The excited states of a porphine-quinone complex under an external electrostatic field calculated by TDDFT

The potential energy curves (PECs) of the Q, B, and the lowest charge transfer (CT) states of a porphine-2,5-dimethyl-1,4-benzoquinone (PQ) complex have been studied by using the time-dependent density functional theory (TDDFT) with the CAM-B3LYP functional without and with the presence of an external electrostatic field. The PECs calculated using CAM-B3LYP with the original parameters α = 0.19, β = 0.65, and μ = 0.33 a0-1 are practically identical with those obtained using BH&HLYP. Applying of CAM-B3LYP with parameters α = 0.19, β = 0.81, and μ = 0.25 a0-1 yields PECs of the excited states that agree well with the PECs calculated previously using the CC2 method.

The CC2 approach and TDDFT combined with the CAM-B3LYP functional predict similar behaviors for the CT excited state of the porphine-2,5-dimethyl-1,4-benzoquinone complex under the influence of an external electrostatic field of 1 × 109 V/m directed either from porphine to quinone or from quinone to porphine.30Research highlights► CAM-B3LYP is suitable for studying the excited states of porphine-quinone systems. ► Parameters α, β, and μ have strong influence on the performance of CAM-B3LYP. ► For reliable determination of the CT excited states it is inevitable that α + β = 1. ► For the studied porphine-quinone complex μ = 0.25 a0-1 is a good value. ► At low fields PECs calculated with CAM-B3LYP agree well those obtained with CC2.