A structural comparison of a series of paramagnetic transition metal complexes: the interplay between octahedral distortion and secondary coordination domains

Four new mononuclear complexes of the form [ML]X₂ were synthesized using a previously reported ligand, tris((((1-(pyridin-4-yl)-1H-imidazole-4-yl)methylene)amino)ethyl)ethane-1,2-diamine, L. The new metal complexes bearing Mn(II), Co(II), Ni(II), or Cu(II) have been characterized both in solution and in the solid state. X-ray diffraction studies were used to investigate how the ligand backbone responds to changes in the coordination sphere (e_g orbital population of the respective transition metals). The results presented herein indicate that small differences arise in the octahedral distortion parameters, average mutual bonding axis, and ligand torsion upon the formation of the different metal complexes. This study provides insight into how the positions of secondary coordination domains may be changed following the complexation of different transition metals to assist future studies in determining the position of different metal ions in more complex heteronuclear structures, which may have implications for solid-solution magnetic and/or optical properties.