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71.
Jurriaan M Zwier Albert M Brouwer Tamás Keszthelyi Gurusamy Balakrishnan Jesper F Offersgaard Robert Wilbrandt Frédérique Barbosa Urs Buser Jér?me Amaudrut Georg Gescheidt Stephen F Nelsen Charles D Little 《Journal of the American Chemical Society》2002,124(1):159-167
The radical cation of 1,3,6,8-tetraazatricyclo [4.4.1.1(3,8)]dodecane (TTD) has been studied using magnetic resonance and optical spectroscopic methods and computational techniques. With the help of deuterated isotopomers, assignments of EPR and resonance Raman spectra could be unequivocally established. The results demonstrate that the radical cation has D(2d) symmetry, and instantaneous electron delocalization over the four equivalent nitrogen atoms occurs. This extensive delocalization in a completely saturated system is a unique feature of the TTD radical cation. The spectroscopy of TTD, in contrast to that of simpler diamines such as 1,4-diaza[2.2.2]bicyclooctane, simultaneously reveals the consequences of orbital interactions through space and through bonds. The relationship between nitrogen pyramidalization and hyperfine coupling constants in nitrogen-centered radical cations with a number of different bonding arrangements is reviewed. 相似文献
72.
A. Little H. C. Jain S. M. Lazarus T. K. Saylor B. B. Triplett S. S. Hanna 《Hyperfine Interactions》1980,8(1-3):3-18
Magnetic hyperfine interactions in highly stripped oxygen ions recoiling in vacuum have been measured with perturbed angular correlations. The second excited state of16O(I
=3–,E
X=6.13 MeV, =26.6 psec, |g|=0.55) was produced with the nuclear reactions19F(p,)16O and16O(,)16O and the angular correlation of the -rays observed in coincidence with particles emitted at 180°. Five recoil velocities between 1.0 and 3.3% c produced average ion charge states from 2.1 to 5.5. The perturbation of the angular correlation and hence the decoupling of the hyperfine interactions was observed as a function of an external axial magnetic field varied between 0 and 33 kG. The perturbation is expected to arise primarily from hyperfine interactions of unpaired 1s electrons with smaller contributions from 2s electrons and other configurations. The maximum external field was strong enough to decouple all hyperfine interactions except that of the 1s electrons. The decoupling curves obtained were successfully fitted by calculations using the hyperfine interactions of the pertinent atomic Hartree-Fock-Slater orbitals.Supported in part by the National Science Foundation. 相似文献
73.
H. W. Rowell Stone C. Reichard Chancel Salkowski Sendhoff A. Staehler W. Scharfenberg F. J. Metzger H. T. Beans Ch. E. Swett H. F. V. Little E. Cahen und A. Guthier 《Fresenius' Journal of Analytical Chemistry》1920,59(1):18-26
Ohne Zusammenfassung 相似文献
74.
W. Claus P. E. Klopsteg H. Menzel F. Krüger N. Bjerrum W. Nernst M. Planck P. Henderson Erich Müller R. Luther L. Michaelis Alfred Schmid M. Trénel A. Lessing F. Haber R. Russ E. Greppi C. Lucchini V. K. La Mer T. R. Parsons E. Little E. M. Durand O. Tomiek W. A. Roth J. C. Baker und L. L. van Slyke 《Fresenius' Journal of Analytical Chemistry》1930,79(3-4):137-145
Ohne Zusammenfassung 相似文献
75.
David P. Little 《Journal of Combinatorial Theory, Series A》2009,116(1):223-231
In 1840, V.A. Lebesgue proved the following two series-product identities:
76.
Nishiguchi GA Graham J Bouraoui A Jacobs RS Little RD 《The Journal of organic chemistry》2006,71(16):5936-5941
We (a) describe the completion of a total synthesis of 7,11-epi-thyrsiferol (4), (b) compare the antimitotic activities of thyrsiferol (2), Delta15,28-dehydrothyrsiferol (3), and 7,11-epi-thyrsiferol (4), (c) evaluate the synergistic behavior of the title compound and colchicine to inhibit cell proliferation, and (d) describe the results of conformational searches that provide additional insight concerning the SAR profile of the thyrsiferol family of natural products. 相似文献
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