Azo-containing pyridine amide ligand. A six-coordinate nickel(II) complex and its one-electron oxidized species: Structure and properties

作者：Sharma Anuj Kumar; Biswas Saikat; Barman Suman Kumar; Mukherjee Rabindranath^*

来源：Inorganica Chimica Acta, 2010, 363(12): 2720-2727.

DOI：10.1016/j.ica.2010.03.056

• Azo group containing pyridine amide ligand
• Ni(II) complex
• Crystal structure
• Redox properties
• Electrochemically-generated nickel(III)
• EPR spectra

A new potentially tridentate ligand HL(11) consisting of 2-pyridinecarboxamide unit and azo functionality has been used, in its deprotonated form, to prepare a nickel(II) complex which has been structurally characterized. The ligand L(11)( ) affords a bis-complex [Ni(II)(L(11))(2)] (1). In 1, the two L(11)( ) ligands bind to the NiII center in a mer configuration. The relative orientations within the pairs of pyridyl-N, deprotonated amido-N, and azo-N atoms are cis, trans, and cis, respectively. The Ni(II)N(2)(pyridyl)N'(2)(amide)N"(2)(azo) coordination environment is severely distorted from ideal octahedral geometry. The Ni-N(am) (am = amide) bond lengths are the shortest and the Ni-N(azo) bond lengths are the longest. Complex 1 exhibits a quasi-reversible Ni(III)/Ni(II) redox process. Moreover, the complex displays two ligand-centered (azo group) quasi-reversible redox processes. Spectroscopic (absorption and EPR) properties have been studied on coulometrically-generated nickel(III) species. To understand the nature of metal-ligand bonding interactions Density Functional Theory (DFT) calculations have been performed on 1 at the B3LYP level of theory. Calculations have also been done for closely related nickel(II) complexes of deprotonated pyridine amide ligands and comparative discussion has been made using observed results.

• 出版日期2010-10-15