Near-Infrared Magnetic Circularly Polarized Luminescence and Slow Magnetic Relaxation in a Tetrazinyl-Bridged Erbium Metallocene.

The magnetic and magneto-optical properties of a tetrazinyl radical-bridged Er metallocene, [(Cp*Er)(bpytz)][BPh] (; Cp* = pentamethylcyclopentadienyl, bpytz = 3,6-bis(3,5-dimethyl-pyrazolyl)-1,2,4,5-tetrazine), are reported. As confirmed by these studies strong Ln-rad coupling is achieved, with exhibiting slow magnetic relaxation under a 1000 Oe dc field. The optical and magneto-optical profile of is completed by both near-infrared (NIR) luminescence and magnetic circularly polarized luminescence (MCPL), representing the first example of NIR MCPL with Er.

Ligand Effects on the Emission Characteristics of Molecular Eu(II) Luminescence Thermometers.

Discrete molecular organometallic europium(II) complexes are promising functional materials due to their ability to behave as highly sensitive band-shift luminescence thermometers. Furthering our understanding of the design principles salient to the emission behavior of such systems is important for developing them in this emerging application. To this end, a series of pseudo--symmetric organometallic europium(II) complexes bearing systematically varying ligand sets were synthesized and characterized to probe the influence of subtle structural modification on their optical properties.

Distortion Engineering: A Strategy to Modulate Molecular Upconversion with Molecular Cluster-Aggregates.

The rational engineering of molecules is a powerful chemistry tool of pivotal importance in the fields of molecular magnetism and luminescence. Hence, systems that can be modulated via molecular engineering and composition control are expected to present extra versatility regarding the tunability of their properties. This is the case with molecular cluster aggregates (MCAs), high nuclearity molecular compounds.

Stabilizing an exotic dianionic tetrazine bridge in a Ln metallocene.

The unique electronic nature of the 1,2,4,5-tetrazine or -tetrazine (tz) ring has sparked tremendous scientific interest over the last few years. Tetrazines have found numerous applications, and their ability to coordinate to metal ions has opened the possibility of exploring their chemistry in both molecular systems and extended networks. The rich redox chemistry of -tetrazines allows them to exchange electrons and switch between their dihydro (Htz), neutral (tz), and radical (tz˙) forms.

Formation of a Decanuclear Organometallic Dysprosium Complex via a Radical-Radical Cross-Coupling Reaction.

Over the years, polynuclear cyclic or torus complexes have attracted increasing interest due to their unique metal topologies and properties. However, the isolation of polynuclear cyclic organometallic complexes is extremely challenging due to their inherent reactivity, which stems from the labile and reactive metal-carbon bonds. In this study, the pyrazine ligand undergoes a radical-radical cross-coupling reaction leading to the formation of a decanuclear [(Cp*)Dy(L1)] ⋅ 12(CH) (1; where L1 = anion of 2-prop-2-enyl-2H-pyrazine; Cp* = pentamethylcyclopentadienyl) complex, where all Dy metal centres are bridged by the anionic L1 ligand.

Confining single Er ions in sub-3 nm NaYF nanoparticles to induce slow relaxation of the magnetisation.

Molecular systems known as single-molecule magnets (SMMs) exhibit magnet-like behaviour of slow relaxation of the magnetisation and magnetic hysteresis and have potential application in high-density memory storage or quantum computing. Often, their intrinsic magnetic properties are plagued by low-energy molecular vibrations that lead to phonon-induced relaxation processes, however, there is no straightforward synthetic approach for molecular systems that would lead to a small amount of low-energy vibrations and low phonon density of states at the spin-resonance energies. In this work, we apply knowledge accumulated over the last decade in molecular magnetism to nanoparticles, incorporating Er ions in an ultrasmall sub-3 nm diamagnetic NaYF nanoparticle (NP) and probing the slow relaxation dynamics intrinsic to the Er ion.

Slow magnetic relaxation in a europium(II) complex.

Single-ion anisotropy is vital for the observation of Single-Molecule Magnet (SMM) properties (i.e., a slow dynamics of the magnetization) in lanthanide-based systems.

Dual-signalled magneto-optical barcodes with lanthanide-based molecular cluster-aggregates.

A proof-of-concept for magneto-optical barcodes is demonstrated for the first time. The dual-signalled spectrum observed magnetic circular dichroism spectroscopy can be used to develop anti-counterfeiting materials with extra layers of security when compared with the widely studied luminescent barcodes.

Probing the magnetic and magneto-optical properties of a radical-bridged Tb single-molecule magnet.

