Supramolecular Iron Metallocubanes Exhibiting Site-Selective Thermal and Light-Induced Spin-Crossover.
Izar Capel BerdiellTim HochdörfferCédric DesplanchesRafal KulmaczewskiNamrah ShahidJuliusz A WolnyStuart L WarrinerOscar CespedesVolker SchünemannGuillaume ChastanetMalcolm A HalcrowPublished in: Journal of the American Chemical Society (2019)
Treatment of Fe[BF4]2·6H2O with 4,6-di(pyrazol-1-yl)-1H-pyrimid-2-one (HL1) or 4,6-di(4-methylpyrazol-1-yl)-1H-pyrimid-2-one (HL2) affords solvated crystals of [{FeIII(OH2)6}⊂FeII8(μ-L)12][BF4]7 (1, HL = HL1; 2, HL = HL2). The centrosymmetric complexes contain a cubic arrangement of iron(II) centers, with bis-bidentate [L]- ligands bridging the edges of the cube. The encapsulated [Fe(OH2)6]3+ moiety templates the assembly through 12 O-H···O hydrogen bonds to the [L]- hydroxylate groups. All four unique iron(II) ions in the cages are crystallographically high-spin at 250 K, but they undergo a gradual high → low spin-crossover on cooling, which is predominantly centered on one iron(II) site and its symmetry-related congener. This was confirmed by magnetic susceptibility data, light-induced excited spin state trapping (LIESST) effect measurements, and, for 1, Mössbauer spectroscopy and diffuse reflectance data. The clusters are stable in MeCN solution, and 1 remains high-spin above 240 K in that solvent. The cubane assembly was not obtained from reactions using other iron(II) salts or 4,6-di(pyrazol-1-yl)pyrimidine ligands, highlighting the importance of hydrogen bonding in templating the cubane assembly.
Keyphrases
- room temperature
- single molecule
- density functional theory
- ionic liquid
- iron deficiency
- transition metal
- electronic health record
- biofilm formation
- randomized controlled trial
- open label
- escherichia coli
- combination therapy
- pseudomonas aeruginosa
- molecularly imprinted
- smoking cessation
- liquid chromatography
- replacement therapy
- data analysis
- drug induced
- metal organic framework