Due to the exceptional optical and electronic properties of the lanthanide (Ln) metals, a recent resurgence has been seen in fundamental research of this class of valuable elements. Design of coordination complexes to take full advantage particularly of the unique Ln photophysical properties has been examined in efforts to develop advanced emissive materials (e.g., display screens and bioassay agents). Luminescent lanthanide complexes, most notably those of Eu(III) or Tb(III), have been proposed as sensors of biologically relevant anions. Utilizing a Ln complex in aqueous solution to detect various anions can be accomplished as luminescence spectral changes are monitored upon addition of potentially binding anion. Using this approach, emission intensity tends to increase as anions bind the Ln ion due to displacement of metal-bound water molecules that effectively quench luminescence. In this study, a tripodal TREN-capped imine/pyridine ligand (TRIPy) and its Ln complexes were prepared and studied with regard to basic luminescence properties as well as anion sensor potential. As part of our investigations into the energy transfer between ligand and Ln emitting states, the triplet state of the ligand was determined by analysis of the low temperature phosphorescence spectrum of the Gd-TRIPy complex. Further studies included the measurement of luminescence decay lifetimes of the Eu(III) analog as well as relaxometric characterization of the Gd(III) derivative to gain additional insight into solution structure. This multifaceted investigation into the solution behavior and coordination chemistry will be presented, along with an assessment of the Eu-TRIPy complex as a luminescent anion sensor.

Lanthanide luminescence and anion binding properties of tripodal iminopyridine complexes

255th National Meeting (2018)

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