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The First Inert and Photostable Encapsulated Lanthanide(III) Complexes Based on Dendritic 9,10‐Diphenylanthracene Ligands: Synthesis, Strong Near‐Infrared Emission Enhancement, and Photophysical Studies
Author(s) -
Baek N. S.,
Kim Y. H.,
Roh S.G.,
Kwak B. K.,
Kim H. K.
Publication year - 2006
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.200500835
Subject(s) - anthracene , photochemistry , excited state , lanthanide , luminescence , materials science , ion , fluorescence , dendrimer , chemistry , optoelectronics , organic chemistry , atomic physics , polymer chemistry , physics , quantum mechanics
A series of inert and photostable encapsulated lanthanide(III) complexes—based on dendritic anthracene ligands—is shown for the first time to exhibit strong near‐IR emission bands via efficient energy transfer from the excited states of the peripheral antenna to the Ln 3+ ions (Er 3+ , Yb 3+ , and Nd 3+ ). A significant decrease in the fluorescence of the anthracene ligand is accompanied by a strong increase in the near‐IR emission of the Ln 3+ ions. The near‐IR emission intensities of Ln 3+ ions in the encapsulated Ln 3+ –dendrimer complexes are dramatically enhanced on increasing the generation number ( n ) of dendrons, owing to site‐isolation and light‐harvesting effects. Furthermore, a first attempt is made to distinguish between the site‐isolation and light‐harvesting effects in the present complexes. Photophysical studies indicate the sensitization of Ln 3+ luminescence by energy transfer through the excited singlet state of the anthracene ligands, and the energy‐transfer efficiency between the dendritic anthracene ligands and the Ln 3+ ion is evaluated to be in the range of 90 to 97 %. Their energy‐transfer efficiency is in good agreement with the result that the biexponential decays contain a radiative decay of anthracene units (< ca. 10 %) and an energy‐transfer component (> ca. 90 %) from the excited state of anthracene ligands to the Ln 3+ ions. Time‐resolved luminescence spectra show monoexponential decays with a lifetime of 2 μs for the Er 3+ ion 11 μs for the Yb 3+ ion and 0.7 μs for the Nd 3+ ion in thin films, and calculated intrinsic quantum yields of the Ln 3+ ions are in the range of ca. 0.025 to 0.55 %.