Racemic and homochiral coordination polymers based on carboxylates of different lengths

Abstract

Three coordination polymers, {[Ag2(R-PHBU)(S-PHBU)(bpp)2]·H2O}n (1, racemic), {[Ag2(R-PHSU)0.5(S-PHSU)0.5(bpp)2]·2H2O}n (2, racemic), and {[Ag2(CHDA)(bpp)2]·9H2O}n (3, homochiral) (HPHBU = 2-phenylbutyric acid, H2PHSU = 2-phenylsuccinic acid, H2CHDA = 1,1-cyclohexanediacetic acid, bpp = 1,3-bis(4-pyridyl)propane), have been synthesized by solution reactions of Ag(I) with bpp and rac-PHBU−, rac-PHSU2−, or CHDA2−. Single-crystal X-ray diffraction reveals that all three complexes feature “AgAg” subunits extended by bpp ligands in two-dimensional (2-D) cation layers, which are embedded by the PHBU−, PHSU2−, or CHDA2− ligands of different lengths. Adjacent 2-D layers with pillar-shaped fillers are mutually interdigitated to 3-D H-bonded supramolecular coordination polymers with 1-D pores. As the length of the pillar-shaped fillers increases from 5.6, 6.4 to 7.3 Å, the dimensions of the pores range from 5.0 × 3.7 Å (narrow slit), 8.7 × 5.6 Å (elliptical) to 13.4 × 6.8 Å (quadrangular), and the solvent-accessible void volumes range from 3.6, 31.8 to 36.4% of the crystal volumes. The 1-D pores are filled with guest water molecules. The guest water molecules in 1 are discrete. Centrosymmetric water tapes and chiral right-handed 21 helical water tapes are observed in 2 and 3, respectively. Thermal and photoluminescent properties, as well as lead(II) adsorption, are also discussed.