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

Abstract

The ionothermal synthesis of two intercalated two-dimensional zinc benzenedicarboxylates, EMIm2[Zn3(C6H4(COO)2)3Cl2] (I) and BMIm2[Zn3(C6H4(COO)2)3Cl2] (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 [Zn3(C6H4(COO)2)3Cl2]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 C, 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(C6H4(COO)2)(H2O)2is 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 n → π* transitions. © 2013 Elsevier Ltd. All rights reserved.