4-Hydroxypyridine-2,6-dicarboxylatodioxovanadate(V) Complexes:  Solid State and Aqueous Chemistry

Abstract

The aqueous solution and solid state properties of (4-hydroxypyridine-2,6-dicarboxylato)dioxovanadate(V) (also referred to as (4-hydroxydipicolinato)dioxovanadate(V) or (chelidamato)dioxovanadate(V) and abbreviated [VO(2)(dipic-OH)](-)) were investigated. By using (1)H, (13)C, (17)O, and (51)V NMR 1D and 2D spectroscopy, the species present in solution, together with pK(a) values, equilibrium constants, and labilities, were characterized. The complex is most stable at acidic pH down to pH 1 where it is protonated. The stability of this complex is higher than that of the parent dipicolinatodioxovanadate(V) complex. The dipic-OH ligand is coordinated in a tridentate manner throughout the pH range studied, and the vanadium(V) atom is five-coordinate. Solid state structures of (NMe(4))[VO(2)(dipic-OH)].H(2)O (monoclinic, P2(1)/n) and Na[VO(2)(dipic-OH)].2H(2)O (triclinic, P1) were determined. The discrete complex anions in (NMe(4))[VO(2)(dipic-OH)].H(2)O are connected by hydrogen bonding between the hydroxyl group, a water molecule, and a carboxylate oxygen atom. Changing the counterion from NMe(4)(+) to sodium ion in Na[VO(2)(dipic-OH)].2H(2)O leads to the formation of a polymeric structure. Dynamic processes in solution were explored by using (1)H and (13)C EXSY NMR spectroscopy; exchange between complex and free ligand below pH 4 was observed. The differences between the dipicolinatodioxovanadate(V) parent complex and the [VO(2)(dipic-OH)](-) complex in the solid state and in solution demonstrate the subtle consequences of the one substitutional difference between the two ligands. The insulin-mimetic properties of this compound are likely to be of mechanistic interest in developing an understanding of the mode of action of the few known insulin-mimetic vanadium(V) complexes.

A New Family of Insulin‐Mimetic Vanadium Complexes Derived from 5‐Carboalkoxypicolinates

“…Examples are complexes with picolineamides, [10] and picolinates with the substituents 5-I, [11] 6-Me, 6-COO À (dipic), [10,12,13] 6-Et [14,15] and 4-OH-dipic. [16,17] It is noteworthy that the oxidation state of vanadium does not seem to play a crucial role in activity. [18] The complex anion…”

Hydrothermal synthesis, crystal structure and luminescent properties of 2d grid-like polymer based on 3d–4d mixed metals

“…previous report [15]. The tetrahedral conformation of each Ag center consists of four O atoms with distances in the range 2.322-2.401 Å (two from carboxylates and two from oxo ligands).…”

“…Polyhedral representation of the 2D grid-like layer along [0 1 0] showing the connection of VO 4 N pyramids and AgO 4 tetrahedra. 972 B. Zhao et al / Inorganic Chemistry Communications 7 (2004) 971-973previous report [15]. The tetrahedral conformation of each Ag center consists of four O atoms with distances in the range 2.322-2.401 Å (two from carboxylates and two from oxo ligands).…”

Preface: Recent Advances and Highlights of the 5th International Vanadium Symposium

“…19,66,[171][172][173][174][175][176], pyrone, pyridinone and pyrimidinone complexes (177)(178)(179), several types of Schiff bases and related complexes (66, [180][181][182], picolinato (e.g. 183), quinoline derivatives (184) dipicolinato complexes (185), compounds involving ligands such as amino acids or derivatives (28,(186)(187)(188)(189)(190)(191)(192)(193)(194)(195)(196)(197), hydroxycarboxylates (198,199), but novel classes of coordination compounds and other new reports on previously known compounds are too many to name.…”