Search

Studies of the supramolecular chemistry of iso‐tellurazole N‐oxides have been confined to non‐polar media until now. To overcome that limitation, an iso‐tellurazole N‐oxide was derivatized with a primary alcohol group; the compound is soluble in polar solvents and stable in acidic to neutral aqueous media. Nickel (II) and iron (II) form macrocyclic complexes with six molecules of that iso‐tellurazole N‐oxide in a hitherto not‐observed macrocyclic arrangement defined by CTe⋅⋅⋅O chalcogen bonds and κ6‐O bound to the metal ion. This behaviour is in sharp contrast with the κn‐Te (n=1,2,4) complexes formed by soft metal ions. [ABSTRACT FROM AUTHOR]

Reactions of the ethylene hydride complex trans-[(dmpe)2MnH(C2H4)] (1) with secondary hydrogermanes H2GeR2 at 55–60 °C afforded the base-free terminal germylene hydride complexes trans-[(dmpe)2MnH(＝GeR2)] (R = Ph; 2a, R = Et; 2b). Room temperature reactions of 2a or 2b with an excess of the primary hydrogermanes H3GeR′ (R′ = Ph or nBu) afforded trans-[(dmpe)2MnH(＝GeHR′)] (R′ = Ph; 3a, R′ = nBu; 3b) in rapid equilibrium with small amounts of 2a/b, as well as the digermyl hydride complex mer-[(dmpe)2MnH(GeH2R′)2] {R′ = Ph (4a) or nBu (4b)} and the trans-hydrogermane germyl complex trans-[(dmpe)2Mn(GeH2R′)(HGeH2R′)] {R′ = Ph (5a) or nBu (5b)}. Pure 3b was isolated from the reaction of 2b with H3GenBu, whereas 3a decomposed readily in solution in the absence of free H3GePh, and a pure bulk sample was not obtained. Reactions of 1 with H3GeR′ (R′ = Ph or nBu) also proceeded at 55–60 °C to afford mixtures of 3a/b, 4a/b and 5a/b, accompanied by remaining 1. However, upon continued heating to consume 1, various unidentified manganese-containing intermediates were formed, ultimately affording the germanide complex [{(dmpe)2MnH}2(μ-Ge)] (6) in 17–49% spectroscopic yield. Pure trans,trans-6 was isolated in 27% yield from the reaction of 1 with H3GenBu, and it is notable that this reaction involves stripping of all four substituents from the hydrogermane. Complexes 2a, 3a, and 6 were crystallographically characterized, and the nature of the Mn＝Ge bonding in these species (as well as in 2b and 3b) was probed computationally. [ABSTRACT FROM AUTHOR]

Iso-tellurazole N-oxides are promising supramolecular building blocks. While in neutral solutions, they form tetra-and hexameric macrocyclic aggregates linked by Te ... O secondary bonding (t hole interactions or chalcogen bonds), protonation of the oxygen atom in acidic media disrupts such supramolecular association. The process is reversible and, consequently, can be used to switch on and off the self-assembly process. Hammett acidity measurements gave p[K.sub.a] values of-3.2 for the protonated molecules. Adducts with HCl and HBr were isolated and structurally characterized. Protonation in solution led to the crystallization of a new polymorph of 3-methyl-5-phenyl-1,2- tellurazole N-oxide, which features a unique polymeric arrangement. Key words: sigma-hole interactions, secondary bonding, chalcogens, supramolecular chemistry, main-group chemistry. Les isotellurazoles N-oxydes sont des synthons supramoleculaires prometteurs. Bien qu'en solution neutre, ils forment des agregats macrocycliques tetrameriques et hexameriques retenus par des liaisons secondaires Te ... O (interactions de trous t ou liaisons chalcogene), en milieu acide, la protonation des atomes d'oxygene perturbe une association supramoleculaire de ce type. Ce processus d'association est reversible et peut donc etre utilise pour provoquer ou inhiber le processus d'autoassamblage. Nous avons calcule, pour les molecules protonees, une valeur de p[K.sub.a] de -3,2 derivee des mesures de l'acidite en utilisant l'equation de Hammett. En outre, nous avons isole des adduits de HCl et de HBr et en avons caracterise les structures. La protonation en solution a entraine la cristallisation d'un nouveau polymorphe du 3-methyl-5-phenyl-1,2-tellurazole Noxyde presentant une structure polymerique unique. [Traduit par la Redaction] Mots-cles : interactions de trous sigma, liaison secondaire, chalcogenes, chimie supramoleculaire, chimie du groupement principal., Introduction The remarkable success of halogen bonding (1-4) in areas as diverse as crystal engineering, (2,5-14) supramolecular catalysis, (15) anion recognition, (16) optical materials, (17) and biomimetic chemistry (18-20) has [...]

