Neutron diffraction and spectroscopy offer unique insight into structures and properties of solids and molecular materials. All neutron instruments located at the various neutron sources are distinct, even if their designs are based on similar principles, and thus, they are usually less familiar to the community than commercial X-ray diffractometers and optical spectrometers. Major neutron instruments in the USA, which are open to scientists around the world, and examples of their use in coordination chemistry research are presented here, along with a list of similar instruments at main neutron facilities in other countries. The reader may easily and quickly find from this minireview an appropriate neutron instrument for research. The instruments include single-crystal and powder diffractometers to determine structures, inelastic neutron scattering (INS) spectrometers to probe magnetic and vibrational excitations, and quasielastic neutron scattering (QENS) spectrometers to study molecular dynamics such as methyl rotation on ligands. Key and unique features of the diffraction and neutron spectroscopy that are relevant to inorganic chemistry are reviewed.

A cluster-ligand is disclosed in the form of [Ru(CN)(CO)] ([]). Produced by simple reaction of [Ru(CO)] with cyanide, [] serves as a precursor to a series of μ-CN cages. When treated with [Ru(CO)], it readily forms the prism [Ru(μ-CN)(CO)]. With 1.5 equiv of [Cu(MeCN)] [] reacts to give the expanded prism {Cu[Ru(μ-CN)(CO)]}, which features three two-coordinate Cu(I) centers. Sources of Ni and Fe bind two equivalents of [], giving the double cages {M[Ru(μ-CN)(CO)]} (M = Ni, Fe) wherein the central metal is octahedral. The 1:1 reaction using [Fe(HO)] gave the interpenetrated super-tetrahedrane {Fe(μ-O)[Ru(μ-CN)(CO)]}.

To harness radiometals in clinical settings, a chelator forming a stable complex with the metal of interest and targets the desired pathological site is needed. Toward this goal, we previously reported a unique set of chelators that can stably bind to both large and small metal ions, via a conformational switch. Within this chelator class, py-macrodipa is particularly promising based on its ability to stably bind several medicinally valuable radiometals including large La, Bi, and small Sc. Here, we report a 10-step organic synthesis of its bifunctional analogue py-macrodipa-NCS, which contains an amine-reactive -NCS group that is amenable for bioconjugation reactions to targeting vectors. The hydrolytic stability of py-macordipa-NCS was assessed, revealing a half-life of 6.0 d in pH 9.0 aqueous buffer. This bifunctional chelator was then conjugated to a prostate-specific membrane antigen (PSMA)-binding moiety, yielding the bioconjugate py-macrodipa-PSMA, which was subsequently radiolabeled with large La and small Sc, revealing efficient and quantitative complex formation. The resulting radiocomplexes were injected into mice bearing both PSMA-expressing and PSMA-non-expressing tumor xenografts to determine their biodistribution patterns, revealing delivery of both La and Sc to PSMA+ tumor sites. However, partial radiometal dissociation was observed, suggesting that py-macrodipa-PSMA needs further structural optimization.

A series of isomeric bis(alkylthiocarbamate) copper complexes have been synthesized, characterized, and evaluated for antiproliferation activity. The complexes were derived from ligand isomers with 3-methylpentyl (HL) and cyclohexyl (HL) backbone substituents, which each yield a pair of linkage isomers. The thermodynamic products CuL have two imino N and two S donors resulting in three five-member chelate rings (555 isomers). The kinetic isomers CuL have one imino and one hydrazino N donor and two S donors resulting in four-, six-, and five-member rings (465 isomers). The 555 isomers have more accessible Cu potentials (E = -811/-768 mV vs. ferrocenium/ferrocene) and lower energy charge transfer bands than their 465 counterparts (E = -923/-854 mV). Antiproliferation activities were evaluated against the lung adenocarcinoma cell line (A549) and nonmalignant lung fibroblast cell line (IMR-90) using the MTT assay. CuL was potent (EC = 0.080 μM) and selective (EC/EC = 25) for A549. Its linkage isomer CuL had equivalent A549 activity, but lower selectivity (EC/EC = 12.5). The isomers CuL and CuL were less potent with EC values of 1.9 and 0.19 μM and less selective with EC/EC ratios of 2.3 and 2.65, respectively. There was no correlation between reduction potential and A549 antiproliferation activity/selectivity.

