Connecting frontier research with industrial development : Lanthanide and Actinide Chemistry in the European f-Element Network (EUFEN)

The chemistry of f-elements, even though often not known to the general public, forms part of many industrial processes, manufacturing and medical applications, such as medical imaging (e.g. MRI scans), strong magnets, data storage media, superconducters, LEDs, catalysis, as well as energy, and metal extraction. It plays a crucial role in the scientific and industrial landscape of the European Union (EU) in fields of energy, security, training, sustainability, and society. The use of these elements widens the scope of synthetic possibilities in chemistry, and materials with outstanding electromagnetic properties have already been realised. The synthesis of lanthanide containing supramolecular materials with exceptional materials properties has already been reported, e.g. the ability to bind and release gases, high-temperature superconductivity, and all-white light emitting diodes. The EUFEN (European f-Element Network) COST action provides cooperative mobility mechanisms for nationally funded f-element chemists pursuing fundamental frontier research to initiate collaborations, training, networking, and dissemination among each other. Novel developments and results in terms of f-element crystal engineering carried out at the University of Malta are therefore part of EUFEN.peer-reviewe

Von reaktiven molekularen Vorläufern zu höhervernetzten Lanthanoid-Oxonitridocarbonaten und nanokristallinen Lanthanoid-Nitrid-Materialien

During the course of this research project the synthesis of highly reactive lanthanide and O2CN-containing molecular precursor complexes has been investigated. Important issues were the development of new reaction pathways to these species and the structural characterization of the N-containing precursors. The accurate thermal treatment of these complexes using various reaction gases yielded both lanthanide nitrides and highly condensed lanthanide oxo-nitrido carbonates using different types of gases. The observed degradation reactions to the products were characterized thoroughly. According to this procedure, novel and known compounds have been synthesized and investigated carefully regarding their structural and material properties. The application of CO2 as an important preorganized C/O-donor for addition reactions at the Ln/N precursor complex represented one of the major topics in this project. This “green reagent” can be considered as a promising species for future industrial applications. A new reaction pathway utilizing the decomposition reaction of N-containing organo¬lanthanides revealed the formation of highly aggregated nanocrystalline lanthanide nitrides at low temperatures. Novel Ln/O/C/N-solids were synthesized by thermal degradation of CO2-activated precursor complexes. The Ln/N and Ln/O/C/N species obtained can be considered as single-source molecular precursors and potential Ln/O/C/N-dopants for applications in the synthesis of O/C/N materials

Synthesis, Structure, and Dynamics of Tris(η5-cyclopentadienyl)lanthanides and Bis(η5-cyclopentadienyl)[bis(trimethylsilyl)amido]cerium(III)

The crystal structures of tris(η5-cyclopentadienyl)lanthanides (Ln = Ce, Dy, Ho) have been determined using different X-ray diffraction methods. Cp3Ce and Cp3Ho (Cp = cyclopentadienyl) crystal data needed special solution and refinement methods, due to the occurrence of intrinsic twinning in these species. Our results do not agree with the previously published cell constants of Cp3Ho. The space group and unit cell parameters of Cp3Dy have been derived from powder diffraction experiments. High-resolution 13C solid-state NMR data of Cp3La are presented, giving evidence of the dynamics and bonding situation of the Cp ligands. Cp3Ce turned out to be a reactive reagent for the synthesis of bis(η5-cyclopentadienyl)[bis(trimethylsilyl)amido]cerium(III)

Self-assembly of triazatriangulenium-based functional adlayers on Au(111) surfaces

Detailed scanning tunneling microscopy studies of the attachment of freestanding molecular functions to Au(111) surfaces via self-assembly of functional molecules based on triazatriangulenium platforms are presented. As shown for molecules with side chains of different length and phenyl, azobenzyl, or azobenzyl derivatives with different terminal groups (iodo, cyano, or dimethyl) as functional units, this approach allows the preparation of very stable, hexagonally ordered adlayers. The intermolecular spacings in these adlayers are independent of the attached functions with the latter being orientated perpendicular to the Au surface. Due to their open structure, adlayers of platforms with attached functional groups exhibit a tendency towards bilayer formation, which can be suppressed by derivatization with appropriate terminal groups

Copper(I/II) and cobalt(II) coordination chemistry of relevance to controlled radical polymerization processes

International audienceThe reaction of various alkyl halides (1-bromoethylbenzene, BEB; 1-chloroethylbenzene, CEB; methyl iodide; 1-bromoethylacetate, BEA; and ethyl-2-bromopropionate, EBP) with CuBr/L (L = bipy, Me6TREN) has been investigated in the presence of [Co(acac)2] or [Co(acac)2]/py, with the goal of generating radicals by halogen atom transfer to CuI for subsequence trapping by CoII and generation of an alkylcobalt(III) product. No evidence for the formation of the target product has been obtained. The various reactions, carried out under different conditions, have led to the crystallization of the following compounds: {[Cu(bipy)2Br]+}2{[Cu2Br4]2−} (1); [Cu(Me6TREN)Br]Br; [Cu(Me6TREN)Br0.37Cl0.63]Br (2); trans-[Co(acac)2(THF)2] (3); [Co(Me6TREN)Br]Br (4); [Cu(Me7TREN)I]{[Cu2I2(Br0.628I0.372)2]0.9[I]0.2} (5); [C6H8N]2[CoI4] (6); [Co(acac)3]; and [Co(acac)2(THF)2CoBr2] (7). The structures of 1–7 have been determined by single-crystal X-ray diffraction

