Addition reactions of the organic and cyano groups of nitriles through cleavage of the C–CN bonds, namely carbocyanation, have been developed using nickel/Lewis acid (LA) cooperative catalysis. Originally, the reaction was performed with a nickel catalyst alone and was limited to the use of aryl and allyl cyanides as the nitrile substrates. By employing LA cocatalysts, the rate of the arylcyanation was accelerated significantly and the scope of nitriles used in the reaction across alkynes was expanded to include alkenyl, alkynyl, and alkyl cyanides. The high chemo-, regio-, and stereoselectivities of the alkyne–carbocyanation reactions were highlighted by the syntheses of biologically active compounds including the synthetic precursor of P-3622 and plaunotol, which possess defined tri- or tetrasubstituted ethene structures. Intramolecular arylcyanation of alkenes was also achieved by cooperative catalysis. Mechanistic studies on this particular transformation allowed us to identify several reaction intermediates, which revealed the modes of the cooperative catalysis derived from nickel- and aluminum-based LA. Intramolecular arylcyanation was achieved in an enantioselective manner using optically active bidentate phosphorus ligands, affording a protocol to introduce both a quaternary stereocenter and a cyano functionality without by-product generation.
Addition reactions of the organic and cyano groups of nitriles through cleavage of C–CN bonds, namely carbocyanation, have been developed using nickel/Lewis acid (LA) cooperative catalysis.
The short peptides that specifically bind to SnO2 nanoparticles (NPs) were selected by using a phage display method. After the fourth round selection, ten kinds of amino acid sequences were identified, and it was revealed that affinities of the obtained phages for SnO2 NPs were relatively higher than that of the unselected library phages. The identified peptide sequences showed that amino acids having a hydroxy group and hydrophobic amino acids were enriched in the selection process. Binding constants (Ka) of the chemically synthesized heptapeptides having the identified sequences were quantitatively estimated. The pTO-7 peptide (Ser–Ser–Ile–Leu–Arg–Phe–Pro) showed the greatest Ka value (5.80 × 105 M−1 at 25 °C) among the investigated peptides, and also showed binding specificity to SnO2. The SnO2-recognizing peptides functioned as nanostructure stabilizer during pH-dependent preparation of water-insoluble tin-based compound (Sn6O4(OH)4) at room temperature. These effects as stabilizers to disperse nanostructures in water phase were greater than that of a general purpose stabilizer poly(vinylpyrrolidone). Dynamic light scattering and transmission electron microscope analyses revealed that the formed structures in the presence of the pTO-7 peptide were squarish NPs with an approximately 60 nm diameter, and wide-angle powder X-ray diffraction analyses suggested that its crystallinity was increased by existence of the peptide.
The screened heptapeptide (pTO-7; Ser–Ser–Ile–Leu–Arg–Phe–Pro) from phage library that specifically bind to SnO2 could be used for preparation of highly crystallized Sn6O4(OH)4 nanoparticles under ambient conditions.
An improvement on the total energy results reported in Ref. 9 in atomic calculations based on a modified type hyperbolic cosine function cosh(βrμ + γ) is presented. It is shown that the noninteger n-generalized exponential type orbitals rn* - 1e - ζ rμ with modified type hyperbolic cosine as radial basis functions are a much better approximation to the Hartree–Fock orbitals than a double-zeta basis set of Slater type functions. The efficiency of the new basis function is tested by application to some closed and open shell neutral atoms and their ions. A substantial improvement in both the total and orbital energies is obtained within the minimal basis sets framework. The total energy values obtained in this work are significantly close to the numerical Hartree–Fock results. These results supersede all previous minimal basis function total energies achieved in the literature.
Newly developed time-, frequency-, and phase-resolved heterodyne-detected vibrational sum frequency generation (TR-HD-VSFG) spectroscopy opens a new door to explore ultrafast vibrational dynamics of interfacial water. Here, we present the first observation of TR-HD-VSFG spectra of water at a charged monolayer/aqueous solution interface.