A combination of NMR studies and quantum chemical calculations were employed to investigate the structure and energetics of Zr chelates of pNOBn-DOTA. We have demonstrated that two discrete regioisomeric chelates are generated during the complex formation. The nitrobenzyl substituent can adopt either an equatorial corner or side position on the macrocyclic ring. These regioisomers are incapable of interconversion and were isolated by HPLC. The corner isomer is more stable than the side, and the SAP conformer of both regioisomers is energetically more favorable than the corresponding TSAP conformer.

New clathrochelate complexes of manganese, iron and cobalt containing peripheral organometallic manganese moieties cymantrene or tromancenium were synthesized via self-assembly from di/tri-topic dioximes, metal templates and cymantrene/tromancenium boronic acid pinacol esters. These air-stable, highly colored, oligometallic complexes are composed of various combinations of MnFeMn, MnCoMn, MnMnMnMn and MnCoCoMn metal assemblies with corresponding complicated magnetic and electrochemical properties. Full spectroscopic and structural characterization by H/B/C NMR, HRMS, IR, UV-vis, single crystal XRD and CV (cyclic voltammetry) is provided. Tetrametallic complexes containing tromanceniumyl substituents with two Co or Mn central metals exhibit promising anticancer properties against different tumor cell lines.

Amidoximated absorbents (AO-PAN) effectively remove U(VI) from aqueous solution, but previous studies reported more variability for complex natural waters that contain additional confounding ions and molecules. Ternary phases containing U(VI), M(III) (M = Fe(III), Al(III), Ga(III)), and organic molecules exist under these conditions and cause heterogeneous U(VI) uptake on AO-PAN. The goal of the current study is to provide additional insights into the structural features ternary complexes using N-(2-hydroxyethyl)-iminodiacetic acid (HEIDI) as the model organic chelator and explore the relevance of these species on U(VI) capture. Three model compounds ( (), ( () and ()) were characterized by single-crystal X-ray diffraction. Raman spectra of the model compounds were compared with solution data and the ternary phases were noted in the case of Al(III) and Ga(III), but not in the Fe(III) system. U(VI) adsorption onto AO-PAN was not impacted by the presence of HEIDI or the trivalent metal species.

The mitochondrial calcium uniporter (MCU) mediates uptake of calcium ions (Ca) into the mitochondria, a process that is vital for maintaining normal cellular function. Inhibitors of the MCU, the most promising of which are dinuclear ruthenium coordination compounds, have found use as both therapeutic agents and tools for studying the importance of this ion channel. In this study, six Co cage compounds with sarcophagine-like ligands were assessed for their abilities to inhibit MCU-mediated mitochondrial Ca uptake. These complexes were synthesized and characterized according to literature procedures and then investigated in cellular systems for their MCU-inhibitory activities. Among these six compounds, [Co(sen)] (, sen = 5-(4-amino-2-azabutyl)-5-methyl-3,7-diaza-1,9-nonanediamine) was identified to be a potent MCU inhibitor, with IC values of inhibition of 160 and 180 nM in permeabilized HeLa and HEK293T cells, respectively. Furthermore, the cellular uptake of compound was determined, revealing moderate accumulation in cells. Most notably, was demonstrated to operate in intact cells as an MCU inhibitor. Collectively, this work presents the viability of using cobalt coordination complexes as MCU inhibitors, providing a new direction for researchers to investigate in future studies.

