Europium(III) perchlorate is an inorganic compound of europium in the +3 oxidation state and the perchlorate ion, with the formula Eu(ClO4)3. It is known in anhydrous form and as hydrated salts, including the hexahydrate. Anhydrous europium(III) perchlorate crystallizes in the hexagonal structure characteristic of many rare-earth perchlorates.
Preparation Hydrated europium(III) perchlorate can be prepared by dissolving europium(III) oxide in aqueous perchloric acid:
Eu2O3 + 6 HClO4 → 2 Eu(ClO4)3 + 3 H2O
Single crystals of anhydrous Eu(ClO4)3 have been obtained by slow dehydration of a hydrated product prepared from Eu2O3 and perchloric acid.
Properties Anhydrous structure Anhydrous Eu(ClO4)3 crystallizes in the hexagonal crystal system, space group P63/m (No. 176), with lattice parameters a = 9.2496(9) Å and c = 5.7486(8) Å, and two formula units per unit cell. The structure consists of tricapped trigonal EuO9 prisms linked by perchlorate tetrahedra. Each Eu3+ ion is nine-coordinate. One oxygen atom of each perchlorate group does not coordinate to europium and points toward empty channels running parallel to the direction. Powder diffraction refinements place Eu(ClO4)3 within the isostructural hexagonal lanthanide-perchlorate series extending from La through the low-temperature form of Tm.
Hydrates and aqueous solution A hexahydrate, Eu(ClO4)3·6H2O, is a commonly reported hydrated form. In dilute aqueous solution, Eu3+ is strongly hydrated. Raman spectroscopy places europium near the crossover between nona-aqua and octaaqua rare-earth hydration, with the Eu–O symmetric stretching band observed near 367 cm−1. Perchlorate behaves mainly as a weakly coordinating counterion in dilute solution, while ion pairing becomes increasingly important at higher concentrations.
Coordination chemistry Europium(III) perchlorate is used as a soluble source of Eu3+ in coordination and luminescence chemistry, particularly where a weakly coordinating counterion is desirable. Complexes of europium perchlorate with sulfoxide ligands have been studied by fluorescence spectroscopy.
Safety Europium(III) perchlorate is an oxidizing perchlorate salt and should be kept away from combustible and strongly reducing materials.
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