Reaction of the 1,2,4,5-tetrazine (tz˙) radical and {Cp*Tb} has yielded a tetranuclear radical-bridged Tb single-molecule magnet. The strong Ln-radical coupling and the electronic differences of the Tb ions in [(Cp*Tb)(tz˙)]·3CH (1) are probed magnetic, magneto-optical and computational studies.

Intra-cluster energy transfer editing in a dual-emitting system to tap into lifetime thermometry.

The impact of composition control and energy transfer on luminescence thermometry was investigated in a Tb/Eu dual-emitting molecular cluster-aggregate, known as {Ln}. The study of lifetime dynamics sheds new light on how one can take advantage of rational planning to enhance thermometric performance and gaining insights into intriguing optical properties.

High-Spin and Reactive Fe Cluster with Exposed Metal Sites.

Atomically defined large metal clusters have applications in new reaction development and preparation of materials with tailored properties. Expanding the synthetic toolbox for reactive high nuclearity metal complexes, we report a new class of Fe clusters, Tp* W Fe S , displaying a Fe core with M-M bonds that has precedent only in main group and late metal chemistry. M clusters with closed shell electron configurations can show significant stability and have been classified as superatoms.

Composition Control in Molecular Cluster-Aggregates: A Toolbox for Optical Output Tunability Energy Transfer Pathways.

Composition control is a powerful tool for obtaining high-performance lanthanide (Ln) luminescent materials with adjustable optical outputs. This strategy is well-established for hierarchically structured nanoparticles, but it is rarely applied to molecular compounds due to the limited number of metal centers within a single unit. In this work, we present a series of molecular cluster-aggregates (MCAs) with an icosanuclear core {LnEuTb} (Ln = Ce, Pr, Nd, Sm, Gd, Dy, Ho, Er, Tm, and Yb) in which we explore composition control, akin to nanoparticles, to modulate the optical output.

Toward Magneto-Optical Cryogenic Thermometers with High Sensitivity: A Magnetic Circular Dichroism Based Thermometric Approach.

Remote temperature probing at the cryogenic range is of utmost importance for the advancement of future quantum technologies. Despite the notable achievements in luminescent thermometers, accurately measuring temperatures below 10 K remains a challenging endeavor. In this study, we propose a novel magneto-optical thermometric approach based on the magnetic-circular dichroism (MCD) technique, which offers unprecedented capabilities for meticulous temperature variation analysis at cryogenic temperatures.

Improving the performance of β-diketonate-based Dy single-molecule magnets displaying luminescence thermometry.

Herein, we present a luminescent single-molecule magnet, [Dy(acac)bpm] (acac = acetylacetonate, bpm = 2,2'-bipyrimidine), which displays luminescence thermometry with a maximum thermal sensitivity of 1.5% K (70 K) and effective energy barriers (309 K, 0 Oe; 345 K, 1200 Oe) among the largest reported for SMMs with thermometric capabilities.

Lanthanide molecular cluster-aggregates as the next generation of optical materials.

In this perspective, we provide an overview of the recent achievements in luminescent lanthanide-based molecular cluster-aggregates (MCAs) and illustrate why MCAs can be seen as the next generation of highly efficient optical materials. MCAs are high nuclearity compounds composed of rigid multinuclear metal cores encapsulated by organic ligands. The combination of high nuclearity and molecular structure makes MCAs an ideal class of compounds that can unify the properties of traditional nanoparticles and small molecules.

A trivalent 4f complex with two bis-silylamide ligands displaying slow magnetic relaxation.

The best-performing single-molecule magnets (SMMs) have historically relied on pseudoaxial ligands delocalized across several coordinated atoms. This coordination environment has been found to elicit strong magnetic anisotropy, but lanthanide-based SMMs with low coordination numbers have remained synthetically elusive species. Here we report a cationic 4f complex bearing only two bis-silylamide ligands, Yb(III)[{N(SiMePh)}][Al{OC(CF)}], which exhibits slow relaxation of its magnetization.

Boosting the sensitivity with time-gated luminescence thermometry using a nanosized molecular cluster aggregate.

Luminescence thermometry with trivalent lanthanide ions is a promising avenue for contactless temperature probing. The area has been growing exponentially for the last two decades, and its viability has been successfully demonstrated in various research domains. However, moving from laboratory equipment to real-life applications remains a challenging task.

A cationic -lanthanide MOF enhances the uptake of iodine vapour at room temperature.

The first example of a cationic cluster-based -lanthanide metal-organic framework (MOF) bearing an asymmetric linker, herein named UOTT-4, has been designed and fully characterized. Compared to its rare-earth (RE) anionic counterpart (RE-UiO-66), UOTT-4 was found to significantly improve the performance towards adsorption of iodine vapour at room temperature, opening avenues for the design of the next-generation cationic porous materials for the beneficial uptake and confinement of target molecules.

