Polyanionic Polydentate Europium Complexes as Ultrabright One- or Two-photon Bioprobes

Area of Science:

• Coordination Chemistry
• Photophysics
• Bio-imaging

Background:

• Lanthanide complexes are crucial for bio-imaging due to their unique photophysical properties.
• Developing bright and stable lanthanide probes for aqueous environments remains a challenge.

Purpose of the Study:

• To synthesize and characterize novel europium (III) complexes with polydentate ligands and charge-transfer antennae.
• To investigate the photophysical properties, including one- and two-photon luminescence, of these complexes in aqueous media.
• To evaluate their potential as bioprobes for bio-imaging.

Main Methods:

• Synthesis of europium (III) complexes featuring polydentate ligands with charge-transfer antennae.
• Detailed photophysical characterization, including emission spectroscopy and lifetime measurements.
• Symmetry analysis using experimental data and theoretical simulations.
• Evaluation of luminescence brightness and suitability for bio-imaging.

Main Results:

• The synthesized europium (III) complexes display remarkable one- and two-photon photophysical properties in water and buffer solutions.
• Ligand coordination around the europium (III) ion results in Cs symmetry, confirmed by theoretical simulations.
• A significant portion (65-70%) of emission intensity is localized in the hypersensitive 5D0 → 7F2 transition at 615 nm.
• The complexes exhibit excellent brightness, comparable to leading lanthanide bioprobes.

Conclusions:

• The novel europium (III) complexes demonstrate superior photophysical performance in aqueous environments.
• Their structural and luminescent properties make them highly promising for advanced bio-imaging applications.
• These findings contribute to the development of next-generation lanthanide-based bio-imaging agents.