Tuning of Charge Transfer Assisted Phase Transition and Slow Magnetic Relaxation Functionalities in {Fe9–xCox[W(CN)8]6} (x = 0–9) Molecular Solid Solution

• DOI: 10.1021/jacs.5b11924
• Publication Date: 2016-01-14T06:25:03Z
• Authors: Szymon Chorazy; Jan J. Stanek; Wojciech Nogaś; Anna M. Majcher; Michał Rams; Marcin Kozieł; Ewa Juszyńska-Gał...; Koji Nakabayashi; Shin-ichi Ohkoshi; Barbara Sieklucka; Robert Podgajny
• Keywords: Isostructural; Spin Crossover; Stoichiometry; Spin transition

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 series trimetallic cyanido-bridged {Fe(9-x)Co(x)[W(CN)8]6(MeOH)24}·12MeOH (x = 0, 1, ..., 8, 9; compounds 9) clusters. All compounds, 0-9, are isostructural, consist pentadecanuclear clusters six-capped body-centered cube topology, capped by methanol molecules which coordinated 3d centers. Thus, they can be considered as unique type cluster-based molecular solid different Co/Fe ratios introduced while preserving coordination skeleton overall architecture. Depending on ratio, 0-9 exhibit an unprecedented tuning magnetic functionalities relate charge transfer assisted phase transition effects slow relaxation effects. The iron rich 0-5 phases thermally induced reversible structural transitions 180-220 K range critical temperatures being linearly dependent value x. 0 is accompanied (HS)Fe(II) W(V) ↔ (HS)Fe(III) W(IV) (CT) additional minor contribution Fe-based spin crossover (SCO) effect. Co-containing 1-5 reveal two simultaneous electron processes explore CT more complex (HS)Co(II) (LS)Co(III) (CTIST). Detailed structural, spectroscopic, studies help explain specific role both types CN(-)-bridged moieties: Fe-NC-W linkages activate network toward transition, subsequent Co-W CTIST enhances changes enlarges thermal hysteresis susceptibility. On second side series, vanishing cobalt 6-9 results high-spin ground state, occurrence process at low temperatures. energy barrier gradually increases increasing x, reaching up ΔE/kB 22.3(3) for compound 9.