The implications of temperature effects on photochemical processes when it comes to near-infrared DNA photosensitizing agents are discussed in addition to the unique spectroscopic features of a sulfur meso-substituted heptamethine cyanine dye relative to oxygen and nitrogen analogues. Specifically, reactive oxygen scavenger experiments, preliminary kinetic data, and absorption spectra are considered in this continued investigation. Additionally, binding and stability studies indicate that the general structure of the cyanine dye can be further optimized to potentially improve DNA photocleavage yields at physiological temperatures while employing the exceptional properties of sulfur-incorporated polymethine dyes.