Short Radiative Lifetime and Non‐Triplet Sensitization in Near‐Infrared‐Luminescent Yb(III) Complex with Tripodal Schiff Base

Abstract

We prepared Ln(III) (Ln = Eu, Gd, and Yb) complexes with a tripodal Schiff base, tris[2-(5-methylsalicylideneimino)ethyl] amine (H 3 L) and studied their photophysical properties. Upon ligand excitation, YbL showed Yb(III)-centered luminescence in the near-infrared region. While the overall quantum yield (0.60(1)%) of YbL in acetonitrile was moderate among the reported values for Yb(III) complexes, its radiative lifetime (0.33(2) ms) was significantly shorter than those reported previously. We propose that the ligand-to-metal charge-transfer (LMCT) state mediated the sensitization in YbL. The emission and excitation spectra of EuL indicated the participation of the LMCT state in the sensitization. The radiative lifetime (0.84(7) ms) for EuL in the solid state was rather short compared to those of reported Eu(III) complexes. Our results show that the Yb(III) complex with the Schiff base ligand has two features: the short radiative lifetime and the non-triplet sensitization path.

Selective crystallization of dysprosium complex from neodymium/dysprosium mixture enabled by cooperation of coordination and crystallization

“…Recrystallizing the product from a mixed solvent of N , N -dimethylformamide and methanol gave DyL. The isostructurality of DyL to the previously synthesized YbL 18 was confirmed by a PXRD measurement (Fig. S1, ESI†).…”

“…This type of ligand is readily obtained by the condensation of a tripodal amine with three equivalents of salicylaldehyde derivatives. 12–18 Recently, we reported the synthesis and photophysical properties of seven-coordinated complexes (LnL, Scheme 1, Ln = europium (Eu), gadolinium (Gd), and ytterbium (Yb)). 18 During synthesis, we observed that the complexes of large Gd 3+ and Eu 3+ ions were difficult to crystallize compared to that of the small Yb 3+ ion.…”

“…12–18 Recently, we reported the synthesis and photophysical properties of seven-coordinated complexes (LnL, Scheme 1, Ln = europium (Eu), gadolinium (Gd), and ytterbium (Yb)). 18 During synthesis, we observed that the complexes of large Gd 3+ and Eu 3+ ions were difficult to crystallize compared to that of the small Yb 3+ ion. From this observation, we infer that the difference in the ionic radius between neodymium (Nd 3+ ) and dysprosium (Dy 3+ ) ions (∼0.08 Å) 19 leads to differences in their crystallizability, which is considered for Nd 3+ /Dy 3+ separation.…”

“…Seven-coordinated DyL was synthesized according to our previous reports on the one-pot synthesis of LnL, 15,18 where Schiff-base condensation and coordination occur in a single vessel. The condensation of tris(2-aminoethyl)amine (tren) with three equivalents of 5-methylsalicylaldehyde (5-MeSal) in the presence of Dy(CF 3 SO 3 ) 3 in methanol afforded precipitates.…”

S-Heptazine N-ligand based luminescent coordination materials: synthesis, structural and luminescent studies of lanthanide–cyamelurate networks

“…7), but again its τ F falls shorter than the IRF also meaning efficient energy transfer 1 Cy* → Yb 3+ . The emission peaks of the Yb 3+ ions are generally known to be placed in the near-IR region between 900 and 1100 nm, [69][70][71] which makes this ion expectedly silent in the visible region. The rate of energy transfer, k ET , was evaluated from k ET ¼ ð1=τ phos Þ À 1=τ °phos h i where τ phos and τ °phos are the phosphorescence lifetime of the energy donor (here the Cy ligand) in the presence and absence of energy transfer, respectively.…”