Leveraging Surface Siloxide Electronics to Enhance the Relaxation Properties of a Single-Molecule Magnet

International audienceSingle-molecule magnets (SMMs) hold promise for unmatched information storage density as well as for applications in quantum computing and spintronics. To date, the most successful SMMs have been organometallic lanthanide complexes. However, their surface immobilization, one of the requirements for device fabrication and commercial application, remains challenging due to the sensitivity of the magnetic properties to small changes in the electronic structure of the parent SMM. Thus, finding controlled approaches to SMM surface deposition is a timely challenge. In this contribution we apply the concept of isolobality to identify siloxides present at the surface of partially dehydroxylated silica as a suitable replacement for archetypal ligand architectures in organometallic SMMs. We demonstrate theoretically and experimentally that isolated siloxide anchoring sites not only enable successful immobilization but also lead to a 2 orders of magnitude increase in magnetization relaxation times

Tailored Lewis Acid Sites for High-Temperature Supported Single-Molecule Magnetism

International audienceGenerating or even retaining slow magnetic relaxationin surfaceimmobilized single-molecule magnets (SMMs) from promising molecularprecursors remains a great challenge. Illustrative examples are organolanthanidecompounds that show promising SMM properties in molecular systems,though surface immobilization generally diminishes their magneticperformance. Here, we show how tailored Lewis acidic Al-(III) siteson a silica surface enable generation of a material with SMM characteristicsvia chemisorption of (Cp-ttt)(2)DyCl ((Cp-ttt)(-) = 1,2,4-tri-(tert-butyl)-cyclopentadienide).Detailed studies of this system and its diamagnetic Y analogue indicatethat the interaction of the metal chloride with surface Al sites resultsin a change of the coordination sphere around the metal center inducingfor the dysprosium-containing material slow magnetic relaxation upto 51 K with hysteresis up to 8 K and an effective energy barrier(U (eff)) of 449 cm(-1),the highest reported thus far for a supported SMM

Reversible Capture and Release of Cl₂ and Br₂ with a Redox-Active Metal–Organic Framework

Extreme toxicity, corrosiveness, and volatility pose serious challenges for the safe storage and transportation of elemental chlorine and bromine, which play critical roles in the chemical industry. Solid materials capable of forming stable nonvolatile compounds upon reaction with elemental halogens may partially mitigate these challenges by allowing safe halogen release on demand. Here we demonstrate that elemental halogens quantitatively oxidize coordinatively unsaturated Co(II) ions in a robust azolate metal-organic framework (MOF) to produce stable and safe-to-handle Co(III) materials featuring terminal Co(III)-halogen bonds. Thermal treatment of the oxidized MOF causes homolytic cleavage of the Co(III)-halogen bonds, reduction to Co(II), and concomitant release of elemental halogens. The reversible chemical storage and thermal release of elemental halogens occur with no significant losses of structural integrity, as the parent cobaltous MOF retains its crystallinity and porosity even after three oxidation/reduction cycles. These results highlight a material operating via redox mechanism that may find utility in the storage and capture of other noxious and corrosive gases.National Science Foundation (U.S.) (Award DMR-1452612