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A Versatile Long‐Wavelength‐Absorbing Scaffold for Eu‐Based Responsive Probes
Author(s) -
Szíjjártó Csongor,
Pershagen Elias,
Ilchenko Nadia O.,
Borbas K. Eszter
Publication year - 2013
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201203957
Subject(s) - coumarin , cyclen , lanthanide , chemistry , luminescence , photochemistry , substituent , absorption band , excitation wavelength , aqueous solution , linker , absorption (acoustics) , excitation , absorption spectroscopy , chelation , combinatorial chemistry , wavelength , materials science , optoelectronics , organic chemistry , ion , electrical engineering , quantum mechanics , computer science , engineering , operating system , physics , optics , composite material
Abstract Coumarin‐sensitized, long‐wavelength‐absorbing luminescent Eu III ‐complexes have been synthesized and characterized. The lanthanide binding site consists of a cyclen‐based chelating framework that is attached through a short linker to a 7‐hydroxycoumarin, a 7‐B(OH) 2 ‐coumarin, a 7‐ O ‐(4‐pinacolatoboronbenzyl)‐coumarin or a 7‐ O ‐(4‐methoxybenzyl)‐coumarin. The syntheses are straightforward, use readily available building blocks, and proceed through a small number of high‐yielding steps. The sensitivity of coumarin photophysics to the 7‐substituent enables modulation of the antenna‐absorption properties, and thus the lanthanide excitation spectrum. Reactions of the boronate‐based functionalities (cages) with H 2 O 2 yielded the corresponding 7‐hydroxycoumarin species. The same species was produced with peroxynitrite in a ×10 6 –10 7 ‐fold faster reaction. Both reactions resulted in the emergence of a strong ≈407 nm excitation band, with concomitant decrease of the 366 nm band of the caged probe. In aqueous solution the methoxybenzyl caged Eu‐complex was quenched by ONOO − . We have shown that preliminary screening of simple coumarin‐based antennae through UV/Vis absorption spectroscopy is possible as the changes in absorption profile translate with good fidelity to changes in Eu III ‐excitation profile in the fully elaborated complex. Taken together, our results show that the 7‐hydroxycoumarin antenna is a viable scaffold for the construction of turn‐on and ratiometric luminescent probes.