1,10-Phenanthroline decorated with substituent groups forming europium(III) complexes: synthesis, crystal structure, photoluminescence properties and their bioimaging in living cells

Abstract

With 2-thenoyltrifluoroacetone (tta) as the first ligand and phenanthroline derivatives as the second ligand, two europium(III) complexes, Eu(tta)₃L₁ (L₁ = 11-nitrodipyrido[3,2-a:2',3'-c]phenazine) (1) and Eu(tta)₃L₂ (L₂ = 11-methoxydipyrido[3,2-a:2',3'-c]phenazine) (2), have been synthesized and their structures were characterized by NMR and single-crystal X-ray crystallography. The two complexes exhibited red emissions that belonged to ⁵D₀→⁷F_j (j = 0-4) transitions of Eu in different solutions and solid state. Complex 2 with the electron-donating group showed preferable luminous properties to that of complex 1 with the electron-withdrawing group. Moreover, complex 2 displayed much longer lifetimes, higher quantum yields and better CIE color coordinates corresponding to pure red in color (x = 0.67, y = 0.33). In addition, the two complexes had strong intracellular luminescence, which indicated that they could be employed in luminescence imaging of living cells.

GRAPHICAL ABSTRACT

Keywords:

• Rare earth complexes
• 1,10-Phenanthroline derivatives
• Photoluminescence
• Bioimaging

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The authors are grateful for financial support from the National Natural Science Foundation of China (21861017, 41867053), the key project of Natural Science Foundation of Jiangxi Province (20192ACBL20011).