A Triphenylamine with Two Phenoxy Radicals Having Unusual Bonding Patterns and a Closed‐Shell Electronic State

Reported herein is the structure and the electronic properties of a novel triphenylamine derivative having two phenoxy radicals appended to the amino nitrogen atom. X‐ray single crystal analysis and the magnetic resonance measurements demonstrates the unexpected closed‐shell electronic structure, even at room temperature, of the molecule and two unusual C? N bonds with multiple‐bond character. The theoretical calculations support the experimentally determined molecular geometry with the closed‐shell electronic structure, and predicted a small HOMO–LUMO gap originating from the nonbonding character of the HOMO. The optical and electrochemical measurements show that the molecule has a remarkably small HOMO–LUMO gap compared with its triphenylamine precursor.     

High‐performance liquid chromatography separation of unsaturated organic compounds by a monolithic silica column embedded with silver nanoparticles

The optimization of a porous structure to ensure good separation performances is always a significant issue in high‐performance liquid chromatography column design. Recently we reported the homogeneous embedment of Ag nanoparticles in periodic mesoporous silica monolith and the application of such Ag nanoparticles embedded silica monolith for the high‐performance liquid chromatography separation of polyaromatic hydrocarbons. However, the separation performance remains to be improved and the retention mechanism as compared with the Ag ion high‐performance liquid chromatography technique still needs to be clarified. In this research, Ag nanoparticles were introduced into a macro/mesoporous silica monolith with optimized pore parameters for high‐performance liquid chromatography separations. Baseline separation of benzene, naphthalene, anthracene, and pyrene was achieved with the theoretical plate number for analyte naphthalene as 36 000 m^?1. Its separation function was further extended to cis/trans isomers of aromatic compounds where cis/trans stilbenes were chosen as a benchmark. Good separation of cis/trans‐stilbene with separation factor as 7 and theoretical plate number as 76 000 m^?1 for cis‐stilbene was obtained. The trans isomer, however, is retained more strongly, which contradicts the long‐ established retention rule of Ag ion chromatography. Such behavior of Ag nanoparticles embedded in a silica column can be attributed to the differences in the molecular geometric configuration of cis/trans stilbenes.     

Molecular design for high-spin molecules in view of vibronic couplings

A high-spin ground state is possible if a molecule has degenerate or pseudo-degenerate frontier orbitals. Since strong vibronic couplings, or electron-vibration interactions give rise to reduce the degeneracy or pseudo degeneracy, a lower-spin state is the ground state in such a molecule. Therefore small vibronic couplings are desirable for designing molecules with a high-spin ground state. Vibronic coupling constants of derivatives of m-phenylene diamine are evaluated. The calculated results are analyzed based on vibronic coupling density which enables us to control the vibronic coupling constants. Based on the vibronic coupling density analysis, we succeed in recovering the high-spin ground state from the closed-shell singlet ground state of a methoxy derivative of m-phenylene diamine by introducing an appropriate substituent.     

Microbial conversion of curcumin into colorless hydroderivatives by the endophytic fungus Diaporthe sp. associated with Curcuma longa

We investigated the microbial conversion of curcumin (1) using endophytic fungi associated with the rhizome of Curcuma longa (Zingiberaceae). We found that Diaporthe sp., an endophytic filamentous fungus, converts curcumin (1) into four colorless derivatives, namely (3R,5R)-tetrahydrocurcumin (2), a novel (3R,5S)-hexahydrocurcumin (3) named neohexahydrocurcumin, (3S,5S)-octahydrocurcumin (4) and meso-octahydrocurcumin (5).     

Spicachlorantins G-J, new lindenane sesquiterpenoid dimers from the roots of Chloranthus spicatus

Four new lindenane sesquiterpenoid dimers, spicachlorantins G-J (1-4), were isolated from the roots of Chloranthus spicatus together with seven known compounds, including chloramultilide A, shizukaol B, shizukaol D, shizukaol F, shizukaol P, chlorahololide D, and cycloshizukaol A. The planar structures of the new compounds were established by 1D-, 2D-NMR, and MS analyses. The absolute configurations of these compounds were determined by analyzing rotating Overhauser enhancement and exchange spectroscopy (ROESY) and circular dichroism (CD) spectra.     

A new synthesis of 7-substituted 2,3-bis(alkylthio)naphth[1,8-bc]-azepines using the tris(alkylthio)cyclopropenyl cation

7-Substituted 2,3-bis(isopropylthio)naphth[1,8-bc]azepines 3a-c were synthesized in good yields by the reactions of 5-substituted 1-naphthylamines 2a-c with tris(isopropylthio)cyclopropenylium perchlorate ( 1 ) in acetonitrile under reflux. This reaction proceeds through the facile ring opening of 1 , followed by the intermediary formation of iminium salts 5a-c and then intramolecular cyclization.     

Carbon chemical shifts of 1,1-diphenylethylene and α-methylstyrene dimer dianions

The natural abundance C-13 NMR spectra of 1,1-diphenylethylene and α-methylstyrene dimer dianions have been obtained using the proton noise decoupling technique. The extra negative charge distributions in the carbanions have been discussed and compared with those obtained from the proton chemical shifts. The chemical shifts of the two ortho carbons in a phenyl ring are equivalent to each other for the former carbanion but not for the latter.     

On tensor products of -very ample line bundles

In this paper, we show that the tensor product of -very ample and -very ample line bundles on a complete algebraic variety is -very ample.

     

The role of the doubly excited configurations in the π-electronic structure of the croconate anion

The electronic structure of the croconate anion is investigated by the semi-empirical VESCF method with CI including up to the doubly excited configurations. The effect of the doubly excited configuration is quite large in the lowest singlet state which turns out to be a ground state, while the calculation including only singly excited configurations produces a triplet ground state. The calculated first transition energy (¹ A₁ ¹ E₁) is in fair agreement with the observed value. The interpretation of the transition moment in case that the doubly excited configurations are included is also discussed.

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Zusammenfassung Die Elektronenstruktur des Croconat-Anions wurde mit der halbempirischen VESCF-Methode mit Konfigurationswechselwirkung, die bis zu zweifach angeregte Konfigurationen einschloß, untersucht. Der Einfluß der zweifach angeregten Konfigurationen ist im niedrigsten Singulettzustand, der sich als Grundzustand herausstellt, sehr stark. Schließt die Rechnung hingegen nur einfach angeregte Konfigurationen ein, so erhält man einen Tripletgrundzustand. Die berechnete erste Übergangsenergie (¹ A₁ ¹ E₁ stimmt gut mit dem beobachteten Wert überein. Ebenso wird die Interpretation des Übergangsmomentes für den Fall, daß auch zweifach angeregte Konfigurationen berücksichtigt werden, diskutiert.

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Resumé La structure électronique de l'anion croconique est étudieé par la méthode VESCF semi-empirique avec IC, configurations diexcitées comprises. L'effet des configurations diexcitées est très important sur l'état singulet le plus has qui est un état fundamental, alors que si l'on ne tient compte que des configurations monoexcitées on obtient un état fundamental triplet. La premiére énergie de transition calculée (¹ A₁ ¹ E₁ est en bon accord avec la valeur observee. Le moment de transition est interprété dans les cas où l'on tient compte des configurations diexcitées.