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. 2021 Feb 26;26(5):1265.
doi: 10.3390/molecules26051265.

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

Sebastiano Di Pietro  1 , Dalila Iacopini  2 , Aldo Moscardini  3 , Ranieri Bizzarri  3   4 , Mauro Pineschi  1 , Valeria Di Bussolo  1 , Giovanni Signore  5
Affiliations

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

Sebastiano Di Pietro et al. Molecules. .

Abstract

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.

Keywords: chemical speciation; coumarin; dipicolinate; europium complex; luminescence.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Scheme 1
Scheme 1
Synthetic pathway for the synthesis of ligands HL1 and HL2 and tris complexes Na3[Eu(L1)3] and Na3[Eu(L2)3]. (i) SOCl2, DMF(cat) and then MeOH; (ii) diethylmalonate, Cs2CO3 and DMSO, 100 °C; (iii) NaOH/MeOH, HCl then MeOH reflux; (iv) salicylaldehyde or iodo-salicylaldehyde, DMSO, piperidine, 90 °C; (v) MeOH/H2O = 3/1, NaOH then HCl; (vi) H2O, NaOH pH = 7–8, EuCl3 × 6H2O, filtration, volume reduction and centrifugation.
Figure 1
Figure 1
1H-NMR (400 MHz, D2O) spectra of L1 (triethylammonium salt, red) and Na3[Eu(L1)3] (blue) with sign guide diagram (for nuclei numbering refer to Scheme 1).
Figure 2
Figure 2
1H-NMR (400 MHz, (CD3)2SO) titration of L12− (triethylammonium salt) with Eu3+ (D2O solution of chloride hexahydrate salt).
Figure 3
Figure 3
Speciation profile from the isolated contribution of I0 in the luminescence decay experiment for the Eu3+/L12− system in water with tendency lines.
Figure 4
Figure 4
Fluorescence spectra comparison (europium centered region, excitation at 360 nm) in DMSO between Eu3+/L12− in 1:2 (blue), 1:3 (red) and 1:4 (black) molar ratios.
Figure 5
Figure 5
Absorption spectra comparison in water of Na3[Eu(L1)3] and Na3[Eu(L2)3] complexes and L12− and L22− ligands (triethylammonium salts).
Figure 6
Figure 6
Luminescence (red) at 360 nm, excitation (black) and absorption (blue) of Na3[Eu(L1)3] (below) and Na3[Eu(L2)3] (above) complexes in water solution.
See this image and copyright information in PMC

References

    1. De Bettencourt-Dias A. In: Luminescence of Lanthanide Ions in Coordination Compounds and Nanomaterials. de Bettencourt-Dias A., editor. John Wiley & Sons Ltd.; Chichester, UK: 2014.
    1. Wei C., Ma L., Wei H., Liu Z., Bian Z., Huang C. Advances in luminescent lanthanide complexes and applications. Sci. China Technol. Sci. 2018;61:1265–1285. doi: 10.1007/s11431-017-9212-7. - DOI
    1. Ma Q., Wang J., Li Z., Lv X., Liang L., Yuan Q. Recent Progress in Time-Resolved Biosensing and Bioimaging Based on Lanthanide-Doped Nanoparticles. Small. 2019;15:1804969. doi: 10.1002/smll.201804969. - DOI - PubMed
    1. Ning Y., Zhu M., Zhang J.-L. Near-infrared (NIR) lanthanide molecular probes for bioimaging and biosensing. Coord. Chem. Rev. 2019;399:213028. doi: 10.1016/j.ccr.2019.213028. - DOI
    1. Heffern M.C., Matosziuk L.M., Meade T.J. Lanthanide Probes for Bioresponsive Imaging. Chem. Rev. 2014;114:4496–4539. doi: 10.1021/cr400477t. - DOI - PMC - PubMed

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