Three new metal-organic frameworks based on 2-propyl-1H-imidazole-4,5-dicarboxylate: Synthesis, crystal structure and luminescent properties

Three new complexes [Cd(H2pimda)2(H2O)2]·4H2O (1), [Zn(H2pimda)2(H2O)2].3.5H2O (2) and [Cd2(Hpimda)2(DMF)2]n (3) (H3pimda = 2-propyl-1H-imidazole-4,5-dicarboxy acid, DMF = N,N′-dimethylformamide) have been synthesized under hydrothermal or solvothermal conditions, respectively. Crystal structures of complexes 1-3 were determined by single crystal X-ray diffraction. Crystallographic studies on 1 and 2 reveal that both complexes are six-coordinated, whose geometries can be best described as distorted octahedral. Complex 3 was synthesized based on that of complexes 1 and 2. We change the coordination environment of H3pimda during the synthesis process of complex 3 by using organic acid and solvent, accordingly result in different structures ranging from 0D for 1 and 2 to infinite 2D network for 3. Complexes 1-3 have blue luminescence at room temperature in the dimethylsulfoxide (DMSO) solution, which are potential blue luminescence materials. The blue luminescence of complexes 1-3 is due to π∗ → π transitions of intra-ligand.