Reversible switching of coordination modes of nickel(ΙΙ) complexes using a hemilabile 4,7-diazadecanediamide ligand

The reaction of NiCl2·6H2O with a hemilabile diaminodiamide ligand 4,7-diazadecanediamide gave a pale blue compound [Ni(C8H18N4O2)(H2O)2]·2Cl (1). In basic solution, 1 was transformed to a yellow species [Ni(C8H16N4O2)]·3H2O (2) by the Ni–O to Ni–N bond rearrangement at two amide sites of the complex. Structures of 1 and 2 were characterized by single-crystal X-ray diffraction analysis. Structural data for 1 indicated that the nickel atom adopts a six-coordinated N2O4 environment and gives an octahedral geometry. The structure of 2 showed that the nickel atom adopts a four-coordinated N4 environment, giving a square-planar geometry. Compounds 1 and 2 are structurally switchable in response to pH in an aqueous solution. The results presented could be useful in the design of new Ni(II)-based switching materials.

Graphical abstractThe quantitative reaction of the positively charged Ni(C8H18N4O2)2+ complex and its reversible interconversion with the structurally distinct, neutral Ni(C8H16N4O2) complex in response to pH in aqueous solution was reported. This dynamic structural switching was found to associate with spectral change in aqueous solution.Figure optionsDownload full-size imageDownload as PowerPoint slide