Europium compounds
[2] Many europium compounds fluoresce under ultraviolet light due to the excitation of electrons to higher energy levels.
It has a rock-salt structure, is a deep red solid, and is ferromagnetic at 77 K. It has the potential to become a magnetic refrigeration material (ΔSmag=−143 mg/cm3 K，50 kOe).
They can generally be prepared by reacting europium with selenium or tellurium in a vacuum ampoule at a high temperature.
It is a solid of the triclinic crystal system, with the space group P3m1, and its optical band gap is 4.4 eV.
[31] Of the dihalides, EuF2 and EuI2 are yellow, and EuCl2 and EuBr2 are white, although when irradiated by ultraviolet lite, EuCl2 has a bright blue fluorescence.
Europium(III) nitride shows Van Vleck paramagnetism[33] and crystallises in the rock salt structure.
It crystallizes in the distorted Na2O2 structure, similar to nickel arsenide, and is produced from reacting europium and arsenic at 600 °C.
[47] The complex of cyclononatetraene and europium(II) can be prepared by a similar method, and its toluene solution emits blue-green fluorescence at 516 nm, compared with other organic europium(II) sandwich complexes (about 630 nm) with a clear blue shift.
It is heated and decomposed to generate europium(III) oxide and carbon dioxide.
[63] Europium(III) acetate is a pale pink solid that can crystallize from an aqueous solution as the tetrahydrate, which is dried with sulfuric acid to give the trihydrate.
For example, europium(III) oxide can be used in picture tube televisions[67] and europium-doped yttrium oxysulfide (Y2O2S:Eu3+) can be used as phosphors.
[70] The synthesis of europium(II) oxide, as well as its europium(II) sulfide, because of their potential as laser window materials, insulating ferromagnets, ferromagnetic semiconductors, and magnetoresistant, optomagnetic, and luminescent materials.
[71][72] Europium(II) sulfide was used in an experiment providing evidence of Majorana fermions relevant to quantum computing and the production of qubits.
[73] Eu(OCC(CH3)3CHCOC3F7)3 (abbreviated Eu(fod)3, where the fod ligand is the anion of the commercially available 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedione) serves as a Lewis acid catalyst in organic synthesis including stereoselective Diels-Alder and aldol addition reactions.
For example, Eu(fod)3 catalyzes the cyclocondensations of substituted dienes with aromatic and aliphatic aldehydes to yield dihydropyrans, with high selectivity for the endo product.
