Dinuclear Cadmium(II), Zinc(II), and Manganese(II), Trinuclear Nickel(II), and Pentanuclear Copper(II) Complexes with Novel Macrocyclic and Acyclic Schiff-Base Ligands Having Enantiopure or Racemic Ca

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• 作者：Jue-Chao Jiang ; Zhao-Lian Chu ; Wei Huang ; Gang Wang ; Xiao-Zeng You
• 刊名：Inorganic Chemistry
• 出版年：2010
• 出版时间：July 5, 2010
• 年：2010
• 卷：49
• 期：13
• 页码：5897-5911
• 全文大小：1332K
• 年卷期：v.49,no.13(July 5, 2010)
• ISSN：1520-510X

文摘

Four novel [3 + 3] Schiff-base macrocyclic ligands I−IV condensed from 2,6-diformyl-4-substituted phenols (R = CH₃ or Cl) and enantiopure or racemic camphoric diamines have been synthesized and characterized. Metal-ion complexations of these enantiopure and racemic [3 + 3] macrocyclic ligands with different cadmium(II), zinc(II), manganese(II), nickel(II), and copper(II) salts lead to the cleavage of Schiff-base C═N double bonds and subsequent ring contraction of the macrocyclic ligands due to the size effects and the spatial restrictions of the coordination geometry of the central metals, the steric hindrance of ligands, and the counterions used. As a result, five [2 + 2] and one [1 + 2] dinuclear cadmium(II) complexes (1−6), two [2 + 2] dinuclear zinc(II) (7 and 8), and two [2 + 2] dinuclear manganese(II) (9 and 10) complexes together with one [1 + 1] trinuclear nickel(II) complex (11) and one [1 + 2] pentanuclear copper(II) complex (12), bearing enantiopure or racemic ligands, different substituent groups in the phenyl rings, and different anionic ligands (Cl⁻, Br⁻, OAc⁻, and SCN⁻), have been obtained in which the chiral carbon atoms in the camphoric backbones are arranged in different ways (RRSS for the enantiopure ligands in 1, 2, 4, 5, and 7−10 and RSRS for the racemic ligands in 3, 6, 11, and 12). The steric hindrance effects of the methyl group bonded to one of the chiral carbon atoms of camphoric diamine units are believed to play important roles in the formation of the acyclic [1 + 1] trinuclear complex 11 and [1 + 2] dinuclear and pentanuclear complexes 6 and 12. In dinuclear cadmium(II), zinc(II), and manganese(II) complexes 1−10, the sequence of separations between the metal centers is consistent with that of the ionic radii shortened from cadmium(II) to manganese(II) to zinc(II) ions. Furthermore, UV−vis, circular dichroism, ¹H NMR, and fluorescence spectra have been used to characterize and compare the structural differences between related compounds.