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561.
The rotational spectra of CF(3)I···NH(3) and CF(3)I···N(CH(3))(3) are measured between 6.7 and 18 GHz using a chirped-pulse Fourier transform microwave spectrometer. Transitions in each spectrum are assigned to A and E species associated with ground and excited internal rotor states respectively. Rotational constants, B(0), centrifugal distortion constants, D(J), D(Jm), D(JKm), nuclear quadrupole coupling constants of the (14)N and (127)I atoms, χ(aa)(N) and χ(aa)(I), are determined for each complex. D(JK) is additionally determined for CF(3)I···NH(3). Results are presented for both (14)N and (15)N-substituted isotopologues. All data are consistent with C(3v) symmetric top structures for both complexes. The nuclear quadrupole coupling constants of iodine are determined to be -2230.030(83) MHz and -2241.61(17) MHz in CF(3)I···(14)NH(3) and CF(3)I···(14)N(CH(3))(3) respectively. The data are interpreted through a model that accounts for the internal dynamics of the complexes in order to determine the length of the halogen bond between the iodine and nitrogen atoms, r(N···I). Values of r(N···I) are thus determined to lie in the ranges 3.054 ? > r(N···I) > 3.034 ? and 2.790 ? > r(N···I) > 2.769 ? for CF(3)I···NH(3) and CF(3)I···N(CH(3))(3) respectively. 相似文献
562.
Adora G. Graham Dr. Saul H. Lapidus Casey G. Hawkins Prof. Peter W. Stephens Prof. Joel S. Miller 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(67):15565-15572
The reactions of MnII(O2CCH3)2 with NEt3Me+CN− and NEt2Me2+CN− form (NEt3Me)2MnII5(CN)12 ( 1 ) and (NEt2Me2)2MnII5(CN)12 ( 2 ), respectively. Structure model-building and Rietveld refinement of high-resolution synchrotron powder diffraction data revealed a cubic [a=24.0093 Å ( 1 ), 23.8804 Å ( 2 )] 3D extended structural motif with adjacent tetrahedral and octahedral MnII sites in a 3:2 ratio. Each tetrahedral MnII site is surrounded by four low-spin octahedral MnII sites, and each octahedral MnII site is surrounded by six high-spin tetrahedral MnII sites; adjacent sites are antiferromagnetically coupled in 3D. Compensation does not occur, and magnetic ordering as a ferrimagnet is observed at Tc=13 K for 2 based on the temperature at which remnant magnetization, Mr(T)→0. The hysteresis has an unusual constricted shape with inflection points around 50 and 1.2 kOe with a 5 K coercivity of 16 Oe and remnant magnetization, Mr, of 2050 emuOe mol−1. The unusual structure and stoichiometry are attributed to the very ionic nature of the high-spin N-bonded MnII ion, which enables the maximization of the attractive van der Waals interactions through minimization of void space via a reduced ∠ MnNC. This results in an additional example of the AxMnIIy(CN)x+2y (x=0, y=1; x=1, y=3; x=2, y=1; x=2, y=2; x=2, y=3; x=3, y=5; and x=4, y=1) family of compounds possessing an unprecedented stoichiometry and lattice motif that are cation adaptive structured materials. 相似文献
563.
564.
A new highly cytotoxic iridoid has very recently been isolated from Prismatomeris tetrandra and shown to have the structure 3, similar to that of the iridoid oruwacin, 2. We report the determination of the absolute configuration (AC) of the new iridoid, prismatomerin, using vibrational circular dichroism (VCD) spectroscopy. The VCD spectrum of the acetate derivative of 3, 4, is analyzed using the Stephens theory of VCD and density functional theory (DFT). The AC of the naturally occurring 3 is shown to be 1R,5S,8S,9S,10S, identical to that of the naturally occurring iridoid plumericin, 1, also determined using VCD spectroscopy. The [alpha]D values of the natural products 3 and 1 are negative and positive, respectively. Since the ACs of 3 and 1 are identical, it follows that the AC of 3 cannot be correctly determined by empirical comparison of the signs of the [alpha]D values of 3 and 1. 相似文献
565.
Stephens PJ Aamouche A Devlin FJ Superchi S Donnoli MI Rosini C 《The Journal of organic chemistry》2001,66(11):3671-3677
We report the determination of the absolute configuration (AC) of the chiral sulfoxide, 1-(2-methylnaphthyl) methyl sulfoxide, 1, using vibrational circular dichroism (VCD) spectroscopy. The VCD of 1 has been measured in the mid-IR spectral region in CCl(4) solution. Analysis employs the ab initio DFT/GIAO methodology. DFT calculations predict two stable conformations of 1, E and Z, Z being lower in energy than E by <1 kcal/mol. In both conformations the S-O bond is rotated from coplanarity with the naphthyl moiety by 30-40 degrees. The predicted unpolarized absorption ("IR") spectrum of the equilibrium mixture of the two conformations permits assignment of the experimental IR spectrum in the mid-IR spectral region. The presence of both E and Z conformations is clearly evident. The VCD spectrum predicted for S-1 is in excellent agreement with the experimental spectrum of (-)-1, unambiguously defining the AC of 1 as R(+)/S(-). 相似文献
566.
Yukio Yamaguchi Brian C. Hoffman Jeffrey C. Stephens Henry F. Schaefer III 《ChemInform》1999,30(51):no-no
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option. 相似文献
567.
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option. 相似文献