Mechanistic investigations of the Fe(ii) mediated synthesis of squaraines.

The scission and homologation of CO is a fundamental process in the Fischer-Tropsch reaction. However, given the heterogeneous nature of the catalyst and forcing reaction conditions, it is difficult to determine the intermediates of this reaction. Here we report detailed mechanistic insight into the scission/homologation of CO by two-coordinate iron terphenyl complexes.

Slow magnetic relaxation in Fe(II) -terphenyl complexes.

Two-coordinate transition metal complexes are exciting candidates for single-molecule magnets (SMMs) because their highly axial coordination environments lead to sizeable magnetic anisotropy. We report a series of five structurally related two-coordinate Fe(II) -terphenyl complexes (4-R-2,6-XylCH)Fe [R = Bu (1), SiMe (2), H (3), Cl (4), CF (5)] where, by changing the functionalisation of the -substituent (R), we alter their magnetic function. All five complexes are field-induced single-molecule magnets, with relaxation rates that are well-described by a combination of direct and Raman mechanisms.

Mapping blood biochemistry by Raman spectroscopy at the cellular level.

We report how Raman difference imaging provides insight on cellular biochemistry as a function of sub-cellular dimensions and the cellular environment. We show that this approach offers a sensitive diagnostic to address blood biochemistry at the cellular level. We examine Raman microscopic images of the distribution of the different hemoglobins in both healthy (discocyte) and unhealthy (echinocyte) blood cells and interpret these images using pre-calculated, accurate pre-resonant Raman tensors for scattering intensities specific to hemoglobins.

Group 11 -Terphenyl Complexes Featuring Metallophilic Interactions.

A series of group 11 -terphenyl complexes have been synthesized via a metathesis reaction from the iron(II) complexes (2,6-MesCH)Fe and (2,6-XylCH)Fe (Mes = 2,4,6-MeCH; Xyl = 2,6-MeCH). [2,6-MesCHM] (, M = Cu; , M = Ag; , M = Au) and [2,6-XylCHM] (, M = Cu; , M = Ag) are dimeric in the solid state, although different geometries are observed depending on the ligand. These complexes feature short metal-metal distances in the expected range for metallophilic interactions.

Structural and electronic studies of substituted m-terphenyl lithium complexes.

The effect of para-substitution upon the structural and electronic properties of a series of m-terphenyl lithium complexes [R-Ar-Li] (R = t-Bu 1, SiMe2, H 3, Cl 4, CF5; where R-Ar = 2,6-{2,6-Xyl}-4-R-CH and 2,6-Xyl = 2,6-MeCH) has been investigated. X-ray crystallography reveals the complexes to be structurally similar, with little variation in C-M-C bond lengths and angles across the series. However, in-depth NMR spectroscopic studies reveal notable electronic differences, showing a linear correlation between the Li{H} NMR chemical shifts of the para-substituted complexes and their Hammett constants.

A transition metal-gallium cluster formed via insertion of "GaI".

The reaction between a two-coordinate Co(ii) diaryl complex and "GaI" affords 2,6-Pmp2C6H3CoGa3I5, in a new geometry for a heavier group 13-transition metal cluster. Experimental and computational investigations show that this compound is best described as a nido metalla-group 13 cluster.

Carbene-Induced Rescue of Catalytic Activity in Deactivated Nitrite Reductase Mutant.

The role of His145 in the T1 copper center of nitrite reductase (NiR) is pivotal for the activity of the enzyme. Mutation to a glycine at this position enables the reconstitution of the T1 center by the addition of imidazole as exogenous ligands, however the catalytic activity is only marginally rescued. Here, we demonstrate that the uptake of 1,3-dimethylimidazolylidene as N-heterocyclic carbene (NHC) by the H145G NiR mutant instead of imidazole yields a significantly more active catalyst, suggesting a beneficial role of such C-bonding.

Influence of molecular design on radical spin multiplicity: characterisation of BODIPY dyad and triad radical anions.

A strategy to create organic molecules with high degrees of radical spin multiplicity is reported in which molecular design is correlated with the behaviour of radical anions in a series of BODIPY dyads. Upon reduction of each BODIPY moiety radical anions are formed which are shown to have different spin multiplicities by electron paramagnetic resonance (EPR) spectroscopy and distinct profiles in their cyclic voltammograms and UV-visible spectra. The relationship between structure and multiplicity is demonstrated showing that the balance between singlet, biradical or triplet states in the dyads depends on relative orientation and connectivity of the BODIPY groups.

