A journey toward 3D phenyl network : synthesis, optoelectronic properties and packing behavior of novel π-conjugated polyphenyl mult-marcocyles

Abstract

The phenyl ring represents the smallest aromatic unit. Linkages of phenyls in various fusion create numerous carbon-based nanostructures with diverse topologies, resulting in different properties. For instance, linearly linked poly(para-phenylene) can be used as a conductor in donor-acceptor (DA) type functional polymers and serve as electrical conductivity and energy storage materials. Phenyl-based macrocycles, which possess a rich electron density, are among the most intriguing hosts in supramolecular chemistry. With various synthetic methods and well-designed routes developed by numerous talented scientists, we can foresee a brighter future for phenyl-based macrocycles or cyclic networks. The properties of these macrocycles, including photo/electronic characteristics, dynamic conformation transformations, redox behaviors, and supramolecular assembly, inspire us to pursue more sophisticated and elegant nanostructures. In this thesis, we designed and obtained a series of phenyl-based 3D macrocycles with specific topologies and further explored their properties and applications. We modulated the connecting modes of benzene rings to create brand novel topologies and introduced heteroatoms to further tune the optoelectrical properties of conjugated macrocycles. By rationally designing and synthesizing these macrocycles, we aimed to understand the relationships between their structures and properties. The details are as follows: In chapter 2, we described our synthetic efforts toward the subunit of the “cubic graphite”, the covalently interlocked macrocycles [2]CIM and the model compound bismacrocycle cyclophane (M), via stepwise coupling reactions. The interlocked macrocyclic nanostructure of [2]CIM was confirmed by its single crystal. The electronic, optical properties and the solid-state packing of M and [2]CIM were well investigated. To our surprise, high quantum yield (ΦPL = 0.69) was observed with blue emission for [2]CIM. Interesting, this [2]CIM with phenyl-based 3D nanostructures demonstrated high gas uptake and selectivity, which is superior to most other small molecules. In chapter 3, we have successfully synthesized a DA-type tetra-benzothiadiazole-based 3D covalently interlocked macrocycle (BT[2]CIM) via a novel multi-fold intramolecular Suzuki reaction. This compound was comprehensively characterized and demonstrated red-shifted dual emission, higher quantum yield (ΦPL = 0.82), and longer fluorescence lifetime (τ = 8.1 ns) in comparison to its pure benzene analogue ([2]CIM). Low temperature investigation revealed a type B anti-Kasha character of BT[2]CIM. The successful synthesis of [2]CIM and BT[2]CIM provides a new approach for constructing novel 3D nanocarbons, opening up new opportunities for exploring their fascinating properties. In Chapter 4, a new type of phenyl-based 3D nanostructures with novel topologies and their corresponding polymers were designed and synthesized. Their properties were thoroughly investigated. We developed double-strand phenyl-based multi-macrocycles with a short synthetic route and an extremely high conversion rate in the final step. The formation of these polymers involves intermolecular molecular-size growth reactions and highly efficient intramolecular macrocycle formation reactions. We designed and obtained a series of linear double-strand porous macrocycles, including Monomer, Dimer, Trimer and polymer. This methodology has good functional group tolerance, moreover, the precursors with different sizes could also afford desired linear double-strand nanostructures with different porosity. Solid state packing of small oligomers and gas uptake and selectivity of functionalized polymers were well investigated.