title: A versatile long-wavelength-absorbing scaffold for Eu-based responsive probes.
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.
authors.affiliation: Department of Chemistry, BMC, Uppsala University, Box 576, 75123 Uppsala, Sweden.
authors.forename: Csongor
authors.initials: C
authors.lastname: Szíjjártó
authors.forename: Elias
authors.initials: E
authors.lastname: Pershagen
authors.forename: Nadia O
authors.initials: NO
authors.lastname: Ilchenko
authors.forename: K Eszter
authors.initials: KE
authors.lastname: Borbas
mesh_terms: D000042:Absorption; D002614:Chelating Agents / Q000737:chemistry*; D003374:Coumarins / Q000737:chemistry*; D005063:Europium / Q000737:chemistry*; D028581:Lanthanoid Series Elements / Q000737:chemistry*; D049449:Luminescence; D008163:Luminescent Measurements; D015394:Molecular Structure; D013056:Spectrophotometry, Ultraviolet; D014468:Umbelliferones / Q000737:chemistry*
chemical_list: D002614:Chelating Agents; D003374:Coumarins; D028581:Lanthanoid Series Elements; D014468:Umbelliferones; D005063:Europium; C031477:7-hydroxycoumarin; C030123:coumarin