Magnetic Control over the Fractal Dimension of Supramolecular Rod Networks.

Controlling supramolecular polymerization is of fundamental importance to create advanced materials and devices. Here we show that the thermodynamic equilibrium of Gd3+-bearing supramolecular rod networks is shifted reversibly at room temperature in a static magnetic field of up to 2 T. Our approach opens opportunities to control the structure formation of other supramolecular or coordination polymers that contain paramagnetic ions.

Detection of the Faraday Chiral Anisotropy.

The connection between chirality and electromagnetism has attracted much attention through the recent history of science, allowing the discovery of crucial nonreciprocal optical phenomena within the context of fundamental interactions between matter and light. A major phenomenon within this family is the so-called Faraday chiral anisotropy, the long-predicted but yet unobserved effect which arises due to the correlated coaction of both natural and magnetically induced optical activities at concurring wavelengths in chiral systems. Here, we report on the detection of the elusive anisotropic Faraday chiral phenomenon and demonstrate its enantioselectivity. The existence of this fundamental effect reveals the accomplishment of envisioned nonreciprocal electromagnetic metamaterials referred to as Faraday chiral media, systems where novel electromagnetic phenomena such as negative refraction of light at tunable wavelengths or even negative reflection can be realized. From a more comprehensive perspective, our findings have profound implications for the general understanding of parity-violating photon-particle interactions in magnetized media.

Modulating Structural and Electronic Properties of Rare Archimedean and Johnson-Type Mn Cages.

High-nuclearity Mn complexes have attracted significant scientific attention due to their fascinating magnetic properties and their relevance to bioinorganic systems and catalysis. In this work, we demonstrate how the strong binding characteristics of phosphonate ligands can be coupled with sterically hindered carboxylate groups to influence the symmetry of Mn coordination clusters. We describe the structure of two high-nuclearity Mn coordination cages, {Mn12} and {Mn15}, synthesized using this approach. These cages are structurally related to the truncated tetrahedral geometry and adopt rare topological features of Archimedean and Johnson-type solids. Their structural attributes distinctively influence their magnetic properties and electrocatalytic H2O oxidation characteristics.

Helium Ion Microscopy for Reduced Spin Orbit Torque Switching Currents.

Spin orbit torque driven switching is a favorable way to manipulate nanoscale magnetic objects for both memory and wireless communication devices. The critical current required to switch from one magnetic state to another depends on the geometry and the intrinsic properties of the materials used, which are difficult to control locally. Here, we demonstrate how focused helium ion beam irradiation can modulate the local magnetic anisotropy of a Co thin film at the microscopic scale. Real-time in situ characterization using the anomalous Hall effect showed up to an order of magnitude reduction of the magnetic anisotropy under irradiation, with multilevel switching demonstrated. The result is that spin-switching current densities, down to 800 kA cm-2, can be achieved on predetermined areas of the film, without the need for lithography. The ability to vary critical currents spatially has implications not only for storage elements but also neuromorphic and probabilistic computing.

Supramolecular approach by using Jahn-Teller sites to construct a {Mn13}-based coordination polymer and modify its magnetic properties.

Put a spin on it: a {Mn(13)} coordination cluster has been used as a secondary building unit for the preparation of an open-framework structure for which the magnetic properties can be modified by solution adsorption of tetracyanoquinodimethane radical anions (TCNQ·(-)). The applied supramolecular approach takes advantage of kinetically labile Jahn-Teller sites and can be generalised for the construction and post-synthetic modification of multifunctional materials.

Ex situ and in situ Magnetic Phase Synthesised Magneto-Driven Alginate Beads.

Biocompatible magnetic hydrogels provide a great source of synthetic materials, which facilitate remote stimuli, enabling safer biological and environmental applications. Prominently, the ex situ and in situ magnetic phase integration is used to fabricate magneto-driven hydrogels, exhibiting varied behaviours in aqueous media. Therefore, it is essential to understand their physicochemical properties to target the best material for each application. In this investigation, three different types of magnetic alginate beads were synthesised. First, by direct, ex situ, calcium chloride gelation of a mixture of Fe3O4 nanoparticles with an alginate solution. Second, by in situ synthesis of Fe3O4 nanoparticles inside of the alginate beads and third, by adding an extra protection alginate layer on the in situ synthesised Fe3O4 nanoparticles alginate beads. The three types of magnetic beads were chemically and magnetically characterised. It was found that they exhibited particular stability to different pH and ionic strength conditions in aqueous solution. These are essential properties to be controlled when used for magneto-driven applications such as targeted drug delivery and water purification. Therefore, this fundamental study will direct the path to the selection of the best magnetic bead synthesis protocol according to the defined magneto-driven application.

Models for the active site in [FeFe] hydrogenase with iron-bound ligands derived from bis-, tris-, and tetrakis(mercaptomethyl)silanes.

A series of multifunctional (mercaptomethyl)silanes of the general formula type R(n)Si(CH(2)SH)(4-n) (n = 0-2; R = organyl) was synthesized, starting from the corresponding (chloromethyl)silanes. They were used as multidentate ligands for the conversion of dodecacarbonyltriiron, Fe(3)(CO)(12), into iron carbonyl complexes in which the deprotonated (mercaptomethyl)silanes act as µ-bridging ligands. These complexes can be regarded as models for the [FeFe] hydrogenase. They were characterized by elemental analyses (C, H, S), NMR spectroscopic studies ((1)H, (13)C, (29)Si), and single-crystal X-ray diffraction. Their electrochemical properties were investigated by cyclic voltammetry to disclose a new mechanism for the formation of dihydrogen catalyzed by these compounds, whereby one sulfur atom was protonated in the catalytic cycle. The reaction of the tridentate ligand MeSi(CH(2)SH)(3) with Fe(3)(CO)(12) yielded a tetranuclear cluster compound. A detailed investigation by X-ray diffraction, electrochemical, Raman, Mössbauer, and susceptibility techniques indicates that for this compound initially [Fe(2){µ-MeSi(CH(2)S)(2)CH(2)SH}(CO)(6)] is formed. This dinuclear complex, however, is slowly transformed into the tetranuclear species [Fe(4){µ-MeSi(CH(2)S)(3)}(2)(CO)(8)].

