Synthesis and electronic structures of D2h-symmetry tetrabenzoporphyrins

A novel low-symmetry tetrabenzoporphine with D_2h symmetry (1) and its zinc complex (2) were prepared via mixed condensation reaction of 5,6-dimethyl phthalimide and 4,5,6,7-tetraphenyl phthalimide with sodium acetate in the presence of zinc acetate. The zinc complex 2 exhibited a split Q band at 640 and 623 nm and a single Soret band at 435 nm. The absorption spectra of 1 and 2 were calculated and analyzed using Hartree-Fock theory based on INDO/S Hamiltonian.     

NONBRIDGED HALF-TITANOCENES CONTAINING ANIONIC ANCILLARY DONOR LIGANDS: PROMISING NEW CATALYSTS FOR PRECISE SYNTHESIS OF CYCLIC OLEFIN COPOLYMERS (COCs)

Precise,efficient copolymerizations of ethylene with cyclic olefins[norbornene(NBE),cyclopentene(CPE)]using nonbridged half-titanocenes of type,Cp'TiCl_2(L)(Cp'=cyclopentadienyl group,L=aryloxo,ketimide)-MAO catalyst systems have been summarized.CpTiCl_2(N=C'Bu_2)exhibited both remarkable catalytic activity and efficient NBE incorporation for ethylene/NBE copolymerization:the NBE incorporation by Cp'TiCl_2(X)(X=N=C'Bu_2,O-2,6-'Pr_2C_6H_3; Cp'=Cp,C_5Me_5,indenyl)was related to the calculated coordination ...     

High enrichment of 15N by chromatographic chemical process

Nitrogen isotope enrichment experiments were conducted to obtain highly enriched (15)N by ion-exchange process. (15)NH(4)Cl ((15)N=80%) as feeding materials were used to perform the chromatographic operation with two different flow rates and column diameters. Both separation coefficient (epsilon) and height equivalent to a theoretical plate (HETP) have same values in two run experiments. The value of HETP was more enlarged when high enrichment of (15)N was obtained in comparison with that of low enrichment. 99.756% (15)N and 13.63 g (15)N whose percentage was over 99.0% were successfully achieved by 25 m chromatographic migration with the flow rate and column diameter at 50 cm(3)/mL, 3.0 cm, respectively. High flow rate and large column diameter have advantages to the enrichment of (15)N by ion exchange process.     

Electron transfer of quinone self-assembled monolayers on a gold electrode

Dialkyl disulfide-linked naphthoquinone, (NQ-C_n-S)₂, and anthraquinone, (AQ-C_n-S)₂, derivatives with different spacer alkyl chains (C_n: n = 2, 6, 12) were synthesized and these quinone derivatives were self-assembled on a gold electrode. The formation of self-assembled monolayers (SAMs) of these derivatives on a gold electrode was confirmed by infrared reflection-absorption spectroscopy (IR-RAS). Electron transfer between the derivatives and the gold electrode was studied by cyclic voltammetry. On the cyclic voltammogram a reversible redox reaction between quinone (Q) and hydroquinone (QH₂) was clearly observed under an aqueous condition. The formal potentials for NQ and AQ derivatives were −0.48 and −0.58 V, respectively, that did not depend on the spacer length. The oxidation and reduction peak currents were strongly dependent on the spacer alkyl chain length. The redox behavior of quinone derivatives depended on the pH condition of the buffer solution. The pH dependence was in agreement with a theoretical value of E_1/2 (mV) = E′ − 59pH for 2H⁺/2e⁻ process in the pH range 3–11. In the range higher than pH 11, the value was estimated with E_1/2 (mV) = E′ − 30pH , which may correspond to H⁺/2e⁻ process. The tunneling barrier coefficients (β) for NQ and AQ SAMs were determined to be 0.12 and 0.73 per methylene group (CH₂), respectively. Comparison of the structures and the alkyl chain length of quinones derivatives on these electron transfers on the electrode is made.     

Synthesis and properties of DNA complexes containing 2,2,6,6-tetramethyl-1-piperidinoxy (TEMPO) moieties as organic radical battery materials

We report here the first example of organic radical battery with DNA. Though there is a growing interest in DNA/cationic-lipid complexes as promising gene delivery vehicles, few efforts have been focused on the use of such complexes as advanced materials for organic optoelectronic applications. The present article describes how substitution of the sodium counter cation of DNA with cationic amphiphilic lipid(1-4) provided novel DNA-lipid complexes that contain TEMPO radicals, in which the actual mole ratio of phosphate to lipid was 1:0.84 to 1:0.16. All the TEMPO-containing DNA-lipid complexes displayed reversible two-stage charge/discharge processes, the discharge capacities of which were 40.5-60.0 A h kg(-1). In particular, the capacity of a DNA-lipid(3)-based cell reached 60.0 A h kg(-1), which corresponds to 192 % relative to its theoretical value for the single-electron one-stage process, indicating a two-electron process.     

