Application of the dimer approach for the analysis of vibrational spectra of BEDT—TTF-based charge-transfer salts

The dimer approach was proposed for the normal coordinate analysis of BEDT—TTF⁺ molecular vibrations. It was shown that, within the framework of the approximation used, the appearance of additional bands in the IR as well as in Raman spectra may be explained as due to the reduction of symmetry of the dimerized system in comparison with the monomeric one. The strength of intermolecular interaction in the dimer was estimated by adjusting the calculated frequencies to the observed positions of intense “vibronic” bands recorded in the IR spectra of BEDT—TTF-based monovalent charge transfer salts. It was found that for the reproduction of “vibronic shifts” observed for some vibrations it should be assumed that the intermolecular interaction takes effect not only on the totally symmetric a_g modes, but also on the vibrations of other symmetry species.     

Synthesis,properties, and crystal structures of a new charge-transfer salt: Tris (dimethylammonium) hydrogen α-dodecamolybdosilicate

A new charge-transfer salt, [(CH₃)₂NH₂]₃[HSiMo₁₂O₄₀] (I), has been synthesized and characterized by elemental analysis, IR, UV-Vis, XPS, TG-DTA, and single-crystal X-ray diffraction. Crystal data: trigonal, R \(\bar 3\) m, a = 16.4365(8), c = 25.142(2) Å, V = 5882.3(7) ų, Z = 6. The X-ray crystallographic study shows that the title compound comprises three (CH₃)₂NH ₂ ⁺ cations and a heteropolyanion and is formed mainly by electrostatic interactions, hydrogen bonding being very weak. The title compound shows weak photochromic properties on UV irradiation. The TG-DTA curves suggest that I is stable up to 300°C     

Space fullerenes: computer search for new Frank–Kasper structures II

A Frank?CKasper structure is a 3-periodic tiling of the Euclidean space E ³ by tetrahedra such that the vertex figure of any vertex belongs to four specified fullerenes with, respectively, 12, 14, 15, and 16 faces. Frank?CKasper structures occur in the crystallography of metallic alloys, clathrates, zeolites, and in geometrical optimization. 27 such physical structures are known. In Dutour et ai. (Acta Crystallogr A 66:637?C639, 2010) we obtained, by computer enumeration, all 84 such structures with up to 20 cells in a reduced fundamental domain; 13 among them were known physical structures. In the present follow-up study, we managed, by improving the computation, to get all 37 new structures with 21 cells in a reduced fundamental domain. Those structures are described, using six invariants: group, the size of fundamental domain, mean coordination number $ \bar{f} $ , fraction sequence, cell orbits and major skeleton. We found pairs of distinct structures having all six invariants equal. So, we devised a new invariant, zigzag vector, and computed it for all 135 structures known from now; all have this invariant different. New bounds for $ \bar{f} $ and new directions (computational perspectives, number of Kekule structures, space octahedrites, space cubites) are also discussed.     

Sol–gel-derived photonic structures: fabrication,assessment, and application

Sol–gel is a handy, very flexible, and cheap method to fabricate, study, and apply innovative photonic structures. The possibility of starting from molecular precursors and elementary building blocks permits to tailor structures at the molecular level and to create new materials with enhanced performances. Of specific interest for the study of important physical effects as well as for application in light management are confined structures on the nano-micro scale as photonic crystal and planar waveguides. Activation by luminescent species and in particular by rare earth ions allows results in the integrated optics area covering application in sensing, biomedical diagnostic, telecommunication, lightning, and photon management. The present review is focused on some recent results obtained by the authors in Sol–gel photonics. The first part presents colloidal structures including single nano-micro spheres and photonic crystal structures. The second part of the review deals with amorphous and transparent glass–ceramic employed for the fabrication of confined structures in planar format. Some specific application are also reported to highlight the role of sol gel photonics in the development of high performance optical sensors, waveguide lasers, and nanostructured materials.     

