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Co(ii)–N4 complex displays slow magnetisation at zero static field, exhibiting a high spin-reversal energy barrier Ueff = 85 cm−1.

Four-coordinate distorted tetrahedral bis(2-iminopyrrolyl)cobalt(ii) complexes behave as Single-Ion Magnets (SIMs) in the absence of an external magnetic field.

Molecular entities with doublet or triplet ground states find increasing interest as potential molecular quantum bits (qubits). Complexes with higher multiplicity might even function as qudits and serve to encode further quantum bits. Vanadium(II) ions in octahedral ligand fields with quartet ground states and small zero-field splittings qualify as qubits with optical read out thanks to potentially luminescent spin-flip states. We identified two V

Metal–metal bonding is a widely studied area of chemistry1–3, and has become a mature field spanning numerous d transition metal and main group complexes4–7. By contrast, actinide–actinide bonding, which is predicted to be weak8, is currently restricted to spectroscopically detected gas-phase U2 and Th2 (refs. 9,10), U2H2 and U2H4 in frozen matrices at 6–7 K (refs. 11,12), or fullerene-encapsulated U2 (ref. 13). Furthermore, attempts to prepare thorium–thorium bonds in frozen matrices have produced only ThHn (n = 1–4)14. Thus, there are no isolable actinide–actinide bonds under normal conditions. Computational investigations have explored the probable nature of actinide–actinide bonding15, concentrating on localized σ-, π-, and δ-bonding models paralleling d transition metal analogues, but predictions in relativistic regimes are challenging and have remained experimentally unverified. Here, we report thorium–thorium bonding in a crystalline cluster, prepared and isolated under normal experimental conditions. The cluster exhibits a diamagnetic, closed-shell singlet ground state with a valence-delocalized three-centre-two-electron σ-aromatic bond16,17 that is counter to the focus of previous theoretical predictions. The experimental discovery of actinide σ-aromatic bonding adds to main group and d transition metal analogues, extending delocalized σ-aromatic bonding to the heaviest elements in the periodic table and to principal quantum number six, and constitutes a new approach to elaborate actinide–actinide bonding. A crystalline cluster exhibits thorium–thorium bonding, adding to our knowledge of actinide–actinide bonding.

Metal complexes of 1,2-diamidobenzenes have been long studied because of their intriguing redox properties and electronic structures. We present here a series of such complexes with 1,2-bis(sulfonamido)benzene ligands to probe the utility of these ligands for generating a large zero-field splitting (ZFS, D) in metal complexes that possibly act as single-ion magnets. To this end, we have synthesized a series of homoleptic ate complexes of the form (X)n[M{bis(sulfonamido)benzene}2] (n equals 4 minus the oxidation state of the metal), where M (Fe/Co/Ni), X [K+/(K-18-c-6)+/(HNEt3)+, with 18-c-6 = 18-crown ether 6], and the substituents (methyl and tolyl) on the ligand [bmsab = 1,2-bis(methanesulfonamido)benzene; btsab = 1,2-bis(toluenesulfonamido)benzene] were varied to analyze their effect on the ZFS, possible single-ion-magnet properties, and redox behavior of these metal complexes. A combination of X-ray crystallography, (spectro)electrochemistry, superconducting quantum interference device magnetometry, high-frequency electron paramagnetic resonance spectroscopy, and Mossbauer spectroscopy was used to investigate the electronic/geometric structures of these complexes and the aforementioned properties. These investigations show that the cobalt(II) complexes display very high negative D values in the range of -100 to -130 cm-1, and the nickel(II) complexes display very high positive D values of 76 and 58 cm-1. In addition, the cobalt(II) complexes shows barriers of 200-260 cm-1 and slow relaxation of the magnetization in the absence of an external magnetic field, underscoring the robustness of this class of complexes. The iron(II) complex exhibits a D value of -3.29 cm-1 and can be chemically oxidized to an iron(III) complex that has D = -1.96 cm-1. These findings clearly show that bis(sulfonamido)benzenes are ideally suited to stabilize ate complexes, to generate very high ZFSs at the metal centers with single-ion-magnet properties, and to induce exclusive oxidation at the metal center (for iron) despite the presence of ligands that are potentially noninnocent. Our results therefore substantially enhance the scope for this class of redox-active ligands.

