The bromine-rich zinc bromides Zn₆Br₁₂(18-crown-6)₂×(Br₂)₅ (1), Zn₄Br₈(18-crown-6)₂×(Br₂)₃ (2), and Zn₆Br₁₂(18-crown-6)₂×(Br₂)₂ (3) are prepared by reaction of ZnBr₂, 18-crown-6, and elemental bromine in the ionic liquid [MeBu₃N][N(Tf)₂] (N(Tf)₂ = bis(trifluoromethylsulfonyl)amide). Zn₆Br₁₂(18-crown-6)₂×(Br₂)₅ (1) is formed instantaneously by the reaction. Even at room temperature, compound 1 releases bromine, which was confirmed by thermogravimetry (TG) and mass spectrometry (MS). The release of Br₂ can also be directly followed by the color and density of the title compounds. With controlled conditions (2 weeks, 25 °C, absence of excess Br₂) Zn₆Br₁₂(18-crown-6)₂×(Br₂)₅ (1) slowly releases bromine with conconcurrent generation of Zn₄Br₈(18-crown-6)₂×(Br₂)₃ (2) (in ionic liquid) and Zn₆Br₁₂(18-crown-6)₂×(Br₂)₂ (3) (in inert oil). All bromine-rich zinc bromides contain voluminous uncharged (e.g., Zn₃Br₆(18-crown-6), Zn₂Br₄(18-crown-6)) or ionic (e.g., [Zn₂Br₃(18-crown-6)]⁺, [(Zn₂Br₆)×(Br₂)₂]^2–) building units with dibromine molecules between the Zn oligomers and partially interconnecting the Zn-containing building units. Due to the structural similarity, the bromine release is possible via crystal-to-crystal transformation with retention of the crystal shape.

Publications with shared reference:

0 publications found