The magnetic circular dichroism of five-membered ring heterocycles
Journal article, 1978
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.