Aromaticity Relocation in Perylene Derivatives upon Two‐Electron Oxidation To Form Anthracene and Phenanthrene

We prepared perylene dications 1 ²⁺ and 2 ²⁺ by using “capped” perylene derivatives, and for the first time, successfully obtained single crystals of a perylene dication 1 ²⁺ that enabled us to perform its structural analysis. We realized that the substituted aryl groups on perylene control the positions of positive charges, thus the remaining electronic system satisfies Clar's sextet rule toward the highest number of localized sextets. Experimental and theoretical evidence proved that Clar's aromatic π‐sextet rule could be applied even for the dicationic perylenes in a very simple way.     

Synthesis of Heat-resistant Polymers by Thiol–Ene Reaction of N-Allylmaleimide Copolymers Using Glycoluril Crosslinkers with Rigid Molecular Structures

We carried out the thermal curing of the copolymers of N-allylmaleimide (AMI) and 2-ethylhexyl acrylate (2EHA) using 1,3,4,6-tetra(2-mercaproethyl)glycoluril ( G1 ), 1,3,4,6-tetra(3-mercaptopropyl)glycoluril ( G2 ), 1,3,4,6-tetraallylglycoluril ( G3 ), triallylisocyanurate (TAIC), and pentaerythritol tetrakis(3-mercaptobutyrate) (PEMB) as the crosslinkers. Based on the results for the analysis of thiol–ene reactions monitored by IR spectroscopy, it was confirmed that the curing rate significantly depended on the combination of the used crosslinkers. The insoluble fraction after curing was more than 90% for the systems using the glycoluril crosslinkers, while the conversion of the allyl groups was suppressed due to the rigid structure of these crosslinkers. The heat resistance and the mechanical properties of the crosslinked polymers were investigated by thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis, and mechanical tensile tests. For the products cured using the glycoluril crosslinkers, the glass transition temperature (T_g) and the maximum temperature of thermal decomposition (T_max) were 54–59 °C and 395–409 °C, respectively, being higher than those for the cured product prepared with PEMB and TAIC as the conventional crosslinkers. The elasticity (75–139 MPa), the maximum strength (3.0–4.1 MPa), and the adhesion strength (6.7–10.7 MPa) for the polymers cured with the glycoluril crosslinkers, determined by the mechanical tensile and single lap-shear adhesion tests, were higher than those for cured materials produced with PEMB. Thus, the thermal and mechanical properties of the maleimide copolymers were efficiently enhanced by crosslinking using the rigid glycoluril compounds. © 2020 Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58, 923–931     

Palladium(II)‐Catalyzed Dehydroboration via Generation of Boron Enolates

The Pd^II‐catalyzed dehydroboration of boron enolates generated from ketones and 9‐iodo‐9‐borabicyclo[3.3.1]nonane was achieved, providing a synthetically versatile protocol from ketones to α,β‐unsaturated ketones. The Pd^II compound employed in this reaction worked catalytically in the presence of Cu(OAc)₂. The high trans‐selectivity of the olefinic moiety was observed. Aryl halide moieties (‐Br and ‐Cl) remained intact for this reaction in spite of the presence of a Pd species. An ester substrate could also be applied when a stoichiometric amount of Pd^II was used. The crossover reactions using boron and silyl enolates revealed that the oxidation reaction is much faster than the Saegusa‐Ito reaction.     

Relativistic Lagrangians for the Lorentz–Dirac equation

We present two types of relativistic Lagrangians for the Lorentz–Dirac equation written in terms of an arbitrary world-line parameter. One of the Lagrangians contains an exponential damping function of the proper time and explicitly depends on the world-line parameter. Another Lagrangian includes additional cross-terms consisting of auxiliary dynamical variables and does not depend explicitly on the world-line parameter. We demonstrate that both the Lagrangians actually yield the Lorentz–Dirac equation with a source-like term.     

Optical anisotropy and columnar structure of obliquely deposited thin films containing fine metal particles ag]

Anisotropic optical properties and nanostructures of thin films prepared by oblique co-deposition of Ag and SiO₂ were studied. At low concentrations of Ag, a columnar structure grew towards the direction of the incident SiO₂ vapor and small Ag particles were embedded in that structure. An inhomogeneous distribution of Ag was observed in cases where the Ag was deposited from the opposite side of the surface normal to the direction of the incident SiO₂ vapor. This inhomogeneous distribution of Ag particles gives rise to optical anisotropy, i.e., the optical transmittance of p-polarized light varies drastically depending on the angle of incidence, while that of s-polarized light remains unchanged. A possible application of the anisotropic optical absorption properties of Ag---SiO₂ hybrid films is in the manufactur of an inorganic thin film polarizer.     

