Dark Photochemistry, as defined in the context of the present conference, implies the production of a "photoprocess" by using a chemiluminophore (for instance, dioxetane or dioxetanone) rather than light to induce the excited-state chemistry [1]. In this process, the bond breaking of the peroxide bond brings the molecular system to the excited state similarly to what happens in chemiluminescence and bioluminescence [2]. However, while chemi-/bio-luminescence ends up with light emission, dark photochemistry gives rise to a photochemical product. The photochemical process without light can takes place intra- or inter-molecularly, i.e., in the same molecule as the chemiluminophore or in a different molecule. In this contribution we will show examples of such processes and discuss about some quantum-chemistry findings obtained for the mechanism of production of cyclobutane pyrimidine dimers in DNA [3] and in relation to the possible role that might have dark photochemistry in the enhancement of vision of some deep-sea fish and some patients of photodynamic therapy [4].

[1] W. J. Baader, C. V. Stevani, E. J. H. Bechara, J. Braz. Chem. Soc. 26, 2430 (2015).

[2] P. Farahani, M. Lundberg, R. Lindh, D. Roca-Sanjuán, Phys. Chem. Chem. Phys. 17, 18653 (2015).

[3] S. Premi, S. Wallisch, C. M. Mano, A. B. Weiner, A. Bacchiocchi, K. Wakamatsu, E. J. H. Bechara, R. Halaban, T. Douki, D. E. Brash, Science 347, 842 (2015).

[4] T. Isayama, D. Alexeev, C. L. Makino, I. Washington, K. Nakanishi, N. J. Turro, Nature, 443, 649 (2006).