The reasonable regulation of porous structure and crystallinity has been focused on supercapacitor development. Here, hierarchical porous carbons have been prepared by a hybrid of chemical activation and template methods using walnut shells as carbon source, and KMnO4 as activator and template agent. The activation mechanism of KMnO4 at different activation temperatures has been studied based on the XRD and TG analysis. Due to the synergy of rich oxygen-containing functional groups and hierarchical porous structure, the hierarchical porous carbon materials show a high capacitance of 380 F g−1 at 0.5 A g−1, good cycling stability with 93% capacitance retention even after 10000 continuous charge-discharge cycles at 5 A g−1. Additionally, the assembled symmetric supercapacitor has a high energy density of 8.95 Wh kg−1. This study shows that KMnO4 activation is a mild and highly efficient way to prepare high performance carbon electrode materials for supercapacitors.
The nitrogen atom is ubiquitous in bioactive molecules and functional materials, and the development of new C–N bond forming strategies is thus one of the long-standing research subjects in the synthetic community. This account describes the nitrogen-umpolung-enabled copper-catalyzed highly chemo- and stereoselective amination protocols developed by the author’s research group. Starting from the C–H amination, electrophilic amination of stable organoboron and organosilicon compounds, aminoboration/hydroamination of alkenes, and their applications to the synthesis of functionality-rich alkylamines are shown. The reaction design, concept, and substrate scope are briefly summarized.
A variety of 1,2,5-triaryl-3,4-cycloalka[c]arsoles were synthesized in this study to control emission color and efficiency. The torsion between the arsole center and the aryl groups at the 2,5-positions was dependent on the size of the fused cycloalkane, resulting in different absorption maxima. In addition, structural relaxation was affected by the fused cycloalkane, which changed the emission color and efficiency. Notably, the cyclopentane-fused arsole showed aggregation-caused quenching (ACQ) in the solid state, while cyclohexane and cycloheptane offered aggregation-induced emission enhancement (AIEE). This trend was also seen in heterocycle-fused arsoles; five- and six-membered rings offered ACQ and AIEE, respectively. The p-(dimethylamino)phenyl and p-(dimesitylboryl)phenyl groups at the 2,5-positions exhibited red-shifted emission owing to the charge transfer character, and they could detect ions such as protons and fluoride anions, respectively.
We elucidate the origin of the two types of observed fluorescence in a complex consisting of nPUA (1-anthracen-n-yl-3-phenylurea; n = 1, 2, 9) and an acetate ion. By calculating the molecular properties related to the proton transfer reaction in the excited state, we clarified a correlation between the acid dissociation constant in the excited state (pKa) in the urea moiety and the rate constant of the excited state proton transfer reaction. The computed pKa suggests that the proton on the anthracenyl group side is transferred in the case of 1PUA and 2PUA, whereas the proton on the phenyl group side is transferred in 9PUA. Low pKa and activation barriers were calculated for 9PUA, which causes the stability of 9PUA due to the absence of the planarity after the proton transfer reaction.
Highly efficient and effective separation between americium (Am3+) and curium ion (Cm3+) was achieved by two simple electrophoresis-based techniques. Am3+ and Cm3+ ions were complexed with fluorophore-modified acyclic hexadentate and octadentate polyaminocarboxylates and then were electrophoretically separated and fluorescently detected in free solution with ternary complexation or in gel medium.
The first examples of planar binuclear phthalocyanines sharing a common carbazole unit were obtained using indirect and direct mixed cyclization approaches. The synthetic route to the starting 9-benzylcarbazole-2,3,6,7-tetranitrile was reconsidered and literature conditions were successfully optimized. In addition to the binuclear complex, a low-symmetry A3B phthalocyanine with free cyano groups was isolated and identified. Accurate assignment of absorption bands in the UV-Vis spectra was performed using magnetic circular dichroism and simplified TD-DFT calculations. The target binuclear complexes demonstrate the ability of singlet oxygen generation, with ΦΔ values reaching 0.15 for the tert-butyl-substituted compound. The products of photodegradation were studied using mass spectrometry and UV-Vis spectroscopy. Electrochemical and spectroelectrochemical studies showed a gradual oxidation of the macrocycle, accompanied by the interruption of an extended binuclear π-system.
