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1.
The 1H and 13C spectra of fluorene, fluorenone, phenanthrene and their 4-methyl and 4,5-dimethyl derivatives have been examined. To complete the analyses for fluorenone and 4-methylfluorenone, 1H spectra were recorded at 270 MHz. The results from the 1H spectra permitted unequivocal assignments for the protonated aryl carbons by selective proton decoupling. A consistent set of assignments for the quaternary carbons was obtained through consideration of the dominant relaxation processes operative at these centres. This series of compounds was examined to investigate the shielding effects produced by the close approach of methyl groups separated by five bonds for comparison with the contrasting trends found for methyl carbons separated by three and four bonds. The results indicate that the relative orientation of the methyl groups is an extremely critical factor governing their shieldings and those of neighboring centres. 相似文献
2.
A procedure for the estimation of the mixing time between the last two 90° pulses in the classic three-pulse sequence NOESY/EXSY is proposed and tested and some considerations for the treatment of the two-dimensional (2D) 1H NMR exchange spectra are given. The rate constants are thus obtained with reasonable precision. This procedure was followed to obtain the 2D spectra of the model compound α-[bis(dimethylamino)methylene]-4-nitrophenylacetonitrile, which represents a four-site exchange system. The barriers to restricted rotations found in this compound were also determined from one-dimensional (1D) 1H NMR spectra, which were processed with the iterative complete lineshape analysis (CLSA) method. The double-fit approach was incorporated in the CLSA method. It is shown that the results from the 2D dynamic NMR spectral studies corroborate those obtained by the CLSA double-fit method. 相似文献
3.
L. M. Babkov J. Baran N. A. Davydova J. I. Kukielskii S. V. Trukhachev 《Journal of Structural Chemistry》2004,45(4):591-598
The vibrational spectra of a solid crystalline sample of 2-biphenylmethanol have been measured at room temperature. The IR absorption spectra were recorded in the range 400 cm–1–3600 cm–1; Raman spectra were measured in the range 10 cm–1–1640 cm–1. The direct mechanical and optoelectronic problems were solved using the fragment method realized as Lev-100 software; the intensity distribution in the IR spectrum of 2-biphenylmethanol was obtained by the same method. The experimental Raman and IR absorption spectra were interpreted by analyzing the calculated data on the frequencies and forms of normal vibrations and their intensities in the IR spectra. IR absorption spectra were simulated for several models of 2-biphenylmethanol conformers that differ in the mutual orientation of fragments. Based on the results of simulation and comparison of the calculated and experimental spectra of conformers we suggested a model for the conformer realized in the solid phase under normal conditions.Original Russian Text Copyright © 2004 by L. M. Babkov, J. Baran, N. A. Davydova, J. I. Kukielskii, and S. V. TrukhachevTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 4, pp. 624–631, July–August, 2004.This revised version was published online in April 2005 with a corrected cover date. 相似文献
4.
Roman Bo
a 《International journal of quantum chemistry》1988,33(2):159-167
The quasirelativistic CNDO /1 method has been in investigating the geometry, electronic structure, and redox stability of metal complexes. The systems of [Co(NH3)6]q and [MCl4]q, M being Ni, Pd, and Pt, have been studied. A modified Germer model of solvation has been implemented into the method. This yields reliable results on the redox stability of complexes in aqueous solutions. The calculated excitation energies resemble the electronic spectra of [MCl4]2? complexes. 相似文献
5.
