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A Thermochromic Europium(III) Room Temperature Ionic Liquid With Thermally Activated Anion-Cation Interactions


In this study we reported the first example of an observable and reversibly stable case of thermochromism due to the interaction of an alkylphosphonium (P6,6,6,14)+ with a β-diketonate (1,1,1,2,2,3,3-heptafluoro-7,7-dimethyloctane-4,6-dionate - fod) of an Eu(III) room temperature ionic liquid. This thermochromism is characterized by the conversion of the light yellow [P6,6,6,14][Eu(fod)4] at room temperature, to a reddish substance around 80 °C. A thorough thermal and photophysical characterization of this compound and the analogue (P6,6,6,14)(fod) (a RTIL with an irreversible thermochromism) allowed us to propose an unusual direct interaction between one of the complex ligands and the phosphonium counter-ion (Figure below). This work is being developed by studies on the applicability of the Eu based RTIL in temperature sensing based on the Eu3+ red/orange emission ratio, and in alcohol sensing based on its yellow/red color change in the absence/presence of alcohols.

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Contact person: Bernardo Monteiro

Selected papers:

B. Monteiro, M. Ottis, H. Cruz, F. Fernandes, J. P. Leal, C. A. T. Laia, C. C. L. Pereira, Thermochromic Europium room temperature ionic liquid with thermally activated charge transfer processes; Chem. Commun., 2017, 53, 850-853. http://dx.doi.org/10.1039/c6cc08593h

J. P. Leal, M. Otis, M. H. Casimiro, L. M. Ferreira, F. Fernandes, B. Monteiro, C. A. L. Laia, C. C. L. Pereira , A case of self-organization in highly emissive Eu(III) ionic liquids; European Journal of Inorganic Chemistry, 2017, 3429-3434. http://dx.doi.org/10.1002/ejic.201700649