Synthesis And Physical Properties Of Large ?-Extended Cycloparaphenylene Based Carbon Nanoring Structures

As a new type of carbon material,carbon nanotubes have attracted widespread attention due to their unique physical properties.As is well known,the properties of CNTs vary with their sidewall diameters and chiralities.Thus,developing an effective method to prepare high-purity carbon nanotubes has become a research hot spot.In recent years,bottom-up organic synthesis strategy has been rising as a promising method to solve this problem.This present PhD thesis mainly focuses on constructing armchair-shaped carbon nanotube fragments with different cycloparaphenylene-based building blocks via bottom up organic synthesis strategy.We have obtained a few ?-extended carbon nanotube segments,curved segments of fullerene,and polymeric segments of armchair SWCNT.Their physical properties were well explored.These detailed studies are as follows:(1)Gram-scale quantities of two novel molecular crown compounds(TCR and HCR)have been synthesized through the bottom up organic synthesis strategy,which can strongly bind with fullerene C60 to form photoconductive heterojunctions.Further research indicates that its binding constant increases with extended?-conjugation structures.These supramolecular complexes films can serve as photoconductive layer on FTO,which generate significant photocurrents under light irradiation.Transient absorption measurements demonstrated the existence of a fast photoinduced electron transfer process between HCR or TCR(electron donor)and fullerene(electron acceptor).This study gives the insights for the fabrication of cycloparaphenylene-derived molecular/C60-based heterojunctions and their potential applications in photoelectroactive devices.(2)By Ni-catalyzed polymerization reaction,a novel ?-extended polymer(PS1)containing poly(para-phenylene)skeletons and cyclo-para-phenylene units was synthesized,which represents the first polymeric segment of armchair[8,8]SWCNT.In PS1,poly(para-phenylene)skeletons mimic linear polyphenylene along the 1D direction in CNT,while cyclo-para-phenylene units mimic the curved cyclic polyphenylene part in CNT.Further electron/hole mobilities measurements indicate that polymer PS1 is promising for applications in both electron-transport layer and hole-transport layer.The successful synthesis of the novel polymeric structure of PS1 represents an important step towards bottom-up precise synthesis of uniform carbon nanotubes,which has potential applications in devices for electron/hole transport.(3)Pentagonal building units were linked with curved hexagonal components via Suzuki coupling reaction,giving a novel conjugated molecular crown(MC3)as a fragment of fullerene C240.Further investigation of photophysical properties indicates that compared with CPP[10],the absorption and emission characteristics were significantly red-shifted,which is probably due to the ? extension.In addition,the supramolecular host-guest interaction in C60@MC3 and C70@MC3 systems were also explored.MC3 and C60@MC3 could be used as seeds or templates for bottom-up synthesis of fullerene C240 and the smallest stable carbon onion(C60@C240),respectively.(4)By palladium-catalyzed coupling reaction,two BINOL units with different chiralities were linked with curved synthons giving two ring-shaped enantiomer structures(RCR,SCR).Unlike the previously reported chiral CNT structure,whose chirality originates from the inherent asymmetric structures,these enantiomers represent the first example of armchair CNT segments with chirality originated from chiral uni.In addition,their photophysical properties were investigated by absorption and fluorescence spectroscopies.(5)A novel porous polymer(PS2)containing radially ?-conjugated carbocycles and a linear phenylene backbone has been fabricated for precise membrane separation of small nanoparticles.Due to the uniform nanocavities within this polymer,the PS2-based membrane has a distinct size cut-off(ca.2.6 nm)effect for the size-selective separation of gold nanoparticles.This polymer structure can shed light on the design and application of a new type of carbon-based separation membrane with high selectivity for ultrasmall nanoparticles.