Single- or double-stranded helices-sustained molecular bilayer architecture

Abstract

Although pillared layered structures are well-known, helices sustained bilayer motif has not been reported to date. Two metal–organic frameworks [Zn₂(OABDC)(OH)]_n (1; OABDC = 5-oxyacetateisophthalate) and [Cd₃(OABDC)₂(bpp)₂]_n·2nH₂O (2; bpp = 1,3-bis(4-pyridyl)propane), have been synthesized on the basis of the assembly of a scorpion-shaped carboxylate and auxiliary pyridine-based ligands with d¹⁰ metal ions under hydrothermal conditions. Complex 1 demonstrates an interesting 3D MOF, which is alternately assembled by 2D metal–organic bilayers and 1D inorganic cylindrical 2₁ helices along the b axis. Complex 2 gives a novel example of 3D MOF comprised of the intra-bilayer and double-stranded helices of interlayer mutual racemization. Photoluminescence studies revealed that both complexes are potentially blue luminescent materials. The thermal stabilities of these complexes were also discussed.