Crystal structure of {aquaimidazole-[2-(2-carbamoylhydrazone)-propionato]} copper(II) nitrate

The crystal structure of {aquaimidazole[2-(2-carbamoylhydrazone)-propionato]}copper(II) nitrate [Cu(L)Im(H₂O)]NO₃ (I), where HL is the semicarbazone of pyruvic acid, Im is imidazole, is dtermined. The crystal structure of I contains two independent complexes IA and IB in which copper atoms coordinate once deprotonated tridentate HL, imidazole, and water molecules. Outer spheres of the complexes contain nitrate ions. In the compounds studied the coordination polyhedron of the copper atom is a distorted tetragonal pyramid. Its base is composed of carboxyl and carbamide oxygen atoms, azomethine nitrogen of monodeprotonated HL molecules, and the imidazole nitrogen atom. In the crystal, nitrate ions and imidazole molecules link the complexes via hydrogen bonds into 2D networks parallel to the (010) plane. These networks in turn are in pairs arranged into layers along the [010] direction due to hydrogen bonds between water molecules and oxygen atoms of nitrate ions, and also by water molecules and O3 atoms of the neighboring 2D networks. In the crystal, the π-π stacking interaction is observed between the imidazole rings from different layers and there is also a N-O…Cg (π ring) interaction inside the layers.     

Insights into the Formation of Symmetrical Trimers of Dialkylated Ketenes Starting from Acid Chloride Precursors

Application of known dialkyl ketene di- and trimerization to more complex precursors could readily open the route to highly functionalized symmetrical cyclobuta-1,3-diones and cyclohexa-1,3,5-triones. We report herein the results on three substrates containing either a C=C double bond or a protected glycol moiety as illustrative functionalized groups. The nature of the substituents is found to be crucial: while cyclopentenyl and more constrained dioxolanocyclopentenyl precursors efficiently dimerize, a diallylic derivative fails. At the millimolar scale, methoxide-catalyzed trimerization shows limited reproducibility, even for the reported substrate tetramethylcyclobuta-1,3-dione. However, systematic studies, including the use of microwaves, demonstrate that formation of symmetrical trimers is favored under solvent-free conditions and conventional heating, which allowed us to isolate and characterize trispiro[4.1.4.1.4.1]octadeca-2,9,15-triene-6,12,18-trione.     

Synthesis and crystal structures of palladium(II) complexes of bis-(<Emphasis Type="Italic">N</Emphasis>-heterocyclic carbenes) on a calix[4]arene platform

A series of calix[4]arene supported N-heterocyclic carbene palladium complexes were successfully prepared and characterised. Their X-ray crystal structures were obtained and are discussed. Notably, the dimeric compound b[5-(3-N-4,5-diphenylimidazol-2-yliden-1-yl)-25,26,27,28-tetrapropyloxy calix[4]arene] palladium(II) dibromide (cone) showed pseudo-polymorphism.     

A Facile Molecular Precursor‐based Synthesis of Ag2Se Nanoparticles and Its Composites with TiO2 for Enhanced Photocatalytic Activity

The reactions of different silver(I) reagents AgX (X^?=iodide, trifluoroacetate, triflate) with selenoethers R₂Se (R=Me, tBu) in a variety of solvents were investigated in relation with their use as precursors for Ag₂Se nanomaterials. Different reaction conditions led to different reactivities and afforded either molecular complexes or metal selenide nanoparticles. The reactions leading to in situ formation of the metal selenide nanoparticles were then extended in the presence of commercial TiO₂ (P25) to prepare silver selenide–titania nanocomposites with different Ag/Ti ratios. These nanocomposites, well characterized by elemental analysis (Ag, Se), PXRD, TEM, BET, XPS and UV/Vis studies, were investigated as photocatalysts for the degradation of formic acid (FA) solution. The xAg₂Se‐TiO₂ nanocomposites (x=0.01, 0.13 and 0.25 mol %) exhibited a much higher catalytic activity as compared to P25, which is an established benchmark for the photocatalysis under UV light, and retained a good photocatalytic stability after recycling for several times.     

