W(V)(CN)8](3-) metalloligand in a methanolic solution to produce a series of trimetallic cyanido-bridged {Fe(9-x)Co(x)[W(CN)8]6(MeOH)24}·12MeOH (x = 0, 1, ..., 8, 9; compounds 0, 1, ..., 8, 9) clusters. All the compounds, 0-9, are isostructural, and consist of pentadecanuclear clusters of a six-capped body-centered cube topology, capped by methanol molecules which are coordinated to 3d metal centers. Thus, they can be considered as a unique type of a cluster-based molecular solid solution in which different Co/Fe metal ratios can be introduced while preserving the coordination skeleton and the overall molecular architecture. Depending on the Co/Fe ratio, 0-9 exhibit an unprecedented tuning of magnetic functionalities which relate to charge transfer assisted phase transition effects and slow magnetic relaxation effects. The iron rich 0-5 phases exhibit thermally induced reversible structural phase transitions in the 180-220 K range with the critical temperatures being linearly dependent on the value of x. The phase transition in 0 is accompanied by (HS)Fe(II) W(V) ↔ (HS)Fe(III) W(IV) charge transfer (CT) and the additional minor contribution of a Fe-based spin crossover (SCO) effect. The Co-containing 1-5 phases reveal two simultaneous electron transfer processes which explore (HS)Fe(II) W(V) ↔ (HS)Fe(III) W(IV) CT and the more complex (HS)Co(II) W(V) ↔ (LS)Co(III) W(IV) charge transfer induced spin transition (CTIST). Detailed structural, spectroscopic, and magnetic studies help explain the specific role of both types of CN(-)-bridged moieties: the Fe-NC-W linkages activate the molecular network toward a phase transition, while the subsequent Co-W CTIST enhances structural changes and enlarges thermal hysteresis of the magnetic susceptibility. On the second side of the 0-9 series, the vanishing phase transition in the cobalt rich 6-9 phases results in the high-spin ground state, and in the occurrence of a slow magnetic relaxation process at low temperatures. The energy barrier of the magnetic relaxation gradually increases with the increasing value of x, reaching up to ΔE/kB = 22.3(3) K for compound 9.
authors.affiliation: Faculty of Chemistry, Jagiellonian University , Ingardena 3, 30-060 Kraków, Poland.|Department of Chemistry, School of Science, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Szymon
authors.initials: S
authors.lastname: Chorazy
authors.affiliation: Institute of Physics, Jagiellonian University , Łojasiewicza 11, 30-348 Kraków, Poland.
authors.forename: Jan J
authors.initials: JJ
authors.lastname: Stanek
authors.affiliation: Faculty of Chemistry, Jagiellonian University , Ingardena 3, 30-060 Kraków, Poland.
authors.forename: Wojciech
authors.initials: W
authors.lastname: Nogaś
authors.affiliation: Institute of Physics, Jagiellonian University , Łojasiewicza 11, 30-348 Kraków, Poland.
authors.forename: Anna M
authors.initials: AM
authors.lastname: Majcher
authors.affiliation: Institute of Physics, Jagiellonian University , Łojasiewicza 11, 30-348 Kraków, Poland.
authors.forename: Michał
authors.initials: M
authors.lastname: Rams
authors.affiliation: Faculty of Chemistry, Jagiellonian University , Ingardena 3, 30-060 Kraków, Poland.
authors.forename: Marcin
authors.initials: M
authors.lastname: Kozieł
authors.affiliation: H. Niewodniczański Insitute of Nuclear Physics PAN , Radzikowskiego 152, 31-342 Kraków, Poland.
authors.forename: Ewa
authors.initials: E
authors.lastname: Juszyńska-Gałązka
authors.affiliation: Department of Chemistry, School of Science, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Nakabayashi
authors.affiliation: Department of Chemistry, School of Science, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Shin-ichi
authors.initials: S
authors.lastname: Ohkoshi
authors.affiliation: Faculty of Chemistry, Jagiellonian University , Ingardena 3, 30-060 Kraków, Poland.
authors.forename: Barbara
authors.initials: B
authors.lastname: Sieklucka
authors.affiliation: Faculty of Chemistry, Jagiellonian University , Ingardena 3, 30-060 Kraków, Poland.
authors.forename: Robert
authors.initials: R
authors.lastname: Podgajny