Functionalized Metallacycles:Design,Synthesis And Properties

In nature,biomacromolecules such as DNA,RNA,protein,and polysaccharide usually tend to form high-ordered nanostructures via supramolecular self-assembly.Inspired by nature,scientists have been interested in the construction of sophisticated assemblies through simple small building blocks,aiming to create artificial molecular complexes and nanomaterials that can mimic or even rival the functionality of the natural systems.Coordination-driven self-assembly has been emerging as one of the most feasible and efficient methodologies for constructing discrete supramolecular coordination complexes(SCCs)ranging from two-dimensional(2-D)polygons to three-dimensional(3-D)polyhedra with well-defined shapes and sizes,which arouses great interest of scientists.Particularly,coordination-driven self-assembly of functionalized supramolecular metallacycles has demonstrated great potential applications in the fields of diagnostic therapeutic,fluorescence imaging,molecular catalysis,and so on,which greatly promotes the development of supramolecular chemistry.This paper focuses on the new functionalized supramolecular metallacycles,including triphenylamine radical metallacycles,stable luminescent radical-based metallacycles,chiral alkynylplatinum bzimpy metallacycles and metallacycles with anion recognition function.The physicochemical properties of these novel functionalized supramolecular metallacycles are systematically studied,and their applications in hierarchical self-assembly,molecular devices,circularly polarized luminescence and recognition are preliminarily explored.This dissertation can be divided into the following main contents:Chapter one.The progress of coordination-driven self-assembly of supramolecular metal-organic complexes was comprehensively reviewed.Particularly,coordination-driven self-assembly of functionalized metallacycles via either pr-eassembly functionalization approach or post-assembly modification approach was discussed and summarized.At the end of this chapter,the objectives and significance of this thesis were then proposed.Chapter two.In this chapter,radical-induced hierarchical self-assembly of triphenylamine-based metallacycles was realized through a pre-assembly functionalization approach.In this work,three triphenylamine-based metallacycles bearing different length of alkyl chains were successfully constructed through coordination-driven self-assembly.Among them,the metallacycle with longer alkyl chains was capable to effectively produce triphenylamine radicals upon visible light irradiation,and thus resulting in the radical-induced hierarchical self-assembly in both solution and solid.Importantly,the stability of triphenylamine radical cations were significantly enhanced in these metallacycles during the hierarchical self-assembly process.Chapter three.In this chapter,a series of luminescent radical-based metallacycles were constructed by pre-assembly functionalization approach,which were employed as the luminescent materials to fabricate the electroluminescent devices.In this work,two stable luminescent radical ligands bearing benzimidazole units were designed and synthesized,subsequently three radical-based supramolecular assemblies were constructed through coordination-driven self-assembly.Interestingly,silver(I)ions significantly enhanced the electroluminescence of the corresponding radical-based metallacycles.On the contrary,platinum(II)ions significantly quenched the electroluminescence of the corresponding radical-based assemblies.It is worth noting that this work successfully demonstrated that coordination-driven self-assembly approach could affect the properties of radicals,such as their electroluminescence.Chapter four.In this chapter,chiral metallacycles were constructed by pre-assembly functionalization approach,which showed enhanced supramolecular chirality and circularly polarized luminescence compared with the corresponding chiral ligands.In this work,two supramolecular chiral metallacycles bearing chiral alkynylplatinum bzimpy were successfully constructed through coordination-driven self-assembly.In solution,the chiral ligands exhibited negligible supramolecular chirality and circularly polarized luminescence through ?-? interactions.Interestingly,coordination-driven self-assembly of the two chiral metallacycles showed a significant enhancement in supramolecular chirality and circularly polarized luminescence through Pt···Pt/?-? interactions.Therefore,the amplification of chirality and circularly polarized luminescence by Pt···Pt/?-? interactions through coordination-driven self-assembly approach was realised in this work.Chapter five.In this chapter,a series of resorcinarenes-based metallacycles with interesting anion recognition were successfully achieved by post-assembly modification approach.In this work,a new family of resorcinarenes-based metallacycles were constructed through simple ligand exchange of the corresponding resorcinarenes and their derivatives.After coordinating to the transition-metal moieties,the electron density inside the cavity of the resulatnt resorcinarenes-based metallacycles was significantly decreased,thus allowing for anion recognition via anion-? interactions.Interestingly,tetranuclear resorcin[4]arenes-based metallacycle was found to form dimers in small polar solvents such as acetone and tetrahydrofuran,which was conductive to the anions encapsulation probably because of the enhanced electronegative effect.Moreover,the anions could be released by adding some polar solvents such as methanol,ethanol and so on since the breaking of the intermolecular hydrogen bond in such process.