Syntheses and Structures of Four Pairs of Coordination Polymers Based on 2,2′-((5-(Methoxycarbonyl)-1,3-phenylene)bis(oxy))dipropanoic Acid

Hydrothermal reactions of rare earth (Nd, Sm, Eu, and Tb) and l- or d-lactic acid are used to construct four pairs of homochiral metal–organic frameworks (HMOFs) with polymetallic building blocks, namely, {[Nd<sub>2</sub>(L)<sub>2</sub>(H<sub>2</sub>O)<sub>3</sub>]·4H<sub>2</sub>O}<sub><i>n</i></sub> (<b>1-r</b>)/(<b>1-s</b>) and {[Ln<sub>2</sub>(L)<sub>2</sub>(H<sub>2</sub>O)<sub>2</sub>]·4H<sub>2</sub>O}<sub><i>n</i></sub> {Ln = Sm (<b>2</b>), Eu (<b>3</b>), Tb (<b>4</b>)} (<b><i>n</i>-r</b>)/(<b><i>n</i>-s</b>). The eight complexes were characterized by single-crystal X-ray diffraction, infrared spectra, elemental analysis, thermogravimetric analysis, electronic circular dichroism (ECD) spectra, and powder X-ray diffraction measurements. The complexes <b>1</b>–<b>4</b> featuring a 3D porous metal–organic framework crystallize in chiral space groups, and their chirality is proven by the solid-state ECD spectra. Moreover, the second-harmonic generation (SHG) investigation reveals that the complexes <b>1-r</b>, <b>2-r, 3-r</b>, and <b>4-r</b> have medium SHG eficiencies. The complexes <b>2</b>, <b>3</b>, and <b>4</b> exhibit relatively high luminescence properties, which could be ascribed to ligand-centered emission. The luminescence of complex <b>4-r</b> could be quenched by nitrobenzaldehyde, which may be used for molecular sensing and recognition.