Electron affinity calculation for selected PAHs using DFT: Effect of cyclopenta ring fusion and aromaticity

Abstract

Quantities like adiabatic electron affinity (AEA), electron density distribution and geometry based aromaticity index are calculated for a set of polycyclic aromatic hydrocarbon (PAH) molecules. The calculated AEA values are compared with experimental values. Presence of a cyclopenta ring is observed to enhance the ability of the molecule to accommodate the extra electron in the anionic form and hence increasing the electron affinity (EA). Electrostatic potential maps and electron spin density distribution are used to analyze electron density distribution over the molecular volume in case of anions. A detailed comparison is made with the help of aromaticity index to quantify the correlation of AEA with the π-electron delocalization. A clear correlation between AEA and the aromaticity index is demonstrated. The effect of sp3 hybridized carbon atom on AEA values in PAHs is studied for the first time.