Chlorides

Uniform inorganic nanocrystals have aroused wide interests during the last 2 decades because of their shape and size dependent properties and self-assembly potential in devices and bioassays. One of the most important categories is lanthanide compound nanocrystals. An increasing interest in the chemistry of lanthanides has been noticed during the last two decades. Europium seems to be the most “popular” among them due to the »anomalous« hydration of Eu³⁺, luminescent, and catalytic properties of its complexes, stability of 2+ oxidation state, etc.

The common binary Europium (Eu^II) compounds, europium dihalides EuX2 (X = F, Cl, Br, I), have been studied since the 1930s. Interesting magnetic properties are found consistently for EuX2 (X = Cl, Br, I), and tunable luminescence around 400-500 nm is also observed for europium dihalides, which originates from the d-f transition of Eu2+ sensitive to the environment.

Europium (II) chloride is a white to pale pink solid. It has an orthorhombic crystal structure of the lead (II) chloride type with the space group Pbnm (space group No. 62, position 3) . The high-temperature modification has a cubic crystal structure with the space group Fm 3 (No. 202). Europium (II) chloride is a stable material. It is very hygroscopic in nature and absorb moisture from the air. Europium (II) chloride is incompatible with strong oxidizing agents.

Europium (II) chloride can be prepared by reduction of europium (III) chloride with hydrogen . The dihydrate can be obtained by reduction of europium (III) compounds (eg europium (III) oxide ) in hydrochloric acid solution with zinc and subsequent reaction with concentrated hydrochloric acid.

The dihydrate of Europium Chloride (II) is a white, slightly bluish, daylight, flaky crystallizing solid. It is very sensitive to oxidation and air and has a monoclinic crystal structure isotypic with that of strontium (II) chloride dihydrate and the space group C 2 /c (# 15) (a = 1167.8 pm , b = 641.3 pm, c = 670.5 pm, β = 105.3 °)