EaStCHEM School of Chemistry, The University of Edinburgh, The Kings Buildings, West Mains Road, Edinburgh, UK EH9 3JJ.
Published: October 2011
AI Article Synopsis
Article Abstract
The serendipitous self-assembly of the complex [Mn(III)(2)Zn(II)(2)(Ph-sao)(2)(Ph-saoH)(4)(hmp)(2)] (1),whose magnetic core consists solely of two symmetry equivalent Mn(iii) ions linked by two symmetry equivalent -N-O- moieties, provides a relatively simple model complex with which to study the magneto-structural relationship in oxime-bridged Mn(III) cluster compounds. Dc magnetic susceptibility measurements reveal ferromagnetic (J = +2.2 cm(-1)) exchange resulting in an S = 4 ground state. Magnetisation measurements performed at low temperatures and high fields reveal the presence of significant anisotropy, with ac measurements confirming slow relaxation of the magnetisation and Single-Molecule Magnetism behaviour. Simulations of high field, high frequency EPR data reveal a single ion anisotropy, D((Mn(III))) = -3.83 cm(-1). DFT studies on a simplified model complex of 1 reveal a pronounced dependence of the exchange coupling on the relative twisting of the oxime moiety with respect to the metal ion positions, as suggested previously in more complicated [Mn(III)(3)] and [Mn(III)(6)] clusters.
This work details how the unusual iridium tetrahydride [Ir(H)(IMes)(sulfoxide)]Na and trihydride [Ir(H)(IMes)(sulfoxide)] can be formed in a solvent dependent reaction of [IrCl(COD)(IMes)] with sulfoxide (dimethyl or methylphenyl), base, and H. In the case of dimethyl sulfoxide, the four hydride ligands of the tetrahydride are equivalent, and the IMes and sulfoxide ligands mutually . However, for phenyl methyl sulfoxide, this isomer of the tetrahydride forms alongside its counterpart where the remarkable symmetry breaking effect of the sulfoxide leads to it presenting four chemically distinct hydride ligands.
One of the key predictions of Parisi's broken replica symmetry theory of spin glasses is the existence of a phase transition in an applied field to a state with broken replica symmetry. This transition takes place at the de Almeida-Thouless (AT) line in the h-T plane. We have studied this line in the power-law diluted Heisenberg spin glass in which the probability that two spins separated by a distance r interact with each other falls as 1/r^{2σ}.
Models for viral populations with high replication error rates (such as RNA viruses) rely on the quasispecies concept, in which mutational pressure beyond the so-called "error threshold" leads to a loss of essential genetic information and population collapse, an effect known as the "error catastrophe." We explain how crossing this threshold, as a result of increasing mutation rates, can be understood as a second-order phase transition, even in the presence of lethal mutations. In particular, we show that, in fitness landscapes with a single peak, this collapse is equivalent to a ferroparamagnetic transition, where the back-mutation rate plays the role of the external magnetic field.
Purpose: The aim of this study was to investigate, using a power vector approach, whether corneal astigmatism follows a mirror symmetry pattern considering both the magnitude and axis, and whether age, sex and spherical equivalent refractive error can influence the pattern.
Methods: The IOLMaster 700 optical biometer was used to measure the radii of curvature of the anterior corneal surface. Refractive error was determined by non-cycloplegic subjective refraction.
ConspectusTriangulene (TRI) and its heterotriangulene (HT) derivatives are planar, triangle-shaped molecules that, via suitable coupling reactions, can form extended organic two-dimensional (2D) crystal (O2DC) structures. While TRI is a diradical, HTs are either closed-shell molecules or monoradicals which can be stabilized in their cationic form.Triangulene-based O2DCs have a characteristic honeycomb-kagome lattice.
