Molecular magnetic switches are expected to form the functional components of future nanodevices.H erein we combine detailed (photo-) crystallography and magnetic studies to reveal the unusual switching properties of an iron(III) complex, between low (LS) and high (HS) spin states.O nc ooling, it exhibits ap artial thermal conversion associated with ar econstructive phase transition from a[ HS-HS] to a[ LS-HS] phase with ah ysteresis of 25 K. Photoexcitation at lowtemperature allows access to a[LS-LS] phase, never observed at thermal equilibrium. As well as reporting the first iron(III) spin crossover complex to exhibit reverse-LIESST (light-induced excited spin state trapping), we also reveal ahidden hysteresis of 30 Kbetween the hidden [LS-LS] and [HS-LS] phases.Moreover,wedemonstrate that Fe III spincrossover (SCO) complexes can be just as effective as Fe II systems,a nd with the advantage of being air-stable,t hey are ideally suited for use in molecular electronics.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.
Molecular devices based on spin-crossover (SCO) compounds are important targets for molecular electronics. In this study, six air-stable FeIII complexes have been prepared: [Fe(naphBzen)2]Cl (1), [Fe(naphBzen)2]Cl·0.5hexane (1·0.5hexane); [Fe(naphBzen)2]Cl·2CHCl3·1.15hexane (1·2CHCl3·1.15hexane), [Fe(naphBzen)2]Br (2), [Fe(naphBzen)2]Br·0.5hexane (2·0.5hexane), and [Fe(naphBzen)2]Br·2CHCl3 (2·2CHCl3). The hexane solvates are isostructural, crystallizing in the tetragonal space group I41/a. Weak van der Waals interactions between the cations result in the Fe1 and Fe2 centers packing into chiral chains and exhibiting two-step SCO. In contrast, the nonisostructural CHCl3 solvates have a single Fe center and crystallize in the triclinic space group P1̅ and are LS up to 350 K. The solvent-free systems are also not isostructural with [Fe(naphBzen)2]Cl, crystallizing in the triclinic space group P1̅, while [Fe(naphBzen)2]Br undergoes a phase transition from tetragonal P43 to P43212 upon heating from 150 to 280 K. In both cases the compounds are trapped in the LS state. Magnetic data reveals that SCO occurs only in the hexane solvates, indicating that even very weak interactions can be critical in observing spin-crossover behavior.
A series of iron(iii) complexes [Fe(naphEen)2]X·sol (naphEen = 1-{[2-(ethylamino)-ethylimino]methyl}-2-naphtholate; X = F, sol = 0.5CH2Cl2·H2O 1; sol = H2O, X = Cl, 2 and X = Br 3) and [Fe(naphEen)2]I 4 has been prepared. The UV-Vis spectra reveal clear differences for 1 which DFT/TDDFT calculations suggest are due to an equilibrium between [Fe(naphEen)2]F and [Fe(naphEen)2F], the latter having a coordinated F ligand. The X-ray crystal structures of 2-4 show LS Fe(iii) centres in all cases and extensive aryl interactions that link the Fe centres into supramolecular squares. In 3 at room temperature the compound loses half an equivalent of water resulting in a change in space group from Monoclinic P21/n to C2/c. Magnetic studies indicate that 1 is trapped in a mixed spin state being ca. 40% HS while 2-4 are effectively low spin up to 350 K. In contrast, Mössbauer spectroscopic studies of 1 indicate a gradual but incomplete spin crossover. The magnetic properties of 2-4 contrast with the related [Fe(salEen-X)2]anion derivatives which are often spin crossover active.
Molecular magnetic switches are expected to form the functional components of future nanodevices.H erein we combine detailed (photo-) crystallography and magnetic studies to reveal the unusual switching properties of an iron(III) complex, between low (LS) and high (HS) spin states.O nc ooling, it exhibits ap artial thermal conversion associated with ar econstructive phase transition from a[ HS-HS] to a[ LS-HS] phase with ah ysteresis of 25 K. Photoexcitation at lowtemperature allows access to a[LS-LS] phase, never observed at thermal equilibrium. As well as reporting the first iron(III) spin crossover complex to exhibit reverse-LIESST (light-induced excited spin state trapping), we also reveal ahidden hysteresis of 30 Kbetween the hidden [LS-LS] and [HS-LS] phases.Moreover,wedemonstrate that Fe III spincrossover (SCO) complexes can be just as effective as Fe II systems,a nd with the advantage of being air-stable,t hey are ideally suited for use in molecular electronics.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.
Alcohol effects in a series of iron(III) spin crossover complexes [Fe(qsal-Cl)2]NO3·ROH (R = Me 1, Et 2, 1-Pr 3) are explored. Despite the solvents differing from each other by only...
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