Here we explore the electronic structure of the diiron complex [(dppf)Fe(CO)3]0/+ [10/+; dppf = 1,1'-bis(diphenylphosphino)ferrocene] in two oxidation states by an advanced multitechnique experimental approach. A combination of magnetic circular dichroism, X-ray absorption and emission, high-frequency electron paramagnetic resonance (EPR), and Mossbauer spectroscopies is used to establish that oxidation of 10 occurs on the carbonyl iron ion, resulting in a low-spin iron(I) ion. It is shown that an unequivocal result is obtained by combining several methods. Compound 1+ displays slow spin dynamics, which is used here to study its geometric structure by means of pulsed EPR methods. Surprisingly, these data show an association of the tetrakis[3,5-bis(trifluoromethylphenyl)]borate counterion with 1+.

We report the synthesis of the lanthanide-(bis)boryloxide complex [Dy{OB(NArCH)2}2(THF)4][BPh4] (2Dy, Ar = 2,6-Pri2C6H3), with idealised D4h@Dy(III) point-group symmetry. Complex 2Dy exhibits single-molecule magnetism (SMM), with one of the highest energy barriers (Ueff = 1565(298) K) of any six-coordinate lanthanide-SMM. Complex 2Dy validates electrostatic model predictions, informing the future design of lanthanide-SMMs.

Hydrogen spillover is mechanistically poorly understood, due to the H˙ donor complexity. We show that HV(CO)4dppe (1) transfers H˙ to MoO3 in separate H+ and e− transfer steps. This is analogous to hydrogen spillover from Pt to MoO3 and suggests that 1 is a good model for H˙ adsorbed on Pt.

The charge delocalization between the N-heterocyclic carbene (NHC) and the metal in cationic molybdenum imido alkylidene NHC mono(nonafluoro-tert-butoxide) complexes has been studied for different ...

A series of heterometallic [TiIV7MIII] rings are reported which contain a single paramagnetic metal centre, either FeIII or CrIII. The structures contain an octagon of metals bridged by oxides within the ring and pivalate ligands outside the ring. The structures encapsulate a single cation, either a secondary ammonium cation or a cesium. Multi-frequency EPR spectroscopy was used to measure the zero-field splitting parameters for the paramagnetic metal sites. The FeIII sites have rhombic anisotropy, with D around − 0.18 cm−1 and λ (= D/E) approximately 0.25. The CrIII have a more axial anisotropy, with D around − 0.5 cm−1 and λ around 0.05. Attempts to find a magneto-structural correlation are vitiated by the difficulty of refining the challenging crystal structures.

Metallonitrenes (M–N) are complexes with a subvalent atomic nitrogen ligand that have been proposed as key reactive intermediates in nitrogen atom transfer reactions. However, in contrast to the common classes of nitride complexes (M≡N) and organic nitrenes (R–N), structurally and spectroscopically well defined ‘authentic’ metallonitrenes with a monovalent atomic nitrogen ligand remain elusive. Here we report that the photolysis of a platinum(ii) pincer azide complex enabled the crystallographic, spectroscopic, magnetic and computational characterization of a metallonitrene that is best described as a singly bonded atomic nitrogen diradical ligand bound to platinum(ii). The photoproduct exhibits selective C–H, B–H and B–C nitrogen atom insertion reactivity. Despite the subvalent metallonitrene character, mechanistic analysis for aldehyde C–H amidation shows nucleophilic reactivity of the N-diradical ligand. Ambiphilic reactivity of the metallonitrene is indicated by reactions with CO and PMe3 to form isocyanate and phosphoraneiminato platinum(ii) complexes, respectively. Transient metallonitrenes (M–N) have been proposed as key intermediates in nitrogen atom transfer reactions, but well-defined examples have remained elusive. Now, a platinum complex with an atomic nitrogen ligand, best described as a subvalent nitrogen diradical singly bonded to a platinum(ii) ion (Pt–N), has been isolated and shows ambiphilic reactivity.

In this work, we demonstrate that high solid-state conductivities of simply spin-coated poly(3-hexylthiophene) (P3HT) films can be obtained by means of an ex situ electrochemical doping strategy us...

