Arene-, Chlorido-, and Imido-Uranium Bis- and Tris(boryloxide) Complexes

We introduce the boryloxide ligand {(HCNDipp)2BO}- (NBODipp, Dipp = 2,6-di-isopropylphenyl) to actinide chemistry. Protonolysis of [U{N(SiMe3)2}3] with 3 equiv of NBODippH produced the uranium(III) tris(boryloxide) complex [U(NBODipp)3] (1). In contrast, treatment of UCl4 with 3 equiv of NBODippK in THF at room temperature or reflux conditions produced only [U(NBODipp)2(Cl)2(THF)2] (2) with 1 equiv of NBODippK remaining unreacted. However, refluxing the mixture of 2 and unreacted NBODippK in toluene instead of THF afforded the target complex [U(NBODipp)3(Cl)(THF)] (3). Two-electron oxidation of 1 with AdN3 (Ad = 1-adamantyl) afforded the uranium(V)-imido complex [U(NBODipp)3(NAd)] (4). The solid-state structure of 1 reveals a uranium-arene bonding motif, and structural, spectroscopic, and DFT calculations all suggest modest uranium-arene δ-back-bonding with approximately equal donation into the arene π4 and π5 δ-symmetry π* molecular orbitals. Complex 4 exhibits a short uranium(V)-imido distance, and computational modeling enabled its electronic structure to be compared to related uranium-imido and uranium-oxo complexes, revealing a substantial 5f-orbital crystal field splitting and extensive mixing of 5f |ml,ms⟩ states and mj projections. Complexes 1-4 have been variously characterized by single-crystal X-ray diffraction, 1H NMR, IR, UV/vis/NIR, and EPR spectroscopies, SQUID magnetometry, elemental analysis, and CONDON, F-shell, DFT, NLMO, and QTAIM crystal field and quantum chemical calculations.

Metal-carbon bonding in early lanthanide substituted cyclopentadienyl complexes probed by pulsed EPR spectroscopy

We examine lanthanide (Ln)-ligand bonding in a family of early Ln3+ complexes [Ln(Cptt)3] (1-Ln, Ln = La, Ce, Nd, Sm; Cptt = C5H3tBu2-1,3) by pulsed electron paramagnetic resonance (EPR) methods, and provide the first characterization of 1-La and 1-Nd by single crystal XRD, multinuclear NMR, IR and UV/Vis/NIR spectroscopy. We measure electron spin T1 and Tm relaxation times of 12 and 0.2 μs (1-Nd), 89 and 1 μs (1-Ce) and 150 and 1.7 μs (1-Sm), respectively, at 5 K: the T1 relaxation of 1-Nd is more than 102 times faster than its valence isoelectronic uranium analogue. 13C and 1H hyperfine sublevel correlation (HYSCORE) spectroscopy reveals that the extent of covalency is negligible in these Ln compounds, with much smaller hyperfine interactions than observed for equivalent actinide (Th and U) complexes. This is corroborated by ab initio calculations, confirming the predominant electrostatic nature of the metal-ligand bonding in these complexes.

Analysis of a Cu-Doped Metal-Organic Framework, MFM-520(Zn1-x Cux ), for NO2 Adsorption

MFM-520(Zn) confines dimers of NO2 with a high adsorption of 4.52 mmol g-1 at 1 bar at 298 K. The synthesis and the incommensurate structure of Cu-doped MFM-520(Zn) are reported. The introduction of paramagnetic Cu2+ sites allows investigation of the electronic and geometric structure of metal site by in situ electron paramagnetic resonance (EPR) spectroscopy upon adsorption of NO2 . By combining continuous wave and electron-nuclear double resonance spectroscopy, an unusual reverse Berry distorted coordination geometry of the Cu2+ centers is observed. Interestingly, Cu-doped MFM-520(Zn0.95 Cu0.05 ) shows enhanced adsorption of NO2 of 5.02 mmol g-1 at 1 bar at 298 K. Whereas MFM-520(Zn) confines adsorbed NO2 as N2 O4 , the presence of monomeric NO2 at low temperature suggests that doping with Cu2+ centers into the framework plays an important role in tuning the dimerization of NO2 molecules in the pore via the formation of specific host-guest interactions.

Photocatalytic Dehalogenative Deuteration of Halides over a Robust Metal-Organic Framework

Deuterium labelling of organic compounds is an important process in chemistry. We report the first example of photocatalytic dehalogenative deuteration of both arylhalides and alkylhalides (40 substrates) over a metal-organic framework, MFM-300(Cr), using CD3 CN as the deuterium source at room temperature. MFM-300(Cr) catalyses high deuterium incorporation and shows excellent tolerance to various functional groups. Synchrotron X-ray powder diffraction reveals the activation of halogenated substrates via confined binding within MFM-300(Cr). In situ electron paramagnetic resonance spectroscopy confirms the formation of carbon-based radicals as intermediates and reveals the reaction pathway. This protocol removes the use of precious-metal catalysts from state-of-the-art processes based upon direct hydrogen isotope exchange and shows high photocatalytic stability, thus enabling multiple catalytic cycles.

