Construction of two 2-D lanthanide(III)-frameworks with triple-stranded double-helical character based on ligand 4-(benzimidazol-1-ylmethyl)benzoate

Two new complexes based on 4-(benzimidazol-1-ylmethyl)benzoic acid (HL), (Sm2L6·H2O)n (1) and (LuL3)n (2), have been synthesized under the solvothermal condition and characterized by single-crystal X-ray diffraction, X-ray powder diffraction (PXRD), thermogravimetric analysis (TGA) and elemental analysis (EA) and IR spectra. The results show that both complexes are isomorphous and possess 2-D pillar-chained frameworks, consisting of 1-D triple-stranded double-helical (PPM/MMP) [Ln(η2-O)(μ2-OCO)2]n (Ln = Sm(1), Lu(2)) motif as chain and μ3-(η1:η1:η1)-bridging ligand L− as pillar, though they have different space groups of triclinic P-1 for 1 and monoclinic P21/c for 2. Two complexes represent the first example of 2-D lanthanide compound containing 4-(benzimidazol-1-ylmethyl)benzoic acid as the sole ligand. Additionally, the photoluminescent property of 1 is also discussed.