New cadmium(II) halides modified by N-heterocyclic molecules

Under the solvothermal condition, the reaction of CdI₂, bpp and KI at pH = 8 afforded compound CdI₂(bpp)] (bpp = 1,2-bis(4-pyridyl)propane) 1, while at the ambient conditions, the reactions of CdX₂, dabco and KX at pH = 4–5 produced compounds H₂(dabco)]CdBr₄]·H₂O (dabco = 1,4-diazabicyclo2,2,2]octane) 2 and (Hdabco)CdI₃] 3. X-ray single-crystal diffraction analysis reveals that (i) compound 1 possesses a one-dimensional (1-D) zigzag chain structure. The large volume bpp molecule controls the Cd²⁺ ion to adopt a tetrahedral geometric configuration; (ii) both compounds 2 and 3 are mononuclear. Interestingly, in the same pH environments, dabco was in situ diprotonated in compound 2, while dabco was in situ monoprotonated in compound 3. The templating effect as well as the X⁻ ion maybe plays a key role in the protonated degree for dabco in an acidic environment. The photoluminescence analysis indicates that compound 1 emits the strong green light, which should be attributed to a combination of two types of charge transfers: the charge transfer between Cd²⁺ and I⁻; the charge transfer between Cd²⁺ and bpp.