Immobilized phthalocyanines as red-light photosensitizers

Phthalocyanines are well known red-light photosensitizers particularly relevant in applications such as cancer therapy and water and blood sterilization. Their homogeneous photochemistry is dominated by their ability to produce singlet molecular oxygen. Triplet quantum yields and lifetimes are the key parameters if type II processes are considered to be responsible for photodynamic action. However, heterogeneity plays a major role in the cellular environment and the proximity of dyes and molecular targets may activate charge transfer processes. Factors controlling the photophysical activity of phthalocyanines forced to interact strongly with themselves and with other molecules are considered.