Tetrahydroxy-p-benzoquinone as a Source of Polydentate O-Donor Ligands. Synthesis, Crystal Structure, and Magnetic Properties of the [Cu(bpy)(dhmal)]2 Dimer and the Two-Dimensional [
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- 作者：Santiago Reinoso ; Pablo Vitoria ; Leire San Felices ; Ainara Montero ; Luis Lezama ; Juan M. Gutié ; rrez-Zorrilla
- 刊名：Inorganic Chemistry
- 出版年：2007
- 出版时间：February 19, 2007
- 年：2007
- 卷：46
- 期：4
- 页码：1237 - 1249
- 全文大小：554K
- 年卷期：v.46,no.4(February 19, 2007)
- ISSN：1520-510X
文摘
The use of tetrahydroxy-<I>p-benzoquinone as a slow source of dihydroxymalonato and oxalato ligands led to theisolation under open-air mild reaction conditions of five different compounds, two of them prepared for the firsttime: [Cu(bpy)(dhmal)]2 (1) and [{SiW12O40}{Cu2(bpy)2(H2O)(ox)}2]·16H2O (5) (bpy, 2,2'-bipyridine; dhmal,dihydroxymalonate; ox, oxalate). A possible mechanism for the oxidation of the benzoquinone to give the croconatedianion, which undergoes further ring-opening oxidation to decompose into dihydroxymalonate and oxalate, isproposed. All compounds have been characterized by elemental analysis, thermogravimetry, infrared spectroscopy,and powder X-ray diffraction. Single-crystal X-ray diffraction, electron paramagnetic resonance, and magneticsusceptibility measurements have been performed for compounds 1 and 5. A complete band assignment of theexperimental FT-IR spectra is given through comparison with the ones calculated using density functional theory(DFT). The neutral dimer 1 constitutes the first structurally characterized example of a transition metal-dhmalcomplex, and it contains two copper atoms bridged by two dihydroxymalonato ligands acting in a 
images/entities/mgr.gif">2-images/gifchars/kappa.gif" BORDER=0 >3O,O',O' ':images/gifchars/kappa.gif" BORDER=0 >1O coordination fashion, so that an equatorial-axial Cu2(images/entities/mgr.gif">2-O)2 rhomboid core is formed. On the other hand, theinorganic-metalorganic hybrid compound 5 shows a two-dimensional arrangement of Keggin polyanions linked byone of the Cu atoms of the oxalate cationic dimers to give layers parallel to the (10images/entities/onemacr.gif">) plane, the remaining ox-Cu-bpy fragments acting as interlamellar separators. In both cases, magnetic and EPR results are discussed withrespect to the crystal structure of the compounds and, for compound 1, also with respect to DFT calculations ofthe exchange coupling constant.