Tricycloquinazoline (TCQ), a molecule of both biological and physical
interest, has been found to function as the core fragment for a new fa
mily of discotic mesogens, which have C3 symmetry and six aliphatic si
de chains. Six representative homologous 2,3,7,8,12,13-hexaalkoxy-TCQ
derivatives 5 were synthesized, with alkyl side chain lengths varying
from 3 to 16 carbon atoms. These highly fluorescent, heteroaromatic co
mpounds are conveniently obtained by alkylation of hexahydroxy-TCQ, 10
. The latter is prepared by trimerization of 5,6-dimethoxyanthranil, 8
, followed by demethylation of the resultant hexamethoxy-TCQ, 9. All c
ompounds, 5, are mesogenic within a very broad temperature range. The
nature of these new mesophases was studied by DSC and by optical micro
scopy with polarized light and X-ray diffraction. DSC measurements sho
w highly reversible behavior at both melting and clearing points, indi
cating high chemical stability. Photomicroscopic pictures show mosaic
textures, characteristic of an ordered hexagonal, columnar phase (D(ho
)), that are very similar to those we reported earlier for hexakis(thi
oalkoxy)-TCQ derivatives 4. The diffraction spacings of two representa
tive compounds (having 5 and 11 carbon atoms in the side chain) in the
mesophase are consistent with a two-dimensional hexagonal lattice hav
ing unit cell sides of a = 21.2 and 28.7 angstrom, respectively, and c
ontaining one molecule per unit cell.