Vanadium(IV)-citrate complex interconversions in aqueous solutions. A pH-dependent synthetic, structural, spectroscopic, and magnetic study.
Vanadium(IV)-citrate complex interconversions in aqueous solutions. A pH-dependent synthetic, structural, spectroscopic, and magnetic study.
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DOI：
10.1021/ic010276n
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发表时间：
2001-10
影响因子：
4.6
通讯作者：
M. Tsaramyrsi;M. Kaliva;A. Salifoglou;C. Raptopoulou;A. Terzis;V. Tangoulis;J. Giapintzakis
中科院分区：
文献类型：
--
作者：
M. Tsaramyrsi;M. Kaliva;A. Salifoglou;C. Raptopoulou;A. Terzis;V. Tangoulis;J. Giapintzakis
柠檬酸盐作为天然金属离子螯合剂在生物体液中大量存在。钒酸钠作为金属酶活性位点的催化剂、代谢调节剂、促有丝分裂激活剂和胰岛素模拟剂参与生物过程。因此，钒化学与天然螯合剂，如柠檬酸盐，可能会直接影响其在细胞环境中的作用，其作为一种生物制剂的作用。为了理解钒的氧化态之一，即V（IV），与其生物活性有关的水化学，在水中进行VCl（3）和柠檬酸的反应，并产生V（IV）-柠檬酸盐络合物，其性质和性质强烈依赖于溶液pH。磁化率数据支持X（4）[[VO（H（-1）Cit）]（2）] xnH（2）O（H（-1）Cit = C（6）H（4）O（7）（4-）; X = K（+），n = 6（1）; X = Na（+），n = 12（2）; X = NH（4）（+），n = 2（3））（pH约8）和X（3）[[V（2）O（2）（H（-1）Cit）（Cit）]] x nH（2）O（X = K（+），n = 7（4））（pH约5）。配合物2属于P2（1）/c空间群，a = 11.3335（9）A，B = 15.788（1）A，c = 8.6960（6）A，β = 104.874（3）度，V = 1503.8（2），Z = 2。配合物3属于P空间群，a = 9.405（1）A，B = 10.007（1）A，c = 13.983（2）A，α = 76.358（4）度，β = 84.056（4）度，γ = 66.102（4）度，V = 1169.2（3），Z = 2。配合物4的空间群为P2（1）nb，a = 9.679（4）A，B = 19.618（8）A，c = 28.30（1）A，V = 5374.0（4），Z = 8.化合物1-4的X-射线结构为V（2）O（2）二聚体，柠檬酸盐显示不同的配位数和模式。1表现出小的铁磁相互作用，而4表现出V（IV）离子之间的反铁磁相互作用。1和4与pH相互转化，从而使pH成为促进V（IV）-柠檬酸盐物质中可变结构、电子和磁性的决定因素。观察到的1-4的水性行为与过去的溶液形态研究一致，有助于理解生物相关的钒（IV）-柠檬酸盐化学的重要方面。
Citrate is abundantly encountered in biological fluids as a natural metal ion chelator. Vanadium participates in biological processes as a catalyst in the active sites of metalloenzymes, as a metabolic regulator, as a mitogenic activator, and as an insulin-mimicking agent. Thus, vanadium chemistry with natural chelators, such as citrate, may have immediate implications on its role in a cellular milieu, and its action as a biological agent. In an effort to comprehend the aqueous chemistry of one of vanadium's oxidation states, namely, V(IV), implicated in its biological activity, reactions of VCl(3) and citric acid were pursued in water and led to V(IV)-citrate complexes, the nature and properties of which depend strongly on the solution pH. Analytical, FT-IR, UV/vis, EPR, and magnetic susceptibility data supported the formulation of X(4)[[VO(H(-1)Cit)](2)] x nH(2)O (H(-1)Cit = C(6)H(4)O(7)(4-); X = K(+), n = 6 (1); X = Na(+), n = 12 (2); X = NH(4)(+), n = 2 (3)) (pH approximately 8) and X(3)[[V(2)O(2)(H(-1)Cit)(Cit)]] x nH(2)O (X = K(+), n = 7 (4)) (pH approximately 5). Complex 2 crystallizes in space group P2(1)/c, a = 11.3335(9) A, b = 15.788(1) A, c = 8.6960(6) A, beta = 104.874(3) degrees, V = 1503.8(2), Z = 2. Complex 3 crystallizes in space group P one macro, a = 9.405(1) A, b = 10.007(1) A, c = 13.983(2) A, alpha = 76.358(4) degrees, beta = 84.056(4) degrees, gamma = 66.102(4) degrees, V = 1169.2(3), Z = 2. Complex 4 crystallizes in space group P2(1)nb, a = 9.679(4) A, b = 19.618(8) A, c = 28.30(1) A, V = 5374.0(4), Z = 8. The X-ray structures of 1-4 are V(2)O(2) dimers, with the citrate displaying varying coordination numbers and modes. 1 exhibits a small ferromagnetic interaction, whereas 4 exhibits an antiferromagnetic interaction between the V(IV) ions. 1 and 4 interconvert with pH, thus rendering the pH a determining factor promoting variable structural, electronic, and magnetic properties in V(IV)-citrate species. The observed aqueous behavior of 1-4 is consistent with past solution speciation studies, and contributes to the understanding of significant aspects of the biologically relevant vanadium(IV)-citrate chemistry.