Among the great challenges facing the Society is the search for solutions to cancer. This disease presents high cellular oxidative stress, as a result of the imbalance between the oxidizing species generated in the cells and antioxidant compounds. One of the strategies used in the treatment of cancer is based on the use of Photodynamic therapy (PDT). PDT is a safe and non-invasive technique for the treatment of different types of cancer in diverse locations, as well as non-cancer diseases.

PDT consists of the local or systemic application of a photosensitive compound (the photosensitizer), which accumulates mainly in the pathological tissues. Photosensitive molecules absorb light of the appropriate wavelength, initiating the activation processes that lead to the selective destruction of tumor cells. An adequate photosensitizer must obey a number of features such as maximum absorption length between 600 and 800 nm, minimum absorption length between 400 and 600 nm, high purity and stability at room temperature, and high selectivity with tumor tissues, among others. In this context, selenopyrylium salts emerge as potential candidates to photosensitizers due to fit with most of these features.

Therefore, the aims in the present work are the synthesis and characterization of monocationic selenopyrillium salts, using a methodology that does not involve organometallic reagents, and the evaluation of their photophysical properties for their possible application as photosensitizers in PDT.