Exploration of Nano-Saturns: A Spectacular Sphere–Ring Supramolecular System

Saturn-like systems consisting of nanoscale rings and spheres are fascinating motifs in supramolecular chemistry. Several ring molecules are known to include spherical molecules at the center of the cavity via noncovalent attractive interactions. In this Minireview, we generalize the molecular design, the structural features, and the supramolecular chemistry of such “nano-Saturns”, which consist of monocyclic rings and fullerene spheres (mainly C₆₀), on the basis of previous experimental and theoretical studies. Ring molecules are classified into three types (loop, belt, and disk) according to their shapes and possible interactions. Whereas typical belt-shaped rings tend to form tight complexes due to the wide contact area via π–π interactions, flat disk-shaped rings generally form weak complexes due to the narrow contact area mainly via CH–π interactions. In spite of the small association energies, disk-shaped rings are attractive because such rings can mimic the planet Saturn precisely as exemplified by an anthracene cyclic hexamer–C₆₀ complex.     

Synthesis,Properties, and Redox Behavior of 1,1,4,4‐Tetracyano‐2‐ferrocenyl‐1,3‐butadienes Connected by Aryl,Biaryl, and Teraryl Spacers

Aryl‐substituted 1,1,4,4‐tetracyano‐1,3‐butadienes (FcTCBDs) and bis(1,1,4,4‐tetracyanobutadiene)s (bis‐FcTCBDs), possessing a ferrocenyl group on each terminal, were prepared by the reaction of a variety of alkynes with tetracyanoethylene (TCNE) in a [2+2] cycloaddition reaction, followed by retro‐electrocyclization of the initially formed [2+2] cycloadducts (i.e., cyclobutene derivatives). The characteristic intramolecular charge transfer (ICT) between the donor (ferrocene) and acceptor (TCBD) moieties were investigated by using UV/Vis spectroscopy. The redox behaviors of FcTCBDs and bis‐FcTCBDs were examined by cyclic voltammetry (CV) and differential pulse voltammetry (DPV), which revealed their properties of multi‐electron transfer depending on the number of ferrocene and TCBD moieties. Moreover, significant color changes were observed by visible spectroscopy under the electrochemical reduction conditions.     

Influence of Intermolecular Interactions on Valence Tautomeric Behaviors in Two Polymorphic Dinuclear Cobalt Complexes

Two polymorphic structures have been well determined in a valence tautomeric (VT) dinuclear cobalt complex. These polymorphs showed distinct thermal‐ and photomagnetic behavior, and are thus ideal for studying the “pure” intermolecular factors to VT transitions. In polymorph 1A , the VT cations are arranged head‐to‐waist with their neighbors and exhibit weak π???π interactions, resulting in a gradual and incomplete thermal VT transition. In contrast, the cations in polymorph 1B are arranged head‐to‐tail and exhibit relatively strong π???π interactions, leading to an abrupt and complete thermal VT transition with adjustable hysteresis loop at around room temperature. The VT process for both polymorphs can be induced by light, but the light‐excited state of 1B? 2H₂O has a higher thermal relaxation temperature than that of 1A? 3H₂O.     

Characterization of atmospheric tritiated water concentration in the vicinity of the fukushima daiichi nuclear power plant

Journal of Radioanalytical and Nuclear Chemistry - This paper discusses the spatiotemporal variation in atmospheric tritiated water (HTO) concentration near the Fukushima Daiichi Nuclear Power...     

Macroscopic Polarization Change of Mononuclear Valence Tautomeric Cobalt Complexes Through the Use of Enantiopure Ligand

The crystallization of a complex having electron transfer properties in a polar space group can induce the polarization switching of a crystal in a specific direction, which is attractive for the development of sensors, memory devices, and capacitors. Unfortunately, the probability of crystallization in a polar space group is usually low. Noticing that enantiopure compounds crystallize in Sohncke space groups, this paper reports a strategy for the molecular design of non-ferroelectric polarization switching crystals based on the use of intramolecular electron transfer and chirality. In addition, this paper describes the synthesis of a mononuclear valence tautomeric (VT) cobalt complex bearing an enantiopure ligand. The introduction of enantiomer enables the crystallization of the complex in the polar space group (P2₁). The polarization of the crystals along the b-axis direction is not canceled out and the VT transition is accompanied by a change in the macroscopic polarization of the polar crystal. Polarization switching via electron transfer is realized at around room temperature.     