Direct Conversion of Methane to Ethylene and Acetylene over an Iron-Based Metal-Organic Framework

Conversion of methane (CH4) to ethylene (C2H4) and/or acetylene (C2H2) enables routes to a wide range of products directly from natural gas. However, high reaction temperatures and pressures are often required to activate and convert CH4 controllably, and separating C2+ products from unreacted CH4 can be challenging. Here, we report the direct conversion of CH4 to C2H4 and C2H2 driven by non-thermal plasma under ambient (25 °C and 1 atm) and flow conditions over a metal-organic framework material, MFM-300(Fe). The selectivity for the formation of C2H4 and C2H2 reaches 96% with a high time yield of 334 μmol gcat-1 h-1. At a conversion of 10%, the selectivity to C2+ hydrocarbons and time yield exceed 98% and 2056 μmol gcat-1 h-1, respectively, representing a new benchmark for conversion of CH4. In situ neutron powder diffraction, inelastic neutron scattering and solid-state nuclear magnetic resonance, electron paramagnetic resonance (EPR), and diffuse reflectance infrared Fourier transform spectroscopies, coupled with modeling studies, reveal the crucial role of Fe-O(H)-Fe sites in activating CH4 and stabilizing reaction intermediates via the formation of an Fe-O(CH3)-Fe adduct. In addition, a cascade fixed-bed system has been developed to achieve online separation of C2H4 and C2H2 from unreacted CH4 for direct use. Integrating the processes of CH4 activation, conversion, and product separation within one system opens a new avenue for natural gas utility, bridging the gap between fundamental studies and practical applications in this area.

Molecular One- and Two-Qubit Systems with Very Long Coherence Times

General-purpose quantum computation and quantum simulation require multi-qubit architectures with precisely defined, robust interqubit interactions, coupled with local addressability. This is an unsolved challenge, primarily due to scalability issues. These issues often derive from poor control over interqubit interactions. Molecular systems are promising materials for the realization of large-scale quantum architectures, due to their high degree of positionability and the possibility to precisely tailor interqubit interactions. The simplest quantum architecture is the two-qubit system, with which quantum gate operations can be implemented. To be viable, a two-qubit system must possess long coherence times, the interqubit interaction must be well defined and the two qubits must also be addressable individually within the same quantum manipulation sequence. Here results are presented on the investigation of the spin dynamics of chlorinated triphenylmethyl organic radicals, in particular the perchlorotriphenylmethyl (PTM) radical, a mono-functionalized PTM, and a biradical PTM dimer. Extraordinarily long ensemble coherence times up to 148 µs are found at all temperatures below 100 K. Two-qubit and, importantly, individual qubit addressability in the biradical system are demonstrated. These results underline the potential of molecular materials for the development of quantum architectures.

Modulation of Uptake and Reactivity of Nitrogen Dioxide in Metal-Organic Framework Materials

We report the modulation of reactivity of nitrogen dioxide (NO2 ) in a charged metal-organic framework (MOF) material, MFM-305-CH3 in which unbound N-centres are methylated and the cationic charge counter-balanced by Cl- ions in the pores. Uptake of NO2 into MFM-305-CH3 leads to reaction between NO2 and Cl- to give nitrosyl chloride (NOCl) and NO3 - anions. A high dynamic uptake of 6.58 mmol g-1 at 298 K is observed for MFM-305-CH3 as measured using a flow of 500 ppm NO2 in He. In contrast, the analogous neutral material, MFM-305, shows a much lower uptake of 2.38 mmol g-1 . The binding domains and reactivity of adsorbed NO2 molecules within MFM-305-CH3 and MFM-305 have been probed using in situ synchrotron X-ray diffraction, inelastic neutron scattering and by electron paramagnetic resonance, high-field solid-state nuclear magnetic resonance and UV/Vis spectroscopies. The design of charged porous sorbents provides a new platform to control the reactivity of corrosive air pollutants.

Mechanistic Study of Glucose Photoreforming over TiO2-Based Catalysts for H2 Production

Glucose is a key intermediate in cellulose photoreforming for H₂ production. This work presents a mechanistic investigation of glucose photoreforming over TiO₂ and Pt/m-TiO₂ catalysts. Analysis of the intermediates formed in the process confirmed the α-scission mechanism of glucose oxidation forming arabinose (C_n-1 sugar) and formic acid in the initial oxidation step. The selectivity to sugar products and formic acid differed over Pt/TiO₂ and TiO₂, with Pt/TiO₂ showing the lower selectivity to formic acid due to enhanced adsorption/conversion of formic acid over Pt/TiO₂. In situ ATR-IR spectroscopy of glucose photoreforming showed the presence of molecular formic acid and formate on the surface of both catalysts at low glucose conversions, suggesting that formic acid oxidation could dominate surface reactions in glucose photoreforming. Further in situ ATR-IR of formic acid photoreforming showed Pt-TiO₂ interfacial sites to be key for formic acid oxidation as TiO₂ was unable to convert adsorbed formic acid/formate. Isotopic studies of the photoreforming of formic acid in D₂O (with different concentrations) showed that the source of the protons (to form H₂ at Pt sites) was determined by the relative surface coverage of adsorbed water and formic acid.

Control of evolution of porous copper-based metal-organic materials for electroreduction of CO2 to multi-carbon products

Electrochemcial reduction of CO₂ to multi-carbon (C₂₊) products is an important but challenging task. Here, we report the control of structural evolution of two porous Cu(ii)-based materials (HKUST-1 and CuMOP, MOP = metal-organic polyhedra) under electrochemical conditions by adsorption of 7,7,8,8-tetracyanoquinodimethane (TNCQ) as an additional electron acceptor. The formation of Cu(i) and Cu(0) species during the structural evolution has been confirmed and analysed by powder X-ray diffraction, and by EPR, Raman, XPS, IR and UV-vis spectroscopies. An electrode decorated with evolved TCNQ@CuMOP shows a selectivity of 68% for C₂₊ products with a total current density of 268 mA cm^-2 and faradaic efficiency of 37% for electrochemcial reduction of CO₂ in 1 M aqueous KOH electrolyte at -2.27 V vs. RHE (reversible hydrogen electrode). In situ electron paramagnetic resonance spectroscopy reveals the presence of carbon-centred radicals as key reaction intermediates. This study demonstrates the positive impact of additional electron acceptors on the structural evolution of Cu(ii)-based porous materials to promote the electroreduction of CO₂ to C₂₊ products.