Mono-, bis-, tris-, and tetrakis[(1-azulenylethynyl)phenylethynyl- and (1-azulenylethynyl)-2-thienylethynyl]benzenes have been prepared by Pd-catalyzed alkynylation of iodobenzene derivatives or 2-iodothiophene derivatives substituted by 1-azulenylethynyl group with polyethynylbenzenes under Sonogashira–Hagihara cross-coupling conditions. These compounds reacted with tetracyanoethylene (TCNE) in a formal [2 + 2] cycloaddition–cycloreversion reaction to afford the corresponding 1,1,4,4-tetracyano-2-(5-isopropyl-3-methoxycarbonyl-1-azulenyl)-1,3-butadien-3-yl chromophores in excellent yields. The redox behavior of the novel azulene-substituted tetracyanobutadiene (TCBD) derivatives was examined by cyclic voltammetry (CV) and differential pulse voltammetry (DPV), which revealed their multistep electrochemical reduction properties. Moreover, a significant color change was observed by visible spectroscopy under the electrochemical reduction conditions.
The mean association number of a porphyrin J aggregate matured in acidic aqueous media (dye concentration, 7.9 × 10−6 M; 0.094 M HClO4; 20 °C) was determined to be 440 by measurements of the sedimentation and diffusion constants on ultracentrifuge. The aggregate forms in a rod-shaped microcrystalline consisting of more than 400 stacked porphyrins which grows for a period of two days in acidic aqueous solutions. MCD (magnetic circular dichroism) B-term extrema and hypochromic reduction observed with J- and H-bands in aggregate were elucidated on the basis of structure of J aggregate. The Stokes shift and bandwidths observed with J bands were also discussed using motional narrowing model. The characteristic J peak appears in an earlier stage of dye association (Dm, m < 10–12), while the transition energy as well as the bandwidth remains unchanged during aggregate growth (DN, 20 < N < 500). The second-order rate law of the association of precursor oligomers reveals the molar absorbance in JB peak (εJB) decreases with increasing association number N (N-dependent hypochromism, εJB/M−1 cm−1 = 0.5 × 106 + 1.65 × 107/N), which makes possible to determine N. Mean association numbers N = 400–500 can be predicted for the molar absorbance varying with mean association number N.
The effect of ethylene glycol (EG), diethylene glycol (DEG) and their monoalkyl (C1–C6) ethers (cellosolves and carbitols) and dimethyl ethers (glymes and diglymes) on the micellar behavior of a cationic surfactant tetradecyltrimethylammonium bromide (TTAB) in aqueous solution was examined from electrical conductivity measurements. The effect of these additives on critical micelle concentration (CMC) and degree of counter ion dissociation (α) is evaluated. While both EG, DEG, their monomethyl/monoethyl ethers and dimethyl ethers increased CMC and α, for monobutyl and monohexyl ethers a decrease in CMC was noticed at studied concentration. For all ethers, the α values increased with concentration. NOESY experiments confirmed the location of glycol ethers in micellar solution. The results are discussed in terms of effect of ethers on water structure and solvent properties.
By placing chiral and achiral proligands on the eight positions of a cubane skeleton of Oh, resulting cubane derivatives are counted as three-dimensional (3D) structural isomers by the partial-cycle-index (PCI) method of the unit-subduced-cycle-index (USCI) approach (S. Fujita, Symmetry and Combinatorial Enumeration in Chemistry, Springer-Verlag, 1991; S. Fujita, Diagrammatical Approach to Molecular Symmetry and Enumeration of Stereoisomers, University of Kragujevac, Kragujevac, 2007), where the numbers of 3D structural isomers with given constitutional formulas are itemized with the subsymmetries of Oh. For this purpose, partial cycle indices with chirality fittingness (PCI-CFs) for respective subgroups of Oh are calculated by using unit subduced cycle indices with chirality fittingness (USCI-CFs) and an inverse matrix of the mark table of Oh. After introducing ligand-inventory functions into the PCI-CFs, expansions of the resulting equations provide us with generating functions for giving the numbers of 3D structural isomers. A Maple program source for counting cubane derivatives as 3D structural isomers is given as an example of practical calculation for listing the resulting data in tabular forms.