KadiyalaV.S.N. Murty Tong Xie Bruno Bernet Andrea Vasella 《Helvetica chimica acta》2006,89(4):675-730
The anthraquinone derivatives T‐x‐x ( x = 2, 4, and 8), possessing two cellobiosyl, cellotetraosyl, and cellooctaosyl chains, respectively, C‐glycosidically bonded at C(1) and C(8) were synthesised as potential mimics of cellulose I. The anthraquinone template enforces a parallel orientation of the cellodextrin chains at a distance corresponding to the one between the crystallographically independent chains of cellulose I, and the ethynyl and buta‐1,3‐diynyl linker units ensure an appropriate phase shift between them. The H‐bonding of the T‐x‐x mimics was analysed and compared to the one of the mono‐chained analogues T‐x and of the known cellulose II mimics N‐x‐x and N‐x where one or two cellodextrin chains are O‐glycosidically bonded to naphthalene‐1,8‐diethanol, or to naphthalene‐1‐ethanol. The OH signals of T‐x and T‐x‐x in solution in (D6)DMSO were assigned on the basis of DQFCOSY, HSQC, and TOCSY (only of T‐4, T‐4‐4 , and T‐8‐8 ) spectra and on a comparison with the spectra of N‐x and N‐x‐x. Hydrogen bonding was analysed on the basis of the chemical shift of OH groups and its temperature dependence, coupling constants, SIMPLE 1H‐NMR experiments, and ROESY spectra. T‐4‐4 and T‐8‐8 in (D6)DMSO appear to adopt a V‐shape arrangement of the cellosyl chains, avoiding inter‐chain H‐bond interactions. The well‐resolved solid‐state CP/MAS 13C‐NMR spectra of the mono‐chained T‐x ( x = 1, 2, 4, and 8) show that only T‐8 is a close mimic of cellulose II. While the solid‐state CP/MAS 13C‐NMR spectrum of the C1‐symmetric diglucoside T‐1‐1 is well‐resolved, the spectra of T‐2‐2 and T‐4‐4 show broad signals, and that of T‐8‐8 is rather well resolved. The spectrum of T‐8‐8 resembles that of cellulose Iβ. A comparison of the X‐ray powder‐diffraction spectra of T‐8‐8 and T‐8 with those of celluloses confirms that T‐8‐8 is a H‐bond mimic of cellulose I and T‐8 one of cellulose II. Surprisingly, there is little difference between the CP/MAS 13C‐NMR spectra of the acetyl protected mono‐chained C‐glycosylated anthraquinone derivatives A‐x and the double‐chained A‐x‐x ( x = 2, 4, and 8). The spectra of A‐4 and A‐4‐4 resemble strongly the one of cellulose triacetate I ( CTA I ). The (less well‐resolved) spectra of the cellooctaosides A‐8 and A‐8‐8 , however, resemble the one of CTA II . The similarity between the solid‐state CP/MAS 13C‐NMR spectra of A‐4 and A‐4‐4 to the one of CTA I , and of A‐8 and A‐8‐8 to the one of CTA II is opposite to the observations in the acetylated cellodextrin series. The mono‐chained A‐x cellulose triacetate mimics 21 ( A‐2 ), 32 ( A‐4 ), and 55 ( A‐8 ) were synthesised by Sonogashira coupling of the cellooligosyl‐ethynes 15, 28 , and 50 , followed by selective deacetylation. Complete deacetylation provided the corresponding T‐x mimics. The double‐chained A‐x‐x mimics 24 ( A‐2‐2 ), 35 ( A‐4‐4 ), and 58 ( A‐8‐8 ) were prepared from A‐x by triflation and Sonogashira coupling with the cellosyl‐buta‐1,3‐diynes 19, 31 , and 53 . Their deacetylation provided the corresponding T‐x‐x mimics 25, 36 , and 59 . The cellooligosyl‐ethynes and cellooligosyl‐buta‐1,3‐diynes required for the Sonogashira coupling were prepared by stepwise glycosylation of the partially O‐benzylated β‐cellobiosyl‐ethyne and β‐cellobiosyl‐buta‐1,3‐diyne 13 and 17 , respectively, with the cellobiosyl donor 2 and the cellohexaosyl donor 47 . 相似文献
6.
Hue T. B. Bui Duy D. Vo Yen N. T. Chau Cuc T. K. Tu Hieu V. Mai Kiet V. Truong 《合成通讯》2013,43(24):2861-2868
A facile synthetic method for the construction of 2-substituted-4-oxo-4H-quinolizine-based core structure has been successfully developed. The synthesis made use of a one-pot Stobbe condensation followed by cyclization starting from the commercially available 2-pyridinecarbaldehyde. The structure of the formed 4-oxo-4H-quinolizine-2-carboxylate was fully confirmed by mass spectra, 1H NMR and 13C NMR, correlation spectrography, heteronuclear multiple bond correlation, and heteronuclear single quantum coherence (HSQC) spectra. The ethyl carboxylate moiety was then further functionalized via direct aminolysis by a range of amines to afford the corresponding 4-oxo-4H-quinolizine-2-carboxamides 4a–i in moderate to good yields. 相似文献
7.
8.
L. A. Fedorov V. I. Dostovalova O. A. Arapov M. Yu. Malov 《Russian Chemical Bulletin》1994,43(4):713-714
The13C NMR spectra of a number of polychiorinated dibenzo-p-dioxins (PCDD) were measured. These and previously known spectra were used for the development of a method for calculation of13C NMR spectra of chloroaromatics in the framework of a two-particle increment scheme for carbon chemical shifts. The scheme one allows to calculate13C chemical shifts for all 75 PCDD.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 760–761, April, 1994. 相似文献
9.
