Synthesis and photophysical characterization of luminescent lanthanide complexes of nucleotide-functionalized cyclen- and dipicolinate-based ligands

Vithanarachchi, Sashiprabha M.; Kovács, Dániel; Borbas, K. Eszter

doi:10.1016/j.ica.2016.07.047

Cited by 9 publications

(9 citation statements)

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“…The metal centered emission for both complexes showed an almost superimposable profile for the 5 D 0 → 7 F J set of transitions, which is in line for shape and multiplicity with a C 3 symmetry europium complex [ 42 , 43 ], and almost identical to the [Eu(DPA) 3 ] 3− fluorescence spectrum: a small, but important, difference was the presence, for both L 1 and L 2 tris complexes, of the weak 580 nm emission band due to the 5 D 0 → 7 F 0 transition, which is, on the contrary, absent in D 3 symmetry for the tris dipicolinate europium complex [ 30 , 43 ]. However, the most glaring difference in emission behaviors was, as planned, the successful suppression of the residual ligand-centered fluorescence for the L 2 tris complex with respect to the dual emission for the L 1 one: it is not unusual for coumarin antennas to display their residual ligand centered fluorescence together with the metal centered one [ 18 , 20 , 23 , 24 ]. Coumarin is a performant and dynamic emitter [ 7 ] which is capable of sensitizing europium (and other lanthanides) ions through an excited triplet state, mainly thanks to the strong effect of such a heavy ion in favoring the intersystem crossing process [ 44 ].…”

Section: Resultsmentioning

confidence: 99%

“…Coumarin-based probes are known to be incredibly versatile systems with photophysical properties dynamically modulated by a large set of boundary conditions (pH, polarity, viscosity, specific analyte) [ 7 , 8 , 9 , 10 ]. However, their use as a lanthanide sensitizer has been limited to just a few examples [ 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 ]: of note, those cases where the coumarin antenna directly coordinates the lanthanide ion are usually characterized by poorly stable complexes with limited application [ 11 , 14 , 21 ], whereas in all the other examples the absence of a tight connection with the metal ion greatly hampers the efficiency of the sensitization process (i.e., low quantum yields) [ 12 , 15 , 16 , 18 , 19 , 20 , 22 , 23 , 24 ]. Moreover, coumarin-based lanthanide complexes, due to the antenna intrinsic photophysical properties, usually display contemporary emission of both the lanthanide ion and the coumarin fragment: although the dual emission is an intriguing feature considering possible applications, it is fundamental to conceive a system which can be easily modified to finely tune the emission properties.…”

Section: Introductionmentioning

confidence: 99%

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New Coumarin Dipicolinate Europium Complexes with a Rich Chemical Speciation and Tunable Luminescence

et al. 2021

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Europium (III) luminescent chelates possess intrinsic photophysical properties that are extremely useful in a wide range of applications. The lack of examples of coumarin-based lanthanide complexes is mainly due to poor photo-sensitization attempts. However, with the appeal of using such a versatile scaffold as antenna, especially in the development of responsive molecular probes, it is worth the effort to research new structural motifs. In this work, we present a series of two new tris coumarin-dipicolinate europium (III) complexes, specifically tailored to be either a mono or a dual emitter, tuning their properties with a simple chemical modification. We also encountered a rich chemical speciation in solution, studied in detail by means of paramagnetic NMR and emission spectroscopy.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

New Coumarin Dipicolinate Europium Complexes with a Rich Chemical Speciation and Tunable Luminescence

et al. 2021

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“…The syntheses of LnL1a Car and LnL1d Cou have been reported previously, except their La, Sm, Yb and Lu analogues [ 19 , 20 , 21 ]. Triamides LnL2a Car , LnL2c Car and LnL2d Cou were synthesized following analogous procedures, these are summarized in Scheme 1 .…”

Section: Resultsmentioning

confidence: 99%

Lanthanide(III) Complexes of Cyclen Triacetates and Triamides Bearing Tertiary Amide-Linked Antennae

et al. 2020

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The coordination compounds of the trivalent lanthanide ions (Ln(III)) have unique photophysical properties. Ln(III) excitation is usually performed through a light-harvesting antenna. To enable Ln(III)-based emitters to reach their full potential, an understanding of how complex structure affects sensitization and quenching processes is necessary. Here, the role of the linker between the antenna and the metal binding fragment was studied. Four macrocyclic ligands carrying coumarin 2 or 4-methoxymethylcarbostyril sensitizing antennae linked to an octadentate macrocyclic ligand binding site were synthesized. Complexation with Ln(III) (Ln = La, Sm, Eu, Gd, Tb, Yb and Lu) yielded species with overall −1, 0, or +2 and +3-charge. Paramagnetic 1H NMR spectroscopy indicated subtle differences between the coumarin- and carbostyril-carrying Eu(III) and Yb(III) complexes. Cyclic voltammetry showed that the effect of the linker on the Eu(III)/Eu(II) apparent reduction potential was dependent on the electronic properties of the N-substituent. The Eu(III), Tb(III) and Sm(III) complexes were all luminescent. Coumarin-sensitized complexes were poorly emissive; photoinduced electron transfer was not a major quenching pathway in these species. These results show that seemingly similar emitters can undergo very different photophysical processes, and highlight the crucial role the linker can play.

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“…Complexes based on dipicolinate derivatives are efficient and versatile ligands for complexing and sensitising lanthanide ions [ 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 ]. In a previous work, we showed that they can be printed on paper and combined to obtain invisible full colour images for anti-counterfeiting of valuable documents [ 9 ].…”

Section: Introductionmentioning

confidence: 99%

Colorimetry of Luminescent Lanthanide Complexes

Andrès

Chauvin

2020

Molecules

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Europium, terbium, dysprosium, and samarium are the main trivalent lanthanide ions emitting in the visible spectrum. In this work, the potential of these ions for colorimetric applications and colour reproduction was studied. The conversion of spectral data to colour coordinates was undertaken for three sets of Ln complexes composed of different ligands. We showed that Eu is the most sensitive of the visible Ln ions, regarding ligand-induced colour shifts, due to its hypersensitive transition. Further investigation on the spectral bandwidth of the emission detector, on the wavelengths’ accuracy, on the instrumental correction function, and on the use of incorrect intensity units confirm that the instrumental correction function is the most important spectrophotometric parameter to take into account in order to produce accurate colour values. Finally, we established and discussed the entire colour range (gamut) that can be generated by combining a red-emitting Eu complex with a green-emitting Tb complex and a blue fluorescent compound. The importance of choosing a proper white point is demonstrated. The potential of using different sets of complexes with different spectral fingerprints in order to obtain metameric colours suitable for anti-counterfeiting is also highlighted. This work answers many questions that could arise during a colorimetric analysis of luminescent probes.

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Synthesis and photophysical characterization of luminescent lanthanide complexes of nucleotide-functionalized cyclen- and dipicolinate-based ligands

Cited by 9 publications

References 57 publications

New Coumarin Dipicolinate Europium Complexes with a Rich Chemical Speciation and Tunable Luminescence

New Coumarin Dipicolinate Europium Complexes with a Rich Chemical Speciation and Tunable Luminescence

Lanthanide(III) Complexes of Cyclen Triacetates and Triamides Bearing Tertiary Amide-Linked Antennae

Colorimetry of Luminescent Lanthanide Complexes

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