Correlation of solid state and solution coordination numbers with infrared spectroscopy in five-, six-, and eight-coordinate transition metal complexes of DOTAM

摘要

Three new DOTAM (1,4,7,10-tetrakis(acetamido)-1,4,7,10-tetraazacyclododecane) complexes have been synthesized and characterized by X-ray crystallography: [Co(DOTAM)]Cl-2 center dot 3H(2)O, [Ni(DOTAM)]Cl(2 center dot)4H(2)O, and [Cu(DOTAM)](ClO4)(2)center dot H2O. Solid state and solution IR spectroscopic features for a series of [M(DOTAM)](2+) complexes (M = Mn, Co, Cu, Ni, Ca, Zn) correlate with solid state and solution coordination numbers. [Co(DOTAM)](2+), [Ni(DOTAM)(2+), and [Zn(DOTAM)](2+) are demonstrated to be six-coordinate in both the solid state and in solution, while [Mn(DOTAM)](2+) and [Ca(DOTAM)](2+) are eight-coordinate in the solid state and remain so in solution. [Cu(DOTAM)](2+), which is five-coordinate by X-ray crystallography, is shown to increase its coordination number in solution to six-coordinate. (C) 2016 Elsevier Ltd. All rights reserved.