The vapor-phase dehydration of 1,3-butanediol (1,3-BDO) to produce 1,3-butadiene (BD) was investigated over yttrium zirconate, Y2Zr2O7, which was prepared through a hydrothermal aging process. 1,3-BDO was initially dehydrated to three unsaturated alcohols, namely 3-buten-2-ol, 3-buten-1-ol, and 2-buten-1-ol, followed by the further dehydration to BD. The catalytic activity of Y2Zr2O7 was strongly dependent on the calcination temperature. Furthermore, the reaction temperature was one of the important factors to produce BD efficiently: the selectivity to BD was increased with increasing reaction temperature up to 375 °C, while coke formation led to catalyst deactivation together with by-product formation at higher temperatures. Y2Zr2O7 catalyst calcined at 900 °C showed a high BD yield of 95% at 375 °C and a time on stream of 10 h.
Molecular dynamics of azetidinium ion (AzH+), a four-membered-ring ammonium, in a cyano-bridged double perovskite compound (AzH)2KCo(CN)6 is studied by spin-lattice relaxation time measurements of 1H NMR as well as 14N NQR in relation to the phase transition associated with considerable change of dielectric property. AzH+ ions are in static and dynamic disorder, respectively, below and above Tc = 199 K. Below Tc, a ring-puckering motion of AzH+ takes place with the activation energy Ea = 17.5 kJ mol−1 and the correlation time τc/s = 2.8 × 10−14 exp(Ea/RT). On the other hand, from sudden decrease of 1H NMR linewidth above Tc, a C3 reorientation of AzH+ ion is shown to be activated in high-temperature phase. The activation energy of the C3 reorientation is estimated to be 18 kJ mol−1 from the temperature dependences of 1H NMR as well as 14N NQR spin-lattice relaxation times T1 and T1Q.
This Award Account focuses on the author’s studies on the theoretical developments of two-component (2c) relativistic quantum chemistry calculations for large systems with high efficiency and high accuracy, with a review of related studies as the background. The local unitary transformation scheme allows the linear-scaling computation cost to be applied to construct a 2c Hamiltonian, such as an infinite-order two-component version. The divide-and-conquer scheme can lead to linear-scaling computation costs to apply not only a Hartree-Fock (HF) method but also post-HF methods such as the second-order Møller-Plesset perturbation and couple cluster theory with singles and doubles for the 2c Hamiltonian in addition to a non-relativistic version. The frozen core potential scheme can naturally connect pseudopotential calculations with all-electron calculations. The accompanying coordinate expansion with a transfer recurrence relation scheme provides an efficient algorithm for the rapid evaluation of electron repulsion integrals for systems including heavy elements, the orbitals of which have long contractions and high angular momenta, such as f- and g-orbitals. Illustrative applications will help readers realize the advantages and usefulness of these schemes.
We report a new protocol to form pentafluorosulfanyl (hetero)arenes via chlorine-fluorine exchange of (hetero)aryl tetrafluorosulfanyl chlorides by AgBF4. The method enables access to electron-deficient pentafluorosulfanyl(hetero)arenes, which are targets that are difficult to synthesize. Two advantages of AgBF4 are its ease of handling and stability. This would be a general transformation protocol.
Shape-controlled metal nanocrystals such as nanorods are attractive because of their potential novel catalytic properties. It is important to improve the stability of the shape-controlled nanocrystals to be applied as nanocatalysts. In this study, α-Al2O3-supported Au nanorods (AuNR/α-Al2O3) and silica-coated α-Al2O3-supported Au nanorods (SiO2/AuNR/α-Al2O3) were prepared as alcohol oxidation catalysts for the transformation of 1-phenylethyl alcohol to acetophenone. The formation rate of acetophenone over AuNR/α-Al2O3 is higher than that over α-Al2O3-supported spherical Au nanoparticles obtained by calcining AuNR/α-Al2O3. In addition, SiO2/AuNR/α-Al2O3 exhibits higher catalytic performance and thermal stability than those of AuNR/α-Al2O3 in alcohol oxidation.
Cathepsin K is a protease expressed in osteoclasts that degrades bone tissue, such as type I collagen fibers. Overexpression of cathepsin K is involved in osteoporosis, rheumatoid arthritis, and bone metastasis. Therefore, detecting cathepsin K activity is important for understanding the mechanism of these diseases and developing new drugs. However, current chemical probes cannot be employed for the detection of cathepsin K activity in animal deep-tissue. In this study, we developed novel 19F magnetic resonance imaging (MRI) probes (FLAME-(Gd-X), X = Acp, Deg, Deg2) to detect cathepsin K. In FLAME-(Gd-X), the Gd3+ complex was modified on the surface of perfluorocarbon-encapsulated silica nanoparticles through cathepsin K substrate and three different hydrophobic/hydrophilic linkers. The 19F NMR signal intensities of these probes were suppressed by the paramagnetic relaxation enhancement (PRE) effect of the Gd3+ complexes. The 19F MRI signal intensities of FLAME-Gd-Acp and FLAME-Gd-Deg specifically increased with the substrate cleavage by cathepsin K. The 19F MRI probes based on the PRE effect can be applied to the in vivo detection of cathepsin K activity.
