ErIII-Cored Complexes Based on Dendritic PtII–Porphyrin Ligands: Synthesis, Near-IR Emission Enhancement, and Photophysical Studies

Autor: Hwan Kyu Kim, Yong Hee Kim, Min Soo Kang, Min-Kook Nah, Joe-Won Ka, Jae Buem Oh
Rok vydání: 2007
Předmět:
Zdroj: Advanced Functional Materials. 17:413-424
ISSN: 1616-3028
1616-301X
DOI: 10.1002/adfm.200600451
Popis: A series of stable and inert complexes with Er ΙΙΙ cores and dendritic Pt"-porphyrin ligands exhibit strong near-IR (NIR) emission bands via highly efficient energy transfer from the excited triplet state of the Pt ΙΙ -porphyrin ligand to Er 3+ ions. The NIR emission intensity of thin films of Er III complexes at 1530 nm, originating from 4f-4f electronic transitions from the first excited state ( 4 I 13/2 ) to the ground state ( 4 I 15 /2) of the Er 3+ ion, is dramatically enhanced upon increasing the generation number (n) of the aryl ether dendrons because of site-isolation and light-harvesting (LH) effects. Attempts are made to distinguish the site-isolation effect from the LH effect in these complexes. Surprisingly, the site-isolation effect is dominant over the LH effect in the Er 3+ -[Gn-PtP] 3 (terpy) (terpy: 2,2':6',2"-terpyridine) series of complexes, even though the present dendrimer systems with Er III cores have a proper cascade-type energy gradient. This might be due to the low quantum yield of the aryl ether dendrons. Thus, the NIR emission intensity of Er 3+ -[G3-PtP] 3 (terpy) is 30 times stronger than that of Er 3+ -[G1-PtP] 3 (terpy). The energy transfer efficiency between the Pt"-porphyrin moiety in the dendritic Pt II -porphyrin ligands and the Ln 3+ ion increases with increasing generation number of the dendrons from 12-43 %. The time-resolved luminescence spectra in the NIR region show monoexponential decays with a luminescence lifetime of 0.98 μs for Er 3+ -[G1-PtP] 3 (terpy), 1.64 μs for Er 3+ -[G2-PtP] 3 (terpy), and 6.85 μs for Er 3+ -[G3-PtP] 3 (terpy) in thin films of these complexes. All the Er III -cored dendrimer complexes exhibit excellent thermal stability and photostability, and possess good solubility in common organic solvents.
Databáze: OpenAIRE
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