The 1 : 2 reaction between Dy(O

An asymmetric bis-phenol-β-diketone (H4L) has been designed as a ligand programmed to promote the assembly of a molecular arrangement composed of three magnetically exchanged [NiCu] pairs, each exhibiting an S = 1/2 spin. The latter are shown by EPR and magnetometry to be good qubit realizations and non-equivalent within the molecule in the solid state, as required for conditional quantum gates., This research was supported by Spanish MINECO (PGC2018-098630-B-I00, PID2020-118329B-I00), the Aragón government (E31_20R PLATON) and the EU (FET-OPEN grant 862893 FATMOLS). G. A. thanks the Generalitat de Catalunya for the prize ICREA Academia 2018. B. L. G. thanks French GENCI/IDRIS-CINES centers for high-performance computing resources. The authors thank the Advanced Light Source, which is a DOE Office of Science User Facility under contract no. DEAC02-05CH11231, and the Zeiss Foundation for funding.

The fine-tuning of intermolecular or intramolecular non-covalent interactions (NCIs) and thus the precise synthesis of metal complexes in which the spin states can be controlled by NCIs remains challenging, even though several such complexes have been intensively studied. In this regard, we present mononuclear cobalt(II) and iron(II) complexes with "click"-derived tripodal ligands that contain fluorinated benzyl substituents in the secondary coordination sphere. The complexes were co-crystallized with different solvent molecules to decipher the effect of the crystallized solvents on NCIs, and on the spin state of the metal ion. Additionally, the fluorine-specific interactions in the secondary coordination sphere were examined. We present a first structure-property correlation between the nature of interaction of the (per)fluorinated aromatic substituents on the ligand periphery, and the spin state of the metal complexes. In particular, the TF5TA containing ligand show interesting stacking motifs depending on the used solvent, and these interactions have an influence on the spin state of the cobalt(II) complexes. Furthermore, the iron(II) complex thereof, Fe(TF5TA)2(BF4)2·2EtOH displays spin crossover (SCO).

The quest for developing quantum technologies is driven by the promise of exponentially faster computations, ultra-high performance sensing and achieving thorough understanding of many-particle quantum systems. Molecular spins are excellent qubit candidates because they feature long coherence times, are widely tunable through chemical synthesis and can be interfaced with other quantum platforms such as superconducting qubits. A present challenge for molecular spin qubits is their integration in quantum devices, which requires arranging them in thin films or monolayers on surfaces. However, clear proof of the survival of quantum properties of molecular qubits on surfaces has not been reported so far. Furthermore, little is known about the change in spin dynamics of molecular qubits going from the bulk to monolayers. Here, we report a versatile bottom-up method to arrange molecular qubits as functional groups of self-assembled monolayers (SAMs) on surfaces, combining molecular self-organization and click chemistry. Coherence times of up to 13 μs demonstrate that qubit properties are maintained or even enhanced in the monolayer. This article is protected by copyright. All rights reserved.

Ge two-dimensional hole gases (2DHG) formed in strained, modulation-doped quantum-wells are highly suitable for future spintronic applications due to their good electronic transport properties. For electrical spin injection into a Ge 2DHG, the ferromagnetic alloy Mn 5 Ge 3 can be used as a contact material. The Mn 5 Ge 3 layer can be grown as an interlayer by interdiffusion between an evaporated Mn layer and the Ge 2DHG. In this paper, we report on the growth of a ferromagnetic Mn 5 Ge 3 thin film directly on the strained Ge. To this end, the Si 20 Ge 80 capping layer covering the channel was selectively removed using Ar+ ion milling. We investigate the magnetic properties of Mn 5 Ge 3 grown on a Ge (111) 2DHG by superconducting quantum interference device magnetometry and compare the results to an unetched Mn 5 Ge 3 on Ge (111) reference. Furthermore, temperature-dependent Hall measurements using the Mn 5 Ge 3 contacts on the Ge (111) 2DHG confirm the electrical contact to the high mobility 2DHG. These results are an important step towards electrical spin injection into a Ge 2DHG which is a promising material for future spintronic applications.