Molecular Capacitors: Accessible 6- and 8-Electron Redox Chemistry from Dimeric "Ti(I)" and "Ti(0)" Synthons Supported by Imidazolin-2-Iminato Ligands.

Reduction of the diamagnetic Ti(III)/Ti(III) dimer [ClTi(μ-NIm)] () (NIm = [1,3-bis(Dipp)imidazolin-2-iminato], Dipp = CH-2,6-Pr) with 4 and 6 equiv of KC generates the intramolecularly arene-masked, dinuclear titanium compounds [(μ-N-η-Im)Ti] () and {[(EtO)K](μ-N-μ:η-Im)Ti} (), respectively, in modest yields. The compounds have been structurally characterized by X-ray crystallographic analysis, and inspection of the bond metrics within the η-coordinated aryl substituent of the bridging imidazolin-2-iminato ligand shows perturbation of the aromatic system most consistent with two-electron reduction of the ring. As such, and can be assigned respectively as possessing metal centers in formal Ti(III)/Ti(III) and Ti(II)/Ti(II) oxidation states.

Ni-Centered Coordination-Induced Spin-State Switching Triggered by Electrical Stimulation.

We herein report the synthesis and magnetic properties of a Ni(II)-porphyrin tethered to an imidazole ligand through a flexible electron-responsive mechanical hinge. The latter is capable of undergoing a large amplitude and fully reversible folding motion under the effect of electrical stimulation. This redox-triggered movement is exploited to force the axial coordination of the appended imidazole ligand onto the square-planar Ni(II) center, resulting in a change in its spin state from low spin ( = 0) to high spin ( = 1) proceeding with an 80% switching efficiency.

Expanding the series of alkali metal plumbolyl complexes to Na and K.

Herein we detail the straightforward and scalable synthesis of sodium and potassium complexes of the 2,5-bis(-butyldimethylsilyl)-3,4-diphenylplumbolyl dianion (Pbl). Their solid-state structures were found to comprise either monomeric solvates or coordination polymers depending on the alkali metal ion and crystallization medium. These complexes were readily prepared with high yields and purity compared to known routes to the dilithium congener of Pbl and are well-positioned to serve as convenient precursors for salt metathesis-type reactions leading to metal complexes of the understudied Pbl ligand.

Actinide arene-metalates: 2. A neutral uranium bis(anthracenide) sandwich complex and elucidation of its electronic structure.

An unprecedented sandwich complex of the actinides is synthesized from the treatment of [UI(HMPA)]I (HMPA = OP(NMe)) (2) with 3 equiv. of K(CH) to give the neutral, bis(arenide) species U(η-CH)(η-CH)(HMPA) (1). Solid-state X-ray, SQUID magnetometry, and XANES analyses are consistent with tetravalent uranium supported by [CH] ligands.

Straightforward Mechanosynthesis of a Phase-Pure Interpenetrated MOF-5 Bearing a Size-Matching Tetrazine-Based Linker.

The archetypal metal-organic framework-5 (MOF-5 or IRMOF-1) has been explored as a benchmark sorbent material with untapped potential to be studied in the capture and storage of gases and chemical confinement. Several derivatives of this framework have been prepared using the multivariate (MTV) strategy through mixing size-matching linkers to isolate, for example, MIXMOFs that outperform same-linker congeners when employed as gas reservoirs. Herein, we describe a straightforward protocol that uses mechanosynthesis (solvent-free grinding) followed by mild activation in dimethylformamide (DMF)/CHCl (40 °C and ambient pressure) to synthesize a functional phase-pure interpenetrated MOF-5 (-MOF-5) bearing the size-matching 1,4-benzene dicarboxylate (BDC) and 1,2,4,5-tetrazine-3,6-dicarboxylate (TZDC) linkers in the backbone of the interpenetrated MIXMOF.

Phonon-assisted molecular upconversion in a holmium(III)-based molecular cluster-aggregate.

Upconversion (UC) is a fascinating process in which higher energy photons can be emitted from excitation by lower energy photons. The current challenge remains in downscaling and effectively achieving upconversion with lanthanide ions at the molecular scale. Here, using a rationally designed molecular cluster-aggregate (MCA), we demonstrate for the first time Ho ion molecular upconversion.

Controlling the Energy-Transfer Processes in a Nanosized Molecular Upconverter to Tap into Luminescence Thermometry Application.

Photon upconversion (UC) in molecular species remains a highly sought-after property with vast potential applications in many fields. Until now, a few reports on molecular upconverters are limited to demonstrating upconversion. The low UC quantum yields (QY) and nuclearities hindered the application capabilities for molecular upconverters.