A new strategy for improving cytotoxicity of a copper complex toward metastatic melanoma cells unveiled by EPR spectroscopy†

A novel strategy of improving cytotoxicity against metastatic melanoma cells using an oxindolimine copper(ii) complex immobilized and dimerized on a modified Polyhedral Oligomeric Silsesquioxane (POSS) matrix was developed, as revealed by electron paramagnetic resonance (EPR) spectroscopy. An assured correlation between continuous-wave (CW) and pulsed EPR spectroscopies provided a complete characterization of the actual active species, its coordination environment, as well as the efficiency/selectivity of the bioconjugate materials.

An oxindolimine-copper(ii) complex with antitumor properties was immobilized in a silica matrix, and verified to be more active and selective due the formation of a dinuclear species, unveiled by continuous wave and pulsed EPR spectroscopy.

Bimetallic Aluminum- and Niobium-Doped MCM-41 for Efficient Conversion of Biomass-Derived 2-Methyltetrahydrofuran to Pentadienes

The production of conjugated C4-C5 dienes from biomass can enable the sustainable synthesis of many important polymers and liquid fuels. Here, we report the first example of bimetallic (Nb, Al)-atomically doped mesoporous silica, denoted as AlNb-MCM-41, which affords quantitative conversion of 2-methyltetrahydrofuran (2-MTHF) to pentadienes with a high selectivity of 91 %. The incorporation of Al^III and Nb^V sites into the framework of AlNb-MCM-41 has effectively tuned the nature and distribution of Lewis and Brønsted acid sites within the structure. Operando X-ray absorption, diffuse reflectance infrared and solid-state NMR spectroscopy collectively reveal the molecular mechanism of the conversion of adsorbed 2-MTHF over AlNb-MCM-41. Specifically, the atomically-dispersed Nb^V sites play an important role in binding 2-MTHF to drive the conversion. Overall, this study highlights the potential of hetero-atomic mesoporous solids for the manufacture of renewable materials.

Bimetallic Aluminum- and Niobium-Doped MCM-41 for Efficient Conversion of Biomass-Derived 2-Methyltetrahydrofuran to Pentadienes

The production of conjugated C4-C5 dienes from biomass can enable the sustainable synthesis of many important polymers and liquid fuels. Here, we report the first example of bimetallic (Nb, Al)-atomically doped mesoporous silica, denoted as AlNb-MCM-41, which affords quantitative conversion of 2-methyltetrahydrofuran (2-MTHF) to pentadienes with a high selectivity of 91 %. The incorporation of AlIII and NbV sites into the framework of AlNb-MCM-41 has effectively tuned the nature and distribution of Lewis and Brønsted acid sites within the structure. Operando X-ray absorption, diffuse reflectance infrared and solid-state NMR spectroscopy collectively reveal the molecular mechanism of the conversion of adsorbed 2-MTHF over AlNb-MCM-41. Specifically, the atomically-dispersed NbV sites play an important role in binding 2-MTHF to drive the conversion. Overall, this study highlights the potential of hetero-atomic mesoporous solids for the manufacture of renewable materials.

Synthesis of Nitro Compounds from Nitrogen Dioxide Captured in a Metal-Organic Framework

Increasing levels of air pollution are driving the need for the development of new processes that take "waste-to-chemicals". Herein, we report the capture and conversion under ambient conditions of a major air pollutant, NO₂, using a robust metal-organic framework (MOF) material, Zr-bptc (H₄bptc = 3,3',5,5'-biphenyltetracarboxylic acid), comprising {Zr₆(μ₃-O)₄(μ₃-OH)₄(COO)₁₂} clusters linked by 4-connected bptc^4- ligands in an ftw topology. At 298 K, Zr-bptc shows exceptional stability and adsorption of NO₂ at both low (4.9 mmol g^-1 at 10 mbar) and high pressures (13.8 mmol g^-1 at 1.0 bar), as measured by isotherm experiments. Dynamic breakthrough experiments have confirmed the selective retention of NO₂ by Zr-bptc at low concentrations under both dry and wet conditions. The immobilized NO₂ can be readily transformed into valuable nitro compounds relevant to construction, agrochemical, and pharmaceutical industries. In situ crystallographic and spectroscopic studies reveal strong binding interactions of NO₂ to the {Zr₆(μ₃-O)₄(μ₃-OH)₄(COO)₁₂} cluster node. This study paves a circular pathway to enable the integration of nitrogen-based air pollutants into the production of fine chemicals.

Evolution of bismuth-based metal-organic frameworks for efficient electroreduction of CO2

Understanding the structural and chemical changes that reactive metal-organic frameworks (MOFs) undergo is crucial for the development of new efficient catalysts for electrochemical reduction of CO₂. Here, we describe three Bi(iii) materials, MFM-220, MFM-221 and MFM-222, which are constructed from the same ligand (biphenyl-3,3',5,5'-tetracarboxylic acid) but which show distinct porosity with solvent-accessible voids of 49.6%, 33.6% and 0%, respectively. We report the first study of the impact of porosity of MOFs on their evolution as electrocatalysts. A Faradaic efficiency of 90.4% at -1.1 V vs. RHE (reversible hydrogen electrode) is observed for formate production over an electrode decorated with MFM-220-p, formed from MFM-220 on application of an external potential in the presence of 0.1 M KHCO₃ electrolyte. In situ electron paramagnetic resonance spectroscopy confirms the presence of ·COOH radicals as a reaction intermediate, with an observed stable and consistent Faradaic efficiency and current density for production of formate by electrolysis over 5 h. This study emphasises the significant role of porosity of MOFs as they react and evolve during electroreduction of CO₂ to generate value-added chemicals.

