Dinuclear [(VVO(putrebactin))2(渭-OCH3)2] Formed in Solution as Established from LC-MS Measurements Using 50V-Enriched V2O5

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• 作者：Cho Zin Soe ; Amalie A. H. Pakchung ; Rachel Codd
• 刊名：Inorganic Chemistry
• 出版年：2014
• 出版时间：June 2, 2014
• 年：2014
• 卷：53
• 期：11
• 页码：5852-5861
• 全文大小：681K
• 年卷期：v.53,no.11(June 2, 2014)
• ISSN：1520-510X

文摘

Analysis of 1:1 solutions of V(V) and the macrocyclic dihydroxamic acid siderophore putrebactin (pbH₂) in 1:1 H₂O/CH₃OH using triple quadrupole liquid chromatography鈥搈ass spectrometry (LC-MS-QQQ) (pH 鈮?4) showed two well-resolved peaks (t_R(1) 10.85 min; t_R(2) 14.27 min) using simultaneous detection modes (absorbance, 450 nm; selective ion monitoring, m/z 437) characteristic of the previously identified oxidoV(V) complex [V^VO(pb)]⁺ ([M]⁺, m/z_calc 437.1). Peak 1 gave mass spectrometry (MS) signals consistent with [V^VO(pb)]⁺, together with [V^VO(pb)(OH)] and the dinuclear complexes [(V^VO(pb))₂(渭-OH)]⁺ and [(V^VO(pb))₂(渭-OH)₂]. Peak 2 gave MS signals consistent with [V^VO(pb)]⁺, together with [V^VO(pb)(OCH₃)] and the dinuclear complexes [(V^VO(pb))₂(渭-OCH₃)]⁺ and [(V^VO(pb))₂(渭-OCH₃)₂]. This analysis showed that two groups of V(V)/pbH₂ complexes with water- or methanol-derived ancillary ligands were resolved by liquid chromatography (LC). The detection of [V^VO(pb)]⁺ in both peaks could be accounted for by its production from dissociation (peak 1: [(V^VO(pb))₂(渭-OH)]⁺ 鈫?[V^VO(pb)]⁺ + [V^VO(pb)(OH)]; peak 2: [(V^VO(pb))₂(渭-OCH₃)]⁺ 鈫?[V^VO(pb)]⁺ + [V^VO(pb)(OCH₃)]). The assignment of the signal at m/z_obs 959.2 (100%) as the dinuclear complex [(V^VO(pb))₂(渭-OCH₃)₂] ([M + Na⁺]⁺, m/z_calc 959.3) and not an ion cluster of mononuclear [V^VO(pb)(OCH₃)] ({2[M] + Na⁺}⁺, m/z_calc 959.3) was made unequivocal by the use of ⁵⁰V-enriched V₂O₅, which gave a signal with an isotope pattern comprising the sum of the patterns of the three constituent ⁵¹V鈥?sup>51V, ⁵¹V鈥?sup>50V, and ⁵⁰V鈥?sup>50V species. Coordination of methoxide was confirmed upon the replacement of CH₃OH with CD₃OD, which generated [(V^VO(pb))₂(渭-OCD₃)₂] ([M + Na⁺]⁺, m/z_calc 965.3, m/z_obs 965.3). Analysis of 1:1 solutions of Mo(VI) and pbH₂ showed a single peak in the LC (t_R 16.04 min), which gave MS signals that were characterized as mononuclear [Mo^VI(O)₂(pb)] ([M + Na⁺]⁺, m/z_calc 523.1, m/z_obs 523.1) and dinuclear [(Mo^VIO(pb))₂(渭-O)₂] ([M + Na⁺]⁺, m/z_calc 1019.1, m/z_obs 1019.2). The steric and electronic effects of the cis-dioxido group(s) in [Mo^VI(O)₂(pb)] mitigated coordination of solvent-derived ancillary ligands. The work highlights the value of using isotopically enriched metal ion sources and deuterated solvents to deconvolute metal/siderophore solution speciation. The results have relevance for an improved understanding of the coordination chemistry of pbH₂ and other marine siderophores in V(V)- and Mo(VI)-rich surface ocean waters.