期刊
DALTON TRANSACTIONS
卷 50, 期 12, 页码 4244-4254出版社
ROYAL SOC CHEMISTRY
DOI: 10.1039/d1dt00616a
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资金
- Swedish Research Council [2017-04077]
- Knut och Alice Wallenbergs Foundation [2018.0066, KAW 2019.0071]
- Swedish Research Council [2017-04077] Funding Source: Swedish Research Council
A series of luminescent lanthanide(iii) complexes with 1,4,7-triazacyclononane frameworks and three secondary amide-linked carbostyril antennae were synthesized in this study. Results showed that complexes with more electron-poor pyridines were less emissive, and cyclic voltammetry was used to determine oxidation and reduction potentials.
A series of luminescent lanthanide(iii) complexes consisting of 1,4,7-triazacyclononane frameworks and three secondary amide-linked carbostyril antennae were synthesised. The metal binding sites were augmented with two pyridylcarboxylate donors yielding octadentate ligands. The antennae carried methyl, methoxymethyl or trifluoromethyl substituents in their 4-positions, allowing for a range of excited state energies and antenna electronic properties. The H-1 NMR spectra of the Eu(iii) complexes were found to be analogous to each other. Similar results were obtained in the solid-state by single-crystal X-ray crystallography, which showed the structures to have nine-coordinate metal ions with heavily distorted tricapped trigonal prismatic geometries. Steady-state and time-resolved luminescence spectroscopy showed that the antennae could sensitize both Tb(iii) and Eu(iii), however, quantum yields were lower than in other octadentate complexes lacking pyridylcarboxylate. Complexes with more electron-poor pyridines were less emissive even when equipped with the same antenna. The oxidation and reduction potentials of the antennae and the pyridinecarboxylates, respectively, were determined by cyclic voltammetry. The obtained values were consistent with electron transfer from the excited antenna to the pyridine providing a previously unexplored quenching pathway that could efficiently compete with energy transfer to the lanthanide. These results show the crucial impact that photophysically innocent ligand binding sites can have on lanthanide luminescence.
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