ABSTRACT
As nitric oxide (NO) is an endogenous reactive molecule that plays important physiological roles in living organisms [1], its delivery to specižc targets receives a great deal of attention through the study of numerous biological processes and therapeutic applications. Only a limited number of exogenous NO donors are available for clinical use, so the development of molecules that can release NO is of considerable interest [2]. The simplest case uses direct inhalation of NO [3], but its clinical use as a gas is technically difžcult to administer [4]. Most exogenous NO donors are organic molecules such as nitrates that do not directly release NO owing to the biotransformations that are initially required [5-7]. More recently, the use of metal nitrosyl complexes appeared very attractive because the only direct NO-releasing drug clinically available in the U.S. is sodium nitroprusside (iron complex) for which žve toxic cyanide ions are released for every NO molecule [8,9]. Different NO-donor complexes based on ruthenium [10], iron [11-14], manganese [15], and cobalt [11,16,17] are described in the literature. Among the most promising cobalt complexes, nitrosyl-cobinamide, a structural analog of vitamin B12 (unsaturated cyclic tetraamine), is an efžcient direct NO-releasing agent [16]. To the best of our knowledge, the use of cobalt(II) derivatives based on saturated cyclic polyamines such as cyclam 1 has not been reported, whereas their §exibility might allow distinct conžgurations of the nitrosyl complexes with specižc properties [18].
