Theoretical study on the mechanochemical reactivity in Diels-Alder reactions.

Mechanochemical reactions sometimes give different yields from those under solvent conditions, and such mechanochemical reactivities depend on the reactions. This study theoretically elucidates what governs mechanochemical reactivities, taking the Diels-Alder reactions as an example. Applying mechanical force can be regarded as the deformation of molecules, and the deformation in an orthogonal direction to a reaction mode can lower the reaction barrier. Here, we introduce a dimensionless cubic force constant, a mechanochemical reaction constant. It tells us how easily the deformation can lower a reaction barrier and enables us to compare the mechanochemical reactivities of different reactions. The constants correlate positively with the yields of the mechanochemical Diels-Alder reactions.

Origin of Stereoselectivity in a Mechanochemical Reaction of Diphenylfulvene and Maleimide.

Mechanochemical reactions sometimes yield unexpected products or product ratios in comparison to conventional reaction conditions. In the present study, we theoretically reveal the origin of the mechanochemical selectivity by considering the Diels-Alder reaction of diphenylfulvene and maleimide as an example. The application of an external force is equivalent to the production of a structural deformation. Here, we show that a mechanical force applied in a direction orthogonal to the reaction mode can lower the activation barrier by varying the potential energy curvature in the transition state. In the case of the Diels-Alder reaction, the endo-type pathway was found to be more mechanochemically favorable than the exo-type pathway, which is consistent with the experimental observations.

Development of Highly Sensitive Raman Spectroscopy for Subnano and Single-Atom Detection.

Direct detection and characterisation of small materials are fundamental challenges in analytical chemistry. A particle composed of dozens of metallic atoms, a so-called subnano-particle (SNP), and a single-atom catalyst (SAC) are ultimate analysis targets in terms of size, and the topic is now attracting increasing attention as innovative frontier materials in catalysis science. However, characterisation techniques for the SNP and SAC adsorbed on substrates requires sophisticated and large-scale analytical facilities. Here we demonstrate the development of an ultrasensitive, laboratory-scale, vibrational spectroscopic technique to characterise SNPs and SACs. The fine design of nano-spatial local enhancement fields generated by the introduction of anisotropic stellate-shaped signal amplifiers expands the accessibility of small targets on substrates into evanescent electromagnetic fields, achieving not only the detection of isolated small targets but also revealing the effects of intermolecular/interatomic interactions within the subnano configuration under actual experimental conditions. Such a development of "in situ subnano spectroscopy" will facilitate a comprehensive understanding of subnano and SAC science.

Reactivity of endohedral metallofullerene la2@c80 in nucleophilic and electrophilic attacks: vibronic coupling density approach.

The regioselectivities of La2@C80 in thermal nucleophilic and electrophilic attacks were theoretically investigated using vibronic coupling density (VCD) analysis. Nucleophilic and electrophilic cycloadditions to La2@C80 were experimentally reported to yield [6,6] and [6,5] adducts, respectively, as major products. VCD analysis provided a clear explanation for these experimental results. For nucleophilic reactions, it was found that the reactive [6,6] bonds did not have a large lowest unoccupied molecular orbital (LUMO) density and Fukui function but a large potential derivative with respect to a reaction mode. The VCD illustrates the origin of the interaction between the electronic and vibrational states. On the other hand, conventional reactivity indices such as frontier orbital density take only the electronic state into account. The result suggested that the stabilization due to vibronic couplings plays an important role in the regioselectivity of nucleophilic cycloadditions. The VCD with respect to the effective mode could provide a picture of the functional groups, which are the double bonds of ethylene moieties. VCD analysis with respect to hypothetical localized modes enabled the quantitative prediction of regioselectivities.

Combinatorial characterization of metastable luminous silver cations.

