Highly crystalline metal ions containing organic polymers are potentially useful to manipulate the magnetic and optical properties to make advanced multifunctional materials. However, it is challenging to synthesise monocrystalline metal complexes of organic polymers and single-phase hybrid materials made up of both coordination and organic polymers by traditional solution crystallisation. This requires an entirely different approach in the solid-state by thermal or photo polymerisation of the ligands. Among the photochemical methods available, [2+2] cycloaddition reaction has been recently employed to generate cyclobutane based coordination polymers from the metal complexes. Cyclobutane polymers have also been integrated into coordination polymers in this way. Recent advancements in the construction of polymeric chains of cyclobutane rings through photo-dimerisation reaction in the monocrystalline solids containing metal complexes, coordination polymers and metal-organic framework structures are discussed here.

In this tutorial review the use of macrocyclic complexes as building blocks in a selection of supramolecular systems is discussed with emphasis on the properties, such as enhanced stabilities, that cyclic ligands and their complexes may impart on the resulting assemblies. An aim of the review is to exemplify the versatility of macrocyclic ligand complexes for use as components in a range of both discrete and polymeric systems. The use of macrocyclic systems for controlling CuI aggregation, as scaffolds for metal-cluster formation, as the cyclic components in interlocked catenane and rotaxane structures, for constructing assemblies based on macrocycle exo-coordination, for forming columnar stacks, as well as their roles as both structural and redox centres in a range of coordination polymer types are all presented.

Organic polymers are usually amorphous or possess very low crystallinity. The metal complexes of organic polymeric ligands are also difficult to crystallize by traditional methods because of their poor solubilities and their 3D structures can not be determined by single-crystal X-ray crystallography owing to a lack of single crystals. Herein, we report the crystal structure of a 1D Zn(II) coordination polymer fused with an organic polymer ligand made in situ by a [2+2] cycloaddition reaction of a six-fold interpenetrated metal-organic framework. It is also shown that this organic polymer ligand can be depolymerized in a single-crystal-to-single-crystal (SCSC) fashion by heating. This strategy could potentially be extended to make a range of monocrystalline metal organopolymeric complexes and metal-organic organopolymeric hybrid materials. Such monocrystalline metal complexes of organic polymers have hitherto been inaccessible for materials researchers.

Distortional isomers, or bond-stretch isomers, differ only in the length of one or more bonds, which is due to crystallographic disorder in most cases. The term distortional isomerism is introduced to describe the structures of polyrotaxane 2D coordination polymers (CPs) that differ only by the relative positions in the neighboring entangled axles. A large ring and a long spacer ligand in 2D CPs yielded four different supramolecular isomers, of which two have an entangled polyrotaxane structure. One pair of C=C bonds in the spacer ligand is well-aligned in one isomer and undergoes [2+2] cycloaddition reaction, whereas the other isomer is photoinert. They also have different sensing efficiency for several aromatic nitro compounds. However, both isomers show selective PL quenching for the Brady's reagent. Structurally similar supramolecular isomers with different photochemical reactivity and sensing abilities appear to be unprecedented.