Singlet�Ctriplet energy gap for trimethylenemethane, oxyallyl diradical, and related species: single- and multireference computational results

We have investigated the through-bond exchange interactions in three non-Kekulé hydrocarbon diradicals on the basis of single- and multireference coupled cluster and related broken-symmetry (BS) methods. The singlet?Ctriplet energy gap (S-T gap) and diradical characters for these species are evaluated. It is found that the spin contamination involved in the BS solutions is non-negligible and the approximate spin-projection method greatly improves the usual BS solutions. As for Mukherjee??s state-specific multireference coupled cluster (MkMRCC) computations, the size-consistent correction with the UHF localized natural orbitals (ULO) is useful to obtain the qualitatively correct 2J values.     

Reconstitution of bacterial photosynthetic unit in a lipid bilayer studied by single-molecule spectroscopy at 5 K

As a model of photosynthetic unit (PSU), self-assembled aggregates of pigment-protein complexes from photosynthetic bacteria were prepared in a lipid bilayer by reconstitution of the light-harvesting 2 (LH2) complex and light-harvesting 1-reaction center (LH1-RC) complex through detergent removal of their micelles in the presence of lipids. By performing polarization-controlled fluorescence and fluorescence-excitation spectroscopy on single aggregates at a temperature of 5 K, the composition of individual aggregates was determined and excitation energy transfer (EET) between constituent complexes was observed. LH2 and LH1-RC from a bacterium, Rhodobacter (Rb.) sphaeroides, were found to form a trimeric aggregate in which EET takes place from one LH2 to two LH1-RCs. In contrast, a heterodimer of LH2 and LH1-RC in which EET works was found to assemble from a combination of complexes of different bacterial species, that is, LH2 from Rb. sphaeroides and LH1-RC from Rhodopseudomonas (Rps.) palustris.     

Crystallization, transformation and microstructures of polymorphic fats in colloidal dispersion states

This article reviews new information about polymorphic structures, kinetic and microscopic properties of fat crystals in colloidal dispersion states such as aggregates (spherulite), oil-in-water (O/W) emulsion and water-in-oil (W/O) emulsion. The kinetic processes of fat crystallization under external factors such as different cooling rates, shear and ultrasound irradiation are reviewed. Microstructures of fats revealed by synchrotron radiation microbeam X-ray diffraction techniques in bulk and emulsion states are also reviewed for the first time.     

Synthetic protocol for diarylethenes through Suzuki-Miyaura coupling

The synthesis of a variety of diarylethenes through the Suzuki-Miyaura coupling reaction of 1,2-dichlorohexafluorocyclopentene with arylboronic acids and esters has been developed. Thiophenes with various substituents such as cyano and ester functionalities can be incorporated.     

Expanding family of π-conjugated trinuclear dithiolenes: the cases of group 8 (Ru(II)) and 10 (Ni(II) and Pt(II)) metals

New π-conjugated trinuclear dithiolenes with group 8 (6, Ru(II)) and 10 (7 and 8, Ni(II) and Pt(II)) metals were synthesized. Compounds 6 and 7 exhibited intense electronic communication through the phenylene bridge among the three dithiolene moieties during oxidation of the metalladithiolene rings, which has not been confirmed in the analogous family of group 9 metals, 1-5. Compound 8 exhibited an intense absorption band across the visible and near-IR regions, which was assigned as a charge transfer to the diimine and was red-shifted and broadened compared to the corresponding band of the mononuclear complex.     

Formation of PtRu alloy nanoparticle catalyst by radiolytic process assisted by addition of <Emphasis Type="SmallCaps">dl</Emphasis>-tartaric acid and its enhanced methanol oxidation activity

PtRu nanoparticle catalysts with 2-nm size supported on carbon were synthesized by a radiolytic process, assisted with the addition of dl-tartaric acid. Gradual alloying with the addition was confirmed by structural analyses with techniques of the X-ray diffraction and the X-ray absorption fine structure. Their methanol oxidation activities evaluated by the linear sweep voltammetry were higher than that of the commercial one, and found to be enhanced in accordance with the gradual change in the bimetallic structure from the Pt-core/Ru-shell to the random alloy. A good correlation was found between the catalytic activity and the indicators, which stands for the occurring frequency of the Pt–Ru bonds, calculated from the coordination numbers determined by the extended X-ray absorption fine structure analysis. It was confirmed that the addition of dl-tartaric acid in the radiolytic process certainly promoted the random alloy formation of PtRu bimetallic nanoparticles and enhanced their methanol oxidation activity.     

Palladium-catalyzed coupling of alkenyl iodides with ethynyl oxiranes: Synthesis of epoxy enediyne core intermediates related to neocarzinostatin chromophore

Coupling of functionalized cyclopentenyl iodides with ethynyl oxiranes has been achieved by using catalytic amount of Pd(CH₃CN)₂Cl₂ and CuI in the presence of i-Pr₂NEt in moderate to good yields.     

Solvent‐ and concentration‐sensitive fluorescence of 2‐(3,4,5,6‐tetrafluoro‐2‐hydroxyphenyl)benzoxazole

2‐(3,4,5,6‐Tetrafluoro‐2‐hydroxyphenyl)benzoxazole ( 2 ) emits the long wavelength fluorescence around 500 nm in nonpolar solvent via the intramolecular proton transfer process in the excited state of 2 (enol‐form) and also emits the intermediate wavelength fluorescence around 440 nm in polar solvent, which is assumed to originate from the excited state of 2 (anion). The ease of formation of 2 (anion), compared to 2‐(2‐hydroxyphenyl)benzoxazole ( 1 ), is explained by the strongly inductive fluorine atoms. In a solvent with the intermediate polarity, 2 emits both fluorescences and their relative intensity is dependent on the concentration of 2 , which is supposed to be caused by the high sensitivity of the intermediate wavelength emission to the concentration quenching.     

Zwitterionic Corroles: Regioselective Nucleophilic Pyridination of a Doubly Linked Biscorrole

Pyridine attacks : Nucleophilic addition of pyridine derivatives to a doubly linked corrole, which is a stable singlet biradical species, occurs at the bay area with high regioselectivity to provide zwitterionic dimers (see picture; Ar=C₆F₅). Charge transfer between the anionic corrole and the pyridinium groups induces effective fluorescence quenching of the corrole dimer, which can be utilized for selective fluoride ion recognition.