Construction of a chiral quaternary carbon center by indium-catalyzed asymmetric alpha-alkenylation of beta-ketoesters

Construction of a nonracemic all-carbon quaternary stereocenter at the alpha-position of beta-ketoesters was achieved by way of an indium(III)-catalyzed diastereoselective alpha-alkenylation reaction of chiral enamines with 1-alkynes. The enamine bearing a chiral auxiliary derived from l-isoleucine was added to the alkyne to give an alpha-alkenylated product in excellent yield and with a stereoselectivity better than 90% ee. One can ascribe the high selectivity to a chelate intermediate involving the auxiliary and the metal atom and the high yield to efficient interactions between the indium(III) atom and the alkyne. The selectivity increased as the reaction temperature was raised to 120 degrees C and decreased at higher temperatures.     

Catalytic use of indium(0) for carbon-carbon bond transformations in water: general catalytic allylations of ketones with allylboronates

We have discovered the unprecedented catalytic use of In(0) for catalytic C-C bond transformations. Remarkably, these general catalytic allylations of ketones proceeded smoothly in water as a sole solvent under mild conditions, and water proved to be essential for these reactions. Both the displayed substrate scope and the functional group tolerance were excellent. Importantly, the In metal catalyst could be easily recovered and reused without loss of catalytic activity. Moreover, when an alpha-substituted allylboronate was used, an unusual constitutional selectivity was observed providing exclusively the formal alpha-adduct. Additionally, the resulting tertiary homoallylic alcohols were obtained with exceptionally high diastereoselectivities. The applicability of this concept to asymmetric catalysis in water by using In(0) combined with a chiral bis(oxazoline) ligand was demonstrated as well.     

An efficient protocol of iridium-catalyzed allylic substitution reaction and its application to polymer synthesis: complementary regio- and stereoselective allylation polycondensation via Ir and Pd catalyses

An efficient protocol of the Ir-catalyzed allylic substitution reaction is reported using N,O-bis(trimethylsilyl)acetamide as a base in the presence of nBu4NF as a cocatalyst. The reaction completely proceeded under very mild conditions, and a branched allylated compound that is not easy to access via the Tsuji-Trost reaction can be synthesized. The reaction system is practical enough to be applicable for polymer syntheses. The Ir- and Pd-catalyzed allylation polycondensations generally show complementary regio- and stereoselectivities. The Ir-catalyzed reaction is versatile, and a mixed dual regioselectivity such as a branched-linear selectivity on each electrophile can also be achieved.     

<Superscript>57</Superscript>Fe emission Mössbauer spectroscopy following dilute implantation of <Superscript>57</Superscript>Mn into In <Subscript>2</Subscript>O<Subscript>3</Subscript>

Emission Mössbauer spectroscopy has been utilised to characterize dilute ⁵⁷Fe impurities in In ₂O₃ following implantation of ⁵⁷Mn (T _1/2 = 1.5 min.) at the ISOLDE facility at CERN. From stoichiometry considerations, one would expect Fe to adopt the valence state 3 + , substituting In ³⁺, however the spectra are dominated by spectral lines due to paramagnetic Fe²⁺. Using first principle calculations in the framework of density functional theory (DFT), the density of states of dilute Fe and the hyperfine parameters have been determined. The hybridization between the 3d-band of Fe and the 2p band of oxygen induces a spin-polarized hole on the O site close to the Fe site, which is found to be the cause of the Fe²⁺ state in In ₂O₃. Comparison of experimental data to calculated hyperfine parameters suggests that Fe predominantly enters the 8b site rather than the 24d site of the cation site in the Bixbyite structure of In ₂O₃. A gradual transition from an amorphous to a crystalline state is observed with increasing implantation/annealing temperature.     

<Superscript>119</Superscript>Sn Mössbauer studies on ferromagnetic and photocatalytic Sn–TiO<Subscript>2</Subscript> nanocrystals

Diluted Sn doped TiO₂ nanocrystals (Sn/Ti ratio: x ≤ 1.37 %) were synthesized by a simple hydrothermal method using pure reagents without any surfactant and dispersant material. The XRD of these samples showed an anatase phase, anatase and rutile mixed phases, and a rutile phase of TiO₂ and SnO₂ with the increase of Sn dopant concentrations. ¹¹⁹Sn Mössbauer spectra gave the broad peaks, which were decomposed into doublets and sextets because almost all these samples showed magnetic hysteresis even at room temperature. The titanium oxides doped with x ≤ 0.12 % showed the relatively large magnetic hysteresis and high photocatalytic activity. Mössbauer spectra of samples doped with x > 0.3 % were analyzed by one doublet and two sextets although the samples showed weak ferromagnetism. Three kinds of Sn species may be distinguished as Sn ⁴⁺ substituted TiO₂ and two different magnetic arrangements of Sn doped TiO₂: one with more oxygen defects and other at the interface of TiO₂ and precipitated SnO₂ containing Ti atoms. The correlation between various amounts of Sn sites and photocatalytic activity and/ or magnetic property was discussed.