Syntheses, structures and luminescent properties of zero-/two-dimensional Cd(II) and Eu(III) complexes

Three metal-organic complexes Cd(HBIDC)(phen) ₂·4H ₂O (1), [Cd(BIC)(phen)] _n (2) and {[Eu(HBIDC)(H ₂BIDC)(H ₂O)]·H ₂O} _n (3) (H ₃BIDC=benzimidazole-5,6-dicarboxylic acid, H ₂BIC= benzimidazole-6-carboxylic acid, phen=1,10-phenanthroline) have been synthesized under hydro(solvo)thermal conditions and structurally characterized by elemental analysis, IR spectrum, and single-crystal X-ray diffraction. With similar reaction conditions, reactions of the same ligand with different metal cations selected from different blocks (d-block and f-block) result in different coordination modes of carboxylate groups and final frameworks of complexes 1 and 3. The decarboxylation was observed in complex 2 and resulted in the formation of BIC ^2- ligand. Complexes 1-3 have intense fluorescent emissions at room temperature in dimethylsulfoxide (DMSO) solution and in the solid-state, which indicate they are potential fluorescence materials. The quantum yields and fluorescence lifetimes of these three complexes were systematically studied.