The formal Cu(III) complex [Cu(CF)] has often served as a paradigmatic example of challenging oxidation state assignment - with many reports proposing conflicting descriptions. Here we report a computational analysis of this compound, employing Energy Decomposition Analysis and Intrinsic Bond Orbital Analysis. We present a perspective of the metal centre, resulting from ambiguities in electron counting. The implications for describing reactions which undergo oxidation state changes, such as the formal reductive elimination from the analogous [Cu(CF)(CHPh)] complex (Paeth . , 141, 3153), are probed. Electron flow analysis finds that the changes in electronic structure may be understood as a to transition at the metal centre, rendering this process essentially redox neutral. This is reminiscent of a previously studied formal Ni(IV) complex (Steen ., . , , 13133-13139), and indicates that our description of electronic structure has implications for the understanding of elementary organometallic reaction steps.

The solid-state thermal structure transformation of methylammonium vanadate, (CHNH)VO, from -150 °C to 350 °C is reported. Variable-temperature X-ray single-crystal structure analysis at 23, 0, -50, -100, and -150 °C reveal (CHNH)VO comprises of methylammonium cations and "snake-like" ([VO]) anion chains propagating along the -direction in the 2 space group. In between -150 and -100 °C, we observe a reversible structural transformation due to the re-orientation of the methylammonium cations in the crystal packing, which is also confirmed by the reversible profiles observed in differential scanning calorimetry. The methylammonium vanadate is stable until at ca. 100 °C and further heating releases methylamine and water and VO is formed at ca. 275 °C . Furthermore, we show that the methylammonium vanadate can be used as a negative staining reagent for visualizing SARS-CoV-2, allowing us to discern the spike proteins from the body of the virus using transmission electron microscopy.

The oxygen-evolving complex (OEC) located in photosystem II (PSII) of green plants is one of the best-known examples of a manganese-containing enzyme in nature, but it is also used in a range of other biological processes. OEC models incorporate two multi-dentate nitrogen-containing ligands coordinated to a bis-μ-oxo Mn(III,IV) core. Open-chain ligands were the initial scaffold used for biomimetic studies, but their macrocyclic counterparts have proven to be particularly appropriate due to their enhanced stability. Dimer and monomer complexes with such ligands have shown to be useful for a wide range of applications, which will be reviewed herein. The purpose of this review is to state with some clarity the different spectroscopic and structural characteristics of the Mn complexes formed with tetraaza macrocyclic ligands both in solution and solid-state that allow the reader to successfully identified the species involved when dealing with similar complexes of Mn.

The generation of diphosphorus molecules P under mild conditions in solution is a useful strategy to generate diphosphines [4+2] cycloadditions. We recently described the release of P units from the nickel butterfly complex [{(IMes)Ni(CO)}(μ,η:η-P)] (IMes=1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene) upon addition of CO gas. Herein, we developed an alternative protocol for the same process using heterocumulenes. In addition to formation of P (the dimerisation product of P), the reactions afford nickel complexes of novel pincer-type ligands. Aryl isothiocyanates undergo a trimerisation within the coordination sphere of nickel and afford square planar nickel complexes with S-C-S pincer-ligand frameworks. Carbon disulfide coordinates to the [(IMes)Ni]-fragment in an η-fashion, affording a dinuclear complex. Similar products are formed when the N-heterocyclic carbene nickel(0) complex [(IMes)Ni(vtms)] is used as a precursor (vtms=vinyltrimethylsilane).

The diorgano(bismuth)alcoholate [Bi((CHCH)S)OPh] () has been synthesized and fully characterized. Stoichiometric reactions, UV/Vis spectroscopy, and (TD-)DFT calculations suggest its susceptibility to homolytic and heterolytic Bi-O bond cleavage under given reaction conditions. Using the dehydrocoupling of silanes with either TEMPO or phenol as model reactions, the catalytic competency of has been investigated (TEMPO=(tetramethyl-piperidin-1-yl)-oxyl). Different reaction pathways can deliberately be addressed by applying photochemical or thermal reaction conditions and by choosing radical or closed-shell substrates (TEMPO vs. phenol). Applied analytical techniques include NMR, UV/Vis, and EPR spectroscopy, mass spectrometry, single-crystal X-ray diffraction analysis, and (TD)-DFT calculations.

