Determination of intramolecular energy-transfer efficiency in ytterbium chelates

Surprisingly Bright Near-Infrared Luminescence and Short Radiative Lifetimes of Ytterbium in Hetero-Binuclear Yb−Na Chelates

“…Thus, according to the crystal structure analysis, the complexes contain 6, 10, and 23 (21 for LCl − ) C−H bonds with intramolecular Yb···H distances less than 5, 6, and 7 Å, respectively. For instance, the reported quantum yields for ytterbium chelates containing C−H groups do not exceed 2.1%, − ,, while for 8-hydroxyquinolates, ,,,,, they are <1.4% …”

“…The trivalent ytterbium ion is one of the most efficient near-infrared (NIR) emitters among lanthanides, a result of the relatively large energy gap, 10 250 cm −1 , between its emitting level and the ground state. The luminescence quantum yields for anhydrous organic complexes of Yb III containing C−H bonds are reported to be in the range 0.6−2.1% − and are substantially increased upon perdeuteration , or perfluorination , of the ligands. With respect to applications, ytterbium chelates are important as emitters in NIR electroluminescence devices − and sensors in biomedical analyses, imaging, and therapy: for instance, its porphyrin complexes have been tested in the photodynamic therapy of cancer and NIR luminescence localization of tumors, , and Yb III emission has been recorded in the presence of proteins , and nucleic acids. , However, attempts to develop practical luminescent bioanalytical labels based on Yb III are hampered by the low quantum yields exhibited by its organic complexes in aqueous solutions, which remain below 0.5%. − …”

4f-ЛЮМІНЕСЦЕНЦІЯ В 3d-4f ГЕТЕРОЯДЕРНИХ КОМПЛЕКСАХ ПОРФІРИНІВ

“…4f-Luminescence is absent in all studied heteronuclear complexes of porphyrins with Cu(II). It is explained by the fact that the T1→S0 intersystem crossing in Cu-porphyrinates has a very high probability about 10 12 s -1 [19], and the probability of transitions T1→ 2 F5/2 (for Yb 3+ ) and T1→ 4 F3/2 (for Nd 3+ ) is about 10 8 s -1 -10 10 s -1 [20][21]. Thus, the process of luminescence sensitization turns out to be uncompetitive: its probability is 2-4 orders of magnitude less than the probability of the T1→S0 intersystem crossing.…”

Luminescence Features of Neodymium(III) Compounds with Various Tetrapyrrole Macrocycles

“…This is very different from the case of metallation of tetrapyrrole rings with paramagnetic lanthanide ions, where energy transfer from the excited chromophore to the lanthanide is quantitative and no residual fluorescence is obtained. [13] 4f-Luminescence is observed in almost all studied Ndcomplexes as a result of intramolecular transition of excitation energy. Low quantum yield of 4f-luminescence (φ 4f ) in case of triple-decker sandwich compound of neodymium can be explained with self-quenching in pair lanthanide-lanthanide (because of energy exchange between Nd ions), [14] since they are located very close to each other.…”