Four Different Crystalline Products from One Reaction: Unexpected Diversity of Products of the CuCl2 Reaction with N-(2-Pyridyl)thiourea

The reaction of N-(2-pyridyl)thiourea with CuCl2 in methanol yields four different crystalline products: yellow dimeric complex, [Cu2Cl2(μ-Cl)2(L)2] (1), red polymeric complex, [Cu3Cl8L2]n (2), orange crystalline product with ionic structure, L2[CuCl4] (3), and colourless ionic compound LCl (4), where L = 2-amino-[1,2,4]thiadiazolo[2,3-a]pyridin-4-ium cation as a result of oxidative cyclization of N-(2-pyridyl)thiourea. The crystal structures of all these crystalline products have been determined by single-crystal X-ray diffraction analysis. Compound 1 involves a copper(I) ion while in 2 and 3 the copper centre is in the divalent state. 1H NMR spectra for compounds 1–3 are identical and confirm deprotonated thioamide groups of N-(2-pyridyl)thiourea and the formation of a thiadiazolopyridinium cation in solution. The hydrogen bonding and π–π stacking interactions were investigated in the solid state. In addition, all crystalline products 1–4 exhibit also S···Cl bonding interactions which consolidate the complexes into networks. The X-ray diffraction analyses indicate the absence of other crystalline phases in the crude reaction mixture.

Theoretical Insights into the Aerobic Hydrogenase Activity of Molybdenum–Copper CO Dehydrogenase

The Mo/Cu-dependent CO dehydrogenase from O. carboxydovorans is an enzyme that is able to catalyse CO oxidation to CO 2 ; moreover, it also expresses hydrogenase activity, as it is able to oxidize H 2 . Here, we have studied the dihydrogen oxidation catalysis by this enzyme using QM/MM calculations. Our results indicate that the equatorial oxo ligand of Mo is the best suited base for catalysis. Moreover, extraction of the first proton from H 2 by means of this basic centre leads to the formation of a Mo–OH–Cu I H hydride that allows for the stabilization of the copper hydride, otherwise known to be very unstable. In light of our results, two mechanisms for the hydrogenase activity of the enzyme are proposed. The first reactive channel depends on protonation of the sulphur atom of a Cu-bound cysteine residues, which appears to favour the binding and activation of the substrate. The second reactive channel involves a frustrated Lewis pair, formed by the equatorial oxo group bound to Mo and by the copper centre. In this case, no binding of the hydrogen molecule to the Cu center is observed but once H 2 enters into the active site, it can be split following a low-energy path.

Copper–oxygen Dynamics in Tyrosinase

To unveil the activation of dioxygen on the copper centre (Cu₂O₂core) of tyrosinase, we performed X-ray crystallograpy with active-form tyrosinase at near atomic resolution. This study provided a novel insight into the catalytic mechanism of the tyrosinase, including the rearrangement of copper-oxygen species as well as the intramolecular migration of copper ion induced by substrate-binding.<br>

Copper–oxygen Dynamics in Tyrosinase

To unveil the activation of dioxygen on the copper centre (Cu₂O₂core) of tyrosinase, we performed X-ray crystallograpy with active-form tyrosinase at near atomic resolution. This study provided a novel insight into the catalytic mechanism of the tyrosinase, including the rearrangement of copper-oxygen species as well as the intramolecular migration of copper ion induced by substrate-binding.<br>

Electrochemical Ultra-Low Detection of Isoniazid Using a Salicylaldamine Functionalised G1-DAB-(NH2)4 Dendritic Sensor vs. UV-VIS Spectrophotometric Detection

A poly(propyleneimine) based dendrimer was synthesised and successfully functionalised with a copper centre within its branches. The dendrimer and corresponding metallodendrimer were successfully characterised using FTIR, HR-TEM and HR-SEM in order to determine the effect of the inclusion of copper into the dendritic structure. The incorporation of copper caused crystallinity as revealed in the HR-TEM and a sheet-like morphology as shown in the HR-SEM images. The resulting metallodendrimer was then applied as an electrocatalytic platform for the sensing of a first line TB drug called isoniazid. This method was compared to a routine laboratory detection using UV-Vis and was found to be much more sensitive to trace amounts of isoniazid in solution. The electrochemical detection was found to have a limit of detection (LOD) of 0.233 nM compared to 11.47 nM using the Ultraviolet-visible spectroscopy method.

CuAAC-based assembly and characterization of a ruthenium–copper dyad containing a diimine–dioxime ligand framework

The design of molecular dyads combining a light-harvesting unit with an electroactive centre is highly demanded in the field of artificial photosynthesis. The versatile Copper-catalyzed Azide–Alkyne Cycloaddition (CuAAC) procedure was employed to assemble a ruthenium tris-diimine unit to an unprecedented azide-substituted copper diimine–dioxime moiety. The resulting RuIICuII dyad 4 was characterized by electrochemistry, 1H NMR, EPR, UV-visible absorption, steady-state fluorescence and transient absorption spectroscopies. Photoinduced electron transfer from the ruthenium to the copper centre upon light-activation in the presence of a sacrificial electron donor was established thanks to EPR-monitored photolysis experiments, opening interesting perspectives for photocatalytic applications.

