Design,Synthesis,and Physical Properties Of π-extended Curved Carbon Nanorings

Carbon nanomaterials have always been a research hotspot in the field of materials chemistry owing to their unique structures and excellent properties.With the development of synthetic techniques,remarkable achievements have been made in the precise synthesis of curved π-conjugated carbon nanomaterials by bottom-up organic synthesis methods.Furthermore,investigating the physical properties of various carbon nanomaterials have been realized.Cycloparaphenylenes(CPPs),considered as the smallest unit of armchair carbon nanotubes,are expected to be used as template molecules to control the growth of single-walled carbon nanotubes(SWCNTs).A variety of methods for the synthesis of CPPs and their derivatives have been reported.In recent years,in order to realize the synthesis of curved molecules with large conjugation,it is highly desired to explore novel conjugated and π-extended curved molecular structures.Owing to the radially oriented πsystems originated from the distortion of the aromatic plane,the curved π-conjugated carbon nanomaterials have interesting physical and chemical properties.Up to now,many new curved π-conjugated carbon nanomaterials have been synthesized.At present,it is still a challenge to design and synthesize π-extended carbon nanoring structures as potential carbon nanotube segment templates and explore their unique properties.In this thesis,I synthesized a series of curved π-extended carbon nanoring systems,and studied their physical properties The details are as follows:1.A novel one-dimensional π-extended curved polymeric segment of SWCNTs(SPh)was synthesized using a small carbon nanoring molecule precursor with ten phenyl groups and two reactive sites.Applying SPh as the supramolecular host and fullerene C60 as the guest,a supramolecular polymer heterojunction(SPh?DC60)was successfully constructed.Steady-state spectra showed that there was a strong supramolecular interaction between SPh and C60.The results of ultrafast transient spectra revealed femtosecond(<<300 fs)electron transfer from photoexcited SPh to C60,followed by nanosecond charge recombination to produce the C60 triplet excited state.In addition,we investigated the potential applications of SPh?C60 as the electron-and hole-transport layers for optoelectronic devices.These results expand the synthesis and potential applications of one-dimensional structures of carbon nanorings.2.A novel curved π-conjugated polymer(poly(cyclo-para-phenylene),PCPP)was successfully synthesized by Yamamoto coupling reaction,which contains only repeated carbon nanorings.The precursor before polymerization contains only eight phenyl groups and the reactive sites of dihalogen are located on the carbon nanoring.The all-carbon long-chain structure of PCPP was fully characterized by High-resolution mass spectrometry(HR-MS)combined with X-ray photoelectron spectroscopy(XPS),Fourier transform infrared(FTIR),and Raman spectroscopy.At the same time,we explored the application of this carbon-rich curved material as an anode material for lithium-ion batteries(LIBs).At a current density of 100 mA g-1,PCPP exhibited the maximum capacity was 557 mAh g-1(better than commercial graphite materials),which fully demonstrates the excellent electrochemical performance of this curved π-conjugated polymer and their potential application in the field of LIBs.3.We report a facile synthesis of a conjugated macrocyclic nanoring([9]CPPH2,11)with graphenic hexabenzocoronene sidewall by the Suzuki-Miyaura cross-coupling reaction.The nanographene-embedded π-extended carbon nanorings possess unique photophysical properties.Furthermore,[9]CPPH2,11 can be used as the electron transport layer and hole transport layer and the electron and hole mobility of[9]CPPH2,11 was measured to be～1.82×10-4 cm2 V-1 s-1 and～9.49×10-6 cm2 V-1 s-1,respectively.The successful synthesis of[9]CPPH2,11 can expand the scope of bottom-up synthesis of large conjugated carbon nanotube segments and potential applications in carrier transport devices.4.Direct π-extension of small highly strained macrocycles can be realized using a fixed two-bond approach by