| Abstrakt: |
By reaction of 3,3',5,5'-biphenyltetracarboxylic acid (H4BPTC) with various lanthanide ions, seven novel three dimensional (3D) lanthanide metal-organic frameworks (MOFs) have been prepared under solvothermal conditions, namely, [Ln3(BPTC)3(H2O)2]·3H3O·4H2O·3DMF (DMF = N,N-dimethylformamide, Ln = Eu (1), Tb (2), Sm (3) Dy (4)), [Nd(BPTC)(H2O)2]·H3O·DMF (5), [Er2(BPTC)(HCOO)3(H2O)2]·(CH3)2NH2 (6), and [Tm12(BPTC)8(HCOO)11(H2O)10]·10DMF·7(CH3)2NH2 (7). Combining different lanthanide ions and diversity of coordination modes of the H4BPTC ligand, the seven compounds display interesting structural characteristics. Of these, compounds 1-4 are isostructural and demonstrate a unique 3D coordination framework containing two types of 1D channel, that is built by the novel trinuclear [Ln3O22] SBUs. Compound 5 can be described as a new 3D open-framework structure with quadrilateral-shaped 1D channels based on [Nd2O16] SBUs. Compound 6 has a new 3D pillar network feature constructed by trapezoidal chains linked by bridging BPTCp4- ligands, whilst compound 7 exhibits a 3D network with a number of rare oval-shaped channels along the [101] direction. The H4BPTC ligand exhibits five new coordination modes, which are firstly reported in M-BPTC frameworks. Compounds 1-7 all display their typical emission bands upon irradiation at the ligand band at room temperature. Compounds 1-4 present strong characteristic emissions in the visible region, of which compounds 1 and 2 show millisecond luminescence lifetimes. The NIR photoluminescent of lanthanide MOFs is less well observed, especially for the Tm(III) compounds. Owing to the good sensitization of the H4BPTC ligand, compounds 5-7 display near-infrared region (NIR) emission with microsecond luminescence lifetimes. In addition, compounds 2, 5, 6 and 7 exhibit global antiferromagnetic behaviors, of which compound 5 shows a weak ferromagnetic coupling at 235 K. [ABSTRACT FROM AUTHOR] |