Bispidine Platform Grants Full Control over Magnetic State of Ferrous Chelates in Water

A bicyclic ligand platform for iron(II), which allows total control over the complex’s magnetic properties in aqueous solution simply by varying one of the six coordination sites of the bispidine ligand, is reported. To achieve this, an efficient synthetic route to an N5 bispidine framework (ligand L4) that features an unsubstituted N‐7 site is established. Then, by choosing appropriate N‐7‐coordinating substituents, the spin state of choice can be imposed on the corresponding ferrous complexes under environmentally relevant conditions in water and near‐room temperature. Importantly, the first low‐spin and diamagnetic iron(II) chelates in the bispidine series, both in the solid state and in aqueous solution, are reported. The eradication of head‐on steric clashes between pendent coordinating arms is at the origin of this success. A new pair of constitutionally similar ferrous coordination compounds of a multidentate ligand system is obtained, which exhibits a distinctly binary (off–on) magnetic relationship. The new synthetic intermediate L4 may be substituted in just one step by any desired pendent arm, thus allowing access to complexes with finely tuned magnetic properties.     

Monosubstituted lower rim thiacalix[4]arene derivatives

A clean and partially green route to monoalkyled thiacalix[4]arenes has been demonstrated. We have discovered that tetraalkylammonium halide can cleave selectively one of the two aryl alkyl ethers of dialkylated para-tert-butylthiacalix[4]arenes. Thus, p-tert-butyl thiacalix[4]arenes differently monoalkyled at the lower rim with acetyl, propyl, and benzyl group were synthesized in good yield.     

Bis(4‐methylbenzylammonium) tetrachloridozincate: a new noncentrosymmetric structure characterized by 13C CP–MAS NMR spectroscopy

A new noncentrosymmetric organic–inorganic hybrid material, (C₈H₁₂N)₂[ZnCl₄], has been synthesized as single crystals at room temperature and characterized by X‐ray diffraction and solid‐state NMR spectroscopy. Its novel structure consists of two 4‐methylbenzylammonium cations and one [ZnCl₄]²⁻ anion connected by N—H...Cl and C—H...Cl hydrogen bonds, two of which are three‐centre interactions. The Zn^II metal centre has a slightly distorted tetrahedral coordination geometry. Results from ¹³C CP–MAS NMR spectroscopy are in good agreement with the X‐ray structure. Density functional theory calculations allow the assignment of the carbon peaks to the independent crystallographic sites.     

Crystal structure and thermal behavior of a new cadmium indium oxalate

A new mixed metal oxalate Cd₃In₂(C₂O₄)₆·9H₂O, with an open-framework structure, has been prepared from a precipitation method at room temperature. Its crystal structure has been solved from single-crystal diffraction data. The compound crystallizes with space group P6₄22 and the cell parameters are a=8.566(5)Å, c=37.811(5) Å, V=2403(2) Å³, and Z=3 (R₁=0.036). The three-dimensional structure is built from three types of MO₈ (M=Cd, In) polyhedra, i.e., triangular dodecahedra, bicapped trigonal prisms and an undefined distorted eight-fold cadmium polyhedron. Relationships with the structures of the related cadmium zirconium oxalates are discussed. The structure overview suggests the possibility to conceive new oxalate-based materials with open-framework structures. The thermal behavior of the new compound is described in details from temperature-dependent X-ray powder diffraction and thermogravimetry measurements. The dehydration process of the precursor is reversible in its stability temperature range. The final product consists of a mixture of nanocrystalline CdIn₂O₄ and the simple oxides.     

Inherently chiral phosphonatocavitands as artificial chemo- and enantio-selective receptors of natural ammoniums

Inherently chiral phosphonatocavitands with various bridging moieties at their wide rim were synthesized. Optical resolution by chiral HPLC was performed with cavitand 8 to afford enantiopure compounds (+)-8 and (-)-8. The molecular structures of hosts 8 and 12 were determined by X-ray diffraction. The host properties were investigated by (1)H and (31)P NMR spectroscopy. The phosphonatocavitands form inclusion complexes with chiral ammonium neurotransmitters, some presenting enantioselectivity towards the right or left-handed host enantiomers.