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

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• 作者：Luqin Yang ; Agnete la Cour ; Oren P. Anderson ; and Debbie C. Crans
• 刊名：Inorganic Chemistry
• 出版年：2002
• 出版时间：December 2, 2002
• 年：2002
• 卷：41
• 期：24
• 页码：6322 - 6331
• 全文大小：194K
• 年卷期：v.41,no.24(December 2, 2002)
• ISSN：1520-510X

文摘

The aqueous solution and solid state properties of (4-hydroxypyridine-2,6-dicarboxylato)dioxovanadate(V) (alsoreferred to as (4-hydroxydipicolinato)dioxovanadate(V) or (chelidamato)dioxovanadate(V) and abbreviated [VO₂(dipic-OH)]^-) were investigated. By using ¹H, ¹³C, ¹⁷O, and ⁵¹V NMR 1D and 2D spectroscopy, the species presentin solution, together with pK_a values, equilibrium constants, and labilities, were characterized. The complex is moststable at acidic pH down to pH 1 where it is protonated. The stability of this complex is higher than that of theparent dipicolinatodioxovanadate(V) complex. The dipic-OH ligand is coordinated in a tridentate manner throughoutthe pH range studied, and the vanadium(V) atom is five-coordinate. Solid state structures of (NMe₄)[VO₂(dipic-OH)]·H₂O (monoclinic, P2₁/n) and Na[VO₂(dipic-OH)]·2H₂O (triclinic, P) were determined. The discrete complexanions in (NMe₄)[VO₂(dipic-OH)]·H₂O are connected by hydrogen bonding between the hydroxyl group, a watermolecule, and a carboxylate oxygen atom. Changing the counterion from NMe₄⁺ to sodium ion in Na[VO₂(dipic-OH)]·2H₂O leads to the formation of a polymeric structure. Dynamic processes in solution were explored by using¹H and ¹³C EXSY NMR spectroscopy; exchange between complex and free ligand below pH 4 was observed. Thedifferences between the dipicolinatodioxovanadate(V) parent complex and the [VO₂(dipic-OH)]^- complex in thesolid state and in solution demonstrate the subtle consequences of the one substitutional difference between thetwo ligands. The insulin-mimetic properties of this compound are likely to be of mechanistic interest in developingan understanding of the mode of action of the few known insulin-mimetic vanadium(V) complexes.