The peculiarities of complex formation and energy transfer processes in lanthanide complexes with 2-(tosylamino)-benzylidene-N-benzoylhydrazone

Abstract

Depending on the local excess of lanthanide ions (Ln = Lu, Yb, Er, Dy, Tb, Gd, Eu, Nd) or 2-(tosylamino)-benzylidene-N-benzoylhydrazone (H₂L), lanthanide complexes, containing either a mono-deprotonated ligand (Ln(HL)₂X, X = Cl, NO₃) or both mono- and dideprotonated ligands (Ln(L)(HL)), were preparatively obtained. The crystal structures of Lu(HL)₂Cl, Yb(L)(HL)(H₂O)₂, Yb(L)(HL)(EtOH)₂(H₂O) and Er(L)(HL), determined by single crystal diffraction data or from powder diffraction data using Rietveld refinement, have shown the surprising resemblance. The study of luminescence temperature dependence of Eu(HL)₂Cl and Eu(L)(HL) showed that europium luminescence is quenched by thermally-activated ⁵D₀ → T₁ energy transfer. Luminescent thermometers based on these complexes demonstrated the sensitivity of up to 7.7% at 85 K which is the highest value above liquid-nitrogen temperatures obtained to date.