Complexes of Lanthanoid Nitrates with 15-Crown-5 and 18-Crown-6 Ethers

✍ Scribed by Jean-Claude G. Bünzli; Denis Wessner

• Publisher: John Wiley and Sons
• Year: 1981
• Tongue: German
• Weight: 860 KB
• Volume: 64
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.19810640223

✦ Synopsis

Complexes between the heavier lanthanoid nitrates Ln(NO~3~)~3~ and 15‐crown‐5 (1) and 18‐crown‐6 (2) ethers were isolated and characterized. Both 1:1 and 4:3 complexes are formed with each Ln(III) ion, except in the case of Gd and 2. The thermal transformation of the 1:1 complexes into the corresponding 4:3 complexes was studied by thermogravimetry and by DSC, X‐ray and vibrational data provide information about the structure of these complexes. The interaction between Ln(III) ions and ligands 1 and 2 in non‐aqueous solutions is discussed on the basis of conductometric, fluorescence, UV./VIS. and ^1^H‐NMR. data. Only 1:1 complexes of 2 formed in solution and their formation constants range from log__K__~f~ = 4.4 (Ln = La) to 2.4 (Ln = Yb); for Eu, K~f~ of the 15‐crown‐5 and 18‐crown‐6 ether complexes are of the same order of magnitude. For La, Pr, Nd, Eu, Yb, a variable temperature NMR. study gave some indications about the chemical exchanges in solution.

The factors which determine the stoichiometry of the complexes are discussed.