科研之友
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摘要
A potential tetradentate indolecarboxamide ligand, H(4)L(3) is synthesized and investigated for its coordination abilities towards Ni(II) and Cu(II) ions. Two H(4)L(3) ligands in their tetra-deprotonated form [L(3)](4), were found to coordinate two metal centers resulting in the formation of [Ni(2)(L(3))(2)](4) (5) and [Cu(2)(L(3))(2)](4) (6) complexes. The crystal structure of 6 displays the formation of a dinuclear structure where two fully deprotonated ligands, [L(3)](4) hold two copper(II) ions together. Even more interesting is the fact that both deprotonated ligands, [L(3)](4) coordinate the copper ions in an identical and symmetrical fashion. The Na(+) cations present in the complex 6 stitch together the dinuclear units resulting in the formation of a coordination chain polymer. Four sodium ions connect two dinuclear units via interacting with the O(amide) groups. Further, Na(+) cations were found to coordinate several DMF molecules; some of them are terminal and a few are bridging in nature. The solution state structure (determined by the NMR spectral analysis) of the diamagnetic complex 5 also supported the fact that two deprotonated ligands, coordinate two nickel ions in an identical and symmetrical fashion. Absorption spectral studies reveal that the solid-state square-planar geometry is retained in solution and both complexes do not show any tendency to coordinate potential axial ligands. The variable-temperature magnetic measurements and EPR spectra indicate spin-spin exchange between two copper centers in complex 6. The electrochemical results for both complexes show three irreversible oxidative responses that correspond to the oxidation of first and second metal ion followed by the ligand oxidation, respectively.
- 出版日期2010-10-15
