Metal complexes of macrocyclic ligands. Part XXIII. Synthesis, properties, and structures of mononuclear complexes with 12- and 14-membered tetraazamacrocycle-N,N′,N″,N‴-tetraacetic Acids

✍ Scribed by Andreas Riesen; Margareta Zehnder; Thomas A. Kaden

• Publisher: John Wiley and Sons
• Year: 1986
• Tongue: German
• Weight: 439 KB
• Volume: 69
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.19860690830

✦ Synopsis

The two tetraazamacrocycle-N.N',N",N"'-tetraacetic acids H,dota and H,teta form with Ni2+, Cu2+, and Zn2+ (M") mononuclear complexes MLH, and M'[ML], M' being an alkaline earth ion. The structures of Ni(H2dota) and Cu(H,dota) have been solved by X-ray structure analysis. The metal ions are in a distorted octahedral geometry coordinated by four amino N-atoms and two carboxylates. In the case of Cu2+, the distortions are more pronounced than for Ni2+ indicating that the Juhn-Teffer effect is operating. Starting from these two structures, the coordination geometry of the other complexes is discussed using VIS and IR spectra.

Experimental. -H,dota [9][3] and H,teta [10][3] were prepared according to the literature. Metal Complexes from Acidic Soln. Equimolar amounts (0.2-0.5 mmol) of ligand and a metal salt (chloride or sulfate) were dissolved in 50-100mI H20. In the case of H,dota, the solns. were adjusted to pH 2.5 and were left for several days to crystallize. In the case of H4teta, which was dissolved by addition of a small quantity of 0 . 1 ~ NaOH the complexation is slower, so that we had to heat and increase the pH in order to obtain the complexes. After the reaction had taken place, the pH was adjusted to 3.54.0 and the soh. were left for crystallization.