Direct photo-oxidation of methane to methanol over a mono-iron hydroxyl site

Natural gas, consisting mainly of methane (CH₄), has a relatively low energy density at ambient conditions (~36 kJ l^-1). Partial oxidation of CH₄ to methanol (CH₃OH) lifts the energy density to ~17 MJ l^-1 and drives the production of numerous chemicals. In nature, this is achieved by methane monooxygenase with di-iron sites, which is extremely challenging to mimic in artificial systems due to the high dissociation energy of the C-H bond in CH₄ (439 kJ mol^-1) and facile over-oxidation of CH₃OH to CO and CO₂. Here we report the direct photo-oxidation of CH₄ over mono-iron hydroxyl sites immobilized within a metal-organic framework, PMOF-RuFe(OH). Under ambient and flow conditions in the presence of H₂O and O₂, CH₄ is converted to CH₃OH with 100% selectivity and a time yield of 8.81 ± 0.34 mmol g_cat^-1 h^-1 (versus 5.05 mmol g_cat^-1 h^-1 for methane monooxygenase). By using operando spectroscopic and modelling techniques, we find that confined mono-iron hydroxyl sites bind CH₄ by forming an [Fe-OH···CH₄] intermediate, thus lowering the barrier for C-H bond activation. The confinement of mono-iron hydroxyl sites in a porous matrix demonstrates a strategy for C-H bond activation in CH₄ to drive the direct photosynthesis of CH₃OH.

Direct Observation of Ammonia Storage in UiO-66 Incorporating Cu(II) Binding Sites

The presence of active sites in metal-organic framework (MOF) materials can control and affect their performance significantly in adsorption and catalysis. However, revealing the interactions between the substrate and active sites in MOFs at atomic precision remains a challenging task. Here, we report the direct observation of binding of NH3 in a series of UiO-66 materials containing atomically dispersed defects and open Cu(I) and Cu(II) sites. While all MOFs in this series exhibit similar surface areas (1111-1135 m2 g-1), decoration of the -OH site in UiO-66-defect with Cu(II) results in a 43% enhancement of the isothermal uptake of NH3 at 273 K and 1.0 bar from 11.8 in UiO-66-defect to 16.9 mmol g-1 in UiO-66-CuII. A 100% enhancement of dynamic adsorption of NH3 at a concentration level of 630 ppm from 2.07 mmol g-1 in UiO-66-defect to 4.15 mmol g-1 in UiO-66-CuII at 298 K is observed. In situ neutron powder diffraction, inelastic neutron scattering, and electron paramagnetic resonance, solid-state nuclear magnetic resonance, and infrared spectroscopies, coupled with modeling reveal that the enhanced NH3 uptake in UiO-66-CuII originates from a {Cu(II)···NH3} interaction, with a reversible change in geometry at Cu(II) from near-linear to trigonal coordination. This work represents the first example of structural elucidation of NH3 binding in MOFs containing open metal sites and will inform the design of new efficient MOF sorbents by targeted control of active sites for NH3 capture and storage.

Unparalleled selectivity and electronic structure of heterometallic [LnLn'Ln] molecules as 3-qubit quantum gates

Heterometallic lanthanide [LnLn'] coordination complexes that are accessible thermodynamically are very scarce because the metals of this series have very similar chemical behaviour. Trinuclear systems of this category have not been reported. A coordination chemistry scaffold has been shown to produce molecules of type [LnLn'Ln] of high purity, i.e. exhibiting high metal distribution ability, based on their differences in ionic radius. Through a detailed analysis of density functional theory (DFT) based calculations, we discern the energy contributions that lead to the unparalleled chemical selectivity of this molecular system. Some of the previously reported examples are compared here with the newly prepared member of this exotic list, [Er₂Pr(LA)₂(LB)₂(py)(H₂O)₂](NO₃) (1) (H₂LA and H₂LB are two β-diketone ligands). A magnetic analysis extracted from magnetization and calorimetry determinations identifies the necessary attributes for it to act as an addressable, conditional multiqubit spin-based quantum gate. Complementary ab initio calculations confirm the feasibility of these complexes as composite quantum gates, since they present well-isolated ground states with highly anisotropic and distinct g-tensors. The electronic structure of 1 has also been analyzed by EPR. Pulsed experiments have allowed the establishment of the quantum coherence of the transitions within the relevant spin states, as well as the feasibility of a coherent control of these states via nutation experiments.

Acetylation Rather than H50Q Mutation Impacts the Kinetics of Cu(II) Binding to α-Synuclein

The front cover artwork is provided by the group of Liming Ying at Imperial College London. The image shows that N-terminal acetylation of α-synuclein shifts the binding from the N-terminus to His50 and significantly slows down the binding reaction. Read the full text of the Article at 10.1002/cphc.202100651.

Self-assembly of a trigonal bipyramidal architecture with stabilisation of iron in three spin states

Self-assembly and characterisation of a supramolecular trigonal bipyramidal iron cage containing an [Fe^III(μ₂-F)₆(Fe^II)₃]³⁺ star motif at its core is reported. The complex can be formed in a one step reaction using an heterotopic ligand that supports site-specific incorporation of iron in three distinct electronic configurations: low-spin Fe^II, high-spin Fe^II and high-spin Fe^III, with iron(II) tetrafluoroborate as the source of the bridging fluorides. Formation of a μ₂-F bridged mixed-valence Fe^II-Fe^III star is unprecedented. The peripheral high-spin Fe^II centres of the mixed-valence tetranuclear star incorporated in the iron cage are highly anisotropic and engage in F-mediated antiferromagnetic exchange with the central Fe^III ion.

