Multiply Twisted Chiral Macrocycles Clamped by Tethered Binaphthyls Exhibiting High Circularly Polarized Luminescence Brightness

Chiral macrocyclic dimers, trimers, and tetramers composed of paraphenylene and tethered binaphthyl were synthesized, and their molecular structures and chiroptical properties were investigated. X-ray analysis and theoretical calculations revealed that multiple twisted molecular structures – dimers, trimers, and tetramers – adopt figure-of-eight, Möbius triangle, and concave rectangle structures, respectively. These homologues have large ϵ values in their UV-vis absorption spectra because of the π-conjugation of the naphthalene-phenylene-naphthalene frameworks. Owing to the shape-persistent ring structure and tethering with −OCH₂CH₂O−, high fluorescence quantum yields and a relatively high dissymmetry factor g_CPL in circularly polarized luminescence (CPL) spectra were achieved. This results in CPL brightness (B_CPL) of over 100, which is greater than that of the conventional organic CPL dye.     

Hydration of Polycationic [5]Radialene with Quintuple 1,3-Dithiol-2-ylidenes Leads to a New Class of π-Extended Tetrathiafulvalene Scaffold

[5]Radialene with quintuple 4,5-benzo-1,3-dithiol-2-ylidenes (DTs) easily forms a stable polycationic salt ( 1 )⁴⁺(BF₄⁻)₄ owing to its aromatic character in the central cyclopentadienide ring. In this work, it was found that the polycationic salt ( 1 )⁴⁺ underwent a hydration reaction in moist polar solvent to give several unexpected products, namely, an oxygen adduct dicationic salt ( 2 )²⁺, a tetrathiafulvalene (TTF) vinylogue ( 3 ) with 1,4-dithiine-2(3H)-one moieties, and an oxygen adduct of π-extended TTF with a cyclopentenone core ( 4 ). Their molecular structures were fully determined by X-ray crystal-structure analysis. In this reaction, irreversible hydration to the polycationic salt might either initiate the ring expansion and lead to the successive hydration at the specific cationic DT ring (for 3 ), or promote the transannular reactions to the next DT ring followed by elimination of the DT ring (for 4 ). Cyclic voltammetry and differential pulse voltammetry measurements for compound 3 indicated the occurrence of multi redox process resulting from electronic delocalization on the vinylogous TTF moiety. The electronic structures of the cationic species of 3 were also investigated by electronic spectra.     

Depolarization field effect on the ferroelectric behavior of polymers

The effect of the depolarization field in crystallites on the ferroelectric behavior of polymers is discussed on the assumption that the crystallite is a prolate ellipsoid with its major axis directed along the electric field. The theory relates the polarization P and the electric field E in the crystallite to the overall values P and E for the polymer. The determination of the P -E hysteresis of a crystallite from the P-E hysteresis is given with examples for poly(vinylidene fluoride) (PVDF) and vinylidene fluoride (VDF)–trifluoroethylene (TrFE) copolymer. The ratio R = J/(P_s ? P), with J the switching current density and P_s the saturation polarization of polymer, is proved to be free from the depolarization field effect and the plot of logR against logarithmic time is shown to have merit for characterization of switching behavior. Examples of the curves are given for PVDF and VDF-TrFE copolymers. The temporal change of local electric field in the unreversed domains in the crystallite in the course of polarization reversal is predicted by the theory and this change is proved to be a significant mechanism of switching acceleration.     

An electron microscopic study of the archaeal feast/famine regulatory protein: 2. Crystal formation by a full length FFRP,pot0434017 (FL11)

In the crystal the archaeal feast/famine regulatory protein pot0434017 (FL11) forms helical cylinders, each extending along the c axis and densely packed with a hexagonal symmetry in the a/b plane. By applying cryo-electron microscopy to protein solutions yielding crystals, with selectively focussing zero-loss electrons accelerated at 200 KV, two types of regular objects were observed, hexagonal (i.e. projections of crystals to their a/b planes) or rectangular (i.e. projections onto planes perpendicular to a/b). The two types of images are different in the ranges of sizes, suggesting that the crystallization might initiate by forming a hexagonal sheet on the a/b plane, subsequently extending along the c axis. Some other images obtained were intermediate between regular and amorphous, suggesting that some crystals were growing inside amorphous precipitates by rearranging the protein molecules, and that some larger crystals were growing by absorbing smaller amorphous precipitates. Tubes running parallel to each other were also observed in pieces of thin films. These tubes have hollows in their centers, and their lateral arrangement with a periodicity of ~150 Å and the presence of a helical component ~50 Å suggest that they are projections of the helical cylinders, forming mono-layers on the a/c or b/c planes.     