Thermodynamically metastable glasses that can contain metastable species are important functional materials. X-ray absorption near-edge structure (XANES) spectroscopy is an effective technique for determining the valence states of cations, especially for the doping element in phosphors. Herein, we first confirm the valence change of silver cations from monovalent to trivalent in aluminophosphate glasses by X-ray irradiation using a combination of Ag L3-edge XANES, electron spin resonance, and simulated XANES spectra based on first-principles calculations. The absorption edge of the experimental and simulated XANES spectra demonstrate the spectral features of Ag(III), confirming that AgO exists as Ag(I)Ag(III)O2. A part of Ag(I) changes to Ag(III) by X-ray irradiation, and the generation of Ag(III) is saturated after high irradiation doses, in good agreement with conventional radiophotoluminescence (RPL) behaviour. The structural modelling based on a combination of quantum beam analysis suggests that the local coordination of Ag cations is similar to that of Ag(III), which is confirmed by density functional theory calculations. This demonstration of Ag(III) in glass overturns the conventional understanding of the RPL mechanism of silver cations, redefining the science of silver-related materials.

Spontaneous-Symmetry-Breaking Charge Separation Induced by Pseudo-Jahn-Teller Distortion in Organic Photovoltaic Material.

The driving force of charge separation in the initial photovoltaic conversion process is theoretically investigated using ITIC, a nonfullerene acceptor material for organic photovoltaic devices. The density functional theory calculations show that the pseudo-Jahn-Teller (PJT) distortion of the S1 excimer state induces spontaneous symmetry-breaking charge separation between the identical ITIC molecules even without the asymmetry of the surrounding environment. The strong PJT effect arises from the vibronic coupling between the pseudodegenerate S1 and S2 excited states with different irreducible representations (irreps), i.e., Au for S1 and Ag for S2, via the asymmetric vibrational mode with the Au irrep. The vibrational mode responsible for the spontaneous polarization, which is opposite in one ITIC monomer and the other, is the intramolecular C-C stretching vibration between the core IT and terminal IC units. These results suggest that controlling the PJT effect can improve the charge separation efficiency of the initial photovoltaic conversion process.

Chemical reactivity in nucleophilic cycloaddition to C70: vibronic coupling density and vibronic coupling constants as reactivity indices.

The chemical reactivity in nucleophilic cycloaddition to C70 is investigated on the basis of vibronic (electron-vibration) coupling density and vibronic coupling constants. Because the e1″ LUMOs of C70 are doubly degenerate and delocalized throughout the molecule, it is difficult to predict the regioselectivity by frontier orbital theory. It is found that vibronic coupling density analysis for the effective mode as a reaction mode illustrates the idea of a functional group embedded in the reactive sites. Furthermore, the vibronic coupling constants for localized stretching vibrational modes enable us to estimate the quantitative reactivity. These calculated results agree well with the experimental findings. The principle of chemical reactivity proposed by Parr and Yang is modified as follows: the preferred direction is the one for which the initial vibronic coupling density for a reaction mode of the isolated reactant is a minimum.

Environment-sensitive emission of anionic hydrogen-bonded urea-derivative-acetate-ion complexes and their aggregation-induced emission enhancement.

Anions often quench fluorescence (FL). However, strong ionic hydrogen bonding between fluorescent dyes and anion molecules has the potential to control the electronic state of FL dyes, creating new functions via non-covalent interactions. Here, we propose an approach, utilising ionic hydrogen bonding between urea groups and anions, to control the electronic states of fluorophores and develop an aggregation-induced emission enhancement (AIEE) system. The AIEE ionic hydrogen-bonded complex (IHBC) formed between 1,8-diphenylnaphthalene (p-2Urea), with aryl urea groups at the para-positions on the peri-phenyl rings, and acetate ions exhibits high environmental sensitivities in solution phases, and the FL quantum yield (QY) in ion-pair assemblies of the IHBC and tetrabutylammonium cations is more than five times higher than that of the IHBC in solution. Our versatile and simple approach for the design of AIEE dye facilitates the future development of environment-sensitive probes and solid-state emitting materials.

Isomerizations of a Pt4 cluster revealed by spatiotemporal microscopic analysis.

