By cyclotrimerization of tert-butyl substituted pyrazine-2,3-dicarbonitrile in the presence of boron trichloride, two positional isomers ([Formula: see text] and [Formula: see text] symmetry) of the corresponding boron(III) tripyrazinosubporphyrazines were first obtained and efficiently separated by column chromatography. The new compounds were characterized by MALDI mass-spectrometry, UV-visible and 1H NMR spectroscopy. A Q-band in the electronic absorption spectra for both fractions was observed at [Formula: see text]530 nm, which is typical for tripyrazinosubporphyrazines. The fluorescence quantum yield for the regioisomer with lower symmetry ([Formula: see text] is 1.5 times higher than for the more symmerical [Formula: see text] species ([Formula: see text] = 0.37 and 0.28, respectively). Comparative spectrophotometric study of the basic properies reveals that hexaaza substitution in benzene rings of tert-butyl substituted subphthalocyanine decreases the basic properties of meso-nitrogen atoms.
Isoindole-diimine, which can be obtained by bubbling ammonia gas into a solution of phthalonitrile derivatives in the presence of Na[Formula: see text] ion, is a final and best precursor for phthalocyanine synthesis. In this study, isoindole-diimine and various derivatives have been prepared without bubbling ammonia gas using in situ generated ammonia that was produced from formamide and a strong alkali such as NaOH and NaNH2. A longer reaction time, higher temperature, and larger amount of formamide were required for phthalonitrile derivatives with electron-donating groups, but this method is recommendable in that an NH3 gas cylinder and concomitant gas regulator, which are not inexpensive, are not required. Attempts were made to interpret the IR and absorption spectra of the resultant diimines. The signals due to imino proton or N-H of diimino compounds were experimentally found to appear at around 8.2[Formula: see text]9.5 ppm in 1H-NMR and ca. 3500–3000 cm[Formula: see text] in IR spectra.