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The present paper illustrates key features of charge transfer between calcium atoms and prototype conjugated hydrocarbons (ethylene, benzene, and coronene) as elucidated by electronic structure calculations. One- and two-electron charge transfer is controlled by two sequential conical intersections. The two lowest electronic states that undergo a conical intersection have closed-shell and open-shell dominant configurations correlating with the [4s.sup.2] and [4s.sup.1][3d.sup.1] states of Ca, respectively. Unlike the neutralionic state crossing in, for example, hydrogen halides or alkali halides, the path from separated reactants to the conical intersection region is uphill and the charge-transferred state is a biradical. The lowest-energy adiabatic singlet state shows at least two minima along a single approach path of Ca to the [pi] system: (i) a van der Waals complex with a doubly occupied highest molecular orbital, denoted [[phi].sup.2.sub.1], and a small negative charge on Ca and (ii) an open-shell singlet (biradical) at intermediate approach (Ca ... C distance [approximately equal to]2.5-2.7 [Angstrom]) with molecular orbital structure [[phi].sub.1][[phi].sub.2], where [[phi].sub.2] is an orbital showing significant charge transfer form Ca to the [pi]-system, leading to a one-electron multicentered bond. A third minimum (iii) at shorter distances along the same path corresponding to a closed-shell state with molecular orbital structure [[phi].sup.2.sub.2] has also been found; however, it does not necessarily represent the ground state at a given Ca ... C distance in all three systems. The topography of the lowest adiabatic singlet potential energy surface is due to the one- and two-electron bonding patterns in Ca-[pi] complexes. metal atom | metastable state | nature of metal-[pi] binding | one- and two-electron multicentered bonds | triplet ground state doi/ 10.1073/pnas.1010287107

Electrochemical studies on the Fc + [e.sup.-] [left and right arrow] [Fc.sup.+] (Fc = ferrocene) process have been undertaken via the oxidation of Fc and reduction of [Fc.sup.+] as the hexafluorophosphate (P[F.sup.-.sub.6]) or tetrafluoroborate (B[F.sub.4]) salts and their mixtures in three ionic liquids (ILs) (1-butyl-1-methylpyrrolidinium bis[(trifluoromethyl)sulfonyl]imide, 1-butyl-3-methylimidazolium tetrafluoroborate, and 1-butyl-3-methylimidazolium hexafluorophosphate). Data obtained at macro- and microdisk electrodes using conventional dc and Fourier-transformed large-amplitude ac (FT-ac) voltammetry reveal that diffusion coefficients for Fc and [Fc.sup.+] differ significantly and are a function of the Fc and [Fc.sup.+] concentration, in contrast to findings in molecular solvents with 0.1 M added supporting electrolyte media. Thus, the Faradaic currents associated with the oxidation of Fc ([Fc.sup.0/+]) and reduction of FcP[F.sub.6] or FcB[F.sub.4] ([Fc.sup.+/0]) when both Fc and Fc are simultaneously present in the ILs differ from values obtained when individual Fc and [Fc.sup.+] solutions are used. The voltammetry for both the [Fc.sup.0/+] and [Fc.sup.+/0] processes exhibited near-Nernstian behavior at a glassy carbon macrodisk electrode and a platinum microdisk electrode, when each process was studied individually in the ILs. As expected, the reversible formal potentials (E[degrees]') and diffusion coefficients (D) at 23 [+ or -] 1 [degrees]C were independent of the electrode material and concentration. However, when Fc and FcP[F.sub.6] or FeB[F.sub.4] were both present, alterations to the mass transport process occurred and apparent D values calculated for Fc and [Fc.sup.+] were found to be about 25-39% and 32-42% larger, respectively, than those determined from individual solutions. The apparent value of the double layer capacitance determined by FT-ac voltammetry from individual and mixed Fc and [Fc.sup.+] conditions at the GC electrode was also a function of concentration. Double layer capacitance values increased significantly with the concentration of Fc and FcP[F.sub.6] or FcB[F.sub.4] when species were studied individually or simultaneously, but had a larger magnitude under conditions where both species were present. Variation in the structure of the ILs and hence mobillties of the ionic species, when Fc and FcP[F.sub.6] or FcB[F.sub.4] are simultaneously present, is considered to be the origin of the nonadditivity of the Faradaic currents and variation in capacitance. 10.1021/ac9020159

