Coordination Chemistry in Water of a Free and a Lipase-Embedded Cationic NCN-Pincer Platinum Center with Neutral and Ionic Triarylphosphines

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• 作者：Birgit Wieczorek ; Dennis J. M. Snelders ; Harm P. Dijkstra ; Kees Versluis ; Martin Lutz ; Anthony L. Spek ; Maarten R. Egmond ; Robertus J. M. Klein Gebbink ; Gerard van Koten
• 刊名：Organometallics
• 出版年：2012
• 出版时间：April 9, 2012
• 年：2012
• 卷：31
• 期：7
• 页码：2810-2820
• 全文大小：515K
• 年卷期：v.31,no.7(April 9, 2012)
• ISSN：1520-6041

文摘

The coordination chemistry in aqueous media was studied for the platinum center of low-molecular-weight cationic NCN-pincer platinum complexes [RC₆H₂(CH₂NMe₂)₂-3,5-Pt(H₂O)-4]p>+p> (R = 鈭?CH₂)₃P(鈺怬)(OEt)(OC₆H₄NO₂-4) (1(OH₂)), H (2(OH₂))) as well as of the platinum center of the NCN-pincer platinum cation embedded in the lipase cutinase (cut-1; molecular weight 20鈥?19.3) with various anionic, neutral, and cationic triarylphosphines. A p>31p>P NMR study of the coordination of triarylphosphines to the cationic NCN-pincer platinum center in low-molecular-weight [2(OH₂)][OTf] in both D₂O and Tris buffer (Tris = tris(hydroxylmethyl)aminomethane) showed that the phosphine鈥損latinum coordination is strongly affected by Tris buffer molecules. Two crystal structures of a NCN-pincer platinum鈥損hosphine and a NCN-pincer platinum鈥揺thanolamine coordination complex with ethanolamine as a functional model of Tris with hydrogen bridges, provoking a dimeric supramolecular structure, confirmed that the coordination observed in solution occurred in the solid state as well. A p>31p>P NMR and ESI-MS study of the lipase cut-1 showed that the coordination of various triarylphosphines to the enzyme-embedded platinum center is affected by the surrounding protein backbone, discriminating between phosphines on the basis of their size and charge. By using p>31p>P NMR spectroscopy and ESI-MS spectrometry, study of the coordination of triarylphosphines to cut-1 was possible, thereby avoiding the need for the application of laborious biochemical procedures. To the best of our knowledge, this is the first example of a study involving the selective binding of organic ligands to the metal center of a semisynthetic metalloprotein, unequivocally demonstrating that the well-established coordination chemistry for small-molecule complexes can be transferred to biological molecules. This initial study allows future explorations in the field of selective protein targeting and identification, as in protein profiling or screening studies.