Hybrid density functional theory studies on the magnetic interactions and the weak covalent bonding for the phenalenyl radical dimeric pair

The phenalenyl radical (1) is a prototype of the hydrocarbon radical. Recently, the single crystal of 2,5,8-tri-tert-butylphenalenyl (2) was isolated and showed that the two phenalenyl radicals form a staggered dimeric pair, giving rise to strong antiferromagnetic interactions. The origin of the antiferromagnetic interactions and the nature of the chemical bond for the dimeric pair are challenging issues for chemists. First, spin-polarized hybrid DFT (Becke's half and half LYP (UB2LYP)) and CASSCF calculations were performed for 2 and its simplified model, the staggered-stacking phenalenyl radical dimeric pair (3a), to elucidate the origin of the strong antiferromagnetic coupling and the characteristics of the chemical bond. The calculated results showed that a SOMO-SOMO overlap effect was responsible for the strong antiferromagnetic interactions and weak or intermediate covalent bonding between phenalenyl radicals. The tert-butyl groups introduced at three beta-positions hardly affected the magnetic coupling, mainly causing steric hindrances in the crystalline state. Next, to obtain insight into ferromagnetic stacking, we investigated the stacking effect of staggered (3a)- and eclipsed (3b)-stacking phenalenyl radical dimeric pairs with a change of the SOMO-SOMO overlap on the basis of the extended McConnell model. We found that the stacking mode of the dimeric pair with both a small SOMO-SOMO overlap and a ferromagnetic spin polarization effect provided a ferromagnetic coupling.     

Introduction of a third meso substituent into 5,10-diaryl chlorins and oxochlorins

Chlorins/oxochlorins bearing distinct patterns of substituents are valuable compounds in bioorganic and materials chemistry. Treatment of a 5,10-diaryl-substituted chlorin or oxochlorin with TFA-d(1) resulted in selective deuteriation of the remaining meso positions (15, 20) rather than any of the beta-pyrrolic positions. Electrophilic iodination or bromination of a 5,10-diaryl-substituted chlorin proceeded with high regioselectivity, affording the 5,10-diaryl-15-halo-substituted chlorin. Iodination or bromination of a free base 5,10-diaryloxochlorin gave a mixture of products arising through halogenation at the 15-, 20-, and beta-pyrrolic positions, while bromination of a zinc 5,10-diaryloxochlorin selectively gave the 5,10-diaryl-20-bromo-substituted oxochlorin. The Suzuki coupling reaction of a phenyl boronic acid derivative and a 5,10-diaryl-15-iodooxochlorin or 5,10-diaryl-20-bromooxochlorin gave the corresponding 5,10,15- or 5,10,20-triaryloxochlorin. The introduction of a third aryl substituent into the chlorin or oxochlorin causes an approximately 5-nm red shift of the long wavelength Q(y) absorption band. Two phenylethyne-linked oxochlorin-oxochlorin dyads in distinct metalation states (zinc/free base, free base/zinc) were prepared by Sonogashira coupling reactions of a 5,10-diaryl-20-bromooxochlorin and a 10-substituted ethynylphenyl oxochlorin. This study provides access to new chlorins/oxochlorins that can be utilized in diverse applications.     

Asymmetric Synthesis of Axially Chiral Anilides by Enantiotopic Lithiation of Tricarbonyl(N-methyl-N-acyl-2,6-dimethylanilide)chromium Complex

Axially chiral N-methylanilides were synthesized by enantioselective lithiation of prochiral tricarbonyl(N-methyl-N-pivaloyl-2,6-dimethylaniline)chromium (1) with the lithium amide of the 4-methylpiperazinylethylamine derivative 13 followed by electrophilic quenching up to 97% ee in good yields. The resulting axially chiral chromium-complexd anilides 2 were oxidized under air to give the axially chiral anilides 14 in enantiomerically active form without axial bond rotation at room temperature.     