Structural Investigations of α-MnS Nanocrystals and Thin Films Synthesized from Manganese(II) Xanthates by Hot Injection, Solvent-Less Thermolysis, and Doctor Blade Routes

Manganese(II) xanthate complexes of the form [Mn(S2COR)2(TMEDA)], where TMEDA = tetramethylethylenediamine and R = methyl (1), ethyl (2), n-propyl (3), n-butyl (4), n-pentyl (5), n-hexyl (6), and n-octyl (7), have been synthesized and structures elucidated using single-crystal X-ray diffraction. Complexes 1-7 were used as molecular precursors to synthesize manganese sulfide (MnS). Olelyamine-capped nanocrystals have been produced via hot injection, while the doctor blading followed by thermolysis yielded thick films. Free-standing polycrystalline powders of MnS are produced by direct thermolysis of precursor powders. All thermolysis techniques produced cubic MnS, as confirmed by powder X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Raman spectroscopy. Magnetic measurements reveal that the α-MnS nanocrystals exhibit ferromagnetic behavior with a large coercive field strength (e.g., 0.723 kOe for 6.8 nm nanocrystals).

Substituent effects on through-space intervalence charge transfer in cofacial metal-organic frameworks

Electroactive metal-organic frameworks (MOFs) are an attractive class of materials owing to their multifunctional 3-dimensional structures, the properties of which can be modulated by changing the redox states of the components. In order to realise both fundamental and applied goals for these materials, a deeper understanding of the structure-function relationships that govern the charge transfer mechanisms is required. Chemical or electrochemical reduction of the framework [Zn(BPPFTzTz)(tdc)]·2DMF, hereafter denoted ZnFTzTz (where BPPFTzTz = 2,5-bis(3-fluoro-4-(pyridin-4-yl)phenyl)thiazolo[5,4-d]thiazole), generates mixed-valence states with optical signatures indicative of through-space intervalence charge transfer (IVCT) between the cofacially stacked ligands. Fluorination of the TzTz ligands influences the IVCT band parameters relative to the unsubstituted parent system, as revealed through Marcus-Hush theory analysis and single crystal UV-Vis spectroscopy. Using a combined experimental, theoretical and density functional theory (DFT) analysis, important insights into the effects of structural modifications, such as ligand substitution, on the degree of electronic coupling and rate of electron transfer have been obtained.

Acetylation Rather than H50Q Mutation Impacts the Kinetics of Cu(II) Binding to α-Synuclein

The interaction between α‐synuclein (αSyn) and Cu²⁺ has been suggested to be closely linked to brain copper homeostasis. Disruption of copper levels could induce misfolding and aggregation of αSyn, and thus contribute to the progression of Parkinson's disease (PD). Understanding the molecular mechanism of αSyn‐Cu²⁺ interaction is important and controversies in Cu²⁺ coordination geometry with αSyn still exists. Herein, we find that the pathological H50Q mutation has no impact on the kinetics of Cu²⁺ binding to the high‐affinity site of wild type αSyn (WT‐αSyn), indicating the non‐involvement of His50 in high‐affinity Cu²⁺ binding to WT‐αSyn. In contrast, the physiological N‐terminally acetylated αSyn (NAc‐αSyn) displays several orders of magnitude weaker Cu²⁺ binding affinity than WT‐αSyn. Cu²⁺ coordination mode to NAc‐αSyn has also been proposed based on EPR spectrum. In addition, we find that Cu²⁺ coordinated WT‐αSyn is reduction‐active in the presence of GSH, but essentially inactive towards ascorbate. Our work provides new insights into αSyn‐Cu²⁺ interaction, which may help understand the multifaceted normal functions of αSyn as well as pathological consequences of αSyn aggregation.

Ultra-thin g-C3N4/MFM-300(Fe) heterojunctions for photocatalytic aerobic oxidation of benzylic carbon centers

In situ growth of the metal-organic framework material MFM-300(Fe) on an ultra-thin sheet of graphitic carbon nitride (g-C3N4) has been achieved via exfoliation of bulk carbon nitride using supercritical CO2. The resultant hybrid structure, CNNS/MFM-300(Fe), comprising carbon nitride nanosheets (CNNS) and MFM-300(Fe), shows excellent performance towards photocatalytic aerobic oxidation of benzylic C-H groups at room temperature under visible light. The catalytic activity is significantly improved compared to the parent g-C3N4, MFM-300(Fe) or physical mixtures of both. This facile strategy for preparing heterojunction photocatalysts demonstrates a green pathway for the efficient and economic oxidation of benzylic carbons to produce fine chemicals.

Atomically Dispersed Copper Sites in a Metal-Organic Framework for Reduction of Nitrogen Dioxide

Metal–organic framework (MOF) materials provide an excellent platform to fabricate single-atom catalysts due to their structural diversity, intrinsic porosity, and designable functionality. However, the unambiguous identification of atomically dispersed metal sites and the elucidation of their role in catalysis are challenging due to limited methods of characterization and lack of direct structural information. Here, we report a comprehensive investigation of the structure and the role of atomically dispersed copper sites in UiO-66 for the catalytic reduction of NO₂ at ambient temperature. The atomic dispersion of copper sites on UiO-66 is confirmed by high-angle annular dark-field scanning transmission electron microscopy, electron paramagnetic resonance spectroscopy, and inelastic neutron scattering, and their location is identified by neutron powder diffraction and solid-state nuclear magnetic resonance spectroscopy. The Cu/UiO-66 catalyst exhibits superior catalytic performance for the reduction of NO₂ at 25 °C without the use of reductants. A selectivity of 88% for the formation of N₂ at a 97% conversion of NO₂ with a lifetime of >50 h and an unprecedented turnover frequency of 6.1 h^–1 is achieved under nonthermal plasma activation. In situ and operando infrared, solid-state NMR, and EPR spectroscopy reveal the critical role of copper sites in the adsorption and activation of NO₂ molecules, with the formation of {Cu(I)···NO} and {Cu···NO₂} adducts promoting the conversion of NO₂ to N₂. This study will inspire the further design and study of new efficient single-atom catalysts for NO₂ abatement via detailed unravelling of their role in catalysis.

