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The interaction of rare earth chlorides with 4,4′-bipyridine for the reversible formation of template based luminescent Ln-N-MOFs†
Christoph J. Höller,Marit Mai,Claus Feldmann,Klaus Müller-Buschbaum
Dalton Transactions Pub Date : 09/14/2009 00:00:00 , DOI:10.1039/B911460B
Abstract

By solvent free syntheses of the rare earth trichlorides LnCl3, Ln = Pr, Nd, Sm, Eu, Tb with melts of 4,4′-bipyridine two-dimensional frameworks of the formula 2[Ln2Cl6(4,4′-bipy)3]·2(4,4′-bipy) are obtained, with 4,4′-bipy = C10H8N2, 4,4′-bipyridine. 4,4′-Bipyridine acts both as a linker ligand as well as a template and populates all cavities in the structures. The template can be evaporated at temperatures >200 °C giving a new high temperature compound with a yet unknown structure. Further heating results in the release of the remaining linking equivalents of the ligand and reformation of LnCl3. Thus the reaction can be run in cycles if the evaporated ligand is collected. Luminescence in the visible range without quenching by concentration is observed for the lanthanides Eu and Tb, which is identified for EuIII with the transitions 5D07FJ and 5D47FJ for TbIII. The hybrid character of the material is reflected by the additional strong antenna effect of the ligand: main excitation is observed via the 4,4′-bipyridine linkers followed by an energy transfer to the metal centres. It is remarkable that both the template containing MOFs as well as the new high temperature compounds exhibit luminescence properties.

Graphical abstract: The interaction of rare earth chlorides with 4,4′-bipyridine for the reversible formation of template based luminescent Ln-N-MOFs
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