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1.
Prof. Dr. Yoshio Teki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(5):980-996
Recently, the potential use of organic π-radicals and related spin systems has been expanded to modern technological applications. The unique excited-state dynamics of organic π-radicals can be useful to improve the stability of photochemically unstable organic compounds, make the polarization transfer applicable to information technology, and achieve effective up-conversion of interest for luminescence bioimaging, among others. Furthermore, highly luminescent stable π-radicals have been recently reported, which are especially interesting for application in organic light-emitting devices owing to their potential to provide an internal quantum efficiency of 100 %. Thus, the excited-state nature of stable π-radicals as well as the control of their excited-state spin dynamics are emerging topics both in terms of fundamental science and related technological applications. In this minireview, we focus on the excited-state dynamics of both photostable non(weakly)-luminescent and luminescent π-radicals, which are opposites of each other. In particular, we cover the following topics: 1) effective generation of high-spin photoexcited states and control of the excited-state dynamics by using non-luminescent π-radicals, 2) unique excited-state dynamics of luminescent π-radicals and radical excimers, and 3) applications utilizing excited-state dynamics of π-radicals. 相似文献
2.
Let SB(X,Y) be the set of the bounded sublinear operators from a Banach space X into a Banach lattice Y. Consider π2(X,Y) the set of 2-summing sublinear operators. We study in this paper a variation of Grothendieck's theorem in the sublinear operators case. We prove under some conditions that every operator in SB(C(K),H) is in π2(C(K),H) for any compact K and any Hilbert H. In the noncommutative case the problem is still open. 相似文献
3.
设G是2-连通图,c(G)是图G的最长诱导圈的长度,c′(G)是图G的最长诱导2-正则子图的长度。本文我们用图的特征值给出了c(G)和c′(G)的几个上界。 相似文献
4.
A. Y. M. Chin 《Acta Mathematica Hungarica》2004,102(4):337-342
Let R be an associative ring with unit and let N(R) denote the set of nilpotent elements of R. R is said to be stronglyπ-regular if for each x∈R, there exist a positive integer n and an element y∈R such that x
n=x
n
+1
y and xy=yx. R is said to be periodic if for each x∈R there are integers m,n≥ 1 such that m≠n and x
m=x
n. Assume that the idempotents in R are central. It is shown in this paper that R is a strongly π-regular ring if and only if N(R) coincides with the Jacobson radical of R and R/N(R) is regular. Some similar conditions for periodic rings are also obtained.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
5.
Martin G Banwell Alison J Edwards Gwion J Harfoot Katrina A Jolliffe 《Tetrahedron》2004,60(3):535-547
An enantiomerically pure cis-1,2-dihydrocatechol, which is readily obtained via a toluene dioxygenase-mediated dihydroxylation of toluene in a whole-cell biotransformation process, has been converted over 17 steps into the linear triquinane (−)-hirsutene. Since the enantiomer of the starting material is also available this work constitutes a formal total synthesis of the naturally occurring (+)-form of hirsutene. Furthermore, minor modifications of the route used here offer the possibility of accessing (+)-hirsutene from the original starting material. 相似文献
6.
Pyrene-azacrown ether hybrid: cation-π interaction 总被引:1,自引:0,他引:1
A pyrene-modified lariat ether was synthesized in order to observe the cation-π interaction in solution. 相似文献
7.
A novel conjugation-elongated bis(ethylenedithio)tetraselenafulvalene (BETS) type donor, 2,5-bis(4,5-ethylenedithio-1,3-diselenol-2-ylidene)-2,3,4,5-tetrahydrothiophene (BEDT-HBDST) and its magnetic and non-magnetic anion salts, (BEDT-HBDST)2MX4 (MX4−=FeCl4−, GaCl4−, FeBr4− and GaBr4−), were prepared. These four salts are isostructural and belong to the space group of P2/c. They showed semiconducting behavior with small activation energies (59-64 meV). The band structures of these salts are quasi one-dimensional and there is a midgap between the upper band and the lower band, since the degree of dimerization is significant in the stacking direction. The MX4− ions are located between the donor columns and near to the ethylenedithio moieties of the donor molecules. The magnetic susceptibilities of the FeCl4− and FeBr4− salts follow the Curie-Weiss law with Curie constants of 4.6 and 4.8 emu K mol−1 (sum of the spins of S=5/2 and S=1/2) and negative Weiss temperatures of θ=−1.2 and −4.9 K, respectively, revealing a weak antiferromagnetic interaction of 3d spins of the FeCl4− and FeBr4− anions. The Fe?Fe (6.66-7.60 Å), Cl?Cl (4.81-4.82 Å) and Br?Br (4.74-4.77 Å) distances in the crystal structures of these salts are significantly long. Therefore, the direct magnetic interaction between the 3d spins of the nearest neighboring Fe3+ ions appears to be not readily accessible. 相似文献
8.
Nicole M. Brunkan 《Journal of organometallic chemistry》2003,683(1):77-82
The complex (dippe)Ni(η3-allyl)(CN) has been prepared and fully characterized (dippe=bis-(diisopropylphosphino)ethane), including X-ray diffraction studies, as a square pyramidal structure. The complex shows dynamic 1H-NMR behavior consistent with substantial structural rearrangements upon π to σ allyl interconversion. A comparison is made with (dippe)Ni(η3-allyl)Br, which also displays a square pyramidal structure. 相似文献
9.
Toshiaki Sunazuka Masaki Handa Tatsuya Shirahata Kazuhiko Otoguro Satoshi ōmura 《Tetrahedron》2004,60(36):7845-7859
In the current studies, we used the Kakisawa-Kashman modification of the Mosher NMR method to determine the complete absolute stereochemistry of arisugacins. We also report the convergent total synthesis of (+)-arisugacins A and B by a sequence including (i) ruthenium complex-catalyzed asymmetric reduction of the cyclohexenone derivative; (ii) stereoselective construction of the arisugacin skeleton by a Knoevenagel-type reaction of an α,β-unsaturated aldehyde derivative with production of a 4-hydroxy-2-pyrone derivative as a key reaction; and (iii) stereoselective dihydroxylation to give the diol derivative, followed by deoxygenation. Accordingly, we defined the absolute structures of arisugacins A and B as 4a-(R),6a-(R),12a-(R), and 12b-(S). Finally, we characterized the bioactivities of the synthetic intermediates to understand the structure-activity relationships of the arisugacins. 相似文献
10.
钒的氨基酸配合物具有重要的生物和医学意义。VO(Ⅱ)-组氨酸配合物及VO(Ⅱ)-π受体二元配合物的ESR研究已有报道。但是VO(Ⅱ)-氨基酸-π受体三元配合物的结构及其ESR研究至今未见报道。本文考察了VOSO_4与组氨酸(His)和邻菲啰啉(Phen)及α,α′-联吡啶(bipy)三元体系在不同酸度(pH=1~14)的乙二醇/水(1:1)溶液中低温(173K)ESR波谱,获得了不同pH条件下配合情况的详细信息。 相似文献