Tin ethyl etiopurpurin
Tin Ethyl Etiopurpurin is a synthetic purpurin with photosensitizing activity.  Tin ethyl etiopurpurin preferentially accumulates in tumor cells due to an increased rate of metabolism. Upon exposure to a light source, this agent absorbs light, forming an extended high energy conformational state that produces high quantum yields of singlet oxygen with local cytotoxic effects. (NCI04)