Visible-light-activated photoCORMs: rational design of CO-releasing organic molecules absorbing in the tissue-transparent window.

To date, most known molecules that release carbon monoxide by the action of light are based on carbonyl complexes of metals. However, they suffer from several disadvantages, so the focus of this perspective is on photoactivatable metal-free CO precursors. The development and design of these systems from the starting point of deep-UV-absorbing hydrophobic molecules and leading to hydrophilic biocompatible visible-light-absorbing CO-releasing molecules (photoCORMs) is described with mechanistic details for several structural motifs. The possibilities of this development are not exhausted and here we discuss the design of new biologically interesting candidates.