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| 2. |
- Hakansson, R., et al.
(författare)
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Magnetic circular dichroism of heterocycles: thiophene
- 1977
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614. ; 50:2, s. 305-308
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Tidskriftsartikel (refereegranskat)abstract
- The existence of two transitions with opposite MCD in the 38000–45000 cm−1 absorption of thiophene is demonstrated. The B-term for the lowest transition is negative, while it is positive for the higher one. Quantum mechanical calculations in the π-electron approximation resulted in energies, oscillator strengths and MCD terms in good agreement with the observed spectra.
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| 3. |
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| 4. |
- Nordén, Bengt, 1945, et al.
(författare)
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Permanent magnet interface for magnetic circular dichroism spectroscopy
- 1977
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Ingår i: Chemica Scripta. - 0004-2056. ; 11:2, s. 52-56
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Tidskriftsartikel (refereegranskat)abstract
- A rotatable magnet system for magnetic circular dichroism (MCD) studies has been designed. It employs permanent magnets and produces effective fields of 0.5-1.3 T depending on the design of magnets and poles. By revolving the magnet, reversing the direction of the field H, the difference spectrum (ϵ1-ϵr)+H-(ϵ1-ϵr)-H≈(ϵ1-ϵr)+2H can be obtained via a data processor. By accumulating such spectra, the signal to noise ratio is further improved. The difference procedure compensates for baseline drift and for the ordinary natural circular dichroism of an optically active sample. The MCD interface has an effective performance comparable to that of a superconducting magnet and is inexpensive to build and to run. It is easy to handle (weight 5-25 kg) and the leak field perturbations on photomultiplier and light source are negligible.
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| 5. |
- Nordén, Bengt, 1945, et al.
(författare)
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The magnetic circular dichroism of five-membered ring heterocycles
- 1978
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Ingår i: Chemical Physics. - : Elsevier BV. - 0301-0104. ; 33:3, s. 355-366
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Tidskriftsartikel (refereegranskat)abstract
- The MCD spectra of pyrrole, furan, thiophene, selenophene and teburophene and some of their derivatives are reported and the corresponding energies, oscillator strengths, transition moment directions, and MCD terms are calculated from semi-empirical quantum mechanical calculations hi the π-electron approximation. The MCD spectrum of thiophene is only slightly perturbed by substituents, and this is also expected to be true of the quite similar MCD spectra of selenophene and tellurophene. These molecules can then be classified as “hard” chromophores. On the other hand, pyrrole and furan have different and much weaker MCD spectra which change shape considerably when substituents are introduced. The implications of these observations are further discussed.
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