Examining NO releasing prospects from a fundamental chemical perspective

Abstract

In this work, relative nitric oxide (NO) releasing abilities of inorganic compounds were probed through the use of an alternative (and straight forward) approach. Complexes from a series of ruthenium nitrosyl derived species were investigated in terms of their NO releasing potential using structural and energetic properties (such as bond dissociation energies, BDEs, and bond orders). More precisely, trans-RuNH34L(NO)3+where L=POCH2CH33,C4H4N2,or NH3, trans-RuNH34L(NO)2+ where L=POCH2CH33,C4H4N2,NH3,orCl-, and trans-RuNH34L(NO)1+ (when L = Cl-) were scrutinized here. All the structures and energetics were determined using density functional theory with the B3LYP functional combined with the DGDZVP basis set for Ru and the 6-31+G(d,p) basis set for the remaining atoms, in water. The effects that different ligands (as well as different numbers of oxidation) have in such properties and, thus, in the ability of a given complex for releasing the NO, were evaluated through comparative analysis. The relative orders for the BDEs regarding the ligand substitution were found to be POCH2CH33<C4H4N2<NH3<Cl-. In this scope, Cl- provided the highest BDEs among the values determined for different ligands, being 31.12 kcal/mol in the case of RuNH34Cl(NO)1+ and 67.44 kcal/mol for RuNH34Cl(NO)2+. On the other hand, complexes containing the neutral nitric oxide in its structure (NO0 instead of NO+) experienced a marked decrease in the BDEs; the lowest BDE overall was obtained for RuNH34POCH2CH33(NO)2+ (12.07 kcal/mol), suggesting such compound to be the most likely (among all the investigated here) to liberate the NO and, thus, a quite promising NORM. Experimental investigations are encouraged in order to verify the findings of the present work.