title: V(IV)O and Cu(II) 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.
authors.affiliation: Istituto CNR di Chimica Biomolecolare, Trav. La Crucca 3, I-07040 Sassari, Italy.
authors.forename: Daniele
authors.initials: D
authors.lastname: Sanna
authors.forename: Péter
authors.initials: P
authors.lastname: Buglyó
authors.forename: Ana Isabel
authors.initials: AI
authors.lastname: Tomaz
authors.forename: João
authors.initials: J
authors.lastname: Costa Pessoa
authors.forename: Slađana
authors.initials: S
authors.lastname: Borović
authors.forename: Giovanni
authors.initials: G
authors.lastname: Micera
authors.forename: Eugenio
authors.initials: E
authors.lastname: Garribba
mesh_terms: D003300:Copper / Q000737:chemistry*; D006573:Heterocyclic Compounds, 1-Ring / Q000737:chemistry; D008024:Ligands; D009584:Nitrogen / Q000737:chemistry; D009942:Organometallic Compounds / Q000737:chemistry*; D010618:Phenanthrolines / Q000737:chemistry; D011725:Pyridines / Q000737:chemistry; D012709:Serum Albumin / Q000737:chemistry; D012996:Solutions; D014638:Vanadates / Q000737:chemistry*
chemical_list: D006573:Heterocyclic Compounds, 1-Ring; D008024:Ligands; D009942:Organometallic Compounds; D010618:Phenanthrolines; D011725:Pyridines; D012709:Serum Albumin; D012996:Solutions; C075743:oxovanadium IV; D014638:Vanadates; D003300:Copper; D009584:Nitrogen; C025205:1,10-phenanthroline