Single-chain magnets (SCMs) that exhibit slow relaxation of their magnetization are attracting considerable attention. To tune the properties of such materials with external stimuli such as light, heat, and pressure is a challenge. Through the exploitation of light and heat induced transformation between diamagnetic Fe(II)(LS)(mu-CN)Co(III)(LS) (LS = low spin) units and paramagnetic Fe(III)(LS)(mu-CN)Co(II)(HS) (HS = high spin) units, we show the photoswitched transformation from a paramagnetic state to an antiferromagnetic ordered SCM state and the thermally induced reverse transformation, thus providing an effective way to control the spin topology of the SCM via light or a thermally induced metal-to-metal charge transfer.
A reversible single-crystal-to-single-crystal transformation from hexanuclear clusters to a one-dimensional double-zigzag chain was established. With the reversible polymerization, the chirality and magnetic interactions are switched between achiral and chiral and between antiferromagnetic in hexanuclear clusters and ferrimagnetic in chains, respectively.
Using reversible polymerization and depolymerization reactions in a single crystal state, we achieved a reversible transformation from a nanocluster to a coordination polymer. During the interconversion, the structural frameworks switched between nonporous hexanuclear clusters and porous double-zigzag chains; the magnetic behaviors switched between paramagnetism and metamagnetism, respectively. The microporous framework, which had 1D channels 1.9 A x 3.6 A in size, exhibited selective gas adsorption of H(2) and CO(2) over N(2).
The design and synthesis of tunable molecular magnets, the magnetic properties of which are sensitive to external stimuli such as light, heat, pressure, and guest molecules, are of current interest. [1][2][3] Advances in porous magnets have been made by combining porosity with spin crossover or long-range magnetic ordering, such as bidirectional chemo-switching of spin crossover, [2] reversible ferromagnetic/antiferromagnetic transformation, [3] and critical-temperature shifts. [4] Moreover, one of the most effective ways to tune the magnetic properties of molecular magnets is through light-or heat-induced metalto-metal charge transfer (MMCT), [5] because the chargetransfer process involves concomitant spin-state changes at the metal centers and is very sensitive to structure transformations.[6] Achim et al. demonstrated that solvent content plays an important role in determining the temperature range in which MMCT occurs in pentanuclear Co 3 Fe 2 complexes.[6c]Beuzen et al. showed that MMCT and photomagnetic properties can be controlled by tuning the ratio of cyanide and water ligands of the cobalt coordination sphere of CoFe Prussian blue analogues.[6d] We aimed at combining porosity and MMCT to realize guest-tunable MMCT through guest adsorption, because host-guest interactions have both profound and subtle effects on the redox potential of redox pairs. [7] Although many examples involving MMCT have been documented, [8] direct coupling of porosity and charge transfer is still undeveloped.Herein we report water-switchable MMCT by dehydration and rehydration in a microporous framework.
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