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A preliminary study involving solid-state [sup.77.Se] NMR spectroscopy and first principles calculations of [sup.77.Se] NMR parameters in Se--N heterocycles is reported. [sup.77.Se] CP/MAS NMR spectra of the ring systems reveal expansive selenium chemical shift (CS) tensors, which are extremely sensitive to molecular geometry, symmetry, ligand substitution, and intermolecular contacts. For systems with known crystal structures, hybrid density functional theory (DFT) calculations of selenium nuclear magnetic shielding (NMS) tensors were carried out, and tensor orientations in the molecular frames examined. Additional DFT calculations of selenium NMS tensors are presented, along with a detailed analysis of pairs of occupied and virtual molecular orbitals that give rise to the Se NMS tensors. A new naturalized local molecular orbital (NLMO) analysis under the same DFT framework is also discussed. Collectively, the NMR data and first principles calculations provide understanding of the influences of electronic structure, bonding, and intermolecular interactions on the selenium NMS tensors, allowing for (i) prediction of unknown molecular structures and (ii) insight into the positions of the stereochemically active selenium lone pairs. Key words: solid-state NMR, [sup.77.Se] NMR, ab initio calculations, chemical shielding, main-group inorganic chemistry, heterocycles, DFT calculations, MO analysis, Gaussian 03, ADF. On rapporte les resultats d'une etude preliminaire de spectroscopie RMN du [sup.77.Se] a l'etat solide et de calculs a partir de principes fondamentaux des parametres RMN du [sup.77.Se] dans des heterocycles Se-N. Les spectres RMN des systemes cycliques par la technique de la rotation a l'angle magique avec polarisation croisee (RAMPC) mettent en evidence l'existence d'un large eventail de tenseurs du deplacement chimique (DC) du selenium qui sont extremement sensibles a la geometrie moleculaire, a la substitution par des ligands et aux contacts intermoleculaires. Pour les systemes dont on connait les structures cristallines, on a effectue des calculs des tenseurs de blindage magnetique nucleaire (BMN) du selenium avec la theorie de la fonctionnelle de la densite (TFD) hybride et on a examine les orientations des tenseurs dans des cadres moleculaires. On rapporte les resultats de calculs effectues sur la base de la TFD des tenseurs de blindage magnetique nucleaire ainsi qu'une analyse detaillee des paires d'orbitales moleculaires occupees et virtuelles qui donnent lieu aux tenseurs de blindage magnetique nucleaire du selenium. On discute aussi d'une nouvelle analyse de l'orbitale moleculaire naturalisee (OMLN) dans le meme cadre de la TFD. Pris collectivement, les donnees de la RMN et les calculs a partir de principes fondamentaux permettent de comprendre les influences de la structure electronique, des liaisons et des interactions intermoleculaires sur les tenseurs de BMN et aussi (i) de faire des predictions pour 15 structures moleculaires inconnues et (ii) de se faire une idee sur les positions des paires d'electrons libres du selenium qui sont actives d'un point de vue stereochimique. Mots-cles : RMN a l'etat solide, RMN du [sup.77.Se], calculs ab initio, blindage chimique, chimie inorganique du groupe principal, heterocycles, calculs TFD, analyse des OM, gaussienne 03, fonctionnelle de la densite d'Amsterdam (FDA). [Traduit par la Redaction], Introduction Carbenes are known to be important reaction intermediates, and there is an enormous amount of literature reporting their syntheses, structures, and reactivities. (1-7) Since the first report of the [...]

N6‐(2‐Deoxy‐α,β‐d‐erythropentofuranosyl)‐2,6‐diamino‐4‐hydroxy‐5‐formamidopyrimidine (Fapy⋅dG) is a major DNA lesion produced from 2′‐deoxyguanosine under oxidizing conditions. Fapy⋅dG is produced from a common intermediate that leads to 7,8‐dihydro‐8‐oxo‐2′‐deoxyguanosine (8‐OxodGuo), and in greater quantities in cells. The impact of Fapy⋅dG on DNA structure and function is much less well understood than that of 8‐OxodGuo. This is largely due to the significantly greater difficulty in synthesizing oligonucleotides containing Fapy⋅dG than 8‐OxodGuo. We describe a synthetic approach for preparing oligonucleotides containing Fapy⋅dG that will facilitate intensive studies of this lesion in DNA. A variety of oligonucleotides as long as 30 nucleotides are synthesized. We anticipate that the chemistry described herein will provide an impetus for a wide range of studies involving Fapy⋅dG. [ABSTRACT FROM AUTHOR]

Numerous solid-state [super 63]Cu and [super 65]Cu NMR spectroscopic studies of inorganic and organometallic copper(I) complexes with different Cu coordination complexes are conducted. These complexes are found to exhibit very large quadrupolar interactions.

X-ray crystallography and solid-state NMR techniques were used to determine the structure and Pt NMR chemical shift (CS) tensor of Pt[[S.sub.2][c.sub.2][(C[F.sub.3]).sub.2]].sub.2]. The Pt NMR CS tensor is highly anisotropic and asymmetric which is attributed to the noninnocent nature of the ligand.

We report a strategic synthesis of poly(cyclosilane), a well-defined polymer inspired by crystalline silicon. The synthetic strategy relies on the design of a functionalized cyclohexasilane monomer for transition-metal-promoted dehydrocoupling polymerization. Our approach takes advantage of the dual function of the phenylsilyl group, which serves a crucial role both in the synthesis of a novel α,ω-oligosilanyl dianion and as a latent electrophile. We show that the cyclohexasilane monomer prefers a chair conformation. The monomer design ensures enhanced reactivity in transition-metal-promoted dehydrocoupling polymerization relative to secondary silanes, such as methylphenylsilane. Comprehensive NMR spectroscopy yields a detailed picture of the polymer end-group structure and microstructure. Poly(cyclosilane) has red-shifted optical absorbance relative to the monomer. We synthesize a σ-π hybrid donor-acceptor polymer by catalytic hydrosilylation. [ABSTRACT FROM AUTHOR]

Magnetic resonance imaging provides a noninvasive method for in situ monitoring of electrochemical processes involved in charge/discharge cycling of batteries. Determining how the electrochemical processes become irreversible, ultimately resulting in degraded battery performance, will aid in developing new battery materials and designing better batteries. Here we introduce the use of an alternative in situ diagnostic tool to monitor the electrochemical processes. Utilizing a very large field-gradient in the fringe field of a magnet, stray-field-imaging (STRAFI) technique significantly improves the image resolution. These STRAFI images enable the real time monitoring of the electrodes at a micron level. It is demonstrated by two prototype half-cells, graphite∥Li and LiFePO₄∥Li, that the high-resolution (7)Li STRAFI profiles allow one to visualize in situ Li-ions transfer between the electrodes during charge/discharge cyclings as well as the formation and changes of irreversible microstructures of the Li components, and particularly reveal a non-uniform Li-ion distribution in the graphite.