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新型双足配体N,N'-双{2-[(2-羟基苄叉基)氨基]乙基}丙二酰胺与钴(II)、镍(II)、铜(II)和锌(II)的电位滴定和分光光度研究

Potentiometric and spectrophotometric study of a new dipodal ligand N,N'-bis{2-[(2-hydroxybenzylidine)amino]ethyl}malonamide with Co(II), Ni(II), Cu(II) and Zn(II).

作者信息

Sahoo Suban K, Muthu S E, Baral Minati, Kanungo B K

机构信息

Department of Chemistry, Sant Longowal Institute of Engineering & Technology, Longowal 148106, Punjab, India.

出版信息

Spectrochim Acta A Mol Biomol Spectrosc. 2006 Mar 1;63(3):574-86. doi: 10.1016/j.saa.2005.06.014. Epub 2005 Jul 18.

Abstract

A new dipodal ligand, N,N'-bis{2-[(2-hydroxybenzylidine)amino]ethyl}malonamide (BHAEM) was synthesized by Schiff base condensation of N,N'-bis(2-aminoethyl)malonamide with two equivalent of salicylaldehyde and characterized on the basis of elemental analyses and various spectral (UV-vis, IR, (1)H NMR and (13)C NMR) data. The complexation reaction of the ligand with H(+), Co(II), Ni(II), Cu(II) and Zn(II) in solution was investigated by spectrophotometric and potentiometric method. Two protonation constants of BHAEM assigned for two hydroxyl groups of aromatic ring were determined and its hydrolysis mechanism was proposed through potentiometric result. In presence of metal ions, BHAEM shows different coordination properties. All metal ions form ML type complex where the ligand coordinates to the metal ion through two N-amine and two O-phenolate groups. In addition, Ni(II) and Cu(II) form additional complex species of the type MLH(-1) and MLH(-2), respectively due to ionization of amide protons. The molecular geometry of BHAEM was examined theoretically using the molecular mechanics MM3 force field followed by semi-empirical PM3 method and various spectral data UV-vis, IR and (1)H NMR were calculated from the energy-minimized structure applying semi-empirical ZINDO, PM3 and TNDO/2 method, respectively and compared with the experimental data. The probable structure of metal complexes in solution were proposed through calculated minimum strain energy by applying molecular mechanics MM(+) force field coupled with molecular dynamics simulation. Further the proposed structure of Cu(BHAEM) was refined through semi-empirical AM1/d method.

摘要

通过N,N'-双(2-氨基乙基)丙二酰胺与两当量水杨醛的席夫碱缩合反应合成了一种新型双足配体N,N'-双{2-[(2-羟基苄叉基)氨基]乙基}丙二酰胺(BHAEM),并通过元素分析和各种光谱(紫外可见光谱、红外光谱、¹H核磁共振谱和¹³C核磁共振谱)数据对其进行了表征。采用分光光度法和电位滴定法研究了该配体与溶液中H⁺、Co(II)、Ni(II)、Cu(II)和Zn(II)的络合反应。测定了BHAEM芳香环上两个羟基的两个质子化常数,并通过电位滴定结果提出了其水解机理。在金属离子存在下,BHAEM表现出不同的配位性质。所有金属离子均形成ML型配合物,其中配体通过两个N-胺基和两个O-酚盐基团与金属离子配位。此外,由于酰胺质子的电离,Ni(II)和Cu(II)分别形成了额外的MLH⁻¹和MLH⁻²型配合物。利用分子力学MM3力场理论研究了BHAEM的分子几何结构,随后采用半经验PM3方法,并分别应用半经验ZINDO、PM3和TNDO/2方法从能量最小化结构计算了各种光谱数据紫外可见光谱、红外光谱和¹H核磁共振谱,并与实验数据进行了比较。通过应用分子力学MM⁺力场结合分子动力学模拟计算的最小应变能,提出了溶液中金属配合物的可能结构。进一步通过半经验AM1/d方法对所提出的Cu(BHAEM)结构进行了优化。

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