Nitrogen-Rich Compounds of the Lanthanoids: Highlights and Summary

✍ Scribed by Georg Steinhauser; Gerald Giester; Nicolae Leopold; Christoph Wagner; Mario Villa; Andreas Musilek

• Publisher: John Wiley and Sons
• Year: 2010
• Tongue: German
• Weight: 899 KB
• Volume: 93
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.200900389

✦ Synopsis

Introduction. -In 2008, the scientific community in Austria celebrated the 150th birthday of Carl Auer von Welsbach, one of Austrias most famous scientists ever. Auer von Welsbach (1858Welsbach ( -1929) ) was a pioneer in several fields of chemical sciences. He not only discovered four rare earth elements (REE) [1] [2] and correctly proclaimed the non-existence of element 61 (promethium) in nature [3], but also made fundamental discoveries in the field of nuclear sciences. Ninety-nine years ago, he reported that ionium ( 230 Th) was able to induce radioactivity in other materials (presumably lanthanoids) if stored next to the ionium sample [4]. Auer von Welsbach proclaimed that in this process, a concussion of the elementary inventory of the irradiated samples takes place as well as changes in their chemical properties. Today, we call the observed scenario simply neutron activation. He was well aware that this observation was not quite in agreement with current theories, but he was confident enough in his separation skills that he did not attribute the radioactivity in the lanthanoid salt to naturally occurring radionuclide impurities, as others interpreted this observation 1 ). In fact, Auer von Welsbach thereby incidentally discovered the production of artificial radionuclides (24 years before Fre ´de ´ric Joliot and Ire `ne Curie [6]), (spontaneous) fission (29 years before Meitner and Frisch [7], and Hahn and Straßmann [8]), the neutron (22 years before Chadwick [5]), and lastly the principle of neutron-activation analysis (26 years before Hevesy and Levi [9]). Auer von Welsbach predicted that this observation might be of importance for the field of radioactivity research. Stunning.

In this study, we present several novel N-rich compounds of the lanthanoids (Ln) and summarize our previous works on this topic [10 -12]. Nitrogen-rich compounds, in particular, tetrazoles, are of interest for several branches of science. Tetrazoles are fivemembered rings with four N-atoms and, due to their high N content, can be applied as energetic materials (e.g., [13 -25]). Nitrogen-rich compounds gain their energy from high heats of formation and not by intramolecular oxidation of a C backbone like conventional explosives such as TNT or PETN. They are also of interest as ligands in coordination chemistry (e.g., [26 -28]). Some of them have interesting optical properties [29 -31], and some can even be used as precursors of functional materials [32] [33]. With our well-proven preparative technique, we were able to synthesize two different products of lanthanum 5,5'-azobis[1H-tetrazol-1-ide] hydrates, as well as a lanthanum 5,5'-azobis[1H-tetrazol-1-ide] carbonate hydrate and a dysprosium 5,5'azobis[1H-tetrazol-1-ide] hydrate -5-azidotetrazole adduct. The 5,5'-azobis[1H-tetrazol-1-ide] dianion (¼ 5,5'-(diazene-1,2-diyl)bis[2H-tetrazole] ion (2 À)) is also called 5,5'-azotetrazolate in literature, has the sum formula C 2 N 2À 10 and is abbreviated with ZT. The compounds presented in this study are fully characterized using X-ray singlecrystal structure analysis, elemental analysis, and vibrational spectroscopy (IR and Raman). Scheme 2. Simplified Scheme of Acidic Decomposition of ZT Yielding 5-Hydrazinotetrazole in Aqueous Media, and Redox Reactions for the Oxidation of 5-Hydrazinotetrazole Yielding 5-Azidotetrazole