Syntheses,crystal structures and properties of two novel imino-π-extended TTF derivatives

Two novel conjugated imino-π-extended tetrathiafulvalenes with p-iminobenzene, N,N′-bis(4,5-bis(methylthio)-1,3-dithiol-2-ylidene)benzene-1,4-diamine (1) and N,N′-bis(4,5-bis(ethylenedithio)-1,3-dithiolo-2-ylidene)benzene-1,4-diamine (2), have been synthesized and characterized by NMR, IR, MS and X-ray single-crystal diffraction. Both the two targets adopt chair-like conformation, and the central rings of p-iminobenzene moieties of the two molecules are severely twisted from the planarity of two dithiole rings, respectively. The UV–vis spectra of 1 and 2 show the lowest-energy absorption bands caused by the HOMO–LUMO one-electron promotion. Cyclic voltammetry (CV) measurements show only one, two-electron irreversible oxidation picks. These experimentally estimated energy levels of the frontier orbital of 1 and 2 (E_HOMO 1: = ?5.45, 2: ?5.47 eV) are in good agreement with those obtained from DFT calculations (E_HOMO 1: = ?5.5, 2: = ?5.3 eV). The high HOMO–LUMO gaps of 1 (4.05 eV) and 2 (4.00 eV) indicate high kinetic stability of the title compounds.     

Organometallic–inorganic charge transfer salts containing a cationic iron mixed sandwich and polyoxomolybdate anions: Syntheses,X-ray molecular structures and spectroscopic properties

Two new organometallic–inorganic charge transfer salts formulated as [(η⁵-Cp)Fe(η⁶-MeO-p-C₆H₄–NHNH₂)]₂[Mo₆O₁₉], 1, and [(η⁵-Cp)Fe(η⁶-MeO-p-C₆H₄–NHNH₂)]₄[β-Mo₈O₂₆], 2, were prepared through a metathesis reaction between the organometallic hydrazine precursor [(η⁵-Cp)Fe(η⁶-MeO-p-C₆H₄–NHNH₂)]⁺PF₆^? and either [n-Bu₄N]₂[Mo₆O₁₉] or [n-Bu₄N]₄[α-Mo₈O₂₆] in acetonitrile. In the second case, the [α-Mo₈O₂₆]^4? anion transforms into the [β-Mo₈O₂₆]^4? isomer. These organometallic–inorganic hybrids were characterized by spectroscopic techniques (IR, ¹H NMR and UV–vis). In addition, the UV–vis diffuse reflectance spectra of 1 and 2 in solid state exhibit a band at λ_max = 475 and 470 nm, respectively, not observed in DMSO solution, which have been attributed to a charge transfer transition. On the other hand, the solid state structure of 2, solved by X-ray diffraction analysis shows the formation of hydrogen bonds between the protons of the –NHNH₂ and C–H groups with the terminal oxo groups of the β-octamolybdate anions [β-Mo₈O₂₆]^4?. Finally, hybrid 3, formulated as [(η⁵-Cp)Fe(η⁶-C₆H₅OMe)]₄[β-Mo₈O₂₆] was prepared in EtOH under solvothermal conditions. The single crystal X-ray structure shows the elimination of the –NHNH₂ group from the organometallic mixed sandwich reducing its associative ability toward the oxo groups of the counterion only to the electrostatic interactions and to the very weak CH?O hydrogen bonds.     

Host–guest complexation of omeprazole, pantoprazole and rabeprazole sodium salts with cyclodextrins: an NMR study on solution structures and enantiodiscrimination power

The application of different cyclodextrins (CDs) as NMR chiral solvating agents (CSAs) for the sodium salts of the proton-pump inhibitors omeprazole, pantoprazole (sesquihydrate) and rabeprazole was investigated. It was proved that the formation of diastereomeric host–guest complexes in D₂O solution between the CDs and those substrates permitted the direct ¹H NMR discrimination of the enantiomers of the sodium salts of these compounds without the need of previous working-up. Rotating frame nuclear overhauser effect spectroscopy (ROESY) was used to ascertain the solution geometries of the host–guest complexes. The results suggested a preferential binding of the benzimidazole moiety of the guest molecules within the macrocyclic cavity of α-CD, whereas the higher dimensions of β- and γ-CD also permitted the inclusion of the highly substituted pyridine moieties. Moreover, the solution stoichiometries and the binding constants of the complexes formed with pantoprazole at room temperature were determined by ¹H and ¹⁹F NMR titration. Diffusion-filtered Spectroscopy was applied to obtain clean spectra without the interference of the HOD signal.     

