The shift of the principal absorption maximum in the visible region by a phenylazo group on the 1-position of azulene has been shown to be ca. f29 mp. Precise solution dipole moments have been obtained for azulene, 1-nitroazulene and 1, 3-dihaloazulenes. On the basis of these ground state data and the dipole moment calculations of Pariser for the appropriate excited state of azulene, an explanation is advanced for the effect of different types of ...