The secondary bonding interactions that link the supramolecular structures assembled by 1,2,5-chalcogenadiazoles were analyzed through explicit orthogonalization of molecular orbitals (NBO), topological analysis of the electron density (AIM), and the electron localization function (ELF). The results of these analyses are consistent with a bonding description that attributes important covalent and electrostatic character to these interactions. Application of these analyses to the individual molecules highlighted the structural features from which each of those contributions originates, namely the polarity and modest strength of the E-N bond. Both of these effects increase along the series S, Se, Te. Perturbations to the heterocycle electronic structure that result in a weaker and more polar E-N bond cause an increase in the Lewis acidity at the chalcogen centre, which in turn leads to stronger secondary bonding interactions with Lewis bases. Additionally, the contribution of dispersion forces is not negligible and is most important in the case of sulfur. Key words: chalcogenadiazoles, secondary bonding interactions, heterocycles, electronic structure, Lewis acids and bases, computational chemistry. On a analyse les interactions de liaisons secondaires qui unissent les structures supramoleculaires assemblees par les 1,2,5-chalcogenadiazoles en faisant appel a l'orthogonalisation explicite des orbitalesmoleculaires (NBO), a l'analyse topologique de la densite electronique (AIM) et a la fonction de localisation electronique (ELF). Les resultats de ces analyses cadrent avec une description des liaisons attribuant un important caractere covalent ainsi qu'electrostatique a ces interactions. L'application de ces analyses auxmolecules individuelles amis en relief les caracteristiques structurelles a l'origine de ces contributions, a savoir la polarite et la force moderee de la liaison E--N. Ces effets augmentent tous deux le long de la serie S, Se, Te. Les perturbations de la structure electronique de l'heterocycle dues a une liaison E--N plus faible et plus polaire causent une augmentation de l'acidite de Lewis au centre chalcogene, qui a son tour entraine des interactions de liaisons secondaires plus fortes avec les bases de Lewis. En outre, la contribution des forces de dispersion n'est pas negligeable et s'avere etre la plus importante dans le cas du soufre. [Traduit par la Redaction] Mots-cles : chalcogenadiazoles, interactions de liaisons secondaires, heterocycles, structure electronique, acides et bases de Lewis, chimie informatique., Introduction The remarkable tendency of molecules containing the 1,2,5-chalcogenadiazole ring (1) toward self-association has inspired their use as supramolecular building blocks. (1-9) Through the [[E-N].sub.2] (E = S, Se, or [...]

Acetylferrocene readily forms an adduct with B[F.sub.3]. The product is a neutral model for protonated acetylferrocene, a species that is a crucial intermediate in the formation of 1,3,5-trisferrocenyl-benzene and other conjugated heterometallic derivatives by cyclocondensation. The title compound's structure was determined in the solid state by X-ray diffraction and its spectroscopic properties were examined in detail, particularly the electronic excitation spectrum, which confirms the previous identification of the in situ generated protonated ketone. Key words: organometallic ketones, B[F.sub.3] adducts, ferrocenyl cations, density functional theory (DFT) calculations. L'acetylferrocene forme facilement un adduit avec le B[F.sub.3]. Le produit est un modele neutre pour un acetylferrocene, une espece qui est un intermediaire crucial dans la formation du 1,3,5-trisferrocenyl-benzene et d'autres derives heterometalliques par cyclocondensation. La structure du compose mentionne dans le titre a ete determinee a l'etat solide par diffraction des rayons X et on a examine ses proprietes spectroscopiques en detail, en particulier son spectre d'excitation electronique qui confirme l'identification anterieure de la cetone protonee generee in situ. Mots-cles : cetones organometalliques, adduits avec le B[F.sub.3], cations ferrocenyles, calculs d'apres la theorie de la fonctionnelle de la densite (TFD). [Traduit par la Redaction], Introduction Aldehydes and ketones are weak bases, with the typical [pK.sub.a] values of their conjugated acids being below -6, e.g., -6.99 in the case of benzaldehyde and -6.04 for acetophenone. [...]

The structural characterization, magnetic properties and heat capacity of newly synthesized [La.sub.3][Re.sub.2][O.sub.10] are reported. The results indicate that the short-range magnetic ordering might consist of 1-dimensional antiferromagnetic linear chains of coupled S = 1/2 dimers.

Dimethylstannylene (SnMe2) and its subsequent decay to tetramethyldistannene are formed from the 193-nmlaser flash photolysis of 1,1-dimethylstannacyclopent-3-ene in the gas phase and 1,1,3,4-tetramethylstannacyclopent-3-ene in solution. Steady-state photolysis leads to the formation of the corresponding dienes, and in solution, SnMe2 is trapped in reaction with M trimethylstannane (Me3SnH)to afford a product of Sn-H insertion.

