The tetra-anthranilide derivatives ()–() have been synthesised. X-Ray crystallography shows that ,′,″-trimethyltetra-anthranilide () adopts a conformation with three - and one -amide linkages in the solid state. Dynamic 1H n.m.r. spectroscopy indicates that -benzyl-′,″,′″-trimethyltetra-anthranilide () exists as an interconverting ternary mixture of chiral non-planar conformational diastereoisomers in solution. 相似文献
Reactions of urotropine (C6H12N4) with trimethylmetal derivatives of Al, Ga, In und Tl in various () molar ratios lead to stable and monomeric , or adducts in good yields, but no addition product could be isolated. The vibrational spectra (IR and Raman) of all compounds are recorded and partly assigned. Some characteristic frequencies of the C6N4-skeletons clearly show the symmetry changes in the series of the → → adducts (C3ν → C2ν → C3ν). The X-ray structure determinations of C6H12N4·.GaMe3 (MeCH3) and C6H12N4·.2GaMe3, are in good agreement with the vibrational spectra. Both compounds crystallize in monoclinic space groups (P21 and C2/c). The GaN distances are around 214 pm, and the values for the C6N4-skeletons are not significantly different from those for free urotropine. 相似文献
The tri-3-methyltrianthranilide derivatives ()–() have been synthesised. Dynamic 1H n.m.r. spectroscopy indicates that the ,′,″-trimethyl derivative () exists in solution as slowly ring inverting ( ? *) enantiomeric helical conformations. X-Ray crystallography shows that the ,′-dimethyl-″-benzyl derivative () undergoes spontaneous resolution when it crystallises as a 1:1 adduct from toluene. The host molecules adopt a helical conformation (Figure 1) within a lattice structure that contains chiral channels (Figure 2) occupied by guest solvent molecules. 相似文献
Microwave—optical double resonance signals have been detected in a mass-selected ion-beam spectrometer for 12C16O+. With the optical excitation of fluorescence from the R1 () line of the (0,0) band of the A2Π ← X2∑ transition of 20350.6 cm?1, the microwave resonances occurred at 118101.8 ± 0.2 MHz and at 117694 ± 2 MHz corresponding to the N= 1, J = ← N = 0, J = and the N = 1, J = ← N = 0, J = transitions. 相似文献
Synthesis and properties of C5H5(CO)2Mn-N2H4-Cr(CC)5, C5H5(CO)2Mn-N2H2-Cr(CO)5 and C5H5(CO)2Mn-N2-Cr(CO)5 are reported. , and constitute the first series of heteronuclear complexes in which N2, N2H2 and N2H4 are bound to identical metal centers. and are obtained by reacting C5H5Mn(CO)2N2H4 respectively with Cr(CO)5THF, by oxidation of . disproportionates by addition of base yielding and H2. The IR Spectrum of allows the assignment of five normal vibrations of the diazene ligand; in the IR spectrum of the deuterated analogue all six normal vibrations can be assigned. The 1H-NMR spectrum of yields the coupling constant of protons on NN double bonds for the first time; the value of 3JHH 23,5 Hz points to a trans structure of . 相似文献
The vicinal n - σ* interaction stabilizes the pyramidal state of the nitrogen geminal system where X and Y are electronegative substituents with high-lying levels of nonbonding n orbitals. A approximate value for the energy of n - σ* stabilization of pyramidal state in ,-dialkoxyamines, equal to ~5.7 kcal/mol, has been found by comparing the average experimental value of the inversion barrier for these compounds with the one calculated according to the additive scheme. The influence of the vicinal n - σ* interaction on the structural peculiarities of -alkoxyisoxazolidines manifests itself in the conformations with the greatest overlapping of n and σ* orbitals being predominantly populated and in a change in NO bond lengths and valence angles. The combination of a ligand having the highest-lying level of n orbital with a ligand, which forms the σ bond with a N atom, having the lowest-lying antibonding level results in the dissociation of a nitrogen geminal system into an ionic planar form of the type. From this is inferred the dual nature of the influence exerted by the vicinal n - σ* interaction upon the inversion barrier of the geminal system. 相似文献