Born out of Fire and Ice: Polymorph Studies of the Antiviral Famciclovir

There is much interest and focus on solid forms of famciclovir. However, in spite of the abundance of reported differences in oral bioavailability, compressibility, and other physical–chemical properties of the various crystal forms of this drug, very little precise structural analysis is available in the literature to date. The form used in the commercial formulation is the anhydrous form I. Patents and patent applications report three different anhydrous crystalline forms on the basis of unindexed powder diffraction patterns. Single-crystal and variable-temperature X-ray diffraction experiments using the commercially available anhydrous form of famciclovir were carried out and led not only to the crystal structure determination of the anhydrous form I, but also to discovery of a new crystal form of anhydrous famciclovir from powder data

Understanding Conformational Polymorphism in Ganciclovir: A Holistic Approach

We present a holistic crystallographic study of the antiviral ganciclovir, including insights into its solid-state behavior, which could prove useful during drug development, making the process more sustainable. A newly developed methodology was used incorporating a combination of statistical and thermodynamic approaches, which can be applied to various crystalline materials. We demonstrate how the chemical environment and orientation of a functional group can affect its accessibility for participation in hydrogen bonding. The difference in the nature and strength of intermolecular contacts between the two anhydrous forms, exposed through full interaction maps and Hirshfeld surfaces, leads to the manifestation of conformational polymorphism. Variations in the intramolecular geometry and intermolecular interactions of both forms of ganciclovir were identified as possible predictors for their relative thermodynamic stability. It was shown through energy frameworks how the extensive supramolecular network of contacts in form I causes a higher level of compactness and lower enthalpy relative to form II. The likelihood of the material to exhibit polymorphism was assessed through a hydrogen bond propensity model, which predicted a high probability associated with the formation of other relatively stable forms. However, this model failed to classify the stability of form I appropriately, suggesting that it might not have fully captured the collective impacts which govern polymorphic stability

Planar versus non-planar: The important role of weak C—H...O hydrogen bonds in the crystal structure of 5-methylsalicylaldehyde

The crystal structure of 5-methylsalicylaldehyde (5-MSA; systematic name 2-hydroxy-5-methylbenzaldehyde), C8H8O2, was discovered to be a textbook example of the drastic structural changes caused by just a few weak C—H...O interactions due to the additional methylation of the aromatic ring compared to salicylaldehyde SA. This weak intermolecular hydrogen bonding is observed between aromatic or methyl carbon donor atoms and hydroxyl or aldehyde acceptor oxygen atoms with d(D...A) = 3.4801 (18) and 3.499 (11) Å. The molecule shows a distorted geometry of the aromatic ring with elongated bonds in the vicinity of substituted aldehyde and hydroxyl carbon atoms. The methyl hydrogen atoms are disordered over two sets of sites with occupancies of 0.69 (2) and 0.31 (2)

The influence of hydrogen bonding on the planar arrangement of melamine in crystal structures of its solvates, cocrystals and salts

The hydrogen bonding patterns of melamine as well as mono- and diprotonated melamine have been analysed in five crystal structures of a solvate, a cocrystal and three organic and inorganic salts, namely, melamine DMSO solvate ([mel]·DMSO (1)), melamine theobromine cocrystal ([mel]·[TBR] 3 (2)), dimelaminium ethylenediaminetetraacetate ([mel-H] 2[EDTA-H2]·2H2O (3)), anhydrous dimelaminium sulfate ([mel-H]2[SO4] (4)), and anhydrous melaminium dinitrate ([mel-H2][NO3]2 (5)). Melamine is a versatile molecular building block (tecton) in cocrystals, solvates and salts. Depending on the degree of protonation and/or other molecules or ions present in the structure, parallels could be drawn to determine whether melamine is arranged in a cross-linked manner, in undulating sheets or in the form of perfectly planar sheets in the structure. Graph set analysis was used to compare the geometry of hydrogen bond interactions of the new structures with those of other structures published in the literature. Solvent drop-assisted solid state reactions (kneading) were performed for "green" synthesis of the compounds. The organic salt 3 has high thermal stability as shown by variable-temperature X-ray powder diffraction, which is presumably related to its extensive hydrogen bond network. Rietveld refinements were carried out on laboratory powder diffraction data to confirm the structures of the compounds obtained from single-crystal data. This journal is © the Partner Organisations 2014