Study on the Luminescence and Coordination Behavior of Semi-rigid Dual-Benzimidazole Ligands and Complexes

摘要

In this work, two novel semi-rigid bisbenzimidazole ligands with different substituents (L-1,2-H; L-2,2H-methyl; L-3, 2H-ethyl; L-4, 2H-isopropyl; L-5, 2H-tertbutyl, which L-1-L-3 have been reported,(19,20)to compare the effects of different substituents on properties, herein, we re-synthesize them) and two coordination compounds are synthesized. Single crystal structure X-ray diffraction data suggests that the ligand(L-1) exhibits boat-like configuration in the crystal lattice which makes the compound 1 crystallizes in the polar space group (C2), otherwise, chair-like structure of ligands (L-2-L-4) makes compound 2-4 grow in centrosymmetric space group (C2/c). Interestingly, polar compound 1 demonstrates typical ferroelectric behavior with remnant electric polarization (Pr) of 0.308 mu C/cm(2) and an electric coercive field (Ec) of 20 kV/cm. In addition, the fluorescence of the compounds 1-4 all are in the blue-violet light region under the combined action of metal ions and organic ligands. Notably, L-5 emits bright charming orange light at 365 nm UV light, and we also verified the reason and possibility of luminescence through density functional theory (DFT) calculations. Besides, the photoluminescence quantum yield (PLQY) of the L-5 is up to 24.6 and fluorescence lifetime is 3.29 ns. In short, this work might provide strategy to construct metal organic frameworks (MOFs) with ferroelectric and photoluminescent properties.