(C3H5N2)3[Be2F7]: the first imidazolium fluoroberyllate with a non-centrosymmetric structure based on linear tetrahedral [Be2F7]3− anions

Abstract

Interaction between aqueous solutions of imidazole and H₂BeF₄ resulted in the formation of a new compound, namely, (C₃H₅N₂)₃[Be₂F₇]. The new fluoroberyllate crystallized in a hexagonal symmetry in a non-centrosymmetric group R32 (a = 9.6083(4) Å and c = 15.7796(5) Å). The structure of the new compound contained fully ordered imidazolium cations C₃H₅N₂⁺ (which is a relatively rare structural phenomenon) and the “diortho” heptafluorodiberyllate anion ([Be₂F₇]³⁻), which interacted via hydrogen bonding. The imidazolium cation formed two strong bonds with two different [Be₂F₇]³⁻ anions, which, in turn, accepted six hydrogen bonds from the six different imidazolium cations. To date, formation of the “diortho” fluoroberyllate anion is rarely reported, and the reported structure is just a second example containing organic cations. In accordance with the non-centrosymmetric character of the structure, the compound is SHG active, yet the response is relatively small.