A Fullerene-Based Molecular Torsion Balance for Investigating Noncovalent Interactions at the C60 Surface

To investigate the nature and strength of noncovalent interactions at the fullerene surface, molecular torsion balances consisting of C₆₀ and organic moieties connected through a biphenyl linkage were synthesized. NMR and computational studies show that the unimolecular system remains in equilibrium between well-defined folded and unfolded conformers owing to restricted rotation around the biphenyl C−C bond. The energy differences between the two conformers depend on the substituents and is ascribed to differences in the intramolecular noncovalent interactions between the organic moieties and the fullerene surface. Fullerenes favor interacting with the π-faces of benzenes bearing electron-donating substituents. The correlation between the folding free energies and corresponding Hammett constants of the substituents in the arene-containing torsion balances reflects the contributions of the electrostatic interactions and dispersion force to face-to-face arene–fullerene interactions.     

A Perturbation Theory for Core Operators of Hilbert-Schmidt Submodules

We discuss a perturbation theory for core operators of Hilbert-Schmidt submodules in the Hardy space over the bidisk. It is shown that eigenvalues of core operators perturbed by automorphisms of the bidisk have a certain continuity, and also we show that the family of eigenspaces of simple eigenvalues has a local cross section.     

Novel heterotetranuclear V2Mo2 or V2W2 complexes with 4,4'-di-tert-butyl-2,2'-bipyridine: syntheses, crystal structures, and catalytic activities

Two novel heterotetranuclear complexes [V(2)O(2)(μ-MeO)(2)(μ-WO(4))(2)(4,4'-(t)Bubpy)(2)] (1) and [V(2)O(2)(μ-MeO)(2)(μ-MoO(4))(2)(4,4'-(t)Bubpy)(2)] (2) were synthesized, and the solid state structures of these complexes were revealed by single crystal X-ray crystallography. The heterotetranuclear complexes 1 and 2 are centrosymmetric building blocks, considered as consisting of two [VO(4,4'-(t)Bubpy)](3+) units bridged by μ-MO(4)(2-) (M = W or Mo) anions connected with methoxy groups. Furthermore, catalytic activities of 1 and 2 in the alcohol oxidation with hydrogen peroxide as terminal oxidants in water as solvent were investigated.     

Structural, magnetic, and electronic properties of phenolic oxime complexes of Cu and Ni

Square planar complexes of the type Ni(L(1))(2), Ni(L(2))(2), Cu(L(1))(2), and Cu(L(2))(2), where L(1)H = 2-hydroxy-5-t-octylacetophenone oxime and L(2)H = 2-hydroxy-5-n-propylacetophenone oxime, have been prepared and characterized by single-crystal X-ray diffraction, cyclic voltammetry, UV/vis spectroscopy, field-effect-transistor measurements, density functional theory (DFT) and time-dependent DFT (TDDFT) calculations, and, in the case of the paramagnetic species, electron paramagnetic resonance (EPR) and magnetic susceptibility. Variation of alkyl groups on the ligand from t-octyl to n-propyl enabled electronic isolation of the complexes in the crystal structures of M(L(1))(2) contrasting with π-stacking interactions for M(L(2))(2) (M = Ni, Cu). This was evidenced by a one-dimensional antiferromagnetic chain for Cu(L(2))(2) but ideal paramagnetic behavior for Cu(L(1))(2) down to 1.8 K. Despite isostructural single crystal structures for M(L(2))(2), thin-film X-ray diffraction and scanning electron microscopy (SEM) revealed different morphologies depending on the metal and the deposition method (vapor or solution). The Cu complexes displayed limited electronic interaction between the central metal and the delocalized ligands, with more mixing in the case of Ni(II), as shown by electrochemistry and UV/vis spectroscopy. The complexes M(L(2))(2) showed poor charge transport in a field-effect transistor (FET) device despite the ability to form π-stacking structures, and this provides design insights for metal complexes to be used in conductive thin-film devices.     

Two-level hierarchical parallelization of second-order Møller-Plesset perturbation calculations in divide-and-conquer method

A two‐level hierarchical parallelization scheme including the second‐order Møller–Plesset perturbation (MP2) theory in the divide‐and‐conquer method is presented. The scheme is a combination of coarse‐grain parallelization assigning each subsystem to a group of processors, with fine‐grain parallelization, where the computational tasks for evaluating MP2 correlation energy of the assigned subsystem are distributed among processors in the group. Test calculations demonstrate that the present scheme shows high parallel efficiency and makes MP2 calculations practical for very large molecules. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2011     

Fabrication of CuInS2 films from electrodeposited Cu/In bilayers: effects of preheat treatment on their structural, photoelectrochemical and solar cell properties