Cubane derivatives with a given chemical formula and a given symmetry are enumerated by applying the elementary-superposition method (S. Fujita, Theor. Chim. Acta1992, 82, 473–498) of the unit-subduced-cycle-index (USCI) approach to a cubane skeleton of the point group Oh. A cycle index (CI) for a regular or an irregular case of chiral and achiral ligands is calculated in accord with such a given chemical formula. The CI is superposed elementarily onto respective subduced cycle indices with chirality fittingness (SCI-CFs), which are calculated by starting from unit subduced cycle indices with chirality fittingness (USCI-CFs). Thereby, the numbers of fixed points (derivatives) are obtained with respect to the respective SCI-CFs to give a fixed-point vector (FPV). The resulting FPV is multiplied by an inverse matrix of the mark table of Oh to give an isomer-counting vector (ICV), which contains the numbers of 3D-structural isomers in an itemized fashion with respect to point-group symmetries. The concept of prochirality is examined by using cubane derivatives enumerated by the ICV.
A series of nonionic alkyl-substituted bissalicylaldehydato copper(II) (alkyl: octyl) complexes were prepared, and their two-dimensional (2D) self-assemblies at liquid/solid (highly oriented pyrolytic graphite, HOPG) interface were imaged by scanning tunneling microscope (STM). The ligands of the complexes were Schiff-base which was functionalized octyl (Ph-octyl) and a series of N-alkyl Cn. STM images were compared with the molecular structure and the crystal packing of C3 obtained by X-ray crystallography. Depending on their varying N-alkyl chain length, aggregation structure could be classified into two different self-assembled nanopatterns (C1–C3; short region and C4–C7; longer region) and the parity effect was observed in longer region. It was considered that the parity effect was originated from N-alkyl chain length.
New tris-fused tetrathiafulvalene analogues, in which the outer two TTF units were replaced by dendralenes with triple 1,3-dithiole rings, were synthesized. A theoretical calculation of the unsubstituted derivative based on density functional theory (DFT) using B3LYP/6-31G(d) method suggested that branching 1,3-dithiole rings were almost perpendicular to the central TTF moiety. Cyclic voltammogram of the octakis(methylthio) derivative exhibited five pairs of redox waves at −0.03, 0.06, 0.37, 0.48, and 1.14 V (V vs. Fc/Fc+, in benzonitrile). The first, the second, and the fifth redox processes corresponded to simultaneous two-electron-transfer processes, while the others corresponded to one-electron transfer. The redox behavior and UV–vis–NIR spectra of the octamethyl derivative suggested that the positive charges in the dication and tetracation states distributed mainly on the outer branching vinylogous TTF moieties. A compressed pellet of the charge-transfer complexes of the octamethyl and octakis(methylthio) derivatives with TCNQF4 exhibited moderate conductivity of σrt = 10−3 S cm−1 and semiconductive behavior with activation energies of 0.10–0.13 eV.
In a C=O···HO hydrogen bond incorporated into a π-conjugation system involving ring structures the hydrogen bond decreases the bond alternation of the system and enhances the aromaticity/antiaromaticity of the involved rings depending on the number of π-electrons, influencing stability of the system and barrier to proton transfer along the hydrogen bond.
Radical copolymer films with alternating layer structure showed anisotropic diffusion of transmitting light. The haze value of these diffuser films increased according to the amount of initiator. Excessive initiator conditions caused disorder of the layer structure and the disordered light-guide paths would randomize the directions of transmitted light and consequently would enlarge the haze values of the films.