Rotaxane CoII Complexes as Field-Induced Single-Ion Magnets

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.

The Origin of Catalytic Benzylic C-H Oxidation over a Redox-Active Metal-Organic Framework

Selective oxidation of benzylic C-H compounds to ketones is important for the production of a wide range of fine chemicals, and is often achieved using toxic or precious metal catalysts. Herein, we report the efficient oxidation of benzylic C-H groups in a broad range of substrates under mild conditions over a robust metal-organic framework material, MFM-170, incorporating redox-active [Cu2 II (O2 CR)4 ] paddlewheel nodes. A comprehensive investigation employing electron paramagnetic resonance (EPR) spectroscopy and synchrotron X-ray diffraction has identified the critical role of the paddlewheel moiety in activating the oxidant t BuOOH (tert-butyl hydroperoxide) via partial reduction to [CuII CuI (O2 CR)4 ] species.

29Si NMR Spectroscopy as a Probe of s- and f-Block Metal(II)-Silanide Bond Covalency

We report the use of ²⁹Si NMR spectroscopy and DFT calculations combined to benchmark the covalency in the chemical bonding of s- and f-block metal-silicon bonds. The complexes [M(Si^tBu₃)₂(THF)₂(THF)_x] (1-M: M = Mg, Ca, Yb, x = 0; M = Sm, Eu, x = 1) and [M(Si^tBu₂Me)₂(THF)₂(THF)_x] (2-M: M = Mg, x = 0; M = Ca, Sm, Eu, Yb, x = 1) have been synthesized and characterized. DFT calculations and ²⁹Si NMR spectroscopic analyses of 1-M and 2-M (M = Mg, Ca, Yb, No, the last in silico due to experimental unavailability) together with known {Si(SiMe₃)₃}^--, {Si(SiMe₂H)₃}^--, and {SiPh₃}^--substituted analogues provide 20 representative examples spanning five silanide ligands and four divalent metals, revealing that the metal-bound ²⁹Si NMR isotropic chemical shifts, δ_Si, span a wide (∼225 ppm) range when the metal is kept constant, and direct, linear correlations are found between δ_Si and computed delocalization indices and quantum chemical topology interatomic exchange-correlation energies that are measures of bond covalency. The calculations reveal dominant s- and d-orbital character in the bonding of these silanide complexes, with no significant f-orbital contributions. The δ_Si is determined, relatively, by paramagnetic shielding for a given metal when the silanide is varied but by the spin-orbit shielding term when the metal is varied for a given ligand. The calculations suggest a covalency ordering of No(II) > Yb(II) > Ca(II) ≈ Mg(II), challenging the traditional view of late actinide chemical bonding being equivalent to that of the late lanthanides.

Electronic Structure of a Diiron Complex: A Multitechnique Experimental Study of [(dppf)Fe(CO) 3]+/0

Here we explore the electronic structure of the diiron complex [(dppf)Fe(CO)₃]^0/+ [1^0/+; 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 Mössbauer 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⁺.

High Ammonia Adsorption in MFM-300 Materials: Dynamics and Charge Transfer in Host-Guest Binding

Ammonia (NH₃) is a promising energy resource owing to its high hydrogen density. However, its widespread application is restricted by the lack of efficient and corrosion-resistant storage materials. Here, we report high NH₃ adsorption in a series of robust metal-organic framework (MOF) materials, MFM-300(M) (M = Fe, V, Cr, In). MFM-300(M) (M = Fe, V^III, Cr) show fully reversible capacity for >20 cycles, reaching capacities of 16.1, 15.6, and 14.0 mmol g^-1, respectively, at 273 K and 1 bar. Under the same conditions, MFM-300(V^IV) exhibits the highest uptake among this series of MOFs of 17.3 mmol g^-1. In situ neutron powder diffraction, single-crystal X-ray diffraction, and electron paramagnetic resonance spectroscopy confirm that the redox-active V center enables host-guest charge transfer, with V^IV being reduced to V^III and NH₃ being oxidized to hydrazine (N₂H₄). A combination of in situ inelastic neutron scattering and DFT modeling has revealed the binding dynamics of adsorbed NH₃ within these MOFs to afford a comprehensive insight into the application of MOF materials to the adsorption and conversion of NH₃.

Control of zeolite microenvironment for propene synthesis from methanol

Optimising the balance between propene selectivity, propene/ethene ratio and catalytic stability and unravelling the explicit mechanism on formation of the first carbon–carbon bond are challenging goals of great importance in state-of-the-art methanol-to-olefin (MTO) research. We report a strategy to finely control the nature of active sites within the pores of commercial MFI-zeolites by incorporating tantalum(V) and aluminium(III) centres into the framework. The resultant TaAlS-1 zeolite exhibits simultaneously remarkable propene selectivity (51%), propene/ethene ratio (8.3) and catalytic stability (>50 h) at full methanol conversion. In situ synchrotron X-ray powder diffraction, X-ray absorption spectroscopy and inelastic neutron scattering coupled with DFT calculations reveal that the first carbon–carbon bond is formed between an activated methanol molecule and a trimethyloxonium intermediate. The unprecedented cooperativity between tantalum(V) and Brønsted acid sites creates an optimal microenvironment for efficient conversion of methanol and thus greatly promotes the application of zeolites in the sustainable manufacturing of light olefins.

Lower olefins are mainly produced from fossil resources and the methanol-to-olefins process offers a new sustainable pathway. Here, the authors show a new zeolite containing tantalum and aluminium centres which shows simultaneously high propene selectivity, catalytic activity, and stability for the synthesis of propene.

