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101.
Naela Assadi Sergey Pogodin Shmuel Cohen Amalia Levy Israel Agranat 《Structural chemistry》2009,20(4):541-556
The naphthalogous mono-bridged tetraarylethylenes 9,9′-di-(1-naphthylmethylene)-9H-fluorene (5) and 9,9′-di-(1-naphthylmethylene)-9H-xanthene (6), analogs of bifluorenylidene (1) and bixanthenylidene (2), have been synthesized and their molecular and crystal structures have been determined. Ene 5 has been prepared by two alternative synthetic routes. The molecular structures of 5 and 6 show that each of these enes has very small twist around the central double bond, but the two naphthalene rings in both 5 and 6 are highly twisted. According to the NMR study, 5 and 6 in solution adopt conformations which are similar to those found by X-ray crystal structure analysis. The notable upfield
shifts of H1 and H8 (6.11 and 6.83 ppm, respectively) and H2 and H7 (6.70 and 6.44 ppm, respectively) in 5 and 6 are due to the shielding caused by the nearly orthogonally twisted naphthalene rings. The B3LYP/6-31G(d) calculations of
5, 6, and their 2-naphthyl and phenyl analogs have been performed. In the 1-naphthyl series, the more efficient conjugation between
the naphthyl substituents and the central C=C and the overcrowding due to the peri-hydrogen atoms lead to higher twists of the naphthyl groups and to lower twists of the central C=C. In the 2-naphthyl series,
the opposite effects are noted.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
相似文献
Israel AgranatEmail: |
102.
In this paper we address the issue of uniformly positive scalar curvature on noncompact 3-manifolds. In particular we show
that the Whitehead manifold lacks such a metric, and in fact that
\mathbbR3{\mathbb{R}^3} is the only contractible noncompact 3-manifold with a metric of uniformly positive scalar curvature. We also describe contractible
noncompact manifolds of higher dimension exhibiting this curvature phenomenon. Lastly we characterize all connected oriented
3-manifolds with finitely generated fundamental group allowing such a metric. 相似文献
103.
104.
S. Nussinov 《Foundations of Physics》1998,28(6):865-880
We suggest scattering experiments which implement the concept of protective measurements allowing the measurement of the complete wave function even when only one quantum system (rather than an ensemble) is available. Such scattering experiments require massive, slow, projectiles with kinetic energies lower than the first excitation of the system in question. The results of such experiments can have a (probabilistic) distribution (as is the case when the Born approximation for the scattering is valid) or be deterministic (in a semiclassical limit). 相似文献
105.
106.
Semyon Cogan Yehuda Haas Shmuel Zilberg 《Journal of photochemistry and photobiology. A, Chemistry》2007,190(2-3):200-206
The energy of the lowest triplet state of organic molecules is intermediate between the ground state and the first excited singlet. At the S1/S0 conical intersection, the two singlet states are degenerate. It is shown that for some molecules (ethylene, benzene, toluene and pyrrole) the T1 state is also degenerate with the two singlet states. Moreover, the spin orbit coupling matrix element at this structure is necessarily large, so that intersystem crossing can be quite efficient. If the lowest triplet state is repulsive (as in the studied molecules) it may significantly contribute to the dissociation yield under certain experimental conditions. 相似文献
107.
S. Nussinov 《Zeitschrift fur Physik C Particles and Fields》1979,3(2):165-169
We suggest that mixed heavy quark bound states like \(b\bar c\) may offer very good testing ground for Q.C.D. We make a prediction within ≈0.3% for the \(b\bar c\) ground state mass and discuss its possible production in weak decays. Various general features of non leptonic decays of heavey flavors and in particular the prediction of absence ofK * 0 resonance inD 0→K -→+→0 arte discussed, and finally we close by commenting on the importance of associated heavy flavor production as a crucial test for the recently advanced preconfinment notion. 相似文献
108.
109.
Reaction of 3,4-dihydroisoquinoline N-oxide 1 with diethyl cyanomethylphosphonate 2 gave the enaminonitrile 1-cyanomethylene-1,2,3,4-tetrahydroisoquinoline 3. Reaction of 1 with trialkyl phosphonoacetate 4 gave 5, the fused aziridine derivative 7 - exo - carbethoxy -1 - aza - 4,5 - benzo - bicyclo[4.1.0]heptene - 4, and the enaminoester 1-carbalkoxymethylene-1,2,3,4-tetrahydroisoquinoline 6. The ratio of 5:6 depends on the reaction conditions. While using 1,2-dimethoxyethane the aziridine 5 is the major product; using alcoholic solvents the yield of 6 increases at the expense of 5 with increasing acidity of the solvent. 相似文献
110.
Galina Temtsin-Krayz Alexander I. Shames Shmuel Bittner 《Research on Chemical Intermediates》2003,29(3):325-333
EPR spectroscopy was used to assess the radicals produced upon basic decomposition of N,N-bis-(3-chloro-1,4-naphthoquinon-2-yl) amine (BClNQA). Three radicals have been trapped and identified: N-bis(3-chloro-1,4-naphthoquinone) hydrazine radical (6), 2-hydroxy-3-chloro-1,4-naphthoquinone anion radical (9) and 2-amino-3-chloro-1,4-naphthoquinone radical (8). The probable reaction mechanism, the structure of intermediates as well as the reaction profile are discussed. 相似文献