Chemistry and biological activities of CO-releasing molecules (CORMs) and transition metal complexes

The advent of CO as a small molecule that, in addition to NO, elicits essential biological functions has initiated the search for compounds and complexes capable of releasing CO in a well defined manner under physiological conditions. Since some pharmacological and therapeutic effects of CO have been established in preclinical studies, tailor-made CO-releasing molecules (CORMs) which could be utilized as pharmaceuticals could be of great benefit for many patients. Release of CO(2) is one of the most common features in chemistry and NO producing molecules are very well established but compounds with CO-releasing properties are rare. Some of the more promising candidates and molecules under study are discussed in this article. Furthermore, molecules that possess intrinsic features to serve as potential CO-RMs and merit in depth investigations are proposed. The focus is thereby on main group compounds and on transition element complexes. It should be emphasized that CORMs not only have encouraging prospects as therapeutic agents but may also be significant for synthetic pathways to novel complexes containing the CO ligand. To underline the prospects of CORMs, the chemical part is embedded in a biological and medicinal context.