Absorption Spectrum of Solid Anthracene—TNB Complex under Pressure

Abstract

The intermolecular charge transfer (CT) and intramolecular absorption spectrum of the crystalline anthracene—TNB complex as well as (for comparison) the crystalline anthracene L_a band have been studied in KBr pellets as a function of pressure to 27 kbar. It is observed that the magnitude of the red shift in the band maxima is ∼1450 cm⁻¹ at 27 kbar for both the CT band and the L_a band, but is only ∼300 cm⁻¹ for the intramolecular donor (anthracene) absorption at 16 kbar. Broadening of the CT band appears absent, but the molar extinction coefficient at the band maximum increases by ∼50% at 16‐kbar applied pressure. The L_a band of anthracene broadens but shows only small changes in band height. Plausible explanations of the observed results are discussed.