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

Three new complexes [Cd(H ₂pimda) ₂(H ₂O) ₂]·4H ₂O (1), [Zn(H ₂pimda) ₂(H ₂O) ₂]·3.5H ₂O (2) and [Cd ₂(Hpimda) ₂(DMF) ₂] _n (3) (H ₃pimda = 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 octahedron. Complex 3 was synthesized based on that of complexes 1 and 2. We change the coordination environment of H ₃pimda during the synthesis process of complex 3 using organic acid and organic solvent, accordingly, result in different structures ranging from 0D molecule (for 1 and 2) to infinite 2D network (for 3). Complexes 1-3 have blue fluorescent emissions at room temperature in the dimethylsulfoxide (DMSO) solution, which indicate they are potential blue luminescence materials. The blue fluorescent emissions of complexes 1-3 are due to the π → π transitions of intra-ligand.