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Instruments / Technical Area	Publication Details	Published	Actions
I19-Small Molecule Single Crystal Diffraction	Probing the structural and electronic response of Magnus green salt compounds [Pt(NH2R)4][PtCl4] (R=H, CH3) to pressure Jonathan G. Richardson , Helen Benjamin , Stephen A. Moggach , Lisette R Warren , Mark R. Warren , David R. Allan , Lucy K. Saunders , Carole A. Morrison , Neil Robertson Physical Chemistry Chemical Physics DOI: 10.1039/D0CP03280H Diamond Proposal Number(s): [19178] Open Access Show Abstract ▼ Abstract: Despite possessing the desirable crystal packing and short Pt···Pt stacking distances required for a large piezoresistive response, the conductivity-pressure response of the Magnus green salt [Pt(NH3)4][PtCl4] is extremely sluggish. Through a combination of high-pressure X-ray diffraction and hybrid-DFT solid state calculations this study demonstrates that the poor conductivity-pressure response is due to a low volumetric compression anisotropy, a relatively large ambient pressure band gap and a lack of dispersion in the conduction band. Ligand modification (from NH3 to NH2CH3) does not enhance the piezoresistive response, causing even lower anisotropy of the volumetric compression and an unexpected phase transition at above 2 GPa. This study demonstrates that consideration of frontier band dispersion is a key design criterion, alongside crystal packing and Pt···Pt stacking distances for piezoresistive materials.	Jul 2020
I19-Small Molecule Single Crystal Diffraction	Pressure-induced non-innocence in bis(1,2-dionedioximato)Pt( ii ) complexes: an experimental and theoretical study of their insulator–metal transitions Helen Benjamin , Jonathan G. Richardson , Stephen A. Moggach , Sergejs Afanasjevs , Lisette Warren , Mark Warren , David R. Allan , Carole A. Morrison , Konstantin V. Kamenev , Neil Robertson Physical Chemistry Chemical Physics 134 DOI: 10.1039/C9CP06749C Diamond Proposal Number(s): [19178] Open Access Show Abstract ▼ Abstract: Bis(1,2-dionedioximato) complexes of Pt(II) are known for their propensity to form linear chains of metal complexes in the solid state, and under the application of pressure members of the family display interesting optical and conductive properties. Two examples, Pt(bqd)2 and Pt(dmg)2, are known to undergo insulator-to-metal-to-insulator transitions, with the metallic state reached at 0.8–1.4 GPa and 5 GPa, respectively. Previous interpretations of these materials’ behaviour focused on the role of the filled dz2 and vacant p orbitals on platinum, with little consideration to the role of the ligand. Here, the pressure-structural behaviour of Pt(bqd)2 is investigated through single crystal X-ray diffraction, the first such study on this material. The difference in conductive behaviour under pressure between Pt(bqd)2 and Pt(dmg)2 is then interpreted through a combination of experimental and computational methods, including conductivity measurements under high pressure and electronic structure calculations. Our computational work reveals the significant contribution from ligand low-lying vacant π-orbitals to the frontier orbitals and bands in these complexes, and provides an explanation for the experimentally observed re-entrant insulator-to-metal-to-insulator transitions, and the differences in behaviour between the two compounds.	Mar 2020

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