The π–π* electronic absorption spectra of 1-amino-, 1,4-diamino-, and 1,4,5,8-tetraaminoanthraquinones were investigated by means of the polarized absorption spectra using stretched PVA sheets and theoretical calculations. Each of these compounds has four absorption bands in the near-ultraviolet region (210–340 nm) and one in the visible region. The bands of the aminoanthraquinones which appear in the visible region can be assigned to the intramolecular charge-transfer transitions associated with the charge migration from the ami no group to the carbonyl groups.

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Vibronic π-π* transition bands of pyrene, 4,5-dihydropyrene (DHP), and 4,5,9,10-tetrahydropyrene (THP) were assigned by means of dichroism analysis using stretched poly(vinyl alcohol) films. The absorption spectra of the samples in the non-stretched films were divided into two component spectra polarized along the long (x) and short (z) axes of the molecular plane. For pyrene, in addition to the four conventionally-assigned band systems (1Lb, 1La, 1Bb, and 1Ba), some forbidden bands were found in the respective band regions. Most of the vibronic DHP and THP bands were also reasonably well assigned from comparisons with the calculated results for phenanthrene and biphenyl, respectively.

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