Sv. Kudrevich et Je. Vanlier, SUBSTITUTED TETRA-2,3-PYRAZINOPORPHYRAZINES .2. BIS(TRI-N-HEXYLSILOXY)SILICON DERIVATIVES, Canadian journal of chemistry, 74(9), 1996, pp. 1718-1723
Dichlorosilicon complexes of substituted tetra-2,3-pyrazinoporphyrazin
es were obtained via condensation of 2,3-dicyanopyrazine, 2,3-dicyano-
5,6-diphenylpyrazine, 2,3-dicyanoquinoxaline, 2,3-dicyano-benzo[f]quin
oxaline, and 2,3-dicyano-dibenzo[f,h]quinoxaline with silicon tetrachl
oride in the presence of urea, quinoline, and tri-n-butylamine. Hydrol
ysis of the Si-Cl bond in concentrated H2SO4, followed by treatment wi
th 0.01 N NaOH and aqueous NH3, afforded the corresponding dihydroxide
s, which were converted to the bis(tri-n-hexylsiloxy)silicon derivativ
es via reaction with tri(n-hexyl)silane in 3-picoline (2,4,6-collidine
) in the presence of tri-n-butylamine. The axial tri-n-hexylsiloxy sub
stituents at the central silicon atom prevent aggregation in organic s
olvents, permitting detailed studies on the effects of structural modi
fications on the electronic spectra of tetraazaphthalocyanines. Our da
ta show that each benzo ring addition, angularly condensed to the tetr
a-2,3-quinoxalinoporphyrazine, induces a hypsochromic shift (similar t
o 10-15 nm) of the main absorption maximum.