Copper Ion Complexes with Derivatized Chelating Pterin Ligands

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• 作者：Dong-Heon Lee ; Narasimha N. Murthy ; Yin Lin ; N. Sarwar Nasir ; and Kenneth D. Karlin
• 刊名：Inorganic Chemistry
• 出版年：1997
• 出版时间：December 31, 1997
• 年：1997
• 卷：36
• 期：27
• 页码：6328 - 6334
• 全文大小：251K
• 年卷期：v.36,no.27(December 31, 1997)
• ISSN：1520-510X

文摘

Pterin-copper ion interactions are of interest for possiblemodeling of enzyme active site chemistry or in couplingreactions of a redox-active metal ion with a redox-active ligandcofactor, Here, we describe the synthesis ofderivatized chelating pterins, provided with enhanced organicsolubility by introduction of a pivalolyl group atthe pterin C2 position and supplied with a good copper ion chelator,through reaction of the 6-(bromomethyl)pterin with a 2-(2-(methylamino)ethyl)pyridine (to giveL') or bis(2-pyrid-2-ylethyl)amine (togive L). Copper(I) and copper(II) complexes have been synthesized andcharacterized. The X-ray structure of[L'Cu(Cl)(CH₃CN)](PF₆) (3-PF₆) is described[space group P2₁/c; a =10.606(3) Å, b = 21.683(3) Å, c =12.188(3) Å; mages/gifchars/beta2.gif" BORDER=0 ALIGN="middle"> =96.67(2)mages/entities/deg.gif">; Z = 4; V = 2784(1)ų] and compared with the previously reported structureof [LCu(Cl)](PF₆)(NaPF₆)(1-PF₆·NaPF₆). In3-PF₆, the Cu(II) is pentacoordinate,including equatorial ligation to the pterin N5atom, achieving one of the goals of the ligand design. Unlikeother pterin-Cu(II) structures, neither1-PF₆·NaPF₆ nor 3-PF₆ binds to the pterincarbonyl oxygen atom (off pterin C4). Other solution spectroscopicdata(e.g., IR, UV-vis, EPR) and a magnetic moment of 1.91mages/entities/mgr.gif">_B are provided and are consistent with thesolid-statestructure observed. Copper(I) complexes[LCu^I](PF₆)(5-PF₆) and[L'Cu^I](PF₆)·0.25CH₂Cl₂(6-PF₆·0.25CH₂Cl₂)have been generated and characterized. Observedcoordination-induced ¹H NMR chemical shifts in6-PF₆·0.25CH₂Cl₂) are consistent with binding through the pterin pyrazineN5 donor; a UV-vis feature at 466 nm (sh, mages/gifchars/epsilon.gif" BORDER=0 > =1200) is considered a MLCT transition. A cyclic voltammogram of6-PF₆·0.25CH₂Cl₂(DMF solvent) reveals areversible redox process with E_1/2 = 286 mV(E_1/2 = 546 mV for ferrocene/ferrocenium; vsAg/AgCl).[L'Cu^II(CH₃CN)](CF₃SO₃)₂(4-(CF₃SO₃)₂)exhibits the identical cyclic voltammogram, indicating common solutionstructures.The analogue complex[(MeL)Cu^I(CH₃CN)](ClO₄)(7-ClO₄) (MeL =(2-(2-pyridyl)ethyl)(2-pyridylmethyl)methylamine) displays a more negative redox potential,E_1/2 = 24 mV, indicating that the pterinpyrazine ring hasan electron-withdrawing effect, which may explain the lack ofO₂ reactivity of copper(I) complexes of Land L'.