We now report the first direct observation of the fluxional nature in which the four-atomic platinum cluster (Pt4) randomly walks through several isomers. Time-lapse analysis by a Cs-corrected transmission electron microscope allowed us to acquire the atomic coordinates at a sub-angstrom space resolution and 0.2 s time resolution for each cluster isomer. The analysis revealed that the isomerization follows a simple first-order kinetic model.

Periodicity of molecular clusters based on symmetry-adapted orbital model.

The periodic table has always contributed to the discovery of a number of elements. Is there no such principle for larger-scale substances than atoms? Many stable substances such as clusters have been predicted based on the jellium model, which usually assumes that their structures are approximately spherical. The jellium model is effective to explain subglobular clusters such as icosahedral clusters. To broaden the scope of this model, we propose the symmetry-adapted orbital model, which explicitly takes into account the level splittings of the electronic orbitals due to lower structural symmetries. This refinement indicates the possibility of an abundance of stable clusters with various shapes that obey a certain periodicity. Many existing substances are also governed by the same rule. Consequently, all substances with the same symmetry can be unified into a periodic framework in analogy to the periodic table of elements, which will act as a useful compass to find missing substances.

Ultrahigh sensitive Raman spectroscopy for subnanoscience: Direct observation of tin oxide clusters.

Subnanometric metal clusters exhibit anomalous catalytic activity, suggesting innovative applications as next-generation materials, although identifying and characterizing these subnanomaterials in atomic detail remains a substantial challenge because of the severely weak signal intensity for the conventional analytical methods. Here, we report a subnanosensitive vibrational technique established based on the surface-enhanced Raman spectroscopy, demonstrating the first-ever detailed vibrational characterization of subnanomaterials. Furthermore, combining with density functional theory calculations, we reveal that inherent surface structures of the tin oxide subnanoclusters determine the size-specific spectral and catalytic characteristics of these clusters. The high-sensitivity characterization methodology elaborated here can provide a comprehensive understanding of the chemical and structural natures of subnanomaterials, which facilitate the rational design of subnanomaterials on the atomic scale for practical applications, such as in catalysts, biosensors, and electronics.

Recent Progress of Varicose Vein Treatment Especially about Endovascular Heat Ablation, SEPS and Foam Sclerotherapy.

There were three epoch making events in therapy of varicose veins. The first one is that the endovascular heat ablation (EVHA) using diode laser was authorized by the Ministry of Health Labor and Welfare in January 2011. The second one is that Subfascial Endoscopic Perforator Surgery (SEPS) was also authorized in April 2014. All of the therapies which were covered by the national insurance system had been the procedures for superficial veins but the SEPS is procedure for the perforating veins. The third one is that the foam usage of Polidocasklerol was listed formally at the medical package insert in September 2016. Moreover stub avulsion was introduced as figure-related improvement method with a smaller operation wound instead of conventional varicectomy and the other existing therapies are progressing every day. Therefore, by this education seminar, I lecture mainly on the EVHA, SEPS and foam sclerotherapy in varicose vein treatment. Finally I show one case which you should remember. (This is a translation of Jpn J Vasc Surg 2017; 26: 225-230.).

Nanomaterials design for super-degenerate electronic state beyond the limit of geometrical symmetry.

Spherical atoms have the highest geometrical symmetry. Due to this symmetry, atomic orbitals are highly degenerate, leading to closed-shell stability and magnetism. No substances with greater degrees of degeneracy are known, due to geometrical limitations. We now propose that realistic magnesium, zinc, and cadmium clusters having a specific tetrahedral framework possess anomalous higher-fold degeneracies than spherical symmetry. Combining density functional theory calculations with simple tight-binding models, we demonstrate that these degeneracies can be attributed to dynamical symmetry. The degeneracy condition is fully identified as an elegant mathematical sequence involving interatomic parameters. The introduction of dynamical symmetry will lead to the discovery of a novel category of substances with super-degenerate orbitals.