Multiphase structure and physical properties of organic composites obtained by mechanochemical reaction between BEDT–TTF and iodine-derived acceptors. An overview

The results of the studies of the physical properties of organic composites obtained by direct solid–solid charge-transfer (CT) reaction between bis(ethylenedithio)tetrathiafulvalene (BEDT–TTF) and iodine or gold iodide are presented and discussed. It is shown that the analysis of experimental data of dc conductivity and thermoelectric power and the relation between morphology of composites and their electrical properties result in understanding the charge transport phenomena and allow to propose the model of electrical transport in these materials. The main factors that affect the electrical properties of composites are recognized and the ways of controlling these factors and tuning the electrical properties are proposed. To cite this article: A. Graja, M. Golub, C. R. Chimie 6 (2003).     

Complex salts of [ReII(NO)Br4(pyz)]−: synthesis,crystal structures,and DFT studies

Two nitrosyl Re(II) complexes formulated as [Ni(bipy)₃][Re(NO)Br₄(pyz)]₂ and [Cu(bipy)₂Br][ReNOBr₄(pyz)] (pyz = pyrazine, bipy = 2,2′-bipyridine) were synthesized and characterized by single-crystal X-ray diffraction. The pyrazine in [Re(NO)Br₄(pyz)]^? was not able to act as bridge toward a second metal ion, and the two salts were obtained. Computational studies at the density functional level of theory show that the charge on the nitrogen, which could be available for bridging, is dramatically reduced to less than half, decreasing its capability to bind a second metal ion.     

The first organically templated gallium phosphite–oxalates: Synthesis,structures, and characterizationseer

Three new gallium phosphite–oxalates formula as (C₆N₂H₁₄)₂[Ga₂(OH)₂(C₂O₄)₂(HPO₃)₂]·2H₂O (1), (C₆N₂H₁₈)_0.5[Ga(OH)(C₂O₄)_0.5(HPO₃)] (2), and Ga(C₂O₄)_0.5(C₃N₂H₄)(HPO₃) (3) have been hydrothermally synthesized by controlling the pH value of the reaction system. Compound 1 possesses a one-dimensional ladder-like chain structure, in which the C₂O₄^2? anion is coordinated to one Ga center and acts as mono-bidentate ligand. In 2 and 3, the C₂O₄^2? anions serve as bis-bidentates ligands bridging between two Ga atoms to form the two-dimensional layered structures. Furthermore, compound 3 displays a neutral layered network, which is decorated by the directly coordinated organic ligand.     

Wholly-rigid rod–rod amphiphiles: synthesis,crystal structures,and self-assembling behavior in water

A series of fully rigid rod–rod type amphiphilic molecules have been constructed by using 4,4′-bipyridin-1-ium or 4,4′-bipyridin-1,1′-diium (viologen) as a hydrophilic segment and phenyl, biphenyl or para-tert-phenyl as a hydrophobic unit. The crystal structures of four of the molecules have been elucidated. TEM, SEM, AFM, and DLS experiments revealed that these stiff amphiphiles could self-assemble into diverse architectures, including spherical micelles, ultra-long straight nanofibers (>1 mm), and nanotubes in water, which depend on the hydrophilic/hydrophobic fraction ratios of the molecules.     