This paper presents the results of the dielectric measurements conducted on polymer nanocompounds consisting of polypropylene (PP) and polyhedral oligomeric siisesquioxane (POSS). The material compounds were analyzed with a scanning electron microscope (SEM) and Raman-atomic force microscope (Raman-AFM). Ac and lightning impulse (LI) breakdown strength of the material compounds were measured. Relative permittivity, loss factor and volume resistivity measurements were also conducted on the material samples. Two types of POSS, octamethyl and isooctyl, were used in different quantities. The thickness of the samples was approximately 600 [micro]m. Statistical analysis was applied to the results to determine the effects of the additive type and amount on the breakdown strength of polypropylene. The paper discusses the possibilities and restrictions in order to achieve advantages in high voltage applications using polyhedral oligomeric silsesquioxanes. Index Terms--Dielectric properties, polyhedral oligomeric silsesquioxane, polypropylene, statistical analysis.

A report is presented on the growth of and evolution of defects in GaN epilayers having single- and double-layer SiN(sub x) nanoporous insertion layers. The SiN(sub x) was formed in situ in the growth chamber of an organometallic vapor-phase epitaxy system by simultaneous flow of diluted silane and ammonia.

The anisotropy of the induced current density (ACID) method is an intuitive and generally applicable method for the investigation and visualization of delocalization and conjugation in ground, excited and transition states and organometallic compounds. ACID is complementary to the electrostatic surface and the electron density that provide information about charge and steric interactions.

The solid-state transformations under heating of cis-[Ir(CO)(sub 2)C1(C(sub 5)H(sub 5)N)] are examined by integrating infrared spectroscopy, conventional and bidimensional X-ray diffraction, thermal analysis, and hot stage optical microscopy. The structural changes associated with the solid-state transformations of organometallic compounds can be successfully achieved by integrating different investigation techniques.

Quantitative evaluations of the aromaticity (antiaromaticity) of neutral exocyclic substituted cyclopropenes [(HC).sub.2]C=X (X = BH to InH), C[H.sub.2] to Sn[H.sub.2], NH to SbH are described. Electronegative X-based substituents are observed to increase the aromaticity of the cyclopropene rings, while electropositive substituents have the opposite effect.

The asymmetric C-H functionalization of norbornene and norbornadiene with five-, six-, and seven-membered cyclic enones mediated by the reactive intermediate [{[[eta].sup.5]-([super t]Bu[Me.sub.2]Si)[C.sub.5][H.sub.4]}Co[(NO).sub.2]] is described. A novel base mixture derived from enantiopure ammonium salts and NaHMDS is used as a source of chirality and the enantioselective desymmetrization of [C.sub.s] alkenes is applied to the asymmetric synthesis of [C.sub.2]- and [C.sub.1]-symmetric diene ligands.

The endohedral fullerene [Sc.sub.3]NC@[C.sub.80]-[I.sub.h] is prepared and analyzed, which has an unprecedented planar quinary cluster in a fullerene cage. The intramolecular dynamics in [Sc.sub.3]NC@[C.sub.80]-[I.sub.h] has enabled the whole molecule to exhibit high polarity and ferroelectricity.

The synthesis, electronic properties and performance in dye-sensitized solar cells (DSSCs) of four cone-shaped organic dyes (ITD, ITD-Th, ITD-Hx, and ITD-OM) containing the isotruxene [pi]-scaffold are reported. The DSSCs fabricated with the cone-shaped organic dyes exhibited high open-circuit voltages and fill factors with a power conversion efficiency ([eta]) up to 5.45%, which is 80% of the ruthenium dye N719-based standard cell fabricated and measured under the same conditions.

Synthesis and characterization of a new trityl-nitroxide biradical TNN14 composed of a pyrrolidinyl-nitroxide and a trityl and its isotopically labeled 15N analogue TNN15 are described. [Super 15]N-labeled TNN15-H with an EPR doublet is found to exhibit improved EPR signal amplitude as compared with that of TNN14-H with an EPR triplet and the result from cyclic voltammetric studies verified the characteristic electrochemical behaviors of the trityl-nitroxide biradicals.

Three-dimensional m * n arrays of metal ion clusters, assembled as aromatic stacks of planar polynuclear metal complexes within columnar coordination cages are described. The reactions between hexanuclear [Au.sub.3]-[Au.sub.3] clusters and Ag(I) ions to prepare a silver-sandwiched hetero-[Au.sub.3]-Ag-[Au.sub.3] cluster are described.

Preparation and crystal structure characterization of first crown-tetracarbene complex of Ni(II) which was reduced by Na/Hg, with an uptake of two electrons is described. The computation study demonstrated that the orbital that receives electrons upon reduction of the complex Ni(II) is predominantly based on the crown carbene ligand.