Base-catalyzed reactions enhanced by solid acids: Amine-catalyzed nitroaldol (Henry) reactions enhanced by silica gel or mesoporous silica SBA-15

The reactions of various aldehydes with CH₃NO₂ catalyzed by Et₃N, n-C₆H₁₃NH₂, and Me₂N(CH₂)₂NH₂ were accelerated by the addition of silica gel to give aromatic (aliphatic) β-nitroalcohols, aromatic nitroalkenes, and aromatic 1,3-dinitroalkanes, respectively. Mesoporous silica SBA-15 showed higher activity than silica gel for the synthesis of aromatic nitroalkenes by the reactions of the corresponding aldehydes with CH₃NO₂ catalyzed by n-C₆H₁₃NH₂.     

Influence of biological activity on <Superscript>65</Superscript>Zn and <Superscript>109</Superscript>Cd removal from tidal water by chronically-polluted mangrove sediments

The biological activity influence on the mangrove sediment capacity to remove ⁶⁵Zn and ¹⁰⁹Cd from tidal water was evaluated in a site chronically polluted. Benthic Activity Indexes (BAI), corresponding to relative estimates of biological impact on radiotracer accumulation, were higher for ¹⁰⁹Cd (~?38%) than for ⁶⁵Zn (~?10%) in the top centimetre of sediment. However, BAI exceeded 96% for deeper sediment layers. This apparent decrease in radiotracer diffusion into deep sediments through biological activity inhibition is stronger than reported for much less polluted mangrove nearby, suggesting that benthic organisms tolerant of chronic metal pollution may affect metal sorption mechanisms.     

Chemical Stimulus‐responsive Folding and Unfolding of a Dendrimeric Assembly

A dendrimeric trimer undergoes folding and unfolding in response to a chemical stimulus. The trimer of interest contains a central dendrimer with a butadiyne‐linked zinc porphyrin dimer ((ZnP)₂) core, in addition to two terminal dendrimers with zinc porphyrin (ZnP) cores. The obtained absorption spectra indicate that the unfolded form is the exclusive conformer in chloroform, while the addition of 1,4‐diazabicyclo[2.2.2]octane (DABCO) in chloroform leads to transformation from the unfolded to the folded structure containing two DABCO units per trimer; the folded structure originates from the cross‐linking of (ZnP)₂ and ZnP with DABCO. Moreover, the addition of excess DABCO promotes the generation of the unfolded structure containing four DABCO units.     

Reconstitution of a Type II Polyketide Synthase that Catalyzes Polyene Formation

While type II polyketide synthases (PKSs) are known for producing aromatic compounds, a phylogenetically new subfamily of type II PKSs have been recently proposed to synthesize polyene structures. Here we report in vitro analysis of such a type II PKS, IgaPKS for ishigamide biosynthesis. The ketoreductase (Iga13) and dehydratase (Iga16) were shown to catalyze the reduction of a β‐keto group and dehydration of a β‐hydroxy group, respectively, to form a trans double bond. Incubation of the acyl carrier protein (Iga10), the ketosynthase/chain length factor complex (Iga11–Iga12), Iga13 and Iga16 with malonyl and hexanoyl‐CoAs and NADPH followed by KOH hydrolysis resulted in the formation of four unsaturated carboxylic acids (C₈, C₁₀, C₁₂, and C₁₄), indicating that IgaPKS catalyzes tetraene formation by repeating the cycle of condensation, keto‐reduction and dehydration with strict stereo‐specificity. We propose “highly reducing type II PKS subfamily” for the polyene‐producing type II PKSs.     

DNA Origami Scaffolds as Templates for Functional Tetrameric Kir3 K+ Channels

In native systems, scaffolding proteins play important roles in assembling proteins into complexes to transduce signals. This concept is yet to be applied to the assembly of functional transmembrane protein complexes in artificial systems. To address this issue, DNA origami has the potential to serve as scaffolds that arrange proteins at specific positions in complexes. Herein, we report that Kir3 K⁺ channel proteins are assembled through zinc‐finger protein (ZFP)‐adaptors at specific locations on DNA origami scaffolds. Specific binding of the ZFP‐fused Kir3 channels and ZFP‐based adaptors on DNA origami were confirmed by atomic force microscopy and gel electrophoresis. Furthermore, the DNA origami with ZFP binding sites nearly tripled the K⁺ channel current activity elicited by heterotetrameric Kir3 channels in HEK293T cells. Thus, our method provides a useful template to control the oligomerization states of membrane protein complexes in vitro and in living cells.