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Unexpected Findings in a Simple Metathesis Reaction of Europium and Ytterbium Diiodides with Perfluorinated Mercaptobenzothiazolates of Alkali Metals
journal contribution
posted on 2020-08-03, 04:52 authored by Liubov I. Silantyeva, Vasily A. Ilichev, Andrey S. Shavyrin, Artem N. Yablonskiy, Roman V. Rumyantcev, Georgy K. Fukin, Mikhail N. BochkarevIn the search for
new f–d luminescent complexes of Eu(II)
and Yb(II) the metathesis reactions of diiodides of these metals with
perfluorinated 2-mercaptobenzothiazolates of alkali metals were studied.
It has been found that the reactions of LnI2(THF)2 (Ln = Eu, Yb) with K(mbtF) (mbtF = perfluorinated
2-mercaptobenzothiazolate anion) in DME result in the formation of
the nonluminescent complexes Ln(mbtF)2(DME)2 and precipitation of KI in high yields. Single-crystal X-ray
diffraction analyses have shown that Eu(mbtF)2(DME)2 has a trans orientation of mbtF ligands,
while in the Yb(mbtF)2(DME)2 molecule
the ligands occupy cis positions. The DFT calculations and estimations
with the invariom model revealed that the complexes have a flexible
coordination sphere of Ln2+ ions and a relatively low energy
of Ln–mbtF binding. The reactions of the same diiodides
with the lithium complex Li(mbtF) are reversible and proceed
through the formation of intermediate complexes of unknown structure
which have been isolated as noncrystalline solids. The europium product
(solid and in DME solution) upon UV excitation exhibited bright luminescence
with λ 510 nm. Data from time-resolved photoluminescence (PL)
spectroscopy indicated the existence in the intermediate substance
of two Eu2+ emission centers with different coordinating
environments. Treatment of the solid intermediate product with toluene
led to its dissociation onto Ln(mbtF)2(DME)2 and [LiI(DME)]n. The back-replacement
of toluene with DME gives again the solutions from which the starting
LnI2 and Li(mbtF)(DME) were precipitated by
slow evaporation of the solvent. The reversibility of the processes
has been confirmed by the reaction of nonluminescent Eu(mbtF)2(DME)2 with LiI in DME medium, which resulted
in the same luminescent solution which gave a mixture of EuI2(DME)3 and Li(mbtF).
