The 2,6- and 4,8-bisarylamino-1,5-naphthoquinone derivatives 3b-d and
6a-e were synthesized by the amination of naphthazarin (1) and naphtha
zarin intermediate (4), respectively. Their chromophoric systems were
evaluated by the PPP MO method, and their absorption spectra in soluti
on and the solid state were investigated to evaluate the intermolecula
r pi-pi interactions of the dye molecules in the solid state. In the c
ase of dyes 3a-d, large Delta lambda values of over 100 nm were obtain
ed, but in 3b-d another absorption maximum at shorter wavelength was a
lso observed. On the other hand, dyes 6c-e showed large Delta lambda v
alues of over 90 nm, but dyes 6a and 6b showed relatively small Delta
lambda values of less than 45 nm. The chain length of the alkyl and al
koxy substituents influenced the molecular stacking of the dye in the
solid state. Copyright (C) 1996 Elsevier Science Ltd