Exogenous acetate ion reaches the type II copper centre in CueO through the water-excretion channel and potentially affects the enzymatic activity

The acetate-bound form of the type II copper was found in the X-ray structure of the multicopper oxidase CueO crystallized in acetate buffer in addition to the conventional OH−-bound form as the major resting form. The acetate ion was retained bound to the type II copper even after prolonged exposure of a CueO crystal to X-ray radiation, which led to the stepwise reduction of the Cu centres. However, in this study, when CueO was crystallized in citrate buffer the OH−-bound form was present exclusively. This fact shows that an exogenous acetate ion reaches the type II Cu centre through the water channel constructed between domains 1 and 3 in the CueO molecule. It was also found that the enzymatic activity of CueO is enhanced in the presence of acetate ions in the solvent water.

Elucidation of the crystal structure ofCoriolopsis caperatalaccase: restoration of the structure and activity of the native enzyme from the T2-depleted form by copper ions

Laccases are members of a large family of multicopper oxidases that catalyze the oxidation of a wide range of organic and inorganic substrates accompanied by the reduction of dioxygen to water. A new laccase was isolated from the basidiomyceteCoriolopsis caperatastrain 0677 and its amino-acid sequence was determined. According to its physicochemical properties and spectroscopic features, the laccase fromC. caperatais a high redox-potential blue laccase. Attempts to crystallize the native enzyme were unsuccessful. The copper type 2-depleted (T2D) laccase was prepared and crystallized. The structure of T2D laccase fromC. caperatawas solved at 1.6 Å resolution, and attempts to reconstruct the T2 copper centre were performed using Cu+and Cu2+ions. The structure of T2D+Cu+laccase was solved at 1.89 Å resolution. It was shown that the T2D+Cu+laccase structure contained four copper ions in the active site. Reconstruction could not be achieved when the T2D laccase crystals were treated with CuSO4.

Self-assembly Through Non-coordinating Intermolecular Forces, Part 2 [1]. Synthesis, Crystal Structure and Packing of [Cu2(μ-phthalazine)3(phthalazine)2][CF3SO3]2

Treatment of the copper(I) trifluoromethanesulphonate toluene complex {[Cu(CF3SO3)]2 · C6H5Me} (1) with phthalazine (phtz, C8H6N2) in dichloromethane-acetonitrile solution yielded, via the bis(acetonitrile)tris(μ-phthalazine)dicopper(I) trifluoromethanesulphonate intermediate (2), the novel bis(phthalazine)tris(μ-phthalazine)dicopper(I) trifluoromethanesulphonate salt (3). Compound 3 was completely characterised and the molecular structure determined by single-crystal X-ray diffraction. Complex 3 crystallises in the monoclinic system, space group C2/c, with a = 26.9527(10), b = 10.9558(7), c = 19.2104(10) Å , β = 127.268(2)◦, V = 4514.3(4) Å3 and Z = 4. The copper(I) coordination geometry is tetrahedral, each copper centre being linked to four phthalazine molecules. Dicationic units of 3 which present an unusual paddle wheel-like shape constitute appropriate organometallic building blocks for the construction of a supramolecular solid-state architecture. The analysis of the packing of the molecules of 3 in the crystal revealed an unprecedented 2-dimensional network, resulting from intermolecular π-π and electrostatic interactions.

Catalytic Performance of Copper-Substituted Polyoxotungstate Materials and X-Ray Structure of a New Sandwich-Type Compound

Mono-substituted and sandwich-type copper substituted polyoxoanions ([PW11CuO39]5− and [Cu4(H2O)2(PW9O34)2]10−) were studied as catalysts for the epoxidation of cyclooctene and geraniol, using the green oxidant H2O2, with the results suggesting good efficiency at room temperature. High selectivity and reasonable conversion data were found after the first minutes of reaction. The copper centre may be responsible for this performance and our on-going research focuses in the preparation of new materials incorporating copper into polyoxometalates (POMs). In this context, we have also isolated a new crystalline dimeric sandwich-type polyoxocoppertungstate {H7.05[Cu3WO(H2O)(CuW9O34)(Cu0.6W9O34)]}7.75−. This compound was isolated as potassium salt and structurally characterized by FTIR and single-crystal X-ray diffraction (XRD). The polyoxoanion is composed by the [CuW9O34]12− and [Cu0.6W9O34]12.8− anionic fragments, joined together by a rhomb-like arrangement of three Cu2+ and one W6+ metallic centres, all exhibiting octahedral coordination geometries.