The synthesis and coordination chemistry of a tris-8-aminoquinoline tripodal ligand

A tripodal tris-8-aminoquinoline ligand was synthesised in high yield via the Bucherer reaction. The septa-dentate ligand was found to give isolable complexes when coordinated with transition metals. Complexes of zinc(II), cadmium(II) and cobalt(III) were isolated and their solid state structures were determined by single crystal X-ray diffraction. The solid state structures of these complexes were compared to the solution 1H NMR data which was obtained for each complex. The two first row metals both gave octahedral six coordinate structures, although the two metals were coordinated by a differing donor set of heteroatoms. The cadmium complex was found to contain a seven coordinate cadmium centre in the solid state. DFT calculations were carried out in order to give an indication as to why the two different six coordinate binding modes were encountered