Polycrystalline CuInS(2) films were fabricated by sulfurization of electrodeposited Cu and In metallic precursor films in a Cu-rich composition at 520 °C in H(2)S (5% in Ar). Structural analyses revealed that the adherence of the thus-formed CuInS(2) film to the Mo substrate was strongly dependent on heating profiles of the Cu/In bilayer film: a CuInS(2) film with poor adherence having many crevices was formed when the Cu/In bilayer film was heated monotonously from room temperature to 520 °C in Ar within 25 min followed by sulfurization, whereas CuInS(2) films with good adherence were obtained when the Cu/In films were pretreated at 110 °C in Ar for 10-60 min just before increasing the temperature up to 520 °C for sulfurization. It was also clarified that the CuInS(2) film obtained without 110 °C pretreatment had pinholes inside the film, whereas the CuInS(2) films formed after 110 °C pretreatment showed no notable pinholes. Photoelectrochemical responses of these CuInS(2) films in an electrolyte solution containing Eu(III) indicated that the CuInS(2) films obtained after 110 °C pretreatment had higher external quantum efficiency (EQE) values than those of films obtained without 110 °C pretreatment, mainly due to better adherence of 110 °C pretreated CuInS(2) films to the Mo substrate than the CuInS(2) film obtained without 110 °C pretreatment. The performance of solar cells with an Al:ZnO/Zn(S,O)/CdS/CuInS(2)/Mo structure also depended on the structural characteristics of the CuInS(2) films, i.e., preliminary conversion efficiencies of ca. 5% were obtained for devices based on the CuInS(2) films obtained after 110 °C pretreatment, whereas the device prepared by the CuInS(2) film without 110 °C pretreatment showed the conversion efficiency less than 1.5%.     

A complementary organic inverter of porphyrazine thin films: low-voltage operation using ionic liquid gate dielectrics

We studied a complementary organic inverter consisting of a p-type semiconductor, metal-free phthalocyanine (H(2)Pc), and an n-type semiconductor, tetrakis(thiadiazole)porphyrazine (H(2)TTDPz), operated through the ionic-liquid gate dielectrics of N,N-diethyl-N-methyl(2-methoxyethyl)ammonium bis(trifluoromethylsulfonyl)imide (DEME-TFSI). This organic inverter exhibits high performance with a very low operation voltage below 1.0 V and a dynamic response up to 20 Hz.     

Intrinsic interaction mode of an inhalation anesthetic with globular proteins: a comparative study on ligand recognition

Interaction mode of an inhalation anesthetic halothane with water-soluble globular proteins, myoglobin (Mgb) and lysozyme (Lys), was studied by differential scanning calorimetry (DSC) and viscometry, and the results were compared with those of bovine serum albumin (BSA). The anesthetic sensitivity was markedly different among the proteins: Mgb was destabilized, Lys was slightly destabilized, and BSA was conversely stabilized. Further, the interaction mode was quite different from those of specific binders for the proteins. The anesthetic sensitivity was highly correlated with the hydrophilicity on the protein surface (Mgb?<?Lys?<?BSA) and the rigidity of the protein structure (BSA????Mgb?<?Lys). We showed that the anesthetic sensitivity among globular proteins can be roughly classified into four categories, and proteins with small hydrophilicity and soft structure are suitable as model proteins of anesthesia. By contrast, the binding of the specific binders was characterized by the lower effective concentrations. The molar ratio of the binder to the protein at the effective concentration was well consistent with the binding number determined from the X-ray structural analysis. Moreover, the interaction mode of the binder was not necessarily in accord with the mode expected from the change in the protein structure. Considering the above facts, we can systematically interpret the effect of an anesthetic on globular proteins by four factors: (1) hydrophobicity of an anesthetic, (2) hydrophilicity of a protein surface, (3) rigidity of a protein structure, and (4) molar ratio of an anesthetic to a protein at the effective concentration.     

Hypervalent nonbonded interactions of a divalent sulfur atom. Implications in protein architecture and the functions

In organic molecules a divalent sulfur atom sometimes adopts weak coordination to a proximate heteroatom (X). Such hypervalent nonbonded S···X interactions can control the molecular structure and chemical reactivity of organic molecules, as well as their assembly and packing in the solid state. In the last decade, similar hypervalent interactions have been demonstrated by statistical database analysis to be present in protein structures. In this review, weak interactions between a divalent sulfur atom and an oxygen or nitrogen atom in proteins are highlighted with several examples. S···O interactions in proteins showed obviously different structural features from those in organic molecules (i.e., π(o) → σ(s)* versus n(o) → σ(s)* directionality). The difference was ascribed to the HOMO of the amide group, which expands in the vertical direction (π(o)) rather than in the plane (n(o)). S···X interactions in four model proteins, phospholipase A? (PLA?), ribonuclease A (RNase A), insulin, and lysozyme, have also been analyzed. The results suggested that S···X interactions would be important factors that control not only the three-dimensional structure of proteins but also their functions to some extent. Thus, S···X interactions will be useful tools for protein engineering and the ligand design.