Dichroic Spectra of 9‐Methylanthracene and 1‐Hydroxyphenazine in Stretched PVA Sheets

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Abstract
Dichroic spectra of 9‐methylanthracene and 1‐hydroxyphenazine were measured in stretched PVA (polyvinylalcohol) sheets. For 9‐methylanthracene, the divided spectra were obtained by using the results of the dichroic spectra. The Pariser‐Parr‐Pople calculations with a variable β approximation were carried out for the above compounds. It was found that 9‐methylanthracene has five absorption bands at 392 mμ (C2‐axis polarization, y‐axis), 370 mμ (x), 280 mμ (y), 260 mμ (x), and about 220 mμ (y). A band corresponding to the 280 mμ band is not observed in the case of anthracene. This band may correspond to the forbidden transition (Ag → Ag) of anthracene. This is also suggested by the MO calculation, that is, the forbidden transition of anthracene becomes allowed one by the introduction of the methyl group at the 9‐carbon atom, in which the effects of the methyl group are treated as inductive. Also in the case of 1‐hydroxyphenazine, an extra band corresponding to the forbidden transition of phenazine was found at 300 mμ.