Photo-switchable systems, such as discrete spin-crossover complexes and bulk iron-cobalt Prussian blue analogues, exhibit, at a given temperature, a bistability between low-and high-spin states, allowing the storage of binary data. Grouping different bistable chromophores in a molecular framework was postulated to generate a complex that could be site-selectively excited to access multiple electronic states under identical conditions. Here we report the synthesis and the thermal and light-induced phase transitions of a tetranuclear iron(II) grid-like complex and its two-electron oxidized equivalent. The heterovalent grid is thermally inactive but the spin states of its constituent metal ions are selectively switched using different laser stimuli, allowing the molecule to exist in three discrete phases. Site-selective photo-excitation, herein enabling one molecule to process ternary data, may have major ramifications in the development of future molecular memory storage technologies.
Two iron/cobalt mixed‐valence clusters were synthesized using multidentate polypyridyl ligands (see picture: FeII orange, FeIII yellow, CoII blue, O red). A heptanuclear helix and a [3×3] grid complex form depending on the metal ion stoichiometry. ESI‐MS measurements suggest that the helical cluster is an intermediate to the grid complex.
A nonanuclear copper grid complex, [Cu(II)9(L)6](BF4)6·1-PrOH·5H2O (1·1-PrOH·5H2O; L = 2,6-bis[5-(2-pyridinyl)-1H-pyrazol-3-yl]pyridine), was synthesized with a [3 × 3] grid structure consisting of nine Cu(II) ions and six deprotonated ligands and displayed four-step quasi-reversible redox behavior from [Cu(II)9] to [Cu(I)4Cu(II)5]. The corresponding heterovalent complex [Cu(I)2Cu(II)7(L)6](PF6)4·3H2O (2·3H2O) was successfully isolated and had a distorted core structure that radically changed the intramolecular magnetic coupling pathways.
Grid magnet: A Co8 ring and a Co9 grid complex are synthesized using a multidentate polypyridine‐type ligand and are shown to exhibit all antiferromagnetic interactions between metal centers, with the grid complex displaying SMM properties as a result of alternating high spin/low spin metal centers in the outer 8‐membered ring.
Two undecanuclear 3d-4f clusters with the general formula {Mn(III)(4)Mn(IV)Ln(III)(6)}, where Ln = Gd or Tb, were synthesized, with both showing large spin ground states, and the Tb species acting as a single molecule magnet.
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