Ruthenium‐Immobilized Periodic Mesoporous Organosilica: Synthesis,Characterization, and Catalytic Application for Selective Oxidation of Alkanes

Periodic mesoporous organosilica (PMO) is a unique material that has a crystal‐like wall structure with coordination sites for metal complexes. A Ru complex, [RuCl₂(CO)₃]₂, is successfully immobilized onto 2,2’‐bipyridine (BPy) units of PMO to form a single‐site catalyst, which has been confirmed by various physicochemical analyses. Using NaClO as an oxidant, the Ru‐immobilized PMO oxidizes the tertiary C?H bonds of adamantane to the corresponding alcohols at 57 times faster than the secondary C?H bonds, thereby exhibiting remarkably high regioselectivity. Moreover, the catalyst converts cis‐decalin to cis‐9‐decalol in a 63 % yield with complete retention of the substrate stereochemistry. The Ru catalyst can be separated by simple filtration and reused without loss of the original activity and selectivity for the oxidation reactions.     

Salt‐Free Reduction of Nonprecious Transition‐Metal Compounds: Generation of Amorphous Ni Nanoparticles for Catalytic C–C Bond Formation

A salt‐free procedure for the generation of a wide variety of metal(0) particles, including Fe, Co, Ni, and Cu, was achieved using 2,3,5,6‐tetramethyl‐1,4‐bis(trimethylsilyl)‐1,4‐diaza‐2,5‐cyclohexadiene ( 1 ), which reduced the corresponding metal precursors under mild conditions. Notably, Ni particles formed in situ from the treatment of Ni(acac)₂ (acac=acetylacetonate) with 1 in toluene exhibited significant catalytic activity for reductive C? C bond‐forming reactions of aryl halides in the presence of excess amounts of 1 . By examination of high‐magnification transmission electron microscopy images and electron diffraction patterns, we concluded that amorphous Ni nanoparticles (Ni aNPs) were essential for the high catalytic activity.     

Caesaljaponins A and B: New Cassane‐Type Furanoditerpenoids from the Seeds of Caesalpinia decapetala var. japonica

Two new cassane‐type furanoditerpenoids, designated caesaljaponin A and caesaljaponin B ( 1 and 2 , resp.), were isolated from seeds of Caesalpinia decapetala var. japonica. The structures were elucidated by spectroscopic data, and the absolute configuration of 1 was determined by X‐ray crystallographic analysis using the anomalous scattering of CuK_α radiation.     

Grafting of Polymers Having Pendant Peroxycarbonate Groups Onto Carbon Black and Postpolymerization of Vinyl Monomers

Abstract

Postpolymerization of vinyl monomers initiated by pendant peroxycarbonate groups of grafted polymer chains on carbon black (CB) was investigated. The grafting of polymers having pendant peroxycarbonate groups onto CB was achieved by the trapping of polymer radicals formed by the thermal decomposition of copolymers of t-butylperoxy-2-methacryloyloxyethyl-carbonate (HEPO) with vinyl monomers such as vinyl acetate (VAc), styrene (St) and methyl methacrylate (MMA). The copolymers having pendant peroxycarbonate groups were prepared by copolym-erization of HEPO with vinyl monomers using azo initiator under irradiation of UV light at room temperature. The amount of remaining pendant peroxycarbonate groups of the poly(VAc-co-HEPO)-grafted CB obtained from the reaction at 90°C was maximum and decreased above the temperature. Furthermore, the postpolymerization of vinyl monomers, such as St, MMA, and VAc was initiated in the presence of poly(VAc-co-HEPO)-grafted and poly(St-co-HEPO)-grafted CB and the corresponding polymers were postgrafted onto CB to give branched polymer-grafted CB. The percentage of poly(St)-postgrafting (proportion of post-grafted poly(St) to poly(MMA-co-HEPO)-grafted CB used) increased with increasing polymerization time, but became constant at 20% after 4 hours.     

Monocyclic rod-type liquid crystals; 2,5-dialkanoyloxytropones and 5-alkanoyloxy-2-alkoxytropones

Two kinds of monocyclic troponoid mesogens, 2,5-dialkanoyloxytropones (4) and 5-alkanoyloxy2-alkoxytropones (5), were prepared. The former showed monotropic smectic A phases and the virtual isotropic liquid-smectic A transitions of the latter were determined by extrapolation of results in a binary phase diagram. Comparing the mesogenic properties between the tropones 4 and the 2-alkanoyloxy-5-alkoxytropones (1), the alkanoyloxy group at C-5 enhances both the melting points and the transition temperatures of the smectic A phases. From the comparison between 5 and 1, the alkanoyloxy group at C-2 lowers the melting points.