RESUMO
The anchoring of K[Ru(III)(edta)(Cl)] on poly(amidoamine) dendrimers (PAMAM of three generations G(x)/Ru (x=0, 2 and 3)) through a peptide type bond yielded the aquo species, [Ru(III)(edta)(H2O)] on dendrimer surface, and upon NO exposure, yielded their nitrosyl analogues, G(x)/RuNO. Characterization of these compounds by elemental analysis, and a UV-vis, IR and 13C NMR spectroscopies indicated the immobilization of 4, 12 and 29 molecules of [Ru(III)(edta)(H2O)] or of the nitrosyl complex [Ru(II)(edta)NO] on the dendrimer surface for G(X)=0, 2 and 3, respectively. For each complex the electrochemical spectrum presented only one redox process with redox potential values of -0.20 and -0.32 V(vs SCE) attributed to the Ru(III)/Ru(II) and NO+/NO(0) couples in G(x)/Ru and G(x)/RuNO, respectively. The one-electron reduction of G(x)/RuNO+ generates G(x)/RuNO(0), which undergoes aquation with a k(-NO) of 2.1+/-0.7 x 10(-3)s(-1) (pH 1.0, mu=0.2 mol/L, CF3COOH/NaCF3COO, 25 degrees C). The G(x)/RuNO species induced a relaxing effect in aortic rings denuded of endothelium and exhibited in vitro assay trypanocidal activity.
Assuntos
Óxido Nítrico/farmacologia , Poliaminas/química , Compostos de Rutênio/farmacologia , Tripanossomicidas/farmacologia , Trypanosoma cruzi/efeitos dos fármacos , Vasodilatação , Animais , Aorta/efeitos dos fármacos , Aorta/fisiologia , Cromatografia em Gel , Dendrímeros , Ácido Edético , Espectroscopia de Ressonância Magnética , Masculino , Óxido Nítrico/química , Óxido Nítrico/farmacocinética , Oxirredução , Pirazinas/análise , Ratos , Ratos Wistar , Compostos de Rutênio/química , Compostos de Rutênio/farmacocinética , Espectrofotometria Infravermelho , Tripanossomicidas/química , Tripanossomicidas/farmacocinética , ÁguaRESUMO
The EPR of NO. can be detected in the liquid and solid states when crystal fields are sufficient to remove the axial symmetry and separate the (pi*)x and (pi*)y orbitals by a few hundred reciprocal centimeters. The theory of the EPR spin Hamiltonian of bound NO. is reviewed, further developed, and then applied to the observed frozen-liquid spectra of NO. bound to Ru(II) obtained from RuIINO+ complexes by reduction. Comparisons to earlier reports on the observation of the EPR spectra of NO. are made.
RESUMO
The reduction of CpTi(NPt-Bu3)Cl2 with Mg powder in benzene proceeds slowly to give [CpTi(NPt-Bu3(mu-Cl)]2 (1). An X-ray crystallographic study confirmed 1 is a centrosymmetric chloro-bridged dimer in the solid state. A single-crystal EPR study of 1 permitted the determination of the best-fitted values for the diagonal spin Hamiltonian parameters. This appears to be the first EPR single-crystal study of a Ti(III)-Ti(III) dimer. The implications of these data are considered and discussed in light of extended Hückel molecular orbital calculations.