Achirality in the low temperature structure and lattice modes of tris(acetylacetonate)iron(iii)

Tris(acetylacteonate) iron(III) is a relatively ubiquitous mononuclear inorganic coordination complex. The bidentate nature of the three acetylacteonate ligands coordinating around a single centre inevitably leads to structural isomeric forms, however whether or not this relates to chirality in the solid state has been questioned in the literature. Variable temperature neutron diffraction data down to T = 3 K, highlights the dynamic nature of the ligand environment, including the motions of the hydrogen atoms. The Fourier transform of the molecular dynamics simulation based on the experimentally determined structure was shown to closely reproduce the low temperature vibrational density of states obtained using inelastic neutron scattering

Anion stabilised hypercloso-hexaalane Al6H6

The authors gratefully acknowledge financial support from the Australian Research Council (C.J. and A.S.), the U.S. Air Force Asian Office of Aerospace Research and Development (grant FA2386-18-1-0125 to C.J.), Deutsche Forschungsgemeinschaft (FR 641/25-2) (G.F.), and Director, Bragg Institute, ANSTO, 2011 approval of DB 1959 (A.J.E. and C.J.).Boron hydride clusters are an extremely diverse compound class, which are of enormous importance to many areas of chemistry. Despite this, stable aluminium hydride analogues of these species have remained staunchly elusive to synthetic chemists. Here we report that reductions of an amidinato-aluminium(III) hydride complex with magnesium(I) dimers lead to unprecedented examples of stable aluminium(I) hydride complexes, [(ArNacnac)Mg]2[Al6H6(Fiso)2] (ArNacnac = [HC(MeCNAr)2]-, Ar = C6H2Me3-2,4,6 Mes; C6H3Et2-2,6 Dep or C6H3Me2-2,6 Xyl; Fiso = [HC(NDip)2]-, Dip = C6H3Pri2-2,6), which crystallographic and computational studies show to possess near neutral, octahedral hypercloso-hexaalane, Al6H6, cluster cores. The electronically delocalised skeletal bonding in these species is compared to that in the classical borane, [B6H6]2-. Thus, the chemistry of classical polyhedral boranes is extended to stable aluminium hydride clusters for the first time.Publisher PDFPeer reviewe

A New Avenue to Relaxor-like Ferroelectric Behaviour Found by Probing the Structure and Dynamics of [NH3NH2]Mg(HCO2)3

The field of relaxor ferroelectrics has long been dominated by ceramic oxide materials exhibiting large polarisations with temperature and frequency dependence. Intriguingly, the dense metal-organic framework (MOF) [NH3NH2]Mg(HCO2)3 was reported as one of the first coordination frameworks to exhibit relaxor-like properties. This work clarifies the origin of these relaxor-like properties through re-examining its unusual phase transition using neutron single crystal diffraction, along with solid-state NMR and quasielastic neutron scattering studies. This reveals that the phase transition is caused by the partial re-orientation of NH3NH2 within the pores of the framework, from lying in the planes of the channel at lower temperatures to along the channel direction above the transition temperature. The transition occurs via a dynamic process such that the NH3NH2 cations can slowly interconvert between parallel and perpendicular orientations, with an estimated activation energy of 60 kJ mol-1. Furthermore these studies are consistent with proton hopping between the hydrazinium cations oriented along the channel direction via a proton site intermediate. This suggests the ferroelectric properties of [NH3NH2]Mg(HCO2)3 likely driven by a hydrogen bonding mechanism. The relaxor behaviour is proposed to be the result of polar regions, which likely fluctuate due to increased cation dynamics at high temperature. The combination of cation reorientation and proton hopping fully describes this material’s relaxor-like behaviour, suggesting a route to future design of non-oxide-based relaxor ferroelectrics

Leveraging a natural murine meiotic drive to suppress invasive populations

Invasive rodents are a major cause of environmental damage and biodiversity loss, particularly on islands. Unlike insects, genetic biocontrol strategies including populationsuppressing gene drives with biased inheritance have not been developed in mice. Here, we demonstrate a gene drive strategy (tCRISPR) that leverages super-Mendelian transmission of the t haplotype to spread inactivating mutations in a haplosufficient female fertility gene (Prl). Using spatially explicit individual-based in silico modeling, we show that tCRISPR can eradicate island populations under a range of realistic field-based parameter values. We also engineer transgenic tCRISPR mice that, crucially, exhibit biased transmission of the modified t haplotype and Prl mutations at levels our modeling predicts would be sufficient for eradication. This is an example of a feasible gene drive system for invasive alien rodent population control.Luke Gierusa, Aysegul Birandc, Mark D. Buntinga, Gelshan I. Godahewa, Sandra G. Piltz Kevin P. Oh, Antoinette J. Piaggio, David W. Threadgill, John Godwin, Owain Edwards, Phillip Cassey, Joshua V. Ross, Thomas A. A. Prowse and Paul Q. Thoma

Structure refinement and chemical analysis of Cs_3Li(DSO_4)_4, formerly ‘Cs_(1.5)Li_(1.5)D(SO_4)_2’

An accurate structure refinement of the deuterated analog of the cesium lithium acid sulfate, formerly identified as ‘Cs₁.₅Li₁.₅D(SO₄)₂’, has been carried out using neutron diffraction methods. Like the protonated material reported earlier (Merinov et al., Solid State Ionics 69 (1994) 53), the compound is cubic, I¯43d; however, the correct stoichiometry is Cs₃Li(DSO₄)₄. There are four formula units per unit cell and six atoms in the asymmetric unit. The lattice constant measured in this work is a=11.743(2)Å, comparable to the earlier results. The structure contains one disordered hydrogen bond, formed between O(2) atoms and located on two of the edges of the single LiO₄ tetrahedron. The Li site occupancy is 1/3; as is that of the deuterium site. This level of site occupancies is consistent with a structure in which hydrogen bonds are formed only when the lithium site is unoccupied, and explains the otherwise close proximity of the Li and D atoms, 1.394(10)Å. This unusual structural feature furthermore leads to a fixed stoichiometry, as confirmed here by chemical analysis of both the deuterated and protonated materials, despite the partial occupancy of the lithium and deuterium (hydrogen) atom sites

Reassessment of large dipole moment enhancements in crystals: A detailed experimental and theoretical charge density analysis of 2-methyl-4-nitroaniline

The molecular dipole moment of MNA in the crystal has been critically reexamined, to test the conclusion from an earlier experimental charge density analysis that it was substantially enhanced due to a combination of strong intermolecular interactions and crystal field effects. X-ray and neutron diffraction data have been carefully measured at 100 K and supplemented with ab initio crystal Hartree−Fock calculations. Considerable care taken in the measurement and reduction of the experimental data excluded most systematic errors, and sources of error and their effects on the experimental electron density have been carefully investigated. The electron density derived from a fit to theoretical structure factors assisted in the determination of the scale and thermal motion model. The dipole moment enhancement for MNA in the crystal is much less than that reported previously and only on the order of 30−40% (~2.5 D). In addition to the dipole moment, experimental deformation electron density maps, bond critical point data, electric field gradients at hydrogen nuclei, and atomic and group charges all agree well with theoretical results and trends. Anisotropic modeling of the motion of hydrogen atoms, integral use of periodic ab initio calculations, and improved data quality are all aspects of this study that represent a considerable advance over previous work