Valence tautomerism has had a remarkable impact on several branches of transition metal chemistry. By switching between different valence tautomeric states, physicochemical properties and reactivities can be triggered reversibly. Is this phenomenon transferrable into the p-block - or is it already happening there? This collects observations of p-block element-ligand systems that might be assignable to valence tautomerism. Further, it discusses occurrences in p-block element compounds that exhibit the related effect of redox-induced electron transfer. As disclosed, the concept of valence tautomerism with p-block elements is at a very early stage. However, given the substantial disparity in the properties of those elements in different redox states, it might offer a valid extension for future developments in main group catalysis.

Due to their transition metal-like behavior divalent group 14 compounds bear huge potential for their application in bond activation reactions and catalysis. Here we report on detailed computational studies on the use of ylide-substituted tetrylenes in the activation of dihydrogen and phenol. A series of acyclic and cyclic ylidyltetrylenes featuring various α-substituents with different - and -donating capabilities have been investigated which demonstrate that particularly -accepting boryl groups lead to beneficial properties and low barriers for single-site activation reactions, above all in the case of silylenes. In contrast, for the thermodynamically more stable germylenes and stannylenes an alternative mechanism involving the active participation of the ylide ligand in the E-H bond (E=H or PhO) activation process by addition across the element carbon linkage was found to be energetically favored. Furthermore, the boryl substituted tetrylenes allowed for a further activation pathway involving the active participation of the boron element bond. These cooperative mechanisms are especially attractive for the heavier cyclic ylidyltetrylenes in which the loss of the protonated ylide group is prevented due to the cyclic framework. Overall, the present studies suggest that cyclic ylide-substituted germylenes and stannylenes bear huge potential for cooperative bond activations at mild conditions which should be experimentally addressed in the future.

A series of Cu(I) complexes of bidentate or tetradentate Schiff base ligands bearing either 1--imidazole or pyridine moieties were synthesized. The complexes were studied by a combination of NMR and X-ray spectroscopic techniques. The differences between the imidazole- and pyridine-based ligands were examined by H, C and N NMR spectroscopy. The magnitude of the N coordination shifts was found to be strongly affected by the nature of the heterocycle in the complexes. These trends showed good correlation with the obtained Cu-N bond lengths from single-crystal X-ray diffraction measurements. Variable-temperature NMR experiments, in combination with diffusion ordered spectroscopy (DOSY) revealed that one of the complexes underwent a temperature-dependent interconversion between a monomer, a dimer and a higher aggregate. The complexes bearing tetradentate imidazole ligands were further studied using Cu K-edge XAS and VtC XES, where DFT-assisted assignment of spectral features suggested that these complexes may form polynuclear oligomers in solid state. Additionally, the Cu(II) analogue of one of the complexes was incorporated into a metal-organic framework (MOF) as a way to obtain discrete, mononuclear complexes in the solid state.

A series of cobalt complexes, stabilized by a monoanionic tridentate NCN pincer ligand, was synthetized and characterized. Preparation of the paramagnetic 15 VE complex [Co(NCN-Et)Br] () was accomplished by transmetalation of Li[2,6-(EtNCH)CH] with CoBr in THF. Treatment of this air-sensitive compound with NO gas resulted in the formation of the diamagnetic Co(III) species [Co(NCN-Et)(NO)Br] () as confirmed by X-ray diffraction. This complex features a strongly bent NO ligand (Co-N-O∠135.0°). The ν is observed at 1609 cm which is typical for a bent metal-N-O arrangement. Coordinatively unsaturated could further be treated with pyridine, isocyanides, phosphines and CO to form five-coordinate 17 VE complexes. Oxidation of with CuBr led to the formation of the Co(III) complex [Co(NCN-Et)Br]. Treatment of [Co(NCN-Et)Br] with TlBF as halide scavenger in acetonitrile led to the formation of the cationic octahedral complex [Co(NCN-Et)(MeCN)](BF). A combination of X-ray crystallography, IR-, NMR- and EPR-spectroscopy as well as DFT/CAS-SCF calculations were used to characterize all compounds.