Although many studies on protein–protein interactions (PPIs) have been conducted and the importance of PPIs in biological processes has been reported, there is still no versatile research approach that enables us to draw a complete picture of PPIs. One orthodox approach to elucidating the mechanism of each PPI would be to inhibit or enhance the PPI of interest and carefully observe its phenotype. However, since the interaction surfaces of PPIs are generally shallow and wide, it is very difficult to design small molecules that can selectively perturb specific PPIs by interaction with these surfaces. In this report, we adopt reconstruction of split green fluorescence protein (splitGFP) as a model of PPI, and obtained RNA aptamers that bind to one of the components. The reconstitution of splitGFP was inhibited by these aptamers, and this inhibition was cancelled by the addition of their complementary sequences. These processes were monitored by the loss and recovery, respectively, of fluorescence from the reconstructed GFP. The successful development of molecules that reversibly regulate specific PPI is expected to make a significant contribution to life science research.
We synthesized two diastereomers comprising the same π-conjugated unit. One diastereomer exhibited a smectic crystal phase in which the chromophores tilted 45 degrees from the layer normal and macroscopic polarization was induced by a DC bias application in a cooling process from the high temperature phase to the smectic crystal phase. The other diastereomer exhibited a smectic crystal phase in which the chromophores were parallel to the layer normal and macroscopic polarization was not induced. The bulk photovoltaic effect and polarization-induced electroluminescence were observed only in the polarized smectic crystal phase in which the chromophores tilted from the layer normal. In the bulk photovoltaic effect in the tilted smectic crystal phase doped with fullerene derivative, the open circuit voltage and short circuit current were 1.03 V and 100 µAcm−2 for white light illumination (20 mWcm−2), respectively. In the polarization-induced electroluminescence in the tilted smectic crystal phase, linearly polarized emission with the dichroic ratio exceeding 10 was obtained and the axis of the linearly polarized emission could be rotated 90 degrees by an inversion of a DC bias of poling treatment.
Total synthesis of (+)-neopeltolide, a potent antiproliferative marine macrolide natural product, was accomplished in 11 steps from a commercially available inexpensive material. The 14-membered macrolactone skeleton embedded with a 2,6-cis-substituted tetrahydropyran ring was synthesized in an expedient fashion by our newly developed macrocyclization/transannular pyran cyclization strategy. A concise synthetic entry to the oxazole-containing side chain was developed by exploiting palladium-catalyzed cross-coupling reactions. Total synthesis of (+)-9-epi-neopeltolide was also achieved in 12 steps by late-stage stereochemical diversification at the C9 position.
It is important to optimize the photoexcited-state conformation of chiral luminescent molecules to enhance the intensity of circularly polarized luminescence (CPL) and control the direction of CPL rotation. In pyrenyl peptide luminophores, the intensity and sign of CPL is determined by the solvent and intramolecular distance between pyrenyl units in addition to peptide chirality. However, the control of CPL properties in water is difficult, and new methods to control CPL in water are required. In this study, we achieved amplification and control of the sign of excimer-origin CPL by adding γ-cyclodextrin to a flexible bipyrenyl peptide luminophore with two arginine groups in water.
Nanosheets of metal–organic frameworks (MOFs)—porous crystalline materials consisting of metal ions and organic ligands—are actively studied for their intrinsic chemical/physical properties attributed to the reduced dimensionality and for their potential to function as ideal components of nanodevices, especially when electrical conduction is present. Air/liquid interfacial synthesis is a promising technique to obtain highly oriented MOF nanosheets. However, rational control of size and shape combined with the aimed functionality remains an important issue to address making it necessary to research the critical factors governing nanosheet characteristics in the interfacial synthesis. Here, we investigate the influence of the solvent—methanol (MeOH) versus N,N-dimethylformamide (DMF)—used to prepare a ligand spread solution on an assembly of MOF nanosheets composed of Ni2+ and 2,3,6,7,10,11-hexaiminotriphenylene (HITP) (HITP-Ni-NS). We find that the macroscopic morphological uniformity in the micrometer scale is higher when DMF is used as the solvent. Regarding the microscopic crystalline domain, molecules of DMF with relatively high polarity and boiling point are involved in HITP-Ni-NS formation, hindering its growth and resulting in nanosheets with slightly smaller lateral size than that grown when MeOH is used. These findings provide crucial guidelines towards establishing a judicious strategy for creating desired MOF nanosheets at the air/liquid interface, thereby driving forward research on both fundamental and applied aspects of this field.