K. Murugavel S. Amirthaganesan R. T. Sabapathy Mohan 《Chemistry of Heterocyclic Compounds》2010,46(3):302-306
A new series of t-4-aryl-3,c-6-dihydroxy-6-methyl-4,5,6,7-tetrahydro-1H-indazole-r-5-carboxylic acid isopropyl esters has
been synthesized by adopting a conventional method from cyclic β-keto esters. 1H, 13C NMR, and IR spectra for all the compounds were investigated. HMBC, HSQC, COSY, and NOESY spectra of the representative compounds
were studied. The stereochemistry of a six-membered ring of the fused indazoles resembled that of keto esters. From the HMBC
correlations the indazole structure was confirmed as 1H-indazole. 相似文献
10.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1978,34(5):549-559
The vibrational spectra of the following compounds were measured: X+AlMe−4; X+GaMe−4 and X+InMe−4 (with X = Na, K, Me4P+, Me4As+ or Me4Sb+). For the purpose of comparison the spectra of compounds of group IV and V elements were taken from the literature or measured a second time. With a new procedure for determination of force-constants a set of comparable force-constants for the tetramethyl compounds of the elements Al, Si, P/Ga, Ge, As/In, Sn, Sb was obtained. 相似文献
11.
Inverse pre-resonance Raman spectra of rhodamine 6G in solution in methanol have been recorded over the concentration range 10?1 to 10?4 mol ??1. The solute and solvent transitions are found to display perfectly normal lorentzian profiles over the whole of this concentration range. Intensities and depolarization ratios of the pre-resonance Raman features are recorded. It is shown that the spectra arise from monomeric rhodamine 6G molecules in the singlet electronic ground state and the relative merits of the CARS and inverse Raman methods for recording resonance Raman spectra are discussed. 相似文献
12.
The Raman spectra of cadmium bromide solutions with bromide to cadmium mole ratios varying from 1.0 to 9.74 were studied at 200°C. Factor analysis revealed that three complexes contributed to the spectra. From a comparison with previous results at 25°C these species were identified as CdBr2, CdBr
3
–
, and CdBr
4
2–
cadmium existed as the tetrabromo complex, CdBr
4
2–
, at mole ratios greater than 5.99. A formation constant of 7±2 was determined for CdBr
4
2–
at 200°C. No evidence of Cd(H2O)
6
2+
or CdBr+ was found, although electroneutrality dictates that one or both of these species must exist at low mole ratios. 相似文献
13.
V. I. Baranov L. A. Gribov V. O. Jenjer D. Yu. Zelentsov 《Journal of Structural Chemistry》1996,37(6):881-888
The absorption and fluorescence spectra of diphenylpolyenes (diphenylbutadiene, diphenylhexatriene, diphenyloctatetraene,
and 1,6-di(4′-methylphenyl)-1,3,5-hexatriene) are calculated by a recently proposed parametric method using the fragmentation
approach for designing molecular models. The parameters of theH>C=molecular fragment (derivatives of the Coulomb and resonance integrals with respect to internal coordinates in the HAO
basis set) obtained in calculation for polyenes were transferred to the molecular models of diphenylpolyenes without changes
(∂He/∂q(0)=0.055 and ∂2He/∂q
k
(0)
∂q
l
(0)
=0.1 au). The theoretical spectra are sufficiently adequate to quantitatively and qualitatively reproduce the main features
of the vibrational structure of the experimental absorption and fluorescence spectra, and the parameters of the models of
the potential surfaces of the excited states of diphenylpolyenes are consistent with the previous estimations. It is shown
that this method allows predictive calculations of the vibronic spectra of complex molecules and the developed parametrization
posesses all needed properties: locality, transferability, invariance to minor changes in electron density, ranking according
to magnitude, small number of parameters for molecular fragments, etc.
K. A. Timiryazev Moscow Agricultural Academy. Translated fromZhurnal Struktumoi Khimii, Vol. 37, No. 6, pp. 1040–1049, November–December, 1996.
Translated by I. Izvekova 相似文献
14.
Vibrational spectra of Ph4Si have been studied from 600 to 20 cm?1 in solution, in the melt and in the crystalline state. The assignments proposed for the substituent sensitive benzene ring vibrations, for the skeletal bending modes and ring librations have been supported by polarized IR and Raman measurements. The crystal spectra are interpreted on the basis of the S4 site symmetry of the molecules in the crystal. Two skeletal bending and four ring librational modes are supposed to appear below 120 cm?1, in the range of the lattice vibrations. 相似文献
15.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1987,43(9):1125-1134
Fine-structure fluorescence spectra and i.r. spectra of the model compound chlorophyll-Zn-octaethylchlorin (Zn OEC), and its three deuterated derivatives at meso-positions and Zn OEC-15N4 have been obtained. Polarization measurements for individual zero-phonon lines show that in the vibronic spectra of the above compounds the totally symmetric vibrations are mainly active. A joint analysis of the experimental data and calculation results of normal vibrations has served as a basis for the interpretation of the spectra obtained as well as resonance Raman spectra. It is pointed out that the vibrations of ethyl substituents largely form a vibrational structure of the vibronic Zn OEC spectrum. An assignment of some lines in a fine-structure spectrum of chlorophyll a is discussed. 相似文献
16.
