Istituto CNR di Chimica Biomolecolare, Trav. La Crucca 3, I-07040 Sassari, Italy.
Inorg Chem. 2011 Oct 17;50(20):10328-41. doi: 10.1021/ic201392d. Epub 2011 Sep 8.
The interaction of VO(2+) ion with ligands of biological interest that are present in important metabolic pathways--2-oxopropanoic acid (pyruvic acid, pyrH), 3-hydroxy-2-oxopropanoic acid (3-hydroxypyruvic acid, hydpyrH), oxobutanedioic acid (oxalacetic acid, oxalH(2)), (S)-hydroxybutanedioic acid (l-malic acid, malH(2)), and 2,3-dihydroxy-(E)-butanedioic acid (dihydroxyfumaric acid, dhfH(2))--was described. Their complexing capability was compared with that of similar ligands: 3-hydroxy-2-butanone (hydbut) and 3,4-dihydroxy-3-cyclobutene-1,2-dione (squaric acid, squarH(2)). All of these ligands (except l-malic acid) exhibit keto-enol tautomerism, and the presence of a metal ion can influence such an equilibrium. The different systems were studied with electron paramagnetic resonance (EPR) and UV-vis spectroscopies and with pH potentiometry. Density functional theory (DFT) methods provide valuable information on the relative energy of the enol and keto forms of the ligands both in the gas phase and in aqueous solution, on the geometry of the complexes, and on EPR and electronic absorption parameters. The results show that most of the ligands behave like α-hydroxycarboxylates, forming mono- and bis-chelated species with (COO(-), O(-)) coordination, demonstrating that the metal ion is able to stabilize the enolate form of some ligands. With dihydroxyfumaric acid, the formation of a non-oxidovanadium(IV) complex, because of rearrangement of dihydroxyfumaric to dihydroxymaleic acid (dhmH(2)), can be observed. With 3-hydroxy-2-butanone and 3,4-dihydroxy-3-cyclobutene-1,2-dione, complexation of VO(2+) does not take place and the reason for this behavior is explained by chemical considerations and computational calculations.
描述了 VO(2+)离子与存在于重要代谢途径中的生物相关配体（2-氧代丙酸（丙酮酸，pyrH）、3-羟基-2-氧代丙酸（3-羟基丙酮酸，hydpyrH）、氧代丁二酸（草酰乙酸，oxalH(2)）、(S)-羟基丁二酸（L-苹果酸，malH(2)）和 2,3-二羟基-(E)-丁二酸（反丁烯二酸二羟，dhfH(2)））的相互作用。比较了它们与类似配体（3-羟基-2-丁酮（hydbut）和 3,4-二羟基-3-环丁烯-1,2-二酮（丁炔二酸，squarH(2)））的络合能力。所有这些配体（除 L-苹果酸外）都表现出酮-烯醇互变异构，金属离子的存在可以影响这种平衡。使用电子顺磁共振（EPR）和紫外可见光谱以及 pH 电位滴定法研究了不同的体系。密度泛函理论（DFT）方法提供了有关配体在气相和水溶液中烯醇和酮形式的相对能量、配合物的几何形状以及 EPR 和电子吸收参数的有价值的信息。结果表明，大多数配体表现为α-羟基羧酸，形成（COO(-)，O(-)）配位的单和双螯合物种，表明金属离子能够稳定一些配体的烯醇形式。与反丁烯二酸二羟反应，由于反丁烯二酸二羟转化为反丁烯二酸二羟（dhmH(2)），可以观察到非氧化钒(IV)配合物的形成。对于 3-羟基-2-丁酮和 3,4-二羟基-3-环丁烯-1,2-二酮，VO(2+)的络合作用不会发生，这种行为的原因通过化学考虑和计算计算来解释。
