Lanthanide complexes (Eu3+, Gd3+ and Tb3+) with the ligand dipicCbz were synthesized and characterized using mass spectrometry and photoluminescence. All the complexes showed emission lifetimes close to 1 ms and quantum yields of 1.8% for Eu and 3.7% for Tb complexes in a TRIS/HCl (pH ~7.4) buffered water:DMSO (25:1 (v/v)) solution. The excitation spectra of the Eu(III) and Tb(III) complexes show a bathochromic shift, when compared with the Cs3[Eu(dpa)3] (dpa = dipicolinic acid), due to the presence of the carbazole unit. The emission intensity of the 5D4 → 7F5 transition of the Tb(III) complex is temperature-dependent in the range 5 – 70 °C. The thermal sensitivity at 35 °C is 1.4x10-2 °C-1. A graph of ln(Intensity) as a function of 1/T showed two different slopes, indicating different deactivation mechanisms. At low temperatures, the quenching mechanism happens through CT states deactivation while, at high temperatures, it is through triplet level deactivation. The Tb(III) complex showed full reversibility after 3 cycles of heating to 70 °C and cooling to 5 °C. The solubility of the compounds in water:DMSO, the bathochromic shift of the excitation spectra and the temperature-dependent emission intensity make these compounds interesting for use as luminescent markers in biological systems and also as temperature probes. Acknowledgments: Fapesp, CNPq, Capes.

Lanthanide complexes as potential luminescent markers and temperature probes

251st National Meeting (2016)

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