The multiredox reactivity of bioinorganic cofactors is often coupled to proton transfers. Here we investigate the structural, thermochemical, and electronic structure of ruthenium-amino/amido complexes with multi- proton-coupled electron transfer reactivity. The bis(amino)ruthenium(II) and bis(amido)ruthenium(IV) complexes [Ru(bpy)(en*)] ( ) and [Ru(bpy)(en*-H)] ( ) interconvert reversibly with the transfer of 2e/2H (bpy = 2,2'-bipyridine, en* = 2,3-diamino-2,3-dimethylbutane). X-ray structures allow correlations between the structural and electronic parameters, and the thermochemical data of the 2e/2H multi-square grid scheme. Redox potentials, acidity constants and DFT calculations reveal potential intermediates implicated in 2e/2H reactivity with organic reagents in non-protic solvents, which shows a strong inverted redox potential favouring 2e/2H transfer. This is suggested to be an attractive system for potential one-step (concerted) transfer of 2eand 2H due to the small changes of the pseudo-octahedral geometries and the absence of charge change, indicating a relatively small overall reorganization energy.

ZF proteins are ubiquitous eukaryotic proteins that play important roles in gene regulation. ZFs contain small domains made up of a combination of four cysteine and histidine residues, and are classified based up on the identity of these residues and their spacing. One emerging class of ZFs are the CysHis (or CCCH) class of ZFs. These ZFs play key roles in regulating RNA. In this minireview, an overview of the CCCH class of ZFs, with a focus on tristetraprolin (TTP) is provided. TTP regulates inflammation by controlling cytokine mRNAs, and there is an interest in modulating TTP activity to control inflammation. Two methods to control TTP activity are to target with exogenous metals (a 'metals in medicine' approach) or to target with endogenous signaling molecules. Work that has been done to target TTP with Fe, Cu, Cd and Au as well as with HS is reviewed. This includes attention to new methods that have been developed to monitor metal exchange with the spectroscopically silent Zn including native electro-spray ionization mass spectrometry (ESI-MS), spin-filter inductively coupled plasma mass spectrometry (ICP-MS) and cryo-electro-spray mass spectrometry (CSI-MS); along with fluorescence anisotropy (FA) to follow RNA binding.

Cooperative reactivity between transition metals and ligands, or between two metals, has created significant opportunities for the development of new transformations that would be difficult to carry out with a single metal. Here we explore cooperativity between transition metals and divalent heavier group 14 elements (tetrylenes), a less-explored facet of the field of cooperativity. Tetrylenes combine their strong -donor properties with an empty -orbital that can accept electron density. This ambiphilicity has allowed them to form metal tetrylene and metallotetrylene complexes that place a reactive site adjacent to the metal. We have selected examples to demonstrate what has been achieved so far regarding cooperative reactivity, as this already spans metal-, tetrylene- or multi-site-centred bond cleavage, cycloaddition, migration, metathesis, and insertion. We also highlight some challenges that need to be overcome for this cooperativity to make it to catalysis.

In continuation of our exploration of metallocenium chemistry we report here on innovative ways toward monofunctionalized rhodocenium salts applying half-sandwich capping reactions of cyclopentadienyl rhodium(III) halide synthons with cyclopentadienyl ylides containing pyridine, phosphine or dinitrogen leaving groups, followed by Zincke and Sandmeyer reactions. Thereby amino, diazonio, bromo, azido and iodo rhodocenium salts containing valuable functional groups are accessible for the first time. Target compounds were characterized by spectroscopic (H/C/Rh-NMR, IR, HR-MS), structural (single crystal XRD) and electrochemical (CV) methods and their properties were compared to those of isoelectronic cobaltocenium compounds. These new functionalized rhodocenium complexes significantly expand the so far extremely limited chemical space of rhodocenium salts with promising options for the future development in the area of rhodocenium chemistry.