Browsing by Author "Real, JA"

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    Guest removal and external pressure variation induce spin crossover in halogen-functionalized 2-D Hofmann frameworks
    (American Chemical Society, 2020-09-27) Brennan, AT; Zenere, KA; Brand, HEA; Price, JR; Bhadbhade, MM; Turner, GF; Moggach, SA; Valverde-Muñoz, FJ; Real, JA; Clegg, JK; Kepert, CJ; Neville, SM
    The effect of halogen functionalization on the spin crossover (SCO) properties of a family of 2-D Hofmann framework materials, [Fe(II)Pd(CN)4(thioX)2]·2H2O (X = Cl and Br; thioCl = (E)-1-(5-chlorothiophen-2-yl)-N-(4H-1,2,4-triazol-4-yl)methanimine) and thioBr = (E)-1-(5-bromothiophen-2-yl)-N-(4H-1,2,4-triazol-4-yl)methanimine)), is reported. Inclusion of both the chloro- and bromo-functionalized ligands into the Hofmann-type frameworks (1Cl·2H2O and 2Br·2H2O) results in a blocking of spin-state transitions due to internal chemical pressure effects derived by the collective steric bulk of the halogen atoms and guest molecules. Cooperative one-step SCO transitions are revealed by either guest removal or the application of external physical pressure. Notably, removal of solvent water reveals a robust framework scaffold with only marginal variation between the solvated and desolvated structures (as investigated by powder and single crystal X-ray diffraction). Yet, one-step complete SCO transitions are revealed in 1Cl and 2Br with a transition temperature shift between the analogues due to various steric, structural, and electronic considerations. SCO can also be induced in the solvated species, 1Cl·2H2O and 2Br·2H2O, with the application of physical pressure, revealing a complete one-step SCO transition above 0.62 GPa (as investigated by magnetic susceptibility and single crystal X-ray diffraction measurements). © 2020 American Chemical Society
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    Temperature- and pressure-dependent structural study of {Fe(pmd)2[Ag(CN)2]2}n spin-crossover compound by neutron laue diffraction
    (Wiley, 2014-06-04) Rodríguez-Velamazán, JA; Canadillas-Delgado, L; Castro, M; McIntyre, GJ; Real, JA
    The effect of pressure (up to 0.17 GPa) on the spin-crossover compound {Fe(pmd)2[Ag(CN)2]2}n [orthorhombic isomer (II), pmd = pyrimidine] has been investigated by temperature- and pressure-dependent neutron Laue diffraction and magnetometry. The cooperative high-spin [left right arrow] low-spin transition, centred at ca 180 K at ambient pressure, is shifted to higher temperatures as pressure is applied, showing a moderate sensitivity of the compound to pressure, since the spin transition is displaced by ca 140 K GPa-1. The space-group symmetry (orthorhombic Pccn) remains unchanged over the pressure-temperature (P-T) range studied. The main structural consequence of the high-spin to low-spin transition is the contraction of the distorted octahedral [FeN6] chromophores, being more marked in the axial positions (occupied by the pmd units), than in the equatorial positions (occupied by four [Ag(CN)2]- bridging ligands). © 1999-2020 John Wiley & Sons, Inc.