Cd(II) enantiomers embedding helices from 3D frameworks to 2D layers controlled by shapes of ancillary ligands

Abstract

Two pairs of chiral coordination polymers, [Cd₂((R)-CBA)₂(1,4-BMIB)]_n (1-R), [Cd₂((R)-CBA)₂(1,4-BMIB)]_n (1-S), {[Cd((R)-CBA)(1,3-BMIB)]·H₂O}_n (2-R), and {[Cd((R)-CBA)(1,3-BMIB)]·H₂O}_n (2-S) (H₂CBA = 4-(1-carboxyethoxy) benzoic acid, 1,4-BMIB = 1,4-bis(2-methyl-1H-imidazol-1-yl)benzene, 1,3-BMIB = 1,3-bis(2-methyl-1H-imidazol-1-yl)benzene), were constructed from lactate derivatives H₂CBA and imidazole ancillary ligands under hydrothermal conditions. These complexes show different structures depending on shapes of ancillary ligands. For the linear 1,4-BMIB, complexes 1-R and 1-S are three dimensional (3D) frameworks with dinuclear clusters of Cd(II). For the V-shaped 1,3-BMIB, complexes 2-R and 2-S are two dimensional (2D) layers, where 4-connected Cd(II) centers were isolated by imidazole groups and carboxylic groups from 1,3-BMIB and H₂CBA, respectively. The resulting complexes were characterized by PXRD, TGA, UV-visible absorptions and CD measurements. Additionally, 1 and 2 exhibit different photoluminescence behavior in the solid state compared to free H₂CBA.

Graphical Abstract

Keywords:

• Chiral coordination polymer
• helical structure
• effect of ancillary ligand
• 3D framework
• 2D layer

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The work was supported by the National Nature Science Foundation of China (Grant No. 21761036) and the Science and Technology of Guizhou Province (Grant No. 20181181).