Heterometallic 3d-4f Complexes as Air-Stable Molecular Precursors in Low Temperature Syntheses of Stoichiometric Rare-Earth Orthoferrite Powders

Four 3d-4f hetero-polymetallic complexes [Fe₂Ln₂((OCH₂)₃CR)₂(O₂C^tBu)₆(H₂O)₄] (where Ln = La (1 and 2) and Gd (3 and 4); and R = Me (1 and 3) and Et (2 and 4)) are synthesized and analyzed using elemental analysis, Fourier transform infrared spectroscopy, thermogravimetric analysis, and SQUID magnetometry. Crystal structures are obtained for both methyl derivatives and show that the complexes are isostructural and adopt a defective dicubane topology. The four heavy metals are connected with two alkoxide bridges. These four precursors are used as single-source precursors to prepare rare-earth orthoferrite pervoskites of the form LnFeO₃. Thermal decomposition in a ceramic boat in a tube furnace gives orthorhombic LnFeO₃ powders using optimized temperatures and decomposition times: LaFeO₃ formed at 650 °C over 30 min, whereas GdFeO₃ formed at 750 °C over 18 h. These materials are structurally characterized using powder X-ray diffraction, Raman spectroscopy, scanning electron microscopy, energy-dispersive X-ray map spectroscopy, and SQUID magnetometry. EDX spectroscopy mapping reveals a homogeneous spatial distribution of elements for all four materials consistent with LnFeO₃. Magnetic measurements on complexes 1-4 confirm the presence of weak antiferromagnetic coupling between the central Fe(III) ions of the clusters and negligible ferromagnetic interaction with peripheral Gd(III) ions in 3 and 4. Zero-field-cooled and field-cooled measurements of magnetization of LaFeO₃ and GdFeO₃ in the solid-state suggest that both materials are ferromagnetic, and both materials show open magnetic hysteresis loops at 5 and 300 K, with M_sat higher than previously reported for these nanomaterials. We conclude that this is a new and facile low temperature route to these important magnetic materials that is potentially universal, limited only by what metals can be programmed into the precursor complexes.

Electro-reduction of carbon dioxide at low over-potential at a metal-organic framework decorated cathode

Electrochemical reduction of carbon dioxide is a clean and highly attractive strategy for the production of organic products. However, this is hindered severely by the high negative potential required to activate carbon dioxide. Here, we report the preparation of a copper-electrode onto which the porous metal–organic framework [Cu₂(L)] [H₄L = 4,4′,4″,4′′′-(1,4-phenylenebis(pyridine-4,2,6-triyl))tetrabenzoic acid] can be deposited by electro-synthesis templated by an ionic liquid. This decorated electrode shows a remarkable onset potential for reduction of carbon dioxide to formic acid at −1.45 V vs. Ag/Ag⁺, representing a low value for electro-reduction of carbon dioxide in an organic electrolyte. A current density of 65.8 mA·cm⁻² at −1.8 V vs. Ag/Ag⁺ is observed with a Faradaic efficiency to formic acid of 90.5%. Electron paramagnetic resonance spectroscopy confirms that the templated electro-synthesis affords structural defects in the metal–organic framework film comprising uncoupled Cu(II) centres homogenously distributed throughout. These active sites promote catalytic performance as confirmed by computational modelling.

Electrochemical reduction of carbon dioxide is a highly attractive strategy for the production of organic products of economic value. Here, the authors report the electrochemical reduction of carbon dioxide to formic acid over a copper-based metal–organic framework decorated electrode at low over-potential.

Quantitative Electro-Reduction of CO2 to Liquid Fuel over Electro-Synthesized Metal-Organic Frameworks

Efficient electro-reduction of CO₂ over metal-organic framework (MOF) materials is hindered by the poor contact between thermally synthesized MOF particles and the electrode surface, which leads to low Faradaic efficiency for a given product and poor electrochemical stability of the catalyst. We report a MOF-based electrode prepared via electro-synthesis of MFM-300(In) on an indium foil, and its activity for the electrochemical reduction of CO₂ is assessed. The resultant MFM-300(In)-e/In electrode shows a 1 order of magnitude improvement in conductivity compared with that for MFM-300(In)/carbon-paper electrodes. MFM-300(In)-e/In exhibits a current density of 46.1 mA cm^-2 at an applied potential of -2.15 V vs Ag/Ag⁺ for the electro-reduction of CO₂ in organic electrolyte, achieving an exceptional Faradaic efficiency of 99.1% for the formation of formic acid. The facile preparation of the MFM-300(In)-e/In electrode, coupled with its excellent electrochemical stability, provides a new pathway to develop efficient electro-catalysts for CO₂ reduction.

Adsorption of Nitrogen Dioxide in a Redox-Active Vanadium Metal-Organic Framework Material

Nitrogen dioxide (NO₂) is a toxic air pollutant, and efficient abatement technologies are important to mitigate the many associated health and environmental problems. Here, we report the reactive adsorption of NO₂ in a redox-active metal-organic framework (MOF), MFM-300(V). Adsorption of NO₂ induces the oxidation of V(III) to V(IV) centers in MFM-300(V), and this is accompanied by the reduction of adsorbed NO₂ to NO and the release of water via deprotonation of the framework hydroxyl groups, as confirmed by synchrotron X-ray diffraction and various experimental techniques. The efficient packing of {NO₂·N₂O₄}_∞ chains in the pores of MFM-300(V^IV) results in a high isothermal NO₂ uptake of 13.0 mmol g^-1 at 298 K and 1.0 bar and is retained for multiple adsorption-desorption cycles. This work will inspire the design of redox-active sorbents that exhibit reductive adsorption of NO₂ for the elimination of air pollutants.