The successful 11C-radiolabeling of eribulin, an analog of the marine natural product halichondrin B, and an approved anticancer drug for the treatment of breast cancer and liposarcoma, is reported. A rapid sequence involving a nitroaldol reaction with [11C]nitromethane and subsequent reduction of the nitro group enabled the introduction of a carbon-11 atom at the C35-position of eribulin. Optimization of the reaction and purification conditions led to a reproducible synthetic method for [35-11C]eribulin with 248 ± 104 MBq of radioactivity, 88.2 ± 5.8% radiochemical purity, and 132 ± 32 MBq/nmol molar activity. The total synthetic time was 38.0 ± 1.3 min (n = 12). PET imaging using mice bearing brain tumors revealed a specific accumulation of [35-11C]eribulin in tumors without any significant metabolic changes. These results indicate the applicability of [35-11C]eribulin for the quantitative measurement of eribulin migration into tumor tissue, which would be beneficial for exploring the application of eribulin for glioblastoma treatment and estimating the appropriate dosage for each patient.
The highly effective transformation of CO2 into targeted chemicals has attracted significant attention due to greenhouse gas utilization and value-added chemical synthesis functions. Among all of the proposed CO2 transformation pathways, e.g., electrolytic CO2 reduction, photocatalytic CO2 conversion, and thermal-catalytic CO2 utilization, the latter, especially the thermal-catalytic hydrogenation process with renewable energy-driven H2 supply, is the most promising strategy owing to its high efficiency, fast reaction rate, controllable product selectivity, and industrial application potential. In recent years, our research group has made great efforts to realize various chemical syntheses from CO2 hydrogenation technology, such as production of methanol, ethanol, liquid petroleum gas (LPG), alkenes, aromatics (especially para-xylene, PX), etc. In this account, we summarize the main achievements of our laboratory in the rational design of novel heterogeneous catalysts and innovative reaction pathways for CO2 hydrogenation, including reaction pathway design for new low-temperature methanol synthesis, catalytic metal-surface interaction tailoring to boost methanol synthesis performance, tandem reaction network fabrication for the synthesis of ethanol, LPG, or aromatics, a capsule catalyst concept for tandem reaction, etc. In this account, we want to inspire new ideas and methodologies for the rational design of novel catalysts and reaction pathways for CO2 hydrogenation into value-added chemicals.
Alkenylammonium salts are a unique class of compounds, wherein an electron-withdrawing ammonio group is attached to an olefin. Although these salts are structurally simple, the synthesis of α-substituted alkenylammonium salts has been sparsely explored. Herein we report the synthesis of α-aryl and α-alkynylated alkenylammonium salts through Suzuki–Miyaura and Sonogashira coupling.
Electrochemical faradic deionization (EDI), one of the most promising research branches of capacitive deionization (CDI), has demonstrated considerable potential for water desalination and ion removal (particularly at medium to low salinity). However, the associated relatively slow anion-capturing kinetics have limited the practical applications of EDI. Based on several studies, researchers have attributed this slow anion-capturing rate to the sluggish conversion-reaction-induced anion-capturing process (as most anion-capturing electrodes belong to the conversion type). Herein, we report a strategy for accelerating the anion-capturing process to enhance the desalination rate of EDI by utilizing an intercalation-type FeOOH electrode. The chloride-driven EDI system equipped with hollandite-type FeOOH nanospindles is found to present a high desalination rate (up to 4.44 mg g−1 min−1) and desalination capacity (51.77 mg g−1). The current study can inspire the future design of ultrafast EDI systems and bring the EDI technique closer to its practical application.
K+ channels selectively conduct K+ at a high conduction rate, but not smaller Na+ and Li+. To provide an insight into the conduction mechanism previously, we experimentally observed the temperature dependence of the conformer distributions of a model peptide in K+ channels (Ac-Tyr-NHMe) complexed with alkali metal ions (Li+, Na+, K+, Rb+, and Cs+) by gas phase laser spectroscopy. The K+ and Rb+ complexes showed a more significant temperature dependence than the Li+ complexes, whose conformer distributions barely varied. This different behavior with temperature can be interpreted either thermodynamically (entropy vs. enthalpy) or kinetically (barrier height). Due to the lack of temperature dependence of the Li+ complex, we could not determine which factor, an enthalpy-driven structure or a high energy barrier, governs the Li+ complex’s behavior. To resolve this issue, we carried out DFT transition state calculations and time-dependent simulation of the metal complexes’ conformer distributions based on the theoretical barrier heights. By comparing the experimental and computational data, the origin of the variation in the temperature dependence among different ion complexes was determined to be thermodynamic.