Coordination Diversity in Mono- and Oligonuclear Copper(II) Complexes of Pyridine-2-Hydroxamic and Pyridine-2,6-Dihydroxamic Acids

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• 作者：Elzbieta Gumienna-Kontecka ; Irina A. Golenya ; Agnieszka Szebesczyk ; Matti Haukka ; Roland Kr盲mer ; Igor O. Fritsky
• 刊名：Inorganic Chemistry
• 出版年：2013
• 出版时间：July 1, 2013
• 年：2013
• 卷：52
• 期：13
• 页码：7633-7644
• 全文大小：510K
• 年卷期：v.52,no.13(July 1, 2013)
• ISSN：1520-510X

文摘

Solution and solid state studies on Cu(II) complexes of pyridine-2-hydroxamic acid (HPicHA) and pyridine-2,6-dihydroxamic acid (H₂PyDHA) were carried out. The use of methanol/water solvent allowed us to investigate the Cu(II)鈥?b>HPicHA equilibria under homogeneous conditions between pH 1 and 11. In agreement with ESI-MS indication, the potentiometric data fitted very well with the model usually reported for copper(II) complexes of 伪-aminohydroxamate complexes ([CuL]⁺, [Cu₅(LH_鈥?)₄]²⁺, [CuL₂], [CuL₂H_鈥?]^{鈭?/sup>), however with much higher stability of the 12-MC-4 species. A series of copper(II) complexes has been isolated in the solid state and characterized by a variety of spectroscopic methods, X-ray structure analysis, and magnetic susceptibility measurements. The ligands show the tendency to form bi- and trinuclear species with copper(II) ions due to the {(N,N鈥?; (O,O鈥?} bis-(bidentate) chelating-and-bridging mode involving (O,O鈥?-hydroxamate chelate formation combined with (N,N鈥? chelating with participation of the pyridine and hydroxamic nitrogen atoms, so that the hydroxamate groups play a 渭₂-(N,O)-bridging role. Molecular and crystal structures of three synthesized complexes [Cu₃(PicHA-H)₂(dipy)₂](ClO₄)₂路4/3DMSO路2/3H₂O (1), [Cu₂(PyDHA)(dipy)₂(ClO₄)₂]路DMF路H₂O (4), and [Cu₃(PyDHA-2H)(tmeda)₃](ClO₄)₂ (5) (dipy, 2,2鈥?dipyridyl; tmeda, N,N,N鈥?N鈥?tetramethyl-1,2-diaminoethane) have been determined by single crystal X-ray analysis. In 1, two trans-situated doubly deprotonated hydroxamic ligands play a {(O,O鈥?(N,N鈥?}鈥?bis)bidentate-bridging function forming bridges between the medial, Cu(2) (CuN₄), and the terminal, Cu(1) and Cu(3) (CuN₂O₂), copper(II) ions; the chelating dipy ligands are coordinated to the latter. In 4, the ligand is coordinated in a classical (O,O鈥?-hydroxamate chelating mode with the help of two separate hydroxamic groups while the central tridentate donor compartment remains vacant. In 5, the hydroxamate ligand is coordinated by the {(O,O鈥?;(N,N鈥?N鈥?;(O鈥?O鈥?}-tridentate-(bis)bidentate mode, bridging three copper(II) ions, while the chelating tmeda ligands are coordinated to all three copper(II) ions. Magnetic susceptibility measurements (1.7鈥?00 K) of powdered samples of the trinuclear complexes 1 and 5 revealed strong antiferromagnetic coupling between the copper(II) ions mediated by the hydroxamate bridges.}