Helical Coordination Polymers Configured by Non-covalent Interactions: A Review

Coordination polymers (CPs), also known as metal-organic frameworks (MOFs), can be synthesized using organic bridging ligands and metal ions (or metal clusters). Structures with various architectures including one-, two- or three-dimensional polymeric networks can be formed depending on the bridging ligands, their donor atoms and coordination geometry of metal ions. In the structure of these inorganic-organic hybrid materials, there are different interactions such as coordination bonds, hydrogen bonds, π…π and CH…π interactions. These compounds are of industrial interests owing to their potential applications in the field of gas adsorption and storage, magnetism, drug delivery, heterogeneous catalysis and chemical sensors. Many published reports have made contributions to the preparation of porous coordination polymers with helical conformation using transition metals and chiral/achiral bridging ligands. Helical structural motifs have gained considerable importance because of their similarities in biological systems and useful applications. This paper presents an overview on selected examples of CPs with single-, double- and multi-stranded helical chains and discusses various factors that influence their constructions such as non-covalent interactions, ligand structure and counter ions. The connectivity between chirality of the building blocks and helicity of chains is also explained. Furthermore, the properties of helical CPs and some of their possible applications are explained in this article.