Supramolecular Chiral Assembly,Chiral Induction And Structural Replication Of Hexabenzocoronene

Chirality is a basic characteristic of living matter and nature.It is universal and can be observed at various hierarchical levels from subatomic and molecular to supramolecular,nanoscopic,macroscopic,and galactic scales.The chirality at the supramolecular level is currently attracting great attention due to the rapid developments of supramolecular chemistry and molecular self-assembly.Meanwhile,the chirality at supramolecular level is crucial since it is strongly related to chemistry,physics,biology,materials,and nanoscience.Theπ-conjugated systems are considered as one of the promising components for constructing supramolecular materials because of their strong tendency to form one-dimensional structures viaπ-stacking interactions.Some assembledπ-conjugated systems exhibit excellent physicochemical and photoelectric properties and have been widely used in field-effect transistors（FETs）,light-emitting diodes（LEDs）,photovoltaic cells,etc.In this context,the control of the supramolecular organization ofπ-conjugated systems into chiral helices of nanoscopic dimensions is of fundamental importance,as the resulting structures could find application in the emerging area of supramolecular electronics and photonics.In this dissertation,a series of amphiphilic Gemini-shaped hexabenzocoronene derivatives were designed and synthesized,and the self-assembly behaviors of these derivatives were systematically investigated.Meanwhile,the behaviors of helicity induction,chirality memory,structural replication of the supramolecular helical nanostructures were also studied.The major contents of this dissertation are as follows:1.The synthesis and self-assembly of chiral Gemini-shaped hexabenzocoronene（HBC）derivatives with different chiral hydrophilic chain lengths and different core-substitutions.We designed and synthesized twelve chiral HBC derivatives,CHBCs（CR1-3,CS1-3）and FHBCs（FR1-3,FS1-3）.All the chiral HBC derivatives were unambiguously characterized by ¹H NMR spectra and MALDI-TOF mass spectra.The self-assembly behaviors of the HBCs were systematically investigated by scanning electron microscopy（SEM）,transmission electron microscopy（TEM）and circular dichroism（CD）spectra.CHBCs self-assembling to form a nanotubular structure under certain conditions,while FHBCs self-assembling to give non-tubular aggregates.All the ordered assemblies formed by CHBCs and FHBCs are CD-active.It showed that the chirality at the molecular level has been successfully transferred to the supramolecular level.2.The synthesis,self-assembly and host-guest properties of achiral HBC derivatives appended with crown ether groups.We designed and synthesized two achiral HBC derivatives containing crown ether groups,HBC^CE and HBC^TEG-CE.Under appropriate conditions,the newly designed HBC derivatives can self-assemble into racemic nanocoiled structures,such as THF/MeOH(for HBC^CE)and CH₂Cl₂/MeOH(for HBC^TEG-CE).However,in the presence of chiral amino acid guests,HBC^CE formed helical nanocoils with one-handed screw sense.The effects of the concentration,type and configuration of the guests on the induced circular dichroism（ICD）during the co-assembly of HBC^CE with chiral amino acids were also investigated.Additionally,after complete removal of the chiral guests,the optically active nanocoils did not racemize,even in the presence of excess amino acids with the opposite configuration.In contrast,HBC^TEG-CE with a long triethylene glycol（TEG）chain between the crown ether group and the HBC unit did not exhibit ICD during the co-assembly with chiral amino acids.3.The construction of one-dimensional metal-free coated supramolecular block copolymer nanotubes seeded by polymeric assembly.We designed and synthesized six HBC derivatives appended with pyridine groups(HBC^Py and ^FHBC^Py).Then,we systematically investigated the self-assembly behavior of these HBC derivatives,and found that HBC^OTEG-Py and ^FHBC^OTEG-PyTEG-Py with longer hydrophilic chains have good self-assembly ability.Subsequently,using the metal coordination ability of the pyridine groups and the step-by-step assembly strategy,the one-dimensional seamlessly coupled supramolecular block copolymer nanotubular structures were constructed under specific conditions,and the results showed that the second monomer molecule ^FHBC^OTEG-Py can adhere and extend at the seed nanotubes cross section through electron donor-acceptor interaction to form the supramolecular block copolymer structures.Finally,by using the reversible property of the pyridine-metal coordination,the metal ions covered by the surface of the seed nanotubes were successfully removed by the displacement reaction,and the structure of the block nanotubes remained unchanged.Thereby,the optimization and post-modification of the supramolecular assembly materials on the nanoscale are realized.4.The structural replication and chiral transfer behavior of the chiral helical supramolecular assemblies based on hexabenzocoronene.First,in order to obtain a solvent dispersible and chiral seed after self-assembling,the compound HBC^OTEG-Py was coordinated with the chiral metal ligand（R）-or（S）-（BINAP）Pt（OTf）₂.Meanwhile,the achiral second molecular graphene ^FHBC^OMeMe bears four electron-withdrawing fluorine substituents,so it can adhere electronically to the seed termini and self-assemble selectively from their nanotubular facets.Subsequently,the ^FHBC^OMeMe was added to the chiral seed nanotube dispersion for co-assemble stepwise,and the supramolecular structure replication during the co-assembly process was explored.The study revealed the chiral information from the nanotubular seed could be replicated and imprinted into the growth segment during the stepwise co-assembling process,which will provide useful layered helical assemblies as chiral materials for enantioselective separation and catalysis,and opens a new gate for the understanding and designing self-replicating smart systems.