Magnetic circular dichroism and anomalous fluorescence spectra of azulenothiophenes

Abstract

The magnetic circular dichroism and electronic absorption spectra of azuleno[1,2-b]thiophene and azuleno[2,1-b]thiophene, which are iso-π-electron systems of benz[a]azulene, have been measured. The absorption bands of both azulenothiophenes are interpreted by using these observed spectra and the results of molecular-orbital calculations. The anomalous fluorescence spectra have been observed for both azulenothiophenes and benz[a]azulene. From the assignment of the absorption spectra, it has been concluded that these compounds emit the fluorescence from the second excited singlet state.