Color change (yellow \documentclass{article}\pagestyle{empty}\begin{document}$\rightleftharpoons$\end{document} orange) of 4,6,7-tri(alkoxy-substituted aryl)-1,2,5-thiadiazolo[3,4-c]pyridines in the solid phase

Reversible color change of 4,6,7-tri(alkoxy-substituted phenyl)-1,2,5-thiadiazolo[3,4-c]pyridines 5 in the solid state was observed: on grinding, yellow crystals of 5 became an orange amorphous solid which, on heating or washing with an appropriate solvent, gave the original yellow crystals.     

Coherent convergent beam electron diffraction for analysis of lattice fitting in PbTe/MgO bi-crystals

Coherent convergent beam electron diffraction is for the first time applied to the analysis of lattice fitting between vacuum-deposited PbTe and MgO thin crystals in the plan-view mode. The possibility of determination of the rigid-body shift is discussed on the basis of simulated diffraction patterns from the bi-crystals as well as the preliminary experimental results obtained by a 200 kV transmission electron microscope with a field emission electron gun. In the analysis, the importance of the position of interference fringes at overlaps of PbTe 200 and MgO 200 diffraction disks and that of the corresponding mirror symmetry in the whole pattern are emphasized in order to determine the rigid-body shift and the probe-position.     

Enantiomer-selective radical cyclopolymerization of rac-2,4-pentanediyl dimethacrylate using a ruthenium-mediated chiral atom transfer radical polymerization initiating system

The enantiomer-selective radical polymerization of rac-2,4-pentanediyl dimethacrylate, an equimolar mixture of (2S,4S)-2,4-pentanediyl dimethacrylate (SS- 1 ) and (2R,4R)-2,4-pentanediyl dimethacrylate (RR- 1 ), was carried out with a chiral atom transfer radical polymerization initiating system consisting of methyl 2-bromoisobutyrate ( 3 ), dichlorotris(triphenylphosphine)ruthenium [RuCl₂(PPh₃)₃], and a chiral additive in anisole at 60 °C. When (S)-1,1′-bi-2-naphthol ( a-3 ) was used as the chiral additive, the recovered monomer was enriched in SS- 1 , and the enantiomeric excess was 16.9% at a 22.6% monomer conversion. The specific rotation ([α]₄₃₅, c 0.3, CHCl₃) of the resulting polymer was +40.3° at a 22.6% monomer conversion. For the copolymerization of SS- 1 and RR- 1 with 3 /RuCl₂(PPh₃)₃/ a-3 in anisole at 60 °C, the monomer reactivity ratio for RR- 1 (r_R) was determined to be 4.94, and that for SS- 1 (r_S) was 0.27. For the homopolymerizations of SS- 1 and RR- 1 with 3 /RuCl₂(PPh₃)₃/ a-3 in anisole at 60 °C, the polymerization rate of RR- 1 was considerably faster than that of SS- 1 , and the rate constants for the homopolymerizations were determined to be k_SS = 2.0 × 10⁻³ h⁻¹ and k_RR = 8.2 × 10⁻³ h⁻¹, respectively. With the values of k_SS, k_RR, r_R, and r_S, the relative ratio k_SS/k_RR/k_SR/k_RS was determined to be 1.2:4.9:4.5:1, which indicated that both the growing end of SS- 1 and that of RR- 1 preferentially reacted with RR- 1 . © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4563–4569, 2004     

Antimony-121 mössbauer spectra of antimony (III) compounds with a stereochemically active lone pair

The Sb-121 Mössbauer parameters at 20 K for 23 antimony(III) compounds were obtained and the data are discussed in terms of known crystal structures. The isomer shifts and quadrupole coupling constants depend strongly on the type of configuration around the Sb(III) atoms with stereochemically active lone pair electrons.     

A new algorithm of non-Gaussian component analysis with radial kernel functions

We consider high-dimensional data which contains a linear low-dimensional non-Gaussian structure contaminated with Gaussian noise, and discuss a method to identify this non-Gaussian subspace. For this problem, we provided in our previous work a very general semi-parametric framework called non-Gaussian component analysis (NGCA). NGCA has a uniform probabilistic bound on the error of finding the non-Gaussian components and within this framework, we presented an efficient NGCA algorithm called Multi-index Projection Pursuit. The algorithm is justified as an extension of the ordinary projection pursuit (PP) methods and is shown to outperform PP particularly when the data has complicated non-Gaussian structure. However, it turns out that multi-index PP is not optimal in the context of NGCA. In this article, we therefore develop an alternative algorithm called iterative metric adaptation for radial kernel functions (IMAK), which is theoretically better justifiable within the NGCA framework. We demonstrate that the new algorithm tends to outperform existing methods through numerical examples.