The synthesis of colloidal GeS and GeSe nanostructures obtained by heating Ge[I.sub.4], hexamethyldisilazane, oelylamine, oleic acid and dodecanethiol or trioctylphosphine selenide is described. Optimal measurements have shown indirect ban gaps for GeS and GeSe and electrical measurements have shown that drop-cast films of GeSe have displayed p-type conductivity.

A simple and general method is described for switching the repulsive forces responsible for colloidal stabilization of metal chalcogenide complex (MCC)-capped nanocrystals (NCs) from long-range electrostatic to short-range steric through the formation of tight ionic pairs with cationic surfactants. The hybrid inorganic-organic coating is thermally decomposed at lower temperatures when compared to those required for removal of conventional organic ligands.

The design of stable redox active liposomes is described where the organometallic electroactive pendent is covalently bound to the phospholipid headgroup through a phospholipase D (PLD)-catalyzed transphosphatidylation reaction between a choline-bearing phospholipid and a primary alcohol containing a ferrocene derivative. The functionalization of a liposome surface with the organometallic redox phospholipd has helped in studying membrane-bound electrochemical reactions, which are important for designing redox-sensitive liposome delivery systems.

A family of cationic, neutral, and anionic bis(imino)pyridine iron alkyl complexes are prepared and their electronic and molecular structures are analyzed. The studies have established high spin ferrous compounds with neutral, redox-innocent bis(imino)pyridine chelates for the cationic complexes, which are known single-component ethylene polymerization catalysts.

In situ fabrication of [Co.sub.3][O.sub.4] or Pt nanocrystals incorporated into one-dimensional (1D) nanoporous carbons (NPCs) by an organometallic precursor-controlled thermolysis approach is described. The unique 1D metal-carbon hybrids have displayed a promising potential in electrochemical energy storage and NPCs/Pt is applied as an electrocatalyst showing catalytic efficiency toward methanol oxidation in comparison to commercial E-TEK (Pt/C) catalyst.

Density functional theory (DFT) is used for studying the geometric and electronic structure of [[(PCN)Pt[double bond]O].sup.+], composition in solution and reactivity. Stabilization of the Pt-oxo bonding is ascribed to bending of the terminal oxo ligand out of the plane of the complex and to the transfer of electron density from compact low lying Pt 5d orbitals to more diffuse 6s and 6p orbitals.

The dinuclear rhenium complex has produced two polymorphs (yellow and orange) in the solid state, which is either concomitantly or separately obtained on varying the crystallization rate. The behavior has shown the importance of the local organization of molecular dipoles in perturbing the photophysical properties of the molecule in the crystal.

The products of [super Br]U in excess electron transfer are examined and have shown that in DNA the proportion of products has changed with the distance between the donor and acceptor. A labeling experiment using [H.sub.2][super 18]O has shown that hole migration from [Py.sup..+] formed after charge separation is involved in the reaction.

Electrospray-ionization mass spectrometry was used to detect the charge-tagged organometallics due to reaction of the organic iodides bearing a cationic quaternary ammonium group at a remote position with zerovalent Pd complexes, Zn, or In leading to a C-I bond insertion. The proposed method allows a straightforward identification of the rate-limiting step and the determination of the corresponding second-order rate constant.

The EPR-silent trinitrosyliron complex (TNIC or [{Fe[(NO).sub.3]}.sup.10]) has released gaseous NO, producing in the case of S[R.sup.-] = S[Ph.sup.-] the EPR-active, neutral dinitrosyliron complex (DNIC) (IMes)Fe(SPh)[(NO).sub.2]. The solid-state molecular structures of the N-heterocyclic carbene (NHC)-containing trinitrosyliron complexes have shown that all thee complexes have a tetrahedral geometry in which the bulky mesitylene substituents of the carbene ligand appear to umbrella the Fe[(NO).sub.2]L (L = NO, CO, SPh) motif.

The crystals of the highly emissive copper(I) compounds are oxygen gas sensors, where the sensing ability has correlated with the amount of void space calculated from the crystal structures. The compounds have displayed linear Stern-Volmer plots with reproducible [K.sub.SV] constants from sample to sample and these results have shown that the sensing materials are crystalline and the sensing sites are homogeneous within the crystals.

A europium(III) DO3A-tris(amide) complex is described for imaging pH by MRI by using ratiometric chemical exchange saturation transfer (CEST) principles. The collection of two CEST images at two slightly different activation frequencies has provided a direct readout of solution pH without the need of a concentration marker.