The compound [4-C[H.sub.3][C.sub.6][H.sub.4]-SS-C[H.sub.2]C[H.sub.2]-N(C[H.sub.3]) [C.sub.6][H.sub.4]C[([C.sub.6][H.sub.4]N[(C[H.sub.3]).sub.2]-4).sub.2]]Cl (1a) consists of the triarylmethyl chromophore of crystal violet appended to an organic disulfide, to entail direct attachment of this dye to gold surfaces. Addition of 1a to colloidal dispersions of the metal produced a stable dispersion in methanol-water mixtures. Transmission electron microscopy of Freeze-Fracture sections shadowed with carbon and platinum confirmed that the dispersion remains unaggregated. Local-field effects and coupling to the surface plasmon of gold magnified the interaction of the chromophore with optical fields. A large oscillator strength in the visible spectrum (f ca. 35) and a first hyperpolarizability ([beta] ca. [10.sup.-26] esu, hyper-Rayleigh scattering) were observed as the colloid adsorbed dye molecules. A Hill-type analysis indicated that the adsorption process is cooperative. This combination of organic chromophore and nanoparticle was adapted for incorporation into PMMA-based composite films whose electrooptic coefficient ([r.sub.113] = 2.20 pm [V.sup.-1]) is larger than the sum of the individual contributions of dye and metallic particles. Key words: chromophores, colloids, gold, local-field effects, nonlinear optical materials.

Research has been conducted on the eight- and 16-membered cyanuric-sulfanuric ring systems. The preparation of these systems in good yields via sulfur(IV) system reaction with m-chloroperbenzoic acid is discussed.1

An experiment was conducted to study a family of seven-membered dithiadiazepinyl radicals. Density functional theory calculations were used to examine the electronic structure of the parent system. The capability of the radicals to be used as building blocks for molecular conductors was calculated by comparing their dimerization and disproportionation energies with those of the dithiadiazolyl and dithiazolyl radicals. However, the thermal instability of the radicals hindered the possibility of isolating them into pure samples.

The x-ray structures and synthesis of the eight-membered rings and the new sixteen-membered rings of heterocycles were described. The reaction of 4-XC6H4CN2(SiMe3)3 (X=Br,CF3) with PhSCl at 100 degrees yields the eight-membered rings and sixteen-membered rings. The C4N8S4 ring has a cradle-like structure with S4 symmetry. Density functional theory calculations revealed that boat and chair conformers of the C2N4S2 ring have similar energies. The anion (HC)2N4(SH)2 super2- should exhibit transannular S-S interactions.

The structural isomers of the sulfur(II)-containing diazenes with PhSN=C(Ar)=NSPh (Ar = 2-BrC6H4) is characterized by an E,E,E geometry. X-ray analysis of the Z,E,Z isomers indicates the presence of a weak intramolecular sulfur-nitrogen bond which is stabilized by intramolecular E-N interactions. The interaction is characterized by back-donation between the phi lone pairs of the chalcogen and the phi*(N=N). Furthermore, the electron donation between the sigma(N) lone pairs and the sigma*(E-X) and sigma*(E-N) orbitals were also exhibited by the interaction.

The approximate density functional theory is used in conjunction with spectroscopic and x-ray crystallography measurements to study the thermodynamics associated with the decomposition of HCN2(SPh)3 by free radicals. Results show that the major products of the decomposition process are diazene and PhSSPh. The data also suggest that diazene is formed by a mechanism in which the RS radical acts as the catalyst.

The influence of intermolecular forces on substances' macroscopic properties and behavior can be inexpensively and easily demonstrated in the undergraduate chemistry laboratory through iodine and beta-cyclodextrin inclusion compounds. The equipment is readily available in most laboratories, the chemicals are inexpensive and the procedures are simple. Students must detect inclusion compound formation and how the formation influences iodine extraction and the dissolution processes.

The phase that is most stable under ambient pressure and temperature has puckered supramolecular ribbon polymers assembled by Te-N secondary bonding interactions and has disclosed a characteristic red-orange color. Computational DFT studies have shown that the changes in optical properties are related to intermolecular mixing of [pi] orbitals enabled by the supramolecular interactions and the symmetry of the supramolecular synthon.

The use of second-harmonic generation at different wavelengths to compare the resonant contributions of two simple dipolar chromophores, nitroaniline and nitrosulfenamide is reported. The result shows that pi intermolecular interaction does result in excitations that are observable in the linear spectrum of nitroaniline and thus could have an influence on the nonlinear response.

Organochalcogen-nitrogen heterocycles such as the 1,2,5-chalcogenadiazoles have a distinct tendency to establish intermolecular links in the solid state through secondary bonding interactions E...N (E=S, Se, Te). Because of its more polar character and lower-lying antibonding orbitals, the tellerium derivatives possess the strongest association energies.