The pH influence has important role in the bioavailability of coordination compounds. fac-{[}Ru(NO)Cl-2(kappa N-3(4),N-8,N-11{[}1-carboxypropyl]cyclam)](+), 1, and the species found at different pHs, 2-4, were investigated. One series of computational methodologies has been used to investigate these compounds. One special highlight is to interacting quantum atoms method, where the total interaction energy, EintAB, between two atoms has been used as base to estimate the chemical bonds strength. The deprotonation of -CO2H, 12 (pK(a) = 3.3), creates a hydrogen bond in the complex 2, N(3)-HMIDLINE HORIZONTAL ELLIPSIS center dot OCO-, with a more favorable EintAB than the presents in 1, N(3)-HMIDLINE HORIZONTAL ELLIPSIS center dot OCOH. There are no changes in EintAB in Ru-NO bond. The second deprotonation occurs in the N(2) atom of the cyclam group, 23 (pK(a) = 8.0). It promotes an increase in the covalent character of Ru-N(2). In contrast, there is no changes in Ru-N(5)O bond. For higher pHs, there is a 34 equilibrium (pK(a) = 11.5) and the conversion of Ru-N(5)O for Ru-N(5)O-2. The Ru-N(5) of 4 shows a larger ionic character than 3. Thus, Ru-NO in 1-4 has worthy stability about a large pH range, showing potential application as NO scavengers. (AU) |