EU(III)-BASED IONIC LIQUIDS:&NBSP; A THERMOCHROMIC AND SELF-ORGANIZATION CASES IN A FAMILY OF HIGHLY EMISSIVE EU(III) TETRAKIS-Β-DIKETONATE IONIC LIQUIDS WITH AN ALKYLPHOSPHONIUM AS COUNTER-ION
This work identified the first example of an observable and reversible case of thermochromism of an Eu(III) room temperature ionic liquid, [P6,6,6,14][Eu(fod)4] (1). This thermochromism is characterized by the conversion from light yellow (room temperature) to a reddish hue (ca. 80 ºC) due to an unusual interaction between one fod ligand and the phosphonium counter-ion. The reversibility of this optical effect presents applicability as an alcohol sensor adressing the “Food security, (…)” societal challenge (Backcover Picture - Chem. Commun., 2017, 53, 850-853). By changing the β-diketonate of the Eu(II) complex we extended the studies to the self-organization of the family 1, [P6,6,6,14][Eu(fod)3(dbm)] (2) and [P6,6,6,14][Eu(dbm)4] (3) highlighting the role of the cation [P6,6,6,14]+. The luminescence quantum yields determined for 1, 2, and 3 are 34%, 59%, and 64%, respectively, with the highest values being comparable with the maximum values previously reported for complexes of the same type.