Europium(II) complexes with unsubstituted crown ethers

In situ generation of fluorescent macrocyclic europium(II) complexes via zinc reduction

“…Starynowicz et al reported the crystal structure of bisperchlorato(18-crown-6)europium(II) by electrochemical reduction [2]. In the complex, the 18-crown-6 located in the equatorial plane and the two perchlorate anions coordinated to the Eu(II) from the opposite sides.…”

“…Typically, 18-crown-6 formed 1:1 Eu(II) complex which showed the 160-times enhanced fluorescence comparing with EuCl 2 itself [1]. Starynowicz et al [2] reduced Eu(III) complex with 18-crown-6 by electrolysis and obtained the crystal structure of its Eu(II) complex. Since the Eu(II) has large ionic radius and adopts high coordination number, its macrocyclic complexes still have available coordination sites for incoming anions and solvent molecules.…”

Diazabenzo crowns grafted on the polystyrene and application of extraction of metal cations

“…While crown ethers grafted onto a polymeric support through an azo coupling provide a good extraction yield which suggests a sandwich complex (Fig. 18) known in the literature for isolated crown ethers [33].…”

A comparative study of the structure and luminescence of mono- and dinuclear crown-ether lanthanide complexes

“…Among the most versatile coordinating systems, the macrocyclic compounds can be cited [2] and their use in the preparation of lanthanide complexes has been much exploited in view of their ability to ascribe a high thermodynamic stability to the Ln ion due to the macrocycle effect [3]. Many examples of compounds investigated in this area can be mentioned, but we choose to highlight only some, like europium complexes with 12-crown-4 [4,5] and terbium complexes with naphthalene-linked crown ethers [6]. Also, we can cite the case of the ligand benzo-15-crown-5 ether which has proven to be successfully employed as a lanthanide sensor [7].…”