Abstract
The amine-functionalized trans-[Ru(NO)Cl(1-pramcyH)](PF6)3 complex (1-pramcyH = 1-(3-propylammonium)-1,4,8,11-tetraazacyclotetradecane) was synthesized from trans-[RuCl(tfms) (1-pramcyH)](tfms)2 (tfms = trifluoromethanesulfonate) in acidic aqueous solution in the presence of nitric oxide (NO). The complex was characterized by elemental, spectroscopic (UV-Vis, IR, ¹H and 13C NMR) and electrochemical analyses. Two pKa values (7.0 and 8.2) were estimated for trans-[Ru(NO)Cl(1-pramcyH)](PF6)3 and were assigned to one of the cyclam nitrogen protons and to the protonated aminopropyl group. Reduction of trans-[Ru(NO)Cl(1-pramcyH)]3+ results in rapid loss of chloride followed by slower loss of NO, while irradiation of the complex in aqueous deaerated conditions suggests photochemical labilization of NO. The quantum yields for NO photoaquation decrease as the irradiation wavelength increases, being noticeable only at λirr < 370 nm, and increase as pH increases. The behavior of trans-[Ru(NO)Cl(1-pramcyH)]3+, which contains an aminopropyl substituted cyclam, parallels that reported for the analogous complex with the unsubstituted ligand, but differs from that described for the complex in which carboxypropyl is the substituent.
Highlights
The discovery of the participation of nitric oxide (NO) in a wide range of physiological processes and pathologies[1] has launched investigations on NO donors, including metalAmong the NO donors, ruthenium nitrosyl complexes are attractive because they are stable, can be either water soluble or not, deliver NO at different rates upon activation by reduction at biologically accessibleChemical and Photochemical Properties of a Ruthenium Nitrosyl ComplexJ
Efforts from this laboratory have been directed toward this goal, using several strategies. One of such approaches involves the functionalization of ruthenium nitrosyl complexes, so they can be linked to important entities such as antibodies and to surfaces, in order to obtain selective NO donor drugs or devices
In order to verify the effect of the ammoniumpropyl substituent on the configuration of the nitrosyl complex, so as to obtain a wider variety of NO donors, in this paper we report the synthesis, characterization, electrochemical and photochemical properties of the trans-[Ru(NO)Cl(1pramcyH)](PF6)[3] complex
Summary
The discovery of the participation of nitric oxide (NO) in a wide range of physiological processes and pathologies[1] has launched investigations on NO donors, including metalAmong the NO donors, ruthenium nitrosyl complexes are attractive because they are stable, can be either water soluble or not, deliver NO at different rates upon activation by reduction at biologically accessibleChemical and Photochemical Properties of a Ruthenium Nitrosyl ComplexJ. Successive UV-Vis or IR spectra for trans-[Ru(NO)Cl(cyclam)](PF6)[2] and trans-[Ru(NO) Cl(1-pramcyH)](PF6)[3] were recorded during the reduction process of the complexes at 25 oC, with applied potentials of –500 mV vs Ag/AgCl in acetonitrile solutions.
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