Phase equilibria and oxidation mechanisms in the LA-S-O system

The phase diagram of the La-S-O system at 1073 K was established with the vacuum seal technique. Six phases exist at this temperature: La₂O₃ (B-type), LaS₂, La₂S₃, La₂O₂SO₄, La₂O₂S and La₂O₂S₂. The thermodynamic functions for the reaction La₂O₂SO₄=La₂O₃+SO₂+1/2 O₂ were determined by using the emf method at temperatures from 1123 to 1373 K. The mechanisms of the oxidation reactions in the La-S-O system under different partial pressures of oxygen (–4.4 < log <–0.7) were also investigated by means of DTA, TG and powder X-ray diffractometry.

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Zusammenfassung Das Phasendiagramm des La-S-O-Systems bei 1073 K wurde bestimmt. Bei dieser Temperatur liegen 6 Phasen vor, und zwar La₂O₃ (B-Typ), LaS₂, La₂S₃, La₂O₂SO₄, La₂O₂S und La₂O₂S₂. Für die Reaktion La₂O₂SO₄=La₂O₃+SO₂+1/2 O₂ wurden die thermodynamischen Funktionen im Temperaturbereich von 1123–1373 K nach der EMF-Methode bestimmt. DTA, TG und Pulver-Röntgendiffraktometrie wurden zur Untersuchung der Mechanismen der im La-S-O-System verlaufenden Oxydationsreaktionen herangezogen, wobei der Sauerstoffpartialdruck in den Grenzen von – 4.4 < log < <-0.7 variiert wurde.

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La-S-O 1073 . : La₂O₃ (-), LaS₂, La₂S₃, La₂O₂SO₄, La₂O₂S La₂O₂S₂. . . ., La₂O₂SO₄=La₂O₃+ SO₂+1/2 ₂ 1123–1373. , La-S-O –4.4 < log < –0.7.

     

Sparsely substituted chlorins as core constructs in chlorophyll analogue chemistry. III. Spectral and structural properties

The availability of stable chlorins bearing few or no substituents has enabled a variety of fundamental studies. The studies described herein report absorption spectra of diverse chlorins, comparative NMR features of chlorins bearing 0-3 meso-aryl substituents, and X-ray structures of the fully unsubstituted chlorin and the oxochlorin.     

Traffic states and jamming transitions induced by a bus in two-lane traffic flow

We study the traffic states and jamming transitions induced by a bus (slow car) in a two-lane traffic of cars. We use the dynamic model which is an extended one of the optimal velocity model to take into account the lane changing. The fundamental (flow-density) diagram is presented. The fundamental diagram changes highly by introducing a bus on a two-lane roadway. It is found that there are the six distinct states for the two-lane traffic flow including a bus. The spatio-temporal patterns are presented for the distinct traffic states. The dynamical state of traffic changes with density of cars. It is shown that the dynamical transitions among the distinct traffic states occur at some values of density. The phase diagram (region map) is shown for the two-lane traffic flow including a bus.     

On some d-dimensional dual hyperovals in

In [H. Taniguchi, On d-dimensional dual hyperovals in PG(2d,2), Innov. Incidence Geom., in press], we construct d-dimensional dual hyperovals in PG(2d,2) from quasifields of characteristic 2. In this note, we show that, if d-dimensional dual hyperovals in PG(2d,2) constructed from nearfields are isomorphic, then those nearfields are isomorphic. Some results on dual hyperovals constructed from quasifields are also proved.     

An optical system for monitoring torsion in a power transmission shaft in realtime

An optical system has been proposed and verified experimentally for monitoring the torsion of a power transmission shaft in realtime. The system consists of a pair of lasers, mirrors and light receivers as a sensor head, and logic circuit, high-frequency oscillator, and computer as a data processing system. The smallest measurable angle of torsion can be expressed by ω/f, where ω is the rotational frequency of the power transmission shaft and f is the frequency of the oscillator. The experimental error was found to be a few percentage points.