UkJae Lee Jun Woo Bae Hee Reyoung Kim 《Journal of Radioanalytical and Nuclear Chemistry》2017,314(2):617-622
A method of separating beta spectra into each radionuclide spectrum was proposed in this study. Based on mathematical curve fits, the spectrum of each radionuclide was defined by using the maximum energy information and process to separate specific spectra from the whole spectrum. Information on 32P, 90Y, and 106Rh radionuclides from the International Commission on Radiation Units and Measurements was used for applying the proposed method. A relative error of less than 2% was achieved with the application of the method. 相似文献
17.
Summary Reaction between K2[ReI6] and KSCN in boiling MeOH or in the melt gave [Re(NCS)6]2– and a weakly paramagnetic species, isolated as its Cs salt. Tl, Me4N and other salts of this species have been isolated from the reaction medium of from the Cs salt by metathesis. On the basis of magnetic susceptibility and i.r. spectra the new complex has been formulated as [Re2(NCS)12]4– containing metalmetal bond and no bridging thiocyanate. The Me4N salt has also been isolated by bioling aqueous solutions of HReO4 and HSCN and then adding Me4NCL. A pyridinium salt, formulated as (pyH)4[Re2(NCS)12], has been obtained by boiling [ReO2py4]NCS with aqueous HSCN. The two complex species [Re(NCS)6]2– and [Re2(NCS)12]4– show distinctly different magnetic moment and electronic spectra. 相似文献
18.
We present photoelectron spectra for H2 in the excited C 1Πu, υ = 0–4.J = 1 levels prepared by multiphoton excitation. In accordance with the Franck-Condon principle, the H2+ vibrational state distribution is dominated by Δυ = 0 transitions from the C 1Πu state, illustrating a useful method for preparing vibrationally state-selected molecular ions. Equally important observed systematic departures from Franck-Condon factors, which provide detailed information on excited-state photoionization dynamics of molecules. 相似文献
19.
The monomethyl esters of mono(dimethylamides) and the bisdimethylamides of mesoporphyrin-IX, mesoporphyrin-III, and mesoporphyrin-XIII have been obtained, together with their zinc complexes. A relationship has been found between the chemical shifts of the signals for CONMe2 in the PMR spectra and the positions of the substituents in the porphyrin ring, enabling a correct assignment to be made for the first time of these signals to the groups in positions 132 and 172 of the porphyrin ring, to establish the structures of the isomeric monomethyl esters of mesoporphyrin-IX, and to develop a method of identifying monoesters of natural porphyrins by converting them into the monoesters of the mono(dimethylamides) of mesoporphyrin-IX, followed by examination of their PMR spectra.For Communication 23, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 780–786, June 1988. 相似文献
20.
The reduction of 3-oxatricyclo[3.2.1.02,4]octane-endo-6-carbonitrile by lithium aluminum hydride is completed by the formation of exo-2-hydroxy-4-azatricyclo[4.2.1.03,7]nonane with the structure confirmed (1) by the analysis of 1H, 13C, 14N, and 17O NMR spectra and the two-dimensional spectra (COSY-experiment); (2) by comparison with 1H and 13C NMR spectra of the corresponding oxygen analog of heterobrendane; (3) by the calculation of the vicinal constants for the spin-spin interaction in the molecules of both analogs by the MMX program; and (4) by transformation into N-(p-bromophenylsulfonyl)-exo-2-hydroxy-4-azatricyclo[4.2.1.03,7]nonane prepared by an alternative synthesis, viz., epoxidation of N-(p-bromophenylsulfonyl)bicyclo-[2.2.1]hept-2-en-endo-5-methylamine. The reduction of 3-oxatricyclo [3.2.1.02,4]octane-exo-6-carbonitrile affords the epoxide, 3-oxatricyclo[3.2.1.02,4]octane-exo-6-methylamine. Different behaviors of stereoisomers are discussed; analysis of the coefficients of the atomic orbitals in the MO LCAO equation (AM1 method) has been made, and the strengths of the C(SINGLE BOND)O bonds in the epoxy ring has been analyzed. © 1997 John Wiley & Sons, Inc. 相似文献