Rhodium‐Catalyzed Stitching Polymerization of 1,5‐Hexadiynes and Related Oligoalkynes

A new mode of polymerization, rhodium‐catalyzed stitching polymerization, has been developed for the synthesis of π‐conjugated polymers with bridged repeating units from nonconjugated 1,5‐hexadiynes containing both terminal and internal alkyne moieties as monomers. The polymerization proceeded smoothly with a high degree of stitching efficiency under mild conditions, and 1,5,9‐decatriyne and 1,5,9,13‐tetradecatetrayne monomers could also be employed. The present polymerization strategy would be particularly beneficial for the synthesis of polymers consisting of a repeating unit that is difficult to prepare as a stable monomer because it does not require the use of a preformed bridged π‐conjugated monomer.     

Evaluation of measurement uncertainty in the elemental analysis of sintered silicon carbide using laser ablation in liquid—inductively coupled plasma mass spectrometry with external calibration and isotope dilution

Accreditation and Quality Assurance - The goal of this study was to evaluate the uncertainty of elemental analytical methods that use laser ablation in liquid (LAL) as a pretreatment. After LAL...     

Direct Estimation of the Surface Location of Immobilized Functional Groups for Concerted Catalysis Using a Probe Molecule

The location of active sites during concerted catalysis by a metal complex and tertiary amine on a SiO₂ surface is discussed based on the interaction between the functionalized SiO₂ surface and a probe molecule, p‐formyl phenylboronic acid. The interactions of the probe molecule with the surface functionalities, diamine ligand, and tertiary amine, were analyzed by FT‐IR and solid‐state ¹³C and ¹¹B MAS NMR. For the catalyst exhibiting high 1,4‐addition activity, the diamine ligand and tertiary amine base exist in closer proximity than in the catalyst with low activity.     

On the Smith normal form of a skew‐symmetric d‐optimal design of order

We show that the Smith normal form of a skew‐symmetric D ‐optimal design of order is determined by its order. Furthermore, we show that the Smith normal form of such a design can be written explicitly in terms of the order , thereby proving a recent conjecture of Armario. We apply our result to show that certain D ‐optimal designs of order are not equivalent to any skew‐symmetric D ‐optimal design. We also provide a correction to a result in the literature on the Smith normal form of D ‐optimal designs.     

Effects of a lysophosphatidylcholine and a phosphatidylcholine on the morphology of taurocholic acid-based mixed micelles as determined by small-angle X-ray scattering

We previously showed that Caco-2 cell absorption of β-carotene from taurocholic acid (TA)-based mixed micelles differed depending on the composition of the micelles. In this study, the shapes and sizes of TA-based mixed micelles, that is, mixed micelles of TA, 1-oleoyl-rac-glycerol (MG), oleic acid (OLA), and either 1-palmitoyl-sn-glycero-3-phosphocholine (MPPC; i.e., a lysophospholipid) or 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC; i.e., a phospholipid) (60:3:1:0.75–12) were determined by using small-angle X-ray scattering (SAXS). We found that increasing the ratio of MPPC in mixed micelles of TA, MG, OLA, and MPPC was responsible for the previously observed enhanced β-carotene absorption by Caco-2 cells and changed the micelle shape from core–shell spherical to core–shell ellipsoidal. In contrast, increasing the ratio of POPC in mixed micelles of TA, MG, OLA, and POPC was responsible for the suppressed β-carotene absorption by the cells, changed the micelle shape from core–shell spherical to core–shell ellipsoidal to core–shell cylindrical, and caused a rapid increase in micelle volume. These results will be useful for understanding the mechanisms that mediate β-carotene absorption by cells and for developing technologies to improve the intestinal absorption of lipophilic components of drugs and nutrients.     

Phosphine‐Catalyzed anti‐Carboboration of Alkynoates with 9‐BBN‐Based 1,1‐Diborylalkanes: Synthesis and Use of Multisubstituted γ‐Borylallylboranes

Trialkylphosphine organocatalysis has enabled the regioselective anti‐carboboration of alkynoates with 9‐BBN‐based 1,1‐diborylalkanes to produce secondary allylboranes with β‐alkoxycarbonyl and γ‐boryl substituents. The utility of the densely functionalized allylboranes was demonstrated by the highly diastereoselective allylation of N‐(trimethylsilyl)aldimines to produce homoallylamines containing tertiary allylborane and acrylate moieties.     

Hydrogenated tetraazaporphyrins--old but new core-modified phthalocyanine analogues

The synthesis, and spectroscopic and electrochemical properties of hydrogenated tetraazaporphyrins (TAPs), namely tetraazachlorins (TACs), tetraazabacteriochlorins (TABCs) and tetraazaisobacteriochlorins (TAiBCs), have been reviewed. While the first synthesis of this type of hydrogenated aromatic macrocycle was achieved as early as 1958 by Linstead et al. (G. E. Ficken, R. P. Linstead, E. Stephen and M. Whalley, J. Chem. Soc., 1958, 3879), the development of modern synthetic strategies enables us to isolate stable forms of the hydrogenated TAP derivatives. Benzo-, 2,3-naphtho- and 1,2-naphtho-fused derivatives were synthesized extensively, and all structural isomers have been elucidated. The chemical structures have been characterized using a variety of techniques, including mass spectrometry, (1)H and (13)C NMR, X-ray crystallography and IR spectroscopy. The spectroscopic properties (e.g., electronic absorption, magnetic circular dichroism (MCD), and fluorescence) of these compounds differ significantly from those of the original TAPs, or phthalocyanines (Pcs), due to the symmetry-lowering effects of the core aromatic macrocycles. The experimentally observed properties have been rationalized on the basis of electrochemical studies and quantum chemical calculations. As an application of the TAC skeleton, the synthesis and electronic structures of tribenzo TAC (TBTAC)-C(60) conjugates, in which both components are covalently connected directly and thus show remarkable molecular orbital (MO) mixing between the constituting moieties, have also been reviewed.     

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.     

Optical resolution, absolute configuration, and chiroptical properties of three-layered [3.3]paracyclophane

A racemic mixture of three-layered [3.3]paracyclophane ([3.3]PCP), 1, has been resolved into two enantiomers, and their absolute configuration was determined from a comparison of experimental chiroptical properties and density functional theory (DFT) calculations. A simple model comprising two p-xylenes and 1,2,4,5-tetramethylbenzene (durene) was used to explain the origin of the chiroptical properties of the three-layered cyclophane system.