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.

Graphical abstract

Two racemic and one homochiral 3-D H-bonded supramolecular frameworks constructed from the mutually interdigitated 2-D motifs, showing interesting pore structures and properties, have been synthesized by the solution reactions of Ag(I) with bpp and three carboxylates of different lengths.

Keywords:

• Coordination polymer
• H-Bonded
• Carboxylate

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the NSFC [grant number 21101077], the Characteristic Innovation Foundation of Guangdong, China [grant number 2014KTSCX174], and Foundation for Distinguished Young Teachers in Higher Education of Guangdong, China [grant number Yq2013151].