Electronic spectra of benzo[b]biphenylene and benzo[3,4]cyclobuta[1,2–b]quinoxaline

Abstract

The absorption, linear dichroism (l.d.) and magnetic circular dichroism (m.c.d.) spectra of benzo[b]biphenylene (1) and benzo[3, 4]cyclobuta[1, 2-b]quinoxaline (2) have been measured. The induced circular dichroism (i.c.d.) spectra of the β-cyclodextrin complexes with 1 and 2 have also been measured. The absorption bands of 1 and 2 have been assigned by using the observed spectra and the results of CNDO/S CI calculations. The assignment of the absorption bands of 1 has been confirmed by a relationship between the electronic transition energies for α-, p- and β-bands and the ionization potentials obtained from the photoelectron (p.e.) spectra of 1.