Spectroscopy of EDA Complexes at High Pressures. III. Absorption and Fluorescence of Several TCPA Complexes in PMMA

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Abstract
The absorption and fluorescence spectra of several aromatic hydrocarbons complexed with tetrachlorophthalic anhydride (TCPA) dispersed in polymethylmethacrylate (PMMA) have been studied in the 0–25‐kbar range. The pressure effect on the charge transfer (CT) absorption intensity and band maxima have been compared with low‐temperature measurements. The molar extinction coefficient increases ∼100% at 77°K relative to 298°K and increases 100%—400% at 25 kbar relative to atmospheric pressure. The absorption‐band maxima are rather insensitive to temperature, but shift red by ∼1500 cm−1 at 25 kbar. The CT fluorescence shows only ∼500 cm−1 red shift at 30 kbar. The difference can be rationalized in terms of potential‐energy curves for the ground and excited states characterizing the molecular complex.