We report on the first synthesis of a Mn based ferromagnet on SixGe(1-x-y)Sny lattice matched on Ge with Sn content up to 15 %. The ferromagnetic layers were grown using interdiffusion of evaporated Mn and epitaxially grown SixGe(1-x-y)Sny. The Si to Sn ratio of the epitaxial layer is fixed to allow lattice matched growth on Ge. The possibility to grow the ferromagnetic layer directly on a semiconductor opens up the opportunity for large scale manufacturing using a selfaligned interdiffusion process. The compound exhibits a ferromagnetic phase for all samples studied. The observed Curie temperature remains around room temperature and shows no decisive trend with increasing Sn content. The samples show an increasing coercive field and decreasing saturation magnetization with increasing Sn content. This makes Mn-SixGe(1-x-y)Sny an interesting alternative to Mn5Ge3 as a ferromagnetically harder material for spintronics applications.

The energy barrier leading to magnetic bistability in molecular clusters is determined by the magnetic anisotropy of the cluster constituents. By incorporating a highly anisotropic four‐coordinate cobalt(II) building block into a strongly coupled fully air‐ and moisture‐stable three‐spin system, it proved possible to suppress under‐barrier Raman processes leading to 350‐fold increase of magnetization relaxation time and pronounced hysteresis. Relaxation times of up to 9 hours at low temperatures were found.

Developing efficient molecular catalysts for the electrocatalytic hydrogen evolution reaction (HER) is a highly important goal in contemporary science. We report here on a bimetallic triply fused copper porphyrin complex (1) comprising two monomeric porphyrin units linked through β–β, meso–meso, β′–β′ triple covalent linkages, that exhibits remarkable enhancement of catalytic activity for the electrochemical HER in comparison to the analogous monomeric copper porphyrin complex (2). Spectroscopic characterization, in association with magnetic measurements, clearly establish the ground state structures of both the bimetallic and monometallic complexes as containing two and one copper (II) centers, respectively. The fused metalloporphyrin complex is found to undergo electrochemical reduction at a lower negative applied potential compared to the metalloporphyrin monomer, as evident from the significant anodic shift (~800mV) in the potential of the first reduction process. Electrochemical investigations in the presence of a proton source (trifluoroacetic acid) confirm that the catalytic activity of the fused metalloporphyrin occurs at a significantly lower onset potential, (overpotential decreased by ~320 mV), compared to the non-fused monomer. Controlled potential electrolysis combined with the kinetic analysis of catalysts 1 and 2 confirm the production of hydrogen, with 96% and 71% faradaic efficiencies and turnover numbers of 102 and 18, respectively. Kinetic investigations further reveal an observed rate constant of around 107 (s-1), implying high efficiency of the bimetallic catalyst towards hydrogen evolution reaction. Mechanistic insights are presented by using a combination of UV-vis-NIR and EPR spectroscopy and electrochemistry. Our results thus firmly establish the triply fused porphyrin ligands as candidates for generating highly efficient molecular electrocatalysts in combination with transition metal centers.

Nanoscale magnetic systems play a decisive role in areas ranging from biology to spintronics. Although, in principle, THz electron paramagnetic resonance (EPR) provides high-resolution access to their properties, lack of sensitivity has precluded realizing this potential. To resolve this issue, the principle of plasmonic enhancement of electromagnetic fields that is used in electric dipole spectroscopies with great success is exploited, and a new type of resonators for the enhancement of THz magnetic fields in a microscopic volume is proposed. A resonator composed of an array of diabolo antennas with a back-reflecting mirror is designed and fabricated. Simulations and THz EPR measurements demonstrate a 30-fold signal increase for thin film samples. This enhancement factor increases to a theoretical value of 7500 for samples confined to the active region of the antennas. These findings open the door to the elucidation of fundamental processes in nanoscale samples, including junctions in spintronic devices or biological membranes.

Whilst quantum computing has recently taken great leaps ahead, the development of quantum memories has decidedly lagged behind. Quantum memories are essential devices in the quantum technology palette and are needed for intermediate storage of quantum bit states and as quantum repeaters in long-distance quantum communication. Current quantum memories operate at cryogenic, mostly sub-Kelvin temperatures and require extensive and costly peripheral hardware. It is demonstrated that ensembles of weakly coupled molecular spins show long coherence times and can be used to store microwave pulses of arbitrary phase. These studies exploit strong coupling of the spin ensemble to special 3D microwave resonators. Most importantly, these systems operate at room temperature.

