New Derivatives Of Pyridine-2,6-Bis(Oxazoline) For The Sensitization Of Visible And Near Infrared Emitting Lanthanide Ions
Lanthanide ion luminescence can be sensitized when coordinated by a ligand or antenna to give intense and characteristic color emission. Eu(III) and Tb(III) being the most thoroughly studied due to their intense emission in the visible region of the spectrum, the near-infrared emitting ions Yb(III), Nd(III) and Er(III) are gaining interest due to applications in telecommunications and bioimaging. The syntheses of derivatives of pyridine-2,6-bis(oxazoline) and of their lanthanide ion complexes was accomplished. These complexes have potential application as probes in biology and biochemistry, as well as serving as building blocks for polymers for lighting and display applications. Two paths of derivatization were explored, which are the functionalization of the para-position of the pyridine ring and of the á-position of the oxazoline rings. It was found that derivatizing the pyridine-2,6-bis(oxazoline) ligands at the para-position affected the photophysical properties of the resulting complexes very little. Complexes of these ligands display a highly diverse solution and solid state speciation. Among the para derivatives, two water-soluble ligands were described that sensitize Eu(III) and Tb(III) as well as the near-infrared emitting lanthanide ions Yb(III), Nd(III) and Er(III) very efficiently in aqueous solutions. Derivatization of pyridine-2,6-bis(oxazoline) at the oxazoline rings resulted in ligands with different coordination ability, complexes with large ranges in solubility and interesting speciation. The efficiency of the quantum yields was also greatly affected. While moderate to good emission efficiencies were obtained in some cases and significant circularly polarized luminescence was observed in the case of a complex with an asymmetric ligand, another ligand failed to even coordinate to the metal ions.The synthesis and structural and photophysical characterization of the ligands and their lanthanide ion complexes are discussed in detail throughout the presented work.
Crystallography, Emission, Lanthanide, Luminescence, Spectroscopy
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