Germanene belongs to a family of 2D materials structurally similar to graphene. Germanene-based materials prepared from Zintl phase CaGe2 were modified during their synthesis to yield materials with various covalently bonded groups. Germanane and its derivates exhibit strong luminescence properties which can be altered via surface modification and bring even more interesting possible applications. In this work, germananes terminated by hydrogen and methyl groups (Ge-H and Ge-Me) were used for photodegradation of picric acid solution in the presence of H2O2 and violet light irradiation. Here, we show successful decomposition of picric acid solution using both Ge-based materials in a significantly shorter time compared to blank reaction.
We herein report that a visible light/quinuclidine/water-soluble iridium complex system is highly effective for promoting the isomerization reaction of aldoses to 2-deoxyaldonic acids in water. The product yields and functional group compatibility are much better than those observed with a UV light/water-soluble benzophenone system.
Lotus leaf stem is successfully exploited as a sustainable biomass to fabricate multi-heteroatom co-doped carbon with multiscale pore architecture by a readily scalable and effective strategy of pre-carbonization and KOH activation. By taking advantage of 3D hierarchical structure with high surface area and optimized pore size distribution, naturally O-N-S co-doping and nanosized graphitic structure (contributing to large accessible surface for charge storage, short ion diffusion distance, rapid charge transfer and low internal resistance), as-produced carbon is demonstrated as a promising electrode for supercapacitors with a high capacitance of 425 F/g at 0.5 A/g in a three-electrode system and 295 F/g at 0.1 A/g with superb rate capability (84% retention from 0.2 to 20 A/g) and outstanding recyclability (97.8% retention after 10000 charge-discharge cycles at 10 A/g) in a two-electrode system with KOH solution. The excellent recyclability of 93.3% is also achieved after 10000 cycles at 10 A/g for the symmetric supercapacitor using Na2SO4 electrolyte. These values may boost the commercial application of biomass-derived carbon for energy storage.
The asymmetric transfer hydrogenation of α,β-unsaturated aldehyde with Hantzsch ester catalyzed by polymer-supported chiral pyrrolidine organocatalyst was achieved. The effects of the pyrrolidine substituents and linkage configuration on the catalytic performance were examined in detail. We found that the polymer-supported cis-type chiral pyrrolidine organocatalysts showed high enantioselectivities (up to 99.9%) compared with the corresponding trans analogs and monomers in the reaction. The recovered catalyst was reused without any loss of the catalytic activity.
A dynamic factor that determines the product distribution of the photochemical reaction of S2-excited s-cis-1,3-butadiene is examined using the nonadiabatic molecular dynamics method. The excited S2 state of s-cis-1,3-butadiene is relaxed via the S2/S1 and subsequent S1/S0 conical intersections (CIs). After the S1/S0-CI, several products including the trans and cis isomers, cyclobutene, bicyclobutane, and the methylenecyclopropyl diradical, are generated by six identified reaction channels. Channel 6 is another new channel leading to bicyclobutane. The ratio of each product is understood in terms of the allowed range of the ∠C–C–C–C dihedral angle at the S1/S0-CI for each product. When 2,3-dimethyl-1,3-butadiene is used instead of 1,3-butadiene, the product ratio changes because due to the dynamic effects of the Me groups the rotational motion around the central C–C bond slows down and consequently the fluctuation of the ∠C–C–C–C dihedral angle at the S1/S0-CI becomes smaller. Thus, our molecular dynamics simulations show that the fluctuation of the ∠C–C–C–C dihedral angle is an important factor to determine the product distribution.
N5-Modified alloxazinium salts including 5-ethyl-1,3-dimethylalloxazinium and 5-ethyl-1,3-dimethyl-8-(trifluoromethyl)alloxazinium salts were readily prepared as alloxazinium-resins from the corresponding N5-unmodified ingredients via the aerobic oxidation—ion exchange protocol, previously introduced by us for the preparation of isoalloxazine analogues, and their catalysis and reusability in H2O2 oxidations were evaluated.
Vibrational circular dichroism (VCD) spectra were recorded for the intercalation compounds of sodium montmorillonite co-adsorbing two kinds of metal complexes, Δ- (or Λ-)[Ru(phen)3]2+ and Λ- (or Δ-)[Ni(phen)3]2+. The complexes were chosen so as to form a pseudo racemate. Notably some of the VCD signals were enhanced in comparison to the samples adsorbing each complex separately. The results were rationalized in terms of the delocalization of vibrational motions over a tightly bound molecular pair in a coherent way. The model of racemic adsorption of [M(II)(phen)3]2+ (M(II) = a divalent metal ion) in the interlayer space of a clay mineral was proposed.