The first isolation and structural characterization of an f-element dinitrogen complex was reported in 1988, but an f-element complex with the first heavier group 15 homologue diphosphorus has to date remained unknown. Here, we report the synthesis of a side-on bound diphosphorus complex of uranium(IV) using a 7λ3-(dimethylamino)phosphadibenzonorbornadiene-mediated P atom transfer approach. Experimental and computational characterization reveals that the diphosphorus ligand is activated to its dianionic (P2)2- form and that in-plane U-P π-bonding dominates the bonding of the U(μ-η2:η2-P2)U unit, which is supplemented by a weak U-P interaction of δ symmetry. A preliminary reactivity study demonstrates conversion of this diphosphorus complex to unprecedented uranium cyclo-P3 complexes, suggesting in situ generation of transient, reactive phosphido species.

Mechanically chelating ligands have untapped potential for the engineering of metal ion properties by providing reliable control of the number, nature and geometry of donor atoms, akin to how a protein cavity controls the properties of bound metal ions. Here we demonstrate this principle in the context of CoII-based single-ion magnets. Using multi-frequency EPR, susceptibility and magnetization measurements we found that these complexes show some of the highest zero field splittings reported for five-coordinate CoII complexes to date. The predictable coordination behavior of the interlocked ligands allowed the magnetic properties of their CoII complexes to be evaluated computationally a priori and our combined experimental and theoretical approach enabled us to rationalize the observed trends. The predictable magnetic behavior of the rotaxane CoII complexes demonstrates that interlocked ligands offer a new strategy to design metal complexes with interesting functionality.

Mechanically chelating ligands have untapped potential for the engineering of metal ion properties. Here we demonstrate this principle in the context of CoII‐based single‐ion magnets. Using multi‐frequency EPR, susceptibility and magnetization measurements we found that these complexes show some of the highest zero field splittings reported for five‐coordinate CoII complexes to date. The predictable coordination behaviour of the interlocked ligands allowed the magnetic properties of their CoII complexes to be evaluated computationally a priori and our combined experimental and theoretical approach enabled us to rationalize the observed trends. The predictable magnetic behaviour of the rotaxane CoII complexes demonstrates that interlocked ligands offer a new strategy to design metal complexes with interesting functionality., Mechanically interlocked ligands enable predictable metal ion coordination, offering a new strategy to engineer their properties. A series of field‐induced CoII single‐ion magnets illustrates this principle. The predictable coordination behaviour of the rotaxane enables remarkably accurate calculation of their zero‐field splittings, which are in agreement with experimental observations, and can be rationalized in terms of metal–ligand bonding.

Here we explore the electronic structure of the diiron complex [(dppf)Fe(CO)

We report the synthesis of the lanthanide-(bis)boryloxide complex [Dy{OB(NArCH)2}2(THF)4][BPh4] (2Dy, Ar = 2,6-Pri2C6H3), with idealised D4h@Dy(iii) point-group symmetry. Complex 2Dy exhibits single-molecule magnetism (SMM), with one of the highest energy barriers (Ueff = 1565(298) K) of any six-coordinate lanthanide-SMM. Complex 2Dy validates electrostatic model predictions, informing the future design of lanthanide-SMMs.

Low-temperature magnetoresistance measurements of n- and p-doped germanium-tin (Ge

This work reports on the carrier mobilities in heavily doped, pseudomorphically grown Ge1-xSnx-epilayers with Sn-concentrations up to 9.2%. For this purpose, Ge1-xSnx-alloys were grown on a relaxed Ge virtual substrate on top of a commercial Si (100) wafer using molecular beam epitaxy. The crystal structure and quality of the Ge1-xSnx-epilayers were analyzed by high-resolution X-ray diffraction. In order to extract the carrier mobilities in Ge1-xSnx, low temperature hall measurements were carried out, using a Van-der-Pauw-geometry. It is shown that with increasing Sn-concentration we find a decrease in carrier mobility, which corresponds to an increasing sheetresistance.