Evaluation of the electron affinity of substituted 9,10-anthraquinones using molecular anion lifetime data

The dissociative electron attachment (DEA) of anthraquinone (AQ) derivatives, namely, 9,10-AQ (I), 1,4-AQ (II), 1-(methylamino)-9,10-AQ (III), 1-(3-methoxyphenoxy)-9,10-AQ (IV), and 1,8-bis(benzamido)-9,10-anthraquinone (V) has been studied in the gas phase. The most intense negative ion in all DEA spectra is the molecular anion M-, which is observed in three and even four resonance states. In addition, some low-intensity decay channels are observed at higher electron energies: [M-H]-, [M-CH3]-, and [M-OCH3]-, depending on the type of substituent. To complete the picture, the molecules of naphthalene (VI), parabenzoquinone (VII), fluoranyl (VIII), and chloranyl (IX), for which the adiabatic electron affinity (EAa) values are known and the molecular anion lifetimes τa have been measured, have also been considered. The correlation between the EAa values (EALT) estimated in the simple Arrhenius approximation from molecular anion lifetime data and those (EADFT) calculated in the DFT approximation CAM-B3LYP/6-311+G(d,p) has been analyzed.