Three different types of butanolide complexes with EtnAlCl3?n in the molar ratios and have been investigated by IR with 1M NMR spectroscopy. The butanolides form and complexes with ethylaluminium halides, but with triethylaluminium only complexes are formed. The complexes are intermediates in the cleavage of butanolides. 相似文献
Fluorescence decay profiles of NO excited levels slightly above the dissociation limit have been measured by a single-photon counting technique with nanosecond pulse excitation using an iodine flash lamp. Three iodine atomic lines in the vicinity of 180 nm are found to bring NO molecules into the levels A2Σ+(ν = 5, N = 9), B22Π(ν = 8, J = 8.5), C2Π(ν = 1, J = 8.5), D2Σ+(ν = 0, N = 5) and D2Σ+(ν = 1, N = 9). Extrapolated zero-pressure lifetimes for single rotational levels are obtained, except for the C state where only a lifetime of ⩽0.4 ns was obtained. Self-quenching rate constants are also determined under higher-pressure conditions. Helium was found to quench the NO A2Σ+(ν′ = 5) fluorescence very efficiently. 相似文献
tert-Butyl azidoformate () reacts with the conjugate bases of , , (R1 = R2 = CH3), and (R1 = CH3, R2 = H) to give products [, , , and , respectively] in addition to the expected N-(tert-butoxycarbonyl)indole derivatives. 相似文献
The N-hydroxyazetidines and are prepared startinfrom 2,3-dihydroazete 1-oxides ( and 0 by reduction with sodium borohydride and by reaction with a nucleophile, respectively. The N-thydroxyazetidines and can be oxidized with mercury (II) oxide to the corresponding nitrones ; oxidation of the N-hydroxyazetidine (unsubstituted at C-4) with equivalent of lead tetraacetate tyields the N-tacetoxy β-lactam . 相似文献
Five large (25 000 particle) three-dimensional Witten—Sander clusters have been generated, and geometric relationships characterizing this structure have been examined. The quantities measured include the dependence of the radius of gyration. (r2), and (r4) on cluster size N, the mass M(r) contained within a distance r from the center mass, the dependence of the areas of projections of the clusters onto a plane of cluster size N, the density—density correlation function and the distribution of particles (occupied lattice sites) in cubes of side λ as a function of λ. Although uncertainties are quite large, our results are consistent with the concept hat the geometric scaling properties of three-dimensional Witten—Sander clusters can be described in terms of a single effective dimensionality D with a value of = 2.45. Additional results are also presented for two-dimensional Witten—Sander clusters which indicate a single effective dimensionality with a value of = 5/3. 相似文献
Dehydrotripeptides, X-CH(Ri)-ΔPhe-CH(Rk)COOMe (: X = tBOC-NH,CBZ-NH, CF3CONH and N3), were employed for the asymmetric hydrogenation catalyzed by chiral rhodium complexes and it was found that tBOC- brought about by far the best results. Stereoselective dideuteration of a tBOC- was successfully performed. 相似文献
Single crystals of a new compound, FeV2O6H0.5, have been obtained by hydrothermal synthesis at 650°C and 2 kbar. An electron microprobe analysis indicated that the chemical formula is FeV2O6. This compound has an orthorhombic symmetry, space group P212121 with Z = 4. The unit cell dimensions areThese parameters are related to a′, b′, c′ of the diaspore-type VO2 by the relations: . The structure, based on single crystal data, has been determined from Patterson and Fourier syntheses. A structural refinement gave a final R-factor of 2.4%. The new structure can be deduced from that of the diaspore-type VO2, by displacement of one third of the cations from an octahedral site to an adjacent unoccupied tetrahedral site, which is located in a channel parallel to the c axis. The calculation