Structural Consequences of the N7 and C8 Translocation on the Metal Binding Behavior of Adenine

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• 作者：Alicia Dom铆nguez-Mart铆n ; Duane Choquesillo-Lazarte ; Jose A. Dobado ; Henar Mart铆nez-Garc铆a ; Luis Lezama ; Josefa M. Gonz谩lez-P茅rez ; Alfonso Casti帽eiras ; Juan Nicl贸s-Guti茅rrez
• 刊名：Inorganic Chemistry
• 出版年：2013
• 出版时间：February 18, 2013
• 年：2013
• 卷：52
• 期：4
• 页码：1916-1925
• 全文大小：492K
• 年卷期：v.52,no.4(February 18, 2013)
• ISSN：1520-510X

文摘

7-Deaza-8-aza-adenine, namely 4-aminopyrazolo[3,4-d]pyrimidine (H4app), is a bioisoster of adenine (Hade) resulting from the translocation of N7 and C8 atoms on the purine moiety. With the aim of studying the influence of this translocation on the metal binding abilities of H4app, we have prepared and structurally characterized two ternary copper(II) complexes having H4app and one N-benzyl-iminodiacetate chelator (MEBIDA or FBIDA, with a methyl or fluoro group in para- of the benzyl aromatic ring): [Cu₂(MEBIDA)₂(渭₂-N1,N8-H4app)(H₂O)₂]路4H₂O (1) and [Cu₄(FBIDA)₄(渭₂-N8,N9-H4app)₂(H₂O)]路3.5H₂O (2). Furthermore, thermal, spectral, and magnetic properties have been also investigated. In 1, H(N9)4app is disordered over two equally pondered positions and the 渭₂-N1,N8 coordination mode is assisted by N6-H路路路O and N9-H路路路O intramolecular interactions, respectively. The acyclic nonlinear molecular topology of 2 is strongly influenced by two intramolecular H-bonding interactions (O-H路路路O-carboxylate) involving the apical aqua ligand of a terminal Cu(II) atom. Thus, both compounds have in common the Cu鈥揘8 bond. In order to better understand our limited structural information, DFT calculations for the individual tautomers of H4app as well as mononuclear Cu(II) model systems have been carried out. According to previous results, we conclude that H(N9)4app is the most stable tautomer followed by H(N8)4app. When N9 and N8 are metalated, then the tautomer H(N1)4app can come into play as observed in compound 2. Likewise, the findings concerning compound 1 suggest that the formation of a Cu鈥揘1 bond in H4app results was favored compared to neutral adenine, for which only one case has been reported with such coordination despite the large variety of related Cu(II)-Hade described in the literature.