摘要:

The N.M.R. spectrum of pyridine oriented in the nematic phase of anisole-azophenyl-n-capronate has been studied. The analysis has been carried out iteratively using a modified version of the computer programme LAOCOONII (re-named as LAOCOONOR). The details of the modification are discussed.

ISSN:0026-8976    

DOI:10.1080/00268976800101181

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

‘Molecular mechanics’ has been used to calculate the geometry of biphenyl in the gas and crystalline phases. The geometry of the isolated molecule is mainly determined by a balance ofπ-electron and non-bonded energies, while in the crystal the most important forces are the intermolecular C … H attractions. Reasonable agreement is obtained with electron diffraction, x-ray and thermal data.

ISSN:0026-8976    

DOI:10.1080/00268976800101191

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

The parameter values to be used in a theoretical investigation of the ionization potentials, electronic spectra and electron spin resonance spectra of conjugated carbonyl compounds have been established. These values have been used to calculate the lone-pair and π-ionization potentials of the carbonyl compounds by a Pariser-Parr-Pople type method. Where possible the calculated values have been compared with experimentally determined vertical ionization potentials, and the results demonstrate that a good agreement between observed and calculated values may be obtained for a wide range of these compounds.

ISSN:0026-8976    

DOI:10.1080/00268976800101201

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

The energies and intensities of then→π* andπ→π* transitions of eight conjugated carbonyl compounds, ranging from formaldehyde to 9:10-anthraquinone, have been calculated by the Pariser-Parr-Pople method using a set of parameter values which has been used to calculate thenand π-electron ionization potentials of the same molecules. The results for the π→π* transitions generally agree well with experiment although the agreement for the larger molecules is better than that for the smaller. Reasons for this are suggested. Calculated singlet-triplet splittings for then→π* transitions agree well with experiment but the calculated absolute energies of then→1π* transitions are uniformly 1–2 ev too small. This difference can be removed by giving the lone-pair orbital a new energy basis, and the origin of the discrepancy appears to lie in the approximations of Koopmans's theorem.

ISSN:0026-8976    

DOI:10.1080/00268976800101211

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

The unrestricted Hartree-Fock method has been applied to the calculation of theπ-electron spin densities in a number of conjugated carbonyl radicals and anion radicals, the parameters being those previously used in the interpretation of the ionization potentials and electronic spectra of the corresponding closed shell molecules. The results have been compared with measured E.S.R. proton hyperfine coupling constants and, in general, there is a disappointing agreement between theory and experiment. Some reasons for this are suggested.

ISSN:0026-8976    

DOI:10.1080/00268976800101221

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

Relaxation effects are studied in the steady-state proton-proton double resonance spectra of a symmetrical three spin system of the type AB2, formed by the ring protons of 2,6-dibromoaniline. The experiments were performed on a Varian HR-100 high resolution N.M.R. spectrometer suitably modified for field-frequency locking and added by the usual equipment for the purpose of frequency-sweep double resonance. The sample used is a 20 per cent solution in CCl4, purified and sealed in vacuum. The parameters describing the single resonance spectrum of the molecule were obtained to be

ISSN:0026-8976    

DOI:10.1080/00268976800101231

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

Oscillator strengths for dipole transitions between 1s23s2S, 1s23p2P and 1s23d2D states of the lithium isoelectronic sequence in the L-S coupling scheme have been calculated in the Hartree-Fock approximation by perturbation theory through the use of Dalgarno's interchange theorem. The results compare very favourably with the analytical Hartree-Fock results.

ISSN:0026-8976    

DOI:10.1080/00268976800101241

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

A quantum theory is developed for the interpretation of the Cotton-Mouton effect of paramagnetic complexes in solution. The results of this theory differ from those predicted by a classical analysis. The influence of ligand symmetry on the anisotropy in the orbital angular momentum is considered and anomalous dispersion is predicted in the vicinity of electronic absorption bands. Information concerning magnetic and optical anisotropies, the polarization of transition moments, and complex stereochemistries should emerge from experimental investigations.

ISSN:0026-8976    

DOI:10.1080/00268976800101251

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

The general expression giving the N.M.R. band-shape of a spin-1/2 nucleus coupled to a spin-1 nucleus is considered in detail for the ‘fast-exchange’ limit, where the quadrupolar-induced relaxation rates of the spin-1 spin states are much greater than the coupling constant between the nuclei. The problem of obtaining the coupling constant from measurements on the band-shape of the spin-1/2 resonance is discussed, and it is concluded that this is only possible without further information when departures from lorentzian shape are observed. Possible sources of extra data are mentioned. The case of 3,4,5-trichloro-2,6-difluoropyridine is examined. The (N, F) coupling constant is obtained from the15N satellites in19F resonance. Hence values of the spin-lattice relaxation time for14N are derived as a function of temperature.

ISSN:0026-8976    

DOI:10.1080/00268976800101261

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

ISSN:0026-8976    

DOI:10.1080/00268976800101271

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor