Structural and spectroscopic investigations of nine-coordinate redox active lanthanide complexes with a pincer O,N,O ligand
Résumé
The lanthanide complexesEuL(3),GdL3,YbL(3)andLuL(3)of theN,N '-bis(2-hydroxy-di-3,5-tert-butylphenyl)amine were prepared. The X-Ray crystal structures ofGdL(3)andLuL(3)demonstrated a nine-coordinate sphere with three ligand molecules under their anionic diamagnetic form (Cat-N-BQ)(-). The complexes showed three oxidation events (Eox11/2 = 0.15-0.16 V,E-1/2(2)= 0.51-55 V, andE(1/2)(3)= 0.75-0.78 Vvs.Fc(+)/Fc)viacyclic voltammetry, corresponding to the successive oxidation of the aminophenolate moeities to iminosemiquinone species. The complexesGdL(3)andYbL(3)were characterized by EPR spectroscopy, allowing for the determination of the zero field splitting (ZFS) parameters in the first case. The monocations(LnL(3))(+)and monoanions(LnL(3))(-)were electrochemically generated (Ln = Eu, Gd, Yb, Lu), as well as the dicationsYbL(3)(2+)andLuL(3)(2+). The spins are antiferromagnetically exchange coupled in the diradical speciesLuL(3)(2+)(|D| = 260 MHz,E= 0). All the complexes (incl. neutral) possess a strong absorption band in the NIR region (730-840 nm,epsilon> 19 mM(-1)cm(-1)) corresponding to ligand-based transitions.
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