of the cation and oxygen valences indicated that some O2? were in fact OH?. This conjecture was supported by thermogravimetric analysis. The chemical formula was indeed Fe3+2V3+V4+V5+2O11(OH). Some intensities of the powder diffraction lines changed strongly when the preparation temperature was reduced from 650°C to 300°C. This was explained by an increase of the hydrogen ratio in the formula FeV2O6Hx, which implies a structural change. The different phases FeV2O6Hx can be considered as solid solutions between two extreme phases with different structure: one with the present one and the other with a diaspore-type structure. 相似文献
Compounds MIIMeIVF6 requently undergo phase transitions from the cubic ordered ReO3 to the trigonal LiSbF6 structure when lowering the temperature. In case of a strongly Jahn-Teller unstable cation in the MII position additional phases may occur. Results of powder neutron-diffraction studies on CaSnF6, FeZrF6, and CrZrF6 at different temperatures are reported. The high-temperature phases have the space group Fm3m; the F? ligands are either statistically displaced from the MIIMeIV directions or undergo a strong thermal motion perpendicular to these directions (: 165–180°). The thermal ellipsoids of the CrF bonds are strongly indicative of a dynamical Jahn-Teller effect in addition. In the low-temperature phases of CaSnF6 and FeZrF6 (space group ) the is more distinctly bent (?155–160°). CrZrF6 undergoes two reversible phase transitions, which are determined to occur at 415 ± 5 K (cubic → tetragonal, dynamic to static Jahn-Teller distortion of CrF6 octahedra and 150 ± 10 K (tetragonal → (pseudo)monoclinic). 相似文献
Uracil and thymine react with benzoyl chloride in acetonitrile-pyridine solution at room temperature to give first their 1--benzoyl (2b and 3b) and then their 1-, 3--dibenzoyl derivatives (4a and 4b, respectively); the latter compounds are converted into the corresponding 3--benzoyl derivatives (5a and 6a) under mild conditions of basic hydrolysis. 相似文献
Spectroscopic studies of the [1,5-15N2]-labelled title compounds demonstrate the presence of the yellow trans-anti,s-trans () and the red trans-syn,s-cis () isomers in solution. There is no experimental evidence supporting the postulated novel hydrogen bridge . 相似文献
The photochemical reactions of tetracyclic azo compounds () giving and via diazoethane derivatives () were investigated in addition to the nitrogen extrusion reactions leading to tetracyclo[4.3.0.02,9.05,7nonenes (). 相似文献
Emission spectra resulting from reaction of “clean” N2(A3 Σu+) with copper atoms were studied using a flowing afterglow apparatus. The population distribution of the Cu states was calculated from the spectrum; it indicates that Cu atoms are excited by nearly resonant energy transfer processes. N2(A,v') + Cu(2S) → N2(X, v) + Cu* , and that the transfer is most efficient for N2(A,v') → N2(X,v) transitions with large Franck-Condon factors. The preferential energy transfer results in population inversion between some of the Cu states. 相似文献
Triorganyltin compounds react with catechols in organic solvents in the presence of atmospheric oxygen to give at first paramagnetic complexes. The ESR and ENDOR spectra show 1H, 19F, 117Sn and 119Sn splittings. The hyperfine structures observed prove that the triorganyltin cations are chelated by o-benzosemiquinone. As the final product of these reactions, diamagnetic compounds can be isolated. As an example, the structure of 3,5-di-t-butyl-1,2-phenylenedioxy-bis(o-trifluoromethyl-phenyl)methanol-tin(IV) was determined by X-ray crystallography. The monomeric compound crystallizes in the space group P with a 10.451, b 11.905, c 15.379 Å, α 96.42, β 104.17, γ 111.43° and Z = 2. The penta-coordinated tin atom is 0.5 Å above the phenylenedioxy plane, which occupies one equatorial and one axial coordination site. The second axial position is occupied by the solvent methanol. 相似文献