VIVO and CuII complexation by ligands based on pyridine nitrogen donors

Abstract

The binary and ternary systems formed by V(IV)O and Cu(II) ions with ligands (L) based on the pyridine ring (1,10-phenanthroline (phen), 2,2'-bipyridine (bpy), 2,2':6',2''-terpyridine (terpy), 2,2'-bipyrimidine (bpm) and 2,3-bis(2-pyridyl)pyrazine (bpp)) were studied, combining spectroscopic (EPR and UV-vis), pH-potentiometric and computational (DFT calculations) methods. In the systems with V(IV)O, the formation of mono-chelated complexes with equatorial-equatorial and equatorial-axial (phen, bpy, bpm and bpp) or equatorial-equatorial-equatorial and equatorial-axial-equatorial coordination (terpy) and bis-chelated species with cis-octahedral geometry, with a water or a hydroxido ion in the fourth equatorial position, is demonstrated. Phen, bpy, bpm and bpp form also a dinuclear [(VO)(2)L(2)(H(2)O)(2)(OH)(2)](2+) complex with an anti-coplanar arrangement of the two V(IV)O ions and a ferromagnetic coupling between the metal ions. Due to the low basicity of the nitrogen donors, the potentially tetradentate 2,2'-bipyrimidine and 2,3-bis(2-pyridyl)pyrazine behave like simple bidentate ligands, and in the ternary systems with 2,2'-bipyridine the expected dinuclear species, in which the former ligands would act as a bridge between the two metal ions using all four nitrogen donors, are not formed. The interaction of phen and Cu(II)-phen complexes with human serum albumin (HSA) was also studied at pH 7.4 by circular dichroism and EPR spectroscopy, the formation of several HSA-Cu(II)-phen containing species being confirmed and their binding constants determined.

Behavior of the potential antitumor VIVO complexes formed by flavonoid ligands. 2. Characterization of sulfonate derivatives of quercetin and morin, interaction with the bioligands of the plasma and preliminary biotransformation studies

“…On the optimized structures, the 51 V hyperfine coupling constants were calculated using the halfand-half hybrid functional BHandHLYP with the basis set 6-311g(d,p), according to the procedures previously published [76][77][78][79][80][81][82][83]. It must be taken into account that for a V IV O 2+ species A z is usually negative, but in the literature its absolute value is often reported; this formalism was also used in a number of points of this study.…”

Complex formation between [(η6-p-cym)Ru(H2O)3]2+ and oligopeptides containing three histidyl moieties

“…The thermal contribution was estimated by using the ideal gas model and the calculated harmonic vibrational frequencies to determine the correction arising from zero point energy and the thermal population of the vibrational levels. The theory was described in the literature [38][39][40][41][42].…”

Thirty years through vanadium chemistry

“…Several studies involving the binding of V IV O 2+ and V IV O-complexes to human serum albumin (HSA) were also made by using CD, EPR and gel electrophoresis [190,[230][231][232].…”