2,6-Diazaanthracene-9,10-dione and its Radical Anion— A Structural and Spectroscopic Investigation

Abstract

An analysis of the structure, vibrational and electronic spectra, and the molecular orbitals of 2,6-diazaanthracene-9,10-dione (DAAD) (1) and its radical anion is presented. Strong π-stacking is seen in the crystal structure of (1) and observed bond lengths and angles are in good agreement with those calculated with the B3LYP/6-31G(d) method. The vibrational spectra of (1) show strong bands at 1686 cm^–1 (IR) and 1676 cm^–1 (Raman) corresponding to the antisymmetric and symmetric C=O stretch, respectively, in good agreement with calculated data. Electrochemical or chemical reduction to (1)^•- results in a new spectrum with a strong absorption due to the antisymmetric stretch at 1481 cm^–1 (predicted 1470 cm^–1). The lowest energy electronic transition for (1) occurs at 317 nm; new transitions at lower energy (403, 573, and 910 nm) are seen in the spectrum of (1)^•-. The dark purple radical anion (1)^•- was isolated as the Cp₂Co⁺ salt but its ESR spectrum did not display hyperfine coupling.