Synthesis, structure and characterization of novel nickel (II) and iron (II) complexes with a 5, 5'-bis(2-(2, 2'-bipyridin-6-yl)-ethyl)-2, 2'-bipyridine ligand

摘要

A new tris-bipyridine ligand 5, 5'-bis[2-(2, 2'-bipyridin-6-yl)-ethyl]-2, 2'-bipyridine (L) was synthesized, and complexes [ML_3][PF_6]_2 centre dot 2EtOH centre dot 0.5H_2O [M = Ni(II), 1; M = Fe (II), 2] were obtained by reaction of the ligand L with Ni(II) and Fe(II) ions, respectively. X-Ray data of complex 1 show that the central , 5-5'-disubstituted 2, 2'-bipyridine units of each ligand L coordinate to the Ni(II) ion to give a distorted octahedral environment, while all the terminal 6-monosubstituted 2, 2'-bipyridine groups of the ligand keep free of coordination. Complex 2 is isomorphic to 1. The solution behavior of complex 2 was investigated by ~1H NMR spectroscopy. Complexes 1 and 2 were also characterized by ES-MS spectrometry and cyclic voltammetry. The ES-MS spectral data indicate that only the mononuclear complexes formed in the reaction mixtures of the ligand L and M(ClO_4)_2 (M = Fe and Ni) even in the presence of excess metal ion. The results illustrate that the central 5, 5'-disubstituted 2, 2'-bipyridine moiety of each ligand L is selectively coordinated by octahedral geometric metal ions, whereas the 6-substituted 2, 2'-bipyridine unit does not participate in any metal ion coordination.