Peptide nucleic acid (PNA) is a DNA analog, in which the sugar-phosphate backbone in DNA is replaced by poly[N-(2-aminoethyl)glycine]. Since its discovery in the early 1990s, PNA has been widely employed in chemistry, biochemistry, medicine, nanotechnology, and many other fields. This account surveys recent developments on the design of PNA derivatives and their applications. In the first part, PNAs for sequence-specific recognition of DNA and RNA (single-strands, double-strands, G-quadruplexes, i-motifs, and others) are comprehensively covered. Modifications of nucleobases and of the main chain effectively promote both the strength of binding and the selectivity of recognition. In the second half of this account, practical applications of PNA are presented. Structural restraints, induced by complex formation of PNA with DNA and RNA substrates, lead to selective transformation of target sites to desired structures. Applications to regulation of gene expression, gene editing, construction of sophisticated nanostructures, and others are also described. Advantages and disadvantages of PNAs, compared with other sequence-recognizing molecules hitherto reported, are discussed in terms of various physicochemical and biological features.
We employed herein a Linde Type A zeolite as a heterogeneous catalyst to condense amino acid amides with glyoxal affording pyrazinones. The synthesis was conducted in water without using corrosive reagents, organic solvents, or additives. The power of this “aquachemistry” was demonstrated through robust, continuous-flow synthesis.
This review highlights the advancement of molecular triplet donors showing singlet-to-triplet (S–T) absorption and their utilization for triplet-triplet annihilation-based photon upconversion (TTA-UC). Circumvention of thermal energy loss associated with intersystem crossing (ISC) through the use of S–T absorption results in UC from near-infrared (NIR) light to yellow, blue, and even violet light, achieving an unprecedentedly large UC spectral shift. Taking advantage of the molecular donor's ability to be dispersed in solids without aggregation, efficient solid-state UC materials are also achieved.
The self-assembly of molecules into complex superstructures underpins the functionality of many biological processes and physical materials. Many such structures stem from amphiphilic monomer units, with attractions and repulsions between their ends determining the structure and state of the assembled system under equilibrium, which affect its function.
The photophysical and electronic properties of fullerene (C60) have been extensively studied and proven useful in the fabrication of a variety of devices. The simple attachment of alkyl side chains can convert this highly crystalline solid into an alkyl-C60 hydrophobic amphiphile, in which alkyl-alkyl and C60-C60 interactions determine the state, phase, morphology, or architecture of the substance, while the optoelectronic properties of C60 are retained.
In this award article, lipid membranes, crystalline nanostructures, mesophases, and even room-temperature liquid alkyl fullerenes formed through this approach are described. In each case, the effects of chain selection and substitution on morphology and function are explained. The ways in which the inherent properties of C60 can be adapted for particular applications are detailed, such as in superhydrophobic surfaces and photoconductive devices. Thereafter, drawing on these advances, the application of the alkyl chain attachment approach to other functional π-conjugated cores is demonstrated using some examples of functional molecular liquids.
The natural perturbation orbital (NPO) computational method was applied to the analysis of infrared (IR) intensities of CO molecules adsorbed on the surfaces of Pd nanoparticles. Enhancement of the IR intensities for a CO bonded to a single low-coordinate metal adsorbed on the metal surface (low-coordinate model) was compared with those for a CO bonded directly to the metal surface (atop model). This enhancement was ascribed to the mixing between occupied and virtual orbitals induced by molecular vibrations. The occ-virt term, representing this mixing, was efficiently decomposed into contributions from three NPO pairs (, , and ) for each model. The main contributors were the and pairs, which were localized around CO in the atop model, but delocalized throughout the Pd cluster in the low-coordinate model. This variance in orbital delocalization comes from differing interactions between Pd and CO in the atop and low-coordinate models.
The interaction energies between the receptor-binding domain of SARS-CoV-2 spike proteins and neutralizing antibody CC12.1 Fab were calculated using the fragment molecular orbital method. South African and Brazilian variants showed weaker interactions than the wild-type. Mutations, K417N/T and E484K, were considered to be responsible for escape from the antibody.
The formation of well-defined nanostructures comprising assembled semiconductor quantum dots (QDs) is a challenging research task. Recently, we found that the introduction of π-conjugated molecules with a self-assembly ability into small CdSe QDs led to the formation of highly ordered QD arrangements. Here, we demonstrate the in-depth coaggregation process of large-sized CdSe QDs and azobenzene derivative 1 possessing an amino group functioning as an adhesive to the QD surface. Upon mixing the above QDs with assembled azobenzene derivative 1 in apolar solvents, linearly arranged QD structures along assembled azobenzene derivative 1 were formed over time. In the formed coaggregates, efficient energy transfer between the arranged QDs occurred, as confirmed by a change in the emission spectra and lifetimes. Analysis of time-dependent emission properties revealed the coaggregation mechanism of QDs and 1.