Synthesis and characterisation of light lanthanide bis-phospholyl borohydride complexes

Organometallic lanthanide (Ln) chemistry is dominated by complexes that contain substituted cyclopentadienyl (CpR) ligands. Closely related phospholyls have received less attention, and although they have proven utility in stabilising low oxidation state Ln complexes the trivalent Ln chemistry of these ligands is limited in comparison. Herein, we synthesise two families of heteroleptic Ln3+ complexes, [Ln(Htp)2(μ-BH4)]2 (Htp = 2,5-di-tert-butylphospholyl; 1-Ln; Ln = La, Ce, Nd, Sm), and [[Ln(Htp)2(μ-BH4)2K(S)]n (2-Ln, Ln = La, Ce, S = 2 DME, n = 2; 3-Ce, Ln = Ce, S = Et2O and THF, n = ∞) via the reactions of parent [Ln(BH4)3(THF)3.5] with K(Htp), to investigate differences between Ln complexes with substituted phospholyl ligands and analogous CpR complexes. Complexes 1-3-Ln were characterised as appropriate by single crystal XRD, SQUID magnetometry, elemental analysis, multinuclear NMR, ATR-IR and UV-Vis-NIR spectroscopy. Ab initio calculations reveal that small changes in the Ln3+ coordination spheres of these complexes can have relatively large influences on crystal field splitting.

Towards the Molecular Design of Spin-Crossover Complexes of 2,6-Bis(pyrazol-3-yl)pyridines

The molecular design of spin-crossover complexes relies on controlling the spin state of a transition metal ion by proper chemical modifications of the ligands. Herein, the first N,N'-disubstituted 2,6-bis(pyrazol-3-yl)pyridines (3-bpp) are reported that, against the common wisdom, induce a spin-crossover in otherwise high-spin iron(II) complexes by increasing the steric demand of a bulky substituent, an ortho-functionalized phenyl group. As N,N'-disubstituted 3-bpp complexes have no pendant NH groups that make their spin state extremely sensitive to the environment, the proposed ligand design, which may be applicable to isomeric 1-bpp or other families of popular bi-, tri- and higher denticity ligands, opens the way for their molecular design as spin-crossover compounds for future breakthrough applications.

Quantification of the mixed-valence and intervalence charge transfer properties of a cofacial metal-organic framework via single crystal electronic absorption spectroscopy

Gaining a fundamental understanding of charge transfer mechanisms in three-dimensional Metal-Organic Frameworks (MOFs) is crucial to the development of electroactive and conductive porous materials. These materials have potential in applications in porous conductors, electrocatalysts and energy storage devices; however the structure-property relationships pertaining to charge transfer and its quantification are relatively poorly understood. Here, the cofacial Cd(ii)-based MOF [Cd(BPPTzTz)(tdc)]·2DMF (where BPPTzTz = 2,5-bis(4-(pyridin-4-yl)phenyl)thiazolo[5,4-d]thiazole, tdc^2- = 2,5-thiophene dicarboxylate) exhibits Intervalence Charge Transfer (IVCT) within its three-dimensional structure by virtue of the close, cofacial stacking of its redox-active BPPTzTz ligands. The mixed-valence and IVCT properties are characterised using a combined electrochemical, spectroelectrochemical and computational approach. Single crystal electronic absorption spectroscopy was employed to obtain the solid-state extinction coefficient, enabling the application of Marcus-Hush theory. The electronic coupling constant, H _ab, of 145 cm^-1 was consistent with the localised mixed-valence properties of both this framework and analogous systems that use alternative methods to obtain the H _ab parameter. This work demonstrates the first report of the successful characterisation of IVCT in a MOF material using single crystal electronic absorption spectroscopy and serves as an attractive alternative to more complex methods due to its simplicity and applicability.

Magnetization Dynamics and Coherent Spin Manipulation of a Propeller Gd(III) Complex with the Smallest Helicene Ligand

A homoleptic gadolinium(III) complex with the smallest helicene-type ligand, 1,10-phenanthroline-N,N'-dioxide (phendo) [Gd(phendo)₄](NO₃)₃·xMeOH (phendo = 1,10-phenanthroline-N,N'-dioxide, MeOH = methanol), shows slow relaxation of the magnetization characteristic for Single Ion Magnets (SIM), despite negligible magnetic anisotropy, confirmed by ab initio calculations. Solid state dilution magnetic and EPR studies reveal that the magnetization dynamics of the [Gd(phendo)₄]³⁺ cation is controlled mainly by a Raman process. Pulsed EPR experiments demonstrate long phase memory times (up to 2.7 μs at 5 K), enabling the detection of Rabi oscillations at 20 K, which confirms coherent control of its spin state.

Quantitative production of butenes from biomass-derived γ-valerolactone catalysed by hetero-atomic MFI zeolite

The efficient production of light olefins from renewable biomass is a vital and challenging target to achieve future sustainable chemical processes. Here we report a hetero-atomic MFI-type zeolite (NbAlS-1), over which aqueous solutions of γ-valerolactone (GVL), obtained from biomass-derived carbohydrates, can be quantitatively converted into butenes with a yield of >99% at ambient pressure under continuous flow conditions. NbAlS-1 incorporates simultaneously niobium(V) and aluminium(III) centres into the framework and thus has a desirable distribution of Lewis and Brønsted acid sites with optimal strength. Synchrotron X-ray diffraction and absorption spectroscopy show that there is cooperativity between Nb(V) and the Brønsted acid sites on the confined adsorption of GVL, whereas the catalytic mechanism for the conversion of the confined GVL into butenes is revealed by in situ inelastic neutron scattering, coupled with modelling. This study offers a prospect for the sustainable production of butene as a platform chemical for the manufacture of renewable materials.

Identical anomalous Raman relaxation exponent in a family of single ion magnets: towards reliable Raman relaxation determination?

The results described herein suggest that the exponent n for the temperature dependence of the Raman relaxation process in the series of solid-state diluted isostructural Ln^III SIMs should be identical.