Imidazolylidene Cu(II) Complexes: Synthesis Using Imidazolium Carboxylate Precursors and Structure Rearrangement Pathways.

Copper(II) complexes of type (NHC)CuX (X = OAc, Cl, Br, BF, and NO) bearing monodentate -heterocyclic carbenes (NHCs) were prepared by decarboxylation of imidazolium carboxylates as a new synthetic methodology for Cu(II)-NHC complexes. In contrast to the classical deprotonation method, the decarboxylation protocol does not require anaerobic conditions and provides access to complexes with NHCs that are unstable as free carbenes such as ,'-diisopropyl-imidazolylidene and ,'-dimethyl-imidazolylidene. Spectroscopic evidence of the formation of the Cu-C bond is provided by UV-vis and EPR, in particular by the 44 MHz carbene hyperfine coupling constant using a C-labeled imidazolylidene ligand.

Formation of a Copper(II)-Tyrosyl Complex at the Active Site of Lytic Polysaccharide Monooxygenases Following Oxidation by HO.

Hydrogen peroxide is a cosubstrate for the oxidative cleavage of saccharidic substrates by copper-containing lytic polysaccharide monooxygenases (LPMOs). The rate of reaction of LPMOs with hydrogen peroxide is high, but it is accompanied by rapid inactivation of the enzymes, presumably through protein oxidation. Herein, we use UV-vis, CD, XAS, EPR, VT/VH-MCD, and resonance Raman spectroscopies, augmented with mass spectrometry and DFT calculations, to show that the product of reaction of an AA9 LPMO with HO at higher pHs is a singlet Cu(II)-tyrosyl radical species, which is inactive for the oxidation of saccharidic substrates.

Selective reduction and homologation of carbon monoxide by organometallic iron complexes.

Carbon monoxide is a key C feedstock for the industrial production of hydrocarbons, where it is used to make millions of tonnes of chemicals, fuels, and solvents per annum. Many transition metal complexes can coordinate CO, but the formation of new C-C bonds in well-defined compounds from the scission and subsequent coupling of two or more CO moieties at a transition metal centre remains a challenge. Herein, we report the use of low-coordinate iron(II) complexes for the selective scission and homologation of CO affording unusual squaraines and iron carboxylates at ambient temperature and pressure.

Carbene in Cupredoxin Protein Scaffolds: Replacement of a Histidine Ligand in the Active Site Substantially Alters Copper Redox Properties.

N-heterocyclic carbene (NHC) ligands have had a major impact in homogeneous catalysis, however, their potential role in biological systems is essentially unexplored. We replaced a copper-coordinating histidine (His) in the active site of the redox enzyme azurin with exogenous dimethyl imidazolylidene. This NHC rapidly restores the type-1 Cu center, with spectroscopic properties (EPR, UV/Vis) that are identical to those from N-coordination of the His in the wild type.

Author Correction: The inverse-trans-influence in tetravalent lanthanide and actinide bis(carbene) complexes.

This corrects the article DOI: 10.1038/ncomms14137.

Thionated naphthalene diimides: tuneable chromophores for applications in photoactive dyads.

Varying the degree of thionation of a series of naphthalene diimide (NDI) and naphthalic imide (NI) phenothiazine dyad systems affords a systematic approach for tuning the system's donor-acceptor energy gap. Each dyad was compared to model NDI/NI systems and fully characterised through single crystal X-ray diffraction, NMR, cyclic voltammetry, electron paramagnetic resonance (EPR), transient absorption spectroscopy (TA), time-resolved infra-red spectroscopy (TRIR) and DFT. The measurements reveal that thionation increases both electron affinity of the NDI/NI acceptor dyad component and accessibility of the singly or doubly reduced states.

Core-Substituted Naphthalene Diimides: Influence of Substituent Conformation on Strong Visible Absorption.

Functionalization of the aromatic core of naphthalene diimide (NDI) chromophores with morpholine substituents leads to molecules with strong absorbance in the visible spectrum. The shift of absorption maxima to lower energy is determined not only by the degree of substitution but also by the relative conformation and orientation of the tertiary amine with respect to the plane of the NDI.

The inverse-trans-influence in tetravalent lanthanide and actinide bis(carbene) complexes.

