ELECTRONIC ABSORPTION PROPERTIES OF SYMMETRICAL DIALKOXYANTHRACENES - LINEAR DICHROISM AND MAGNETIC CIRCULAR-DICHROISM

Linear dichroism (LD) and magnetic circular dichroism (MCD) of symmetrical dialkoxyanthracenes and some related compounds were recorded in an attempt to elucidate electronic absorption properties and assign the nature of the lowest singlet excited state, recognized to control both the fluorescence and the photodimerization of anthracenes. The spectroscopic measurements proved that the lowest electronic transition is of the 1L(a) type in all the compounds. The peculiar photoreactivity pattern is therefore governed by factors other than an inversion of the order of the 1L(a) and 1L(b) states and may be related to electronic density repartition on the different positions of the anthracene nucleus dictated by the position of the electron-donating substituents.