Surgical methods and clinical results of subfascial endoscopic perforator surgery in Japan.

OBJECTIVES: To clarify the surgical methods and the clinical results of subfascial endoscopic perforator surgery in Japan. METHODS: This study included 1287 limbs of 1091 patients who underwent subfascial endoscopic perforator surgery in 14 hospitals. Simultaneous saphenous vein treatment was performed in 1079 limbs (83.8%), and 118 limbs (9.2%) had deep venous lesions. The venous clinical severity score was calculated before and 6 to 12 months after surgery. The ulcer healing rate and ulcer recurrence rate were calculated cumulatively. RESULTS: Preoperative venous clinical severity score was significantly decreased from 10.0 ± 6.6 to 3.1 ± 3.4 ( P < .0001) postoperatively. The primary ulcer healing rate was 96.2% (332/345 C6 limbs) at an average follow-up of 47.7 months, and the ulcer recurrence rate was 12.0% (49/393 C5, C6 limbs) at the average follow-up of 46.0 months after the ulcer healed. CONCLUSION: These results indicate that subfascial endoscopic perforator surgery is an alternative to improve the long-lasting disease severity and/or clinical outcome.

Fluorescence via Reverse Intersystem Crossing from Higher Triplet States in a Bisanthracene Derivative.

To elucidate the high external quantum efficiency observed for organic light-emitting diodes using a bisanthracene derivative (BD1), non-radiative transition processes as well as radiative ones are discussed employing time-dependent density functional theory. It has been previously reported that the observed high external quantum efficiency of BD1 cannot be explained by the conventional thermally activated delayed fluorescence involving T1 exciton nor triplet-triplet annihilation. The calculated off-diagonal vibronic coupling constants of BD1, which govern the non-radiative transition rates, suggest a fluorescence via higher triplets (FvHT) mechanism, which entails the conversion of a high triplet exciton generated during electrical excitation into a fluorescent singlet exciton. This mechanism is valid as long as the relaxation of high triplet states to lower states is suppressed. In the case of BD1, its pseudo-degenerate electronic structure helps the suppression. A general condition is also discussed for the suppression of transitions in molecules with pseudo-degenerate electronic structures.

Solution-phase synthesis of Al13- using a dendrimer template.

Superatoms, clusters that mimic the properties of elements different to those of which they are composed, have the potential to serve as building blocks for unprecedented materials with tunable properties. The development of a method for the solution-phase synthesis of superatoms would be an indispensable achievement for the future progress of this research field. Here we report the fabrication of aluminum clusters in solution using a dendrimer template, producing Al13-, which is the most well-known superatom. The Al13- cluster is identified using mass spectrometry and scanning transmission electron microscopy, and X-ray photoelectron spectroscopy is used to measure the binding energies. The superatomic stability of Al13- is demonstrated by evaluating its tendency toward oxidation. In addition, the synthesis of Al13- in solution enables electrochemical measurements, the results of which suggest oxidation of Al13-. This solution-phase synthesis of Al13- superatoms has a significant role for the experimental development of cluster science.

Platinum clusters with precise numbers of atoms for preparative-scale catalysis.

Subnanometer noble metal clusters have enormous potential, mainly for catalytic applications. Because a difference of only one atom may cause significant changes in their reactivity, a preparation method with atomic-level precision is essential. Although such a precision with enough scalability has been achieved by gas-phase synthesis, large-scale preparation is still at the frontier, hampering practical applications. We now show the atom-precise and fully scalable synthesis of platinum clusters on a milligram scale from tiara-like platinum complexes with various ring numbers (n = 5-13). Low-temperature calcination of the complexes on a carbon support under hydrogen stream affords monodispersed platinum clusters, whose atomicity is equivalent to that of the precursor complex. One of the clusters (Pt10) exhibits high catalytic activity in the hydrogenation of styrene compared to that of the other clusters. This method opens an avenue for the application of these clusters to preparative-scale catalysis.The catalytic activity of a noble metal nanocluster is tied to its atomicity. Here, the authors report an atom-precise, fully scalable synthesis of platinum clusters from molecular ring precursors, and show that a variation of only one atom can dramatically change a cluster's reactivity.

