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 alpha = 0.19, beta = 0.65, and mu = 0.33 a(0)-1 are practically identical with those obtained using BH&HLYP. Applying of CAM-B3LYP with parameters alpha = 0.19, beta = 0.81, and mu = 0.25 a(0)(-1) yields PECs of the excited states that agree well with the PECs calculated previously using the CC2 method. (C) 2010 Elsevier B.V. All rights reserved.