An assessment of density functional theory methods was used to examine the utility of relatively (computationally) cheap methods in the prediction of the electrochemical properties of substituted pentacenes. Time-dependent B3LYP calculations in solvent, with a triple-zeta basis set, performed on either gas-phase PM3 or B3LYP/6-31G(d) optimized geometries (TD-B3LYP/6-311+G (d,p)//PM3 or TD-B3LYP/6-311+G(d,p)//B3LYP /6-31G(d)) were shown to be reliable methods to accurately predict HOMO energies and HOMO-LUMO gaps. Using these methods, values were calculated which agree with experimentally determined data generally to within 0.04 eV (0.9 kcal/mol) for HOMO energies and to within 0.07 eV (1.6 kcal/mol) for HOMO-LUMO gaps. This study shows that relatively cheap DFT methods are useful in the prediction of the electrochemical properties of substituted acenes. It is therefore now possible to use these methods to provide a basis of study for larger substituted acenes and more complex acene-based systems.
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