Across the periodic table the trans-influence operates, whereby tightly bonded ligands selectively lengthen mutually trans metal-ligand bonds. Conversely, in high oxidation state actinide complexes the inverse-trans-influence operates, where normally cis strongly donating ligands instead reside trans and actually reinforce each other. However, because the inverse-trans-influence is restricted to high-valent actinyls and a few uranium(V/VI) complexes, it has had limited scope in an area with few unifying rules.

Isolation of Elusive HAsAsH in a Crystalline Diuranium(IV) Complex.

The HAsAsH molecule has hitherto only been proposed tentatively as a short-lived species generated in electrochemical or microwave-plasma experiments. After two centuries of inconclusive or disproven claims of HAsAsH formation in the condensed phase, we report the isolation and structural authentication of HAsAsH in the diuranium(IV) complex [{U(Tren)}(μ-η:η-AsH)] (, Tren=N(CHCHNSPr); Pr=CH(CH)). Complex was prepared by deprotonation and oxidative homocoupling of an arsenide precursor.

High-pressure studies of three polymorphs of a palladium(II) oxathioether macrocyclic complex.

The three reported phases of the mononuclear macrocyclic Pd(II) complex [PdCl2([9]aneS2O)] [(1); [9]aneS2O = 1-oxa-4,7-dithiacyclononane] were each studied up to pressures exceeding 9 GPa using high-pressure single-crystal X-ray diffraction. The α- and γ-phases both exhibit smooth compression of the unit-cell parameters with third-order Birch-Murnaghan bulk moduli of 14.4 (8) and 7.

Emergence of comparable covalency in isostructural cerium(iv)- and uranium(iv)-carbon multiple bonds.

We report comparable levels of covalency in cerium- and uranium-carbon multiple bonds in the iso-structural carbene complexes [M(BIPM)(ODipp)] [M = Ce (), U (), Th (); BIPM = C(PPhNSiMe); Dipp = CH-2,6-Pr] whereas for M = Th the M[double bond, length as m-dash]C bond interaction is much more ionic. On the basis of single crystal X-ray diffraction, NMR, IR, EPR, and XANES spectroscopies, and SQUID magnetometry complexes are confirmed formally as metal(iv) complexes. In order to avoid the deficiencies of orbital-based theoretical analysis approaches we probed the bonding of analysis of RASSCF- and CASSCF-derived densities that explicitly treats the orbital energy near-degeneracy and overlap contributions to covalency.

Synthesis and Photophysical Study of a [NiFe] Hydrogenase Biomimetic Compound Covalently Linked to a Re-diimine Photosensitizer.

The synthesis, photophysics, and photochemistry of a linked dyad ([Re]-[NiFe2]) containing an analogue ([NiFe2]) of the active site of [NiFe] hydrogenase, covalently bound to a Re-diimine photosensitizer ([Re]), are described. Following excitation, the mechanisms of electron transfer involving the [Re] and [NiFe2] centers and the resulting decomposition were investigated. Excitation of the [Re] center results in the population of a diimine-based metal-to-ligand charge transfer excited state.

Isolation of Elusive HAsAsH in a Crystalline Diuranium(IV) Complex.

The HAsAsH molecule has hitherto only been proposed tentatively as a short-lived species generated in electrochemical or microwave-plasma experiments. After two centuries of inconclusive or disproven claims of HAsAsH formation in the condensed phase, we report the isolation and structural authentication of HAsAsH in the diuranium(IV) complex [{U(Tren(TIPS) )}2 (μ-η(2) :η(2) -As2 H2 )] (3, Tren(TIPS) =N(CH2 CH2 NSiPr(i) 3 )3 ; Pr(i) =CH(CH3 )2 ). Complex 3 was prepared by deprotonation and oxidative homocoupling of an arsenide precursor.

A Ni(i)Fe(ii) analogue of the Ni-L state of the active site of the [NiFe] hydrogenases.

[Ni(L(1))Fe((t)BuNC)4](PF6)2 is a robust Ni(II)Fe(II) complex that undergoes a reversible one-electron reduction. Spectroscopic and theoretical studies show that [Ni(L(1))Fe((t)BuNC)4](+) is an unprecedented Ni(I)Fe(II) species that reproduces the electronic configuration of the Ni-L state of the [NiFe] hydrogenases.