Electron transfer pathways in photoexcited lanthanide() complexes of picolinate ligands
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 me...
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Published in | Dalton transactions : an international journal of inorganic chemistry Vol. 5; no. 12; pp. 4244 - 4254 |
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Main Authors | , , , , |
Format | Journal Article |
Language | English |
Published |
England
Royal Society of Chemistry
28.03.2021
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Subjects | |
Online Access | Get full text |
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Summary: | 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
1
H 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.
A series of luminescent lanthanide(
iii
) complexes consisting of 1,4,7-triazacyclononane-1,4-picolinate frameworks and three secondary amidelinked carbostyril antennae were synthesised and characterised. |
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Bibliography: | 1 For ESI and crystallographic data in CIF or other electronic format see DOI 13 F NMR spectra. CCDC 10.1039/d1dt00616a 2057882 and H 19 C and Electronic supplementary information (ESI) available: Additional syntheses, photophysical, crystallographic, and electrochemical characterization 2057884-2057886 ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 1477-9226 1477-9234 1477-9234 |
DOI: | 10.1039/d1dt00616a |