Altering the nature of coupling by changing the oxidation state in a {Mn6} cage.

Polynuclear transition metal complexes have continuously attracted interest owing to their peculiar electronic and magnetic properties which are influenced by the symmetry and connectivity of the metal centres. Understanding the full electronic picture in such cases often becomes difficult owing to the presence of multiple bridges between metal centres. We have investigated the electronic structure of a {Mn6} cage complex using computational and experimental approaches with the aim to understand the coupling between the manganese centres. The nature of the various coupling pathways has been determined using a novel methodology that involves perturbing the system while retaining the symmetry and analysing the effect on the coupling strength due to the perturbation. Furthermore, we have investigated the magnetic properties of this complex in higher oxidation states which reveals a switch in the nature of coupling from antiferromagnetic to ferromagnetic in addition to stabilisation of intermediate spin states.

Block copolymer mediated stabilization of sub-5 nm superparamagnetic nickel nanoparticles in an aqueous medium.

This paper presents a facile method for decreasing the size of water dispersible Ni nanoparticles from 30 to 3 nm by the incorporation of a passivating surfactant combination of pluronic triblock copolymer and oleic acid into a wet chemical reduction synthesis. A detailed study revealed that the size of the Ni nanoparticles is not only critically governed by the concentration of the triblock copolymers but also dependent on the hydrophobic nature of the micelle core formed. The synthesized Ni nanoparticles were thoroughly characterized by means of transmission electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy and temperature and field dependent magnetic measurements, along with a comprehensive Fourier transform infrared spectroscopy analysis, in order to predict a possible mechanism of formation.

Hetero-metallic, functionalizable polyoxomolybdate clusters via a "top-down" synthetic method.

Two bi-metallic, organophosphonate-stabilised sandwich-type polyoxomolybdate clusters, [Mo6Cu4O16(OH)2(C4H9PO3)4(C5H5N)2 (CH3O)4(H2O)]2- and [Mo7Cu7O19(OH)(CH3O)7(C4H9PO3)6(C5H5N)2]2-, are reported. These compounds are accessed via the "top-down" in situ disassembly of the [Mo6O19]2- Lindqvist species into reactive oligomers, followed by subsequent reassembly with polynuclear CuII assemblies to form the reported compounds.

Accelerated discovery of new magnets in the Heusler alloy family.

Magnetic materials underpin modern technologies, ranging from data storage to energy conversion to contactless sensing. However, the development of a new high-performance magnet is a long and often unpredictable process, and only about two dozen magnets are featured in mainstream applications. We describe a systematic pathway to the design of novel magnetic materials, which demonstrates a high throughput and discovery speed. On the basis of an extensive electronic structure library of Heusler alloys containing 236,115 prototypical compounds, we filtered those displaying magnetic order and established whether they can be fabricated at thermodynamic equilibrium. Specifically, we carried out a full stability analysis of intermetallic Heusler alloys made only of transition metals. Among the possible 36,540 prototypes, 248 were thermodynamically stable but only 20 were magnetic. The magnetic ordering temperature, TC, was estimated by a regression calibrated on the experimental TC of about 60 known compounds. As a final validation, we attempted the synthesis of a few of the predicted compounds and produced two new magnets: Co2MnTi, which displays a remarkably high TC in perfect agreement with the predictions, and Mn2PtPd, which is an antiferromagnet. Our work paves the way for large-scale design of novel magnetic materials at potentially high speed.

Structural variation in cation-assisted assembly of high-nuclearity Mn arsonate and phosphonate wheels.

Comproportionation reactions between MnCl2 and KMnO4 in the presence of arsonate or phosphonate ligands promote the cation-assisted assembly of high-nuclearity, wheel-shaped or toroidal {Mn8} () and {Mn24} () complexes; the closely corresponding reaction systems provide insights into the complexation behaviour of homologous phosphonate/arsonate ligand species.

A facile "bottom-up" approach to prepare free-standing nano-films based on manganese coordination clusters.

We present herein a novel method to prepare free-standing Dried Foam Films (DFFs) whereby individual polynuclear manganese complexes cover quantitatively the holes of micro-grids; the fabricated, homogeneous films have a cross-sectional thickness of only ca. 5 nm and are characterised by high mechanical stability.

Engineering coordination assemblies of dinuclear CuII complexes.

Hybrid organic-inorganic coordination assemblies are synthesized using modified aminocarboxylic acid ligands as the structure-directing agents. The synthetic approach results in two novel dinuclear copper(II) complexes, K2[CuII(hnida)]2.2H2O (1) and K4[CuII(chnida)]2.4H2O.4MeOH (2) that assemble in the presence of suitable counterions into a densely packed hexagonal array or an open-framework structure. The functionality of the aminocarboxylic acid ligands provides a tool to control the supramolecular structure. The materials combine promising thermal stabilities with the necessary flexibility to withstand structural changes induced by calcinations or the uptake and release of guest molecules. The structural and physicochemical properties of the complexes were investigated using X-ray diffraction, magnetic measurements, thermogravimetric analysis and spectroscopy.