Photo-induced intramolecular electron transfer (IET) of a series of heterodinuclear Ru(II)-Co(III) complexes has been theoretically investigated by density functional theory (DFF) and time-dependent DFF (TD-DFT). The Ru(II)-Co(III) complexes display Ru -> Co metal-to-metal electron transfer (MMET) in the visible region. The photosensitivity involving spectral response range and absorption intensity, and IET rate, are improved by introducing (2)-N-(1H-isoindol-1-ylidene)-2H-isoindol-1-amine as donor ligands. The Ru -> Co LET rate in the newly designed complexes shows at least one order of magnitude larger than that in [(bpy)(2)-Ru(pytp)Co(tren)](5+). These superior performances indicate that heterodinuclear Ru(II) Co(III) complexes could be promising as the effective ligand release carriers for the selective cancer treatment. (C) 2015 Elsevier B.V. All rights reserved.