Syntheses,crystal structures and photochemistry of two new organic–inorganic hybrid compounds based on copper–glycin complexes and paradodecatungstates

Two organic–inorganic hybrid materials built from copper–glycin complexes and paradodecatungstates, Na₆[{Cu(gly)(H₂O)}]₂[{Cu(H₂O)}(H₂W₁₂O₄₂)] ? 21H₂O (1) and Na{Na(H₂O)₆}{Na(H₂O)₄}₃[{Cu(gly)₂}]₂{H₅(H₂W₁₂O₄₂)} ? 8.5H₂O (gly = glycin) (2), have been synthesized in aqueous solution and characterized by IR, UV, TG, elemental analysis, electrochemistry, and single-crystal X-ray analyses. In 1, [H₂W₁₂O₄₂]^10? building block connects two neighboring clusters with [Cu(H₂O)]²⁺ groups to produce an infinite 1-D chain; then these chains are linked through [Cu(gly)(H₂O)]⁺ groups to form a 2-D layer structure, which is further joined by Na⁺ to form a 3-D network. In 2, [H₂W₁₂O₄₂]^10? decorated by two [Cu(gly)₂] moieties connects four adjacent clusters with six Na⁺ into a 2-D layer. In addition, luminescence and photocatalysis properties of these compounds have been investigated.     

Two new lanthanide–radical complexes: synthesis,structure, and magnetic properties

Two new lanthanide–radical complexes, [Tb(hfac)₃(EtVNIT)₂] (1) and [Dy(hfac)₃(EtVNIT)₂] (2) (EtVNIT?=?2-(4′-ethoxy-3′-methoxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, hfac?=?1,1,1,5,5,5-hexafluoroacetylacetonate), were synthesized; both display radical–Ln(III)–radical (Ln=Tb (1), Dy (2)) tri-spin structures. Magnetic studies reveal that interactions between the lanthanide ions and radicals are ferromagnetic.     

A new generation of visible-light-active photocatalysts—The alkaline earth metal bismuthates: Syntheses,compositions, structures,and properties

Semiconductor materials containing bismuth have attracted the attention of researchers over the past several decades, as a result of their high photocatalytic activity in various reactions and/or high efficiency in their photoelectric conversion of solar energy. This interest originated from the observations that bismuth-containing semiconductors have a sufficiently small bandgap, which makes them sensitive to radiation in the visible spectral range; thus, visible-light-active materials. Among the various bismuth-containing semiconductor materials, the bismuthates of alkaline earth metals are distinguished and describe into separate groups. This article reviews research on the known methods of obtaining bismuthates of various alkaline earth metals (magnesium, calcium, strontium, and barium), and further analyzes their composition, structure, and visible-light-active photocatalytic activity.     

Synthesis,crystal structures and catalytic activities of new palladium(II)–bis(oxazoline) complexes

Palladium–bis(oxazoline) complexes (Pd-BOX-A and Pd-BOX-B) were synthesized and characterized by ¹H, ¹³C NMR, IR and elemental analysis. The molecular structures of the complexes were confirmed by single-crystal X-ray analysis. In both cases, the palladium center is coordinated by the nitrogen atoms of the two oxazoline rings and two chloride ligands in a distorted square planar geometry. Despite the fact that the bis(oxazoline) ligand is achiral, the asymmetrical substitution on the phenyl spacer and the rigid backbone of the complex Pd-BOX-A induce inherent chirality and the compound crystallizes as a racemic mixture. Both complexes were found to be highly effective catalysts for Suzuki–Miyaura, Mizoroki–Heck and Sonogashira cross-coupling reactions. They also show excellent catalytic activities toward carbonylative coupling reactions.     

Aplyronines D–H from the sea hare Aplysia kurodai: isolation,structures, and cytotoxicity

Five cytotoxic macrolides, aplyronines D–H (4–8), were isolated from the Japanese sea hare Aplysia kurodai. They are new congeners of the antitumor compound aplyronine A (1), which was previously isolated from the same organism. Their structures were determined by spectroscopic analysis (NMR and MS). The cytotoxicity of these new compounds was evaluated in comparison with that of aplyronines A–C (1–3), suggesting the importance of the 7-O-seryl ester group for mediating the potent cytotoxicity of aplyronines.