The transition of the near-infrared (NIR) region from singlet to triplet excited states (S-T transition) is effective to ensure wideband photosensitization. Here, we synthesize iminopyridine Ru(II) complexes, exhibiting S-T transitions in the NIR region. The dye-sensitized solar cell using the imino-pyridine Ru(II) complex exhibits photoelectric conversion by employing the aforementioned S-T transition.