Whispering Gallery Effect in Relativistic Optics

A relativistic laser pulse, confined in a cylindrical-like target, under specific conditions may perform multiple scattering along the internal target surface. This results in the confinement of the laser light, leading to a very efficient interaction. The demonstrated propagation of the laser pulse along the curved surface is just yet another example of the “whispering gallery” effect, although nonideal due to laser–plasma coupling. In the relativistic domain its important feature is a gradual intensity decrease, leading to changes in the interaction conditions. The process may pronounce itself in plenty of physical phenomena, including very efficient electron acceleration and generation of relativistic magnetized plasma structures.     

Synthesis of a Hemispherical Geodesic Phenine Framework by a Polygon Assembling Strategy

A synthetic strategy to construct large geodesic structures of phenine (1,3,5‐trisubstituted benzene) was devised. In this strategy, five pentagons were assembled on an omphalos pentagon, and bridging peripheral pentagons furnished five additional hexagons. Thirty phenine units were synthetically assembled to afford a large C₂₂₀H₁₈₀ molecule with a phenine framework isoreticular to a hemispherical, bisected segment of C₆₀. Although a hemispherical structure of the phenine framework was suggested by solution‐phase NMR spectra, crystallographic analysis revealed an oval‐like deformation of the molecular shape. In‐depth structural analyses, including theoretical calculations, showed that structural fluctuations observed as variations in the biaryl torsion angles allowed structural deformations and, at the same time, that the dynamic fluctuations resulted in the spectroscopic observation of a hemisphere as a time‐averaged structure.     

Diborane Concatenation Leads to New Planar Boron Chemistry

Diborane has long been realized to be analogous to ethylene in terms of its bonding MOs, both as to symmetries and splitting patterns. This naturally suggests an investigation to see whether other similar conjugated hydrocarbons manifest a similar boron-substituted and H₂ supplemented borane. That is, for a conjugated hydrocarbon structure with a neighbor-paired resonance pattern, we propose to look at boranes where each carbon atom is replaced by a boron atom, and an H-atom pair is added to each double bond of the resonance structure, with one H above the molecular plane and one below. This construction of concatenated diboranes is uniformly different than that for the previously known stable boranes of 4 or more B atoms. We find from quantum-chemical computations that our so constructed polyboranes are stable. All this suggests a possible novel new chapter in borane chemistry – a chapter with some promise of understandings related to that for (alternant) conjugated hydrocarbons.     

Gold and Silver Chains Supported by Linear Hexaphosphine Ligands

A new linear hexaphosphine, rac‐cis,cis,trans‐ bis{[(diphenylphosphinomethyl)phenylphosphinomethyl]phenylphosphino}methane ( P₆ ), was synthesized and isolated as a pure isomer, confirmed by transforming to the corresponding phosphine sulfide. The methylene‐bridged linear hexaphosphine readily organized flexible gold(I) and silver(I) hexanuclear chains, [M₆(μ‐ P₆ )₂]X₆ (X₆=(OTf)₆, M=Au ( 1 ), Ag ( 2 ); X₆=Cl₂(PF₆)₄, M=Au ( 3 )). The hexaphosphine also supported a tetrasilver(I) complex [Ag₄(μ‐ P₆ )₂](OTf)₄ ( 4 ), which was readily transformed by treatment with AgOTf into 3 , revealing a drastic alternation of the two P₆ arrangement. The hexagold(I) chains exhibited a considerably red‐shifted absorption (～410 nm) and emission (540–580 nm) to ¹[5d_σ*→6p_σ] and from ³[5d_σ*→6p_σ] excited states of the metal centers, respectively. The new linear hexaphosphine could be a useful tool to construct linear metal clusters as subnano building blocks.     

Double bond formation based on nitroaldol reaction and radical elimination: A prototype segment connection method for the total synthesis of nigricanoside A dimethyl ester

During the course of our studies toward the total synthesis of nigricanoside A dimethyl ester, a prototype method for the connection of the left- and right-half segments at the C9′–C10′ double bond was developed using a model system. The method was based on a simple three-step process including: (i) a nitroaldol reaction, (ii) chlorination or thionocarbonylation, and (iii) radical elimination.     

Polymeric 1H MRI Probes for Visualizing Tumor In Vivo

Magnetic resonance imaging (MRI) has become a prominent non– or low–invasive imaging technique, providing high–resolution, three–dimensional images as well as physiological information about tissues. Low–molecular–weight Gd–MRI contrast agents (CAs), such as Gd–DTPA (DTPA: diethylenetriaminepentaacetic acid), are commonly used in the clinical diagnosis, while macromolecular Gd–MRI CAs have several advantages over low–molecular–weight Gd–MRI CAs, which help minimize the dose of CAs and the risk of side effects. Accordingly, we developed chiral dendrimer Gd–MRI CAs, which showed high r₁ values. The association constant values (K_a) of S–isomeric dendrimer CAs to bovine serum albumin (BSA) were higher than those of R–isomeric dendrimer CAs. Besides, based on a totally new concept, we developed ¹³C/¹⁵N–enriched multiple–resonance NMR/MRI probes, which realized highly selective observation of the probes and analysis of metabolic reactions of interest. This account summarizes our recent study on developing both chiral dendrimer Gd–MRI CAs, and self–traceable ¹³C/¹⁵N–enriched phosphorylcholine polymer probes for early detection of tumors.     

Direct Ethanol Production from Ionic Liquid-Pretreated Lignocellulosic Biomass by Cellulase-Displaying Yeasts

Among the many types of lignocellulosic biomass pretreatment methods, the use of ionic liquids (ILs) is regarded as one of the most promising strategies. In this study, the effects of four kinds of ILs for pretreatment of lignocellulosic biomass such as bagasse, eucalyptus, and cedar were evaluated. In direct ethanol fermentation from biomass incorporated with ILs by cellulase-displaying yeast, 1-butyl-3-methylimidazolium acetate ([Bmim][OAc]) was the most effective IL. The ethanol production and yield from [Bmim][OAc]-pretreated bagasse reached 0.81 g/L and 73.4% of the theoretical yield after fermentation for 96 h. The results prove the initial concept, in which the direct fermentation from lignocellulosic biomass effectively promoted by the pretreatment with IL.