Two-dimensional anionic zinc benzenedicarboxylates: Ionothermal syntheses, structures, properties and structural transformation

摘要

The ionothermal synthesis of two intercalated two-dimensional zinc benzenedicarboxylates, EMIm_2[Zn_3(C_6H_4(COO)_2)_3Cl_2] (I) and BMIm_2[Zn_3(C_6H_4(COO)_2)_3Cl_2] (II), employing the ionic liquids 1-ethyl-3- methylimidazolium chloride (EMIm-Cl) and 1-butyl-3-methylimidazolium chloride (BMIm-Cl) as solvents, is reported. Detailed characterization by X-ray diffraction, elemental analyses, vibrational and optical spectroscopies, and thermogravimetric analysis is described. The two compounds display an anionic two-dimensional structure with the composition [Zn_3(C_6H_4(COO)_2)_3Cl_2]~(2-) which is intercalated and charge neutralized by the imidazolium cations. The compounds are remarkably stable: neither begins to lose mass until they are heated above 300 ℃, above which temperature ZnO is obtained. The structural transformation of the anionic layered compounds I and II to a neutral one-dimensional structure with the composition Zn(C_6H_4(COO)_2)(H_2O)_2 is described. The derived neutral compound shows better thermal robustness. Both the parent and the transformed structures display blue luminescence, arising from ligand centered π→π* and π→p* transitions.