Three new coordination frameworks based on 2-ethyl-imidazole-4,5-dicarboxylate and 1,10-phenanthroline: syntheses, crystal structures, and luminescence

Three new coordination polymers based on 2-ethyl-imidazole-4,5-dicarboxylate with 1,10-phenanthroline as ligands, Pb(HEIDC)(phen)(2) (1), [Zn(EIDC)(phen)](n) (2), and {[Ba(H2EIDC)(2)(phen)]center dot(phen)(2)center dot[Ba(H2EIDC)(HEIDC)(phen)]}(n) (3) (H3EIDC=2-ethyl-1-Himidazole-4,5-dicarboxylate; phen=1,10-phenanthroline), have been synthesized under hydrothermal conditions and characterized by elemental analysis, infrared spectroscopy, thermogravimetric analysis, and single-crystal X-ray diffraction. Complex 1 displays a tetranuclear square constructed of four Pb(II) centers, four HEIDC, and eight phen, resulting in a 3-D network with a 1-D open channel along the c-axis via C-H center dot center dot center dot O hydrogen bonds, C-H center dot center dot center dot pi, and pi-pi stacking interactions. Complex 2 is an infinite zigzag chain resulting in the final 3-D supramolecular framework via C-H center dot center dot center dot O and pi-pi stacking interactions. Complex 3 is composed of two individual Ba chains, exhibiting a 3-D framework via O-H center dot center dot center dot O, O-H center dot center dot center dot N hydrogen bonds, and pi-pi stacking interactions. The photoluminescence spectra of 1 and 2 in the solid state have been investigated, 1 exhibits green photoluminescence in the solid state at room temperature.