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C. Knoll, D. Müller, Jan Welch, G. Giester, B. Lendl, P. Weinberger, G. Steinhauser:
"5,5´-Azobistetrazolate in lanthanide coordination chemistry - The impact of CO₂ and traces of ²⁴¹Am";
Vortrag: ACS Spring Meeting 2019, Orlando; 31.03.2019 - 04.04.2019; in: "Chemistry for New Frontiers", American Chemical Society (Hrg.); (2019), ISBN: 978-0-8412-3433-8; Paper-Nr. 1137, 1 S.

5,5´-Azobistetrazolate (C₂N₁₀^2-; ZT) reveals a very versatile behavior in its lanthanide coordination chemistry, notably governed by the presence of trace contaminants.
On the one hand side, CO₂ in the atmosphere results in sequestration of the CO₂, forming an isotypic series of mixed-anion ZT-carbonate compounds of the rare earth elements (REE) with the general formula [REE₂(ZT)₂CO₃(H₂O)₁₀] 2H₂O for all La-Yb and Y. This series is quite particular, consisting of isotypic REE coordination compounds with tetrazolide-derived ligands unaffected by the "gadolinium break".
On the other hand side, crystallization of terbium 5,5′-azobis[1H-tetrazol-1-ide] in the presence of picomolar trace amounts (ca. 50 Bq) of 241 americium results the accumulation of the americium tracer in the crystalline solid. Furthermore, the ²⁴¹Am introduces a templating effect, forcing the material to adopt a different crystal structure in its presence, compared to the one formed in the absence of ²⁴¹Am. Americium-doped [Tb(Am)(H₂O)₇ZT] ZT 10 H₂O is isostructural to light lanthanide (Ce-Gd) 5,5′-azobis[1H-tetrazol-1-ide] compounds, rather than to the heavy lanthanide (Tb-Lu) 5,5′-azobis[1H-tetrazol-1-ide] (e.g., [Tb(H₂O)₈]₂ZT 6 H₂O) derivatives. Traces of Am seem to force the Tb compound into a structure normally preferred by the lighter lanthanides, despite a 108-fold Tb excess.

lanthanides; americium; gadolinium break