Crystal structure of a two-dimensional metal–organic framework assembled from lithium(I) and γ-cyclodextrin

Abstract

The crystal structure of the polymeric title compound, catena-poly[[[diaqualithium]-μ-γ-cyclodextrin(1−)-[aqualithium]-μ-γ-cyclodextrin(1−)] pentadecahydrate], {[Li2(C48H79O40)2(H2O)3]·15H2O} n , consists of deprotonated γ-cyclodextrin (CD) molecules assembled by lithium ions into metal–organic ribbons that are cross-linked by multiple O—H...O hydrogen bonds into sheets extending parallel to (0\overline11). Within a ribbon, one Li+ ion is coordinated by one deprotonated hydroxyl group of the first γ-CD torus and by one hydroxyl group of the second γ-CD torus as well as by two water molecules. The other Li+ ion is coordinated by one deprotonated hydroxyl and by one hydroxyl group of the second γ-CD torus, by one hydroxyl group of the first γ-CD torus as well as by one water molecule. The coordination spheres of both Li+ cations are distorted tetrahedral. The packing of the structure constitute channels along the a axis. Parts of the hydroxymethyl groups in cyclodextrin molecules as well as water molecules show two-component disorder. Electron density associated with additional disordered solvent molecules inside the cavities was removed with the SQUEEZE [Spek (2015). Acta Cryst. C71, 9–18] routine in PLATON. These solvent molecules are not considered in the given chemical formula and other crystal data. Five out of the sixteen hydroxymethyl groups and one water molecule are disordered over two sets of sites.

Current Advances in the Synthesis of CD-MOFs and Their Water Stability

“…In an effort to create a new electrode material for lithium-ion batteries, Krukle-Berzina et al [7] synthesized the first lithium-based CD-MOF three years later. The aforementioned Li-based CD-MOF consists of four oxygen atoms arranged in deformed tetrahedra to coordinate both Li + ions.…”

Cyclodextrin metal–organic frameworks and derivatives: recent developments and applications

“…Apart from the classic 3D structures described above, there are also reports on g-CD-MOFs exhibiting 2D structure or 2D layers stacked to form 3D structures. [104][105][106] For instance, one of these studies demonstrated the synthesis of a CD-MOF from polyoxometalate [P 10 Pd 15.5 O 50 ] 19À (POP) and g-CD. 104 It has an asymmetric unit cell that consists of two independent g-CDs and P 10 Pd 15.5 , of which the oxygen functions are mostly coordinated by K + ions.…”

“…On an additional note, metal–organic ribbons (MORs) containing Li + ions and deprotonated CD molecules have also been reported. 106 These MORs exhibit a sheet-like structure due to crosslinking by hydrogen bonding.…”