Subfascial endoscopic perforator surgery for posterolateral perforators performed in the prone position.

OBJECTIVES: Subfascial endoscopic perforator surgery (SEPS) is usually performed for posteromedial perforators in the supine position, but subfascial endoscopic perforator surgery for posterolateral perforators in the prone position has not been reported. METHODS: A 51-year-old male suffered from a venous stasis ulcer around his lateral malleolus because of reflux in the small saphenous vein and incompetent perforating veins around the ulcer. RESULTS: Stripping of the small saphenous vein and subfascial endoscopic perforator surgery utilizing screw-type ports was successfully conducted in the prone position. CONCLUSIONS: The prone position enables interruption of the posterolateral perforators, because gravity-dependent flattening of the muscles enables creation of sufficient subfascial space.

Subfascial endoscopic perforator surgery using screw-type ports is a very useful component of a comprehensive treatment program for chronic venous insufficiency.

BACKGROUND: Subfascial endoscopic perforator surgery (SEPS) with a two-port system utilizing screw-type ports, CO2 insufflation and an ultrasonic coagulation system, is a useful procedure that does not require burdensome apparatus and techniques. SEPS was accepted as a national advanced medical system by the Japanese Ministry of Health, Labor and Welfare in May 2009. PATIENTS AND METHODS: Forty-one limbs of 35 patients with 10 active ulcers (C6) and 2 healed ulcers (C5) were treated by SEPS between February 2010 and December 2011. Thirty-three limbs had concomitant superficial vein surgery. SEPS alone was performed on 8 limbs, in 6 of which the superficial veins had already been ablated. In 2 limbs, incompetent perforating veins (IPVs) existed under the affected skin, around the scars of past surgery. RESULTS: All stasis ulcers of the 10 C6 limbs healed between 1 week and 14 months after SEPS (mean 2.9 months), with no ulcer recurrence during the follow-up period (2 to 24 months). IPVs under the scars were easily and safely interrupted by SEPS. CONCLUSION: SEPS is a very useful component of a comprehensive treatment program for chronic venous insufficiency, especially in patients with venous stasis ulcers and IPVs under the scars of past surgery.

Hepatic arterial infusion of 5-fluorouracil and cisplatin for unresectable or recurrent hepatocellular carcinoma with tumor thrombus of the portal vein.

BACKGROUND AND OBJECTIVES: This study was designed to evaluate the efficacy of hepatic arterial infusion of 5-fluorouracil (5-FU) and cisplatin (CDDP) for unresectable or recurrent hepatocellular carcinoma (HCC) with tumor thrombus of the trunk or first branches of the portal vein (PVTT). METHODS: Seven unresectable or recurrent HCC patients with PVTT were enrolled in this study. A one-week course of chemotherapy consisted of intraarterial administration of CDDP (10 mg on days 1-5) for 1 h and 5-FU (250 mg on days 1-5) for 24 h, followed by cessation of administration for the subsequent 2 days (days 6 and 7). Three or more sequential courses of chemotherapy were given through an implanted reservoir. RESULTS: Serum alpha-fetoprotein (AFP) levels before the chemotherapy were >20 ng/ml in six of the seven patients. Serum AFP levels were decreased in four of the six patients after chemotherapy, including two patients (cases 1 and 7) whose AFP levels later returned to normal. Six of the seven patients had measurable lesions in the liver, with a response rate of 33%. In three of the seven patients (43%), PVTTs decreased in size or disappeared after chemotherapy. The mean and median survival periods of all patients were 8.0 and. 7.5 months, respectively. CONCLUSIONS: The chemotherapy described in this report is beneficial in terms of survival for HCC patients with PVTT for whom transcatheter arterial embolization or surgical treatment is contraindicated.