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 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.
RESUMO
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.