Redox Switches for Single‐Molecule Magnet Activity: An Ab Initio Insight

A dinuclear Co^II complex ( 1 ) featuring unprecedented anodic and cathodic switches for single‐molecule magnet (SMM) activity has been recently investigated (J. Am. Chem. Soc. 2013 , 135, 14670). The presence of sandwiched radicals in different oxidation states of this compound mediates magnetic coupling between the high‐spin (S=3/2) cobalt ions, which gives rise to SMM activity in both the oxidized ([ 1 (OEt₂)]⁺) and reduced ([ 1 ]^?) states. This feature represents the first example of a SMM exhibiting fully reversible, dual ON/OFF switchability. Here we apply ab initio and broken‐symmetry DFT calculations to elucidate the mechanisms responsible for magnetic properties and magnetization blocking in these compounds. It is found that due to the strong delocalization of the magnetic molecular orbital, there is a strong antiferromagnetic interaction between the radical and cobalt ions. The lack of high axiality of the cobalt centres explains why these compounds possess slow relaxation of magnetization only in an applied dc magnetic field.     

BEM-Fading regularization algorithm for Cauchy problems in 2D anisotropic heat conduction

Numerical Algorithms - We investigate the numerical reconstruction of the missing thermal boundary data on a part of the boundary for the steady-state heat conduction equation in anisotropic solids...     

Stable Triarylmethyl Radicals and Cobalt(II) Ions Based 1D/2D Coordination Polymers

The incorporation of organic radicals into coordination polymers was considered as a promising strategy to promote metal-ligand exchange interactions, but there are only a very limited number of stable organic radical-based ligands that can serve well such a purpose. Herein, we report two new tris(2,4,6-trichlorophenyl)methyl (TTM) radical-based ligands L1 and L2 with two and three imidazole substituents, respectively. The imidazole unit serves as a coordination site and it can also stabilize the TTM radical by intramolecular donor–acceptor interaction. Coordination of L1 and L2 with cobalt(II) ions gave the corresponding one- ( CoCP - 1 ) and two-dimensional ( CoCP - 2 ) coordination polymers, the structures of which were confirmed by X-ray crystallographic analysis. Magnetic measurements and theoretical calculations suggest antiferromagnetic coupling between the paramagnetic cobalt(II) ions and the radical ligands. Our study provides a rational design for stable organic radical-based ligands and further demonstrated the feasibility of a metal–radical approach toward magnetic materials.     

A proof-theoretic metatheorem for tracial von Neumann algebras

We adapt a continuous logic axiomatization of tracial von Neumann algebras due to Farah, Hart and Sherman in order to prove a metatheorem for this class of structures in the style of proof mining, a research programme that aims to obtain the hidden computational content of ordinary mathematical proofs using tools from proof theory.     

Supramolecular “Double‐Propeller” Dimers of Hexanuclear CuII/LnIII Complexes: A {Cu3Dy3}2 Single‐Molecule Magnet

Propelling magnetism : Supramolecular organization leads to a remarkable dodecanuclear {Cu₃Dy₃}₂ cluster with a “double–propeller” shape (see picture). The linkages of the CuDy units, both intramolecular and supramolecular, appear to be responsible for a drastic change in the single molecule magnetic behavior.

     

Polydiphenylsilanes bearing photosensitive azocrown groups

This work presents the synthesis and particularities of the reversible trans-cis UV light induced photoisomerization process of a polydiphenylsilane bearing (propyl-oxyphenylazo)dibenzo-18-crown-6 side groups.     

Temperature-responsive protein pores

We describe temperature-responsive protein pores containing single elastin-like polypeptide (ELP) loops. The ELP loops were placed within the cavity of the lumen of the alpha-hemolysin (alphaHL) pore, a heptamer of known crystal structure. The cavity is roughly spherical with a molecular surface volume of about 39,500 A3. In an applied potential, the wild-type alphaHL pore remained open for long periods. In contrast, the ELP loop-containing alphaHL pores exhibited transient current blockades, the nature of which depended on the length and sequence of the inserted loop. Together with similar results obtained with poly(ethylene glycols) covalently attached within the cavity, the data suggest that the transient current blockades are caused by excursions of ELP into the transmembrane beta-barrel domain of the pore. Below its transition temperature, the ELP loop is fully expanded and blocks the pore completely, but reversibly. Above its transition temperature, the ELP is dehydrated and the structure collapses, enabling a substantial flow of ions. Potential applications of temperature-responsive protein pores in medical biotechnology are discussed.