Browsing by Author "Moggach, SA"
Now showing 1 - 3 of 3
Results Per Page
Sort Options
- ItemGuest 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, SMThe 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
- ItemA non-topological mechanism for negative linear compressibility(Royal Society of Chemistry, 2016-05-13) Binns, J; Kamenev, KV; Marriott, KER; McIntyre, GJ; Moggach, SA; Murrie, M; Parsons, SNegative linear compressibility (NLC), the increase in a unit cell length with pressure, is a rare phenomenon in which hydrostatic compression of a structure promotes expansion along one dimension. It is usually a consequence of crystal structure topology. We show that the source of NLC in the Co(II) citrate metal–organic framework UTSA-16 lies not in framework topology, but in the relative torsional flexibility of Co(II)-centred tetrahedra compared to more rigid octahedra.© Open Access CC BY Licence - The Royal Society of Chemistry 2016
- ItemUse of a miniature diamond-anvil cell in high-pressure single-crystal neutron Laue diffraction(International Union of Crystallography, 2016-05) Binns, J; Kamenev, KV; McIntyre, GJ; Moggach, SA; Parsons, SThe first high-pressure neutron diffraction study in a miniature diamond-anvil cell of a single crystal of size typical for X-ray diffraction is reported. This is made possible by modern Laue diffraction using a large solid-angle image-plate detector. An unexpected finding is that even reflections whose diffracted beams pass through the cell body are reliably observed, albeit with some attenuation. The cell body does limit the range of usable incident angles, but the crystallographic completeness for a high-symmetry unit cell is only slightly less than for a data collection without the cell. Data collections for two sizes of hexamine single crystals, with and without the pressure cell, and at 300 and 150 K, show that sample size and temperature are the most important factors that influence data quality. Despite the smaller crystal size and dominant parasitic scattering from the diamond-anvil cell, the data collected allow a full anisotropic refinement of hexamine with bond lengths and angles that agree with literature data within experimental error. This technique is shown to be suitable for low-symmetry crystals, and in these cases the transmission of diffracted beams through the cell body results in much higher completeness values than are possible with X-rays. The way is now open for joint X-ray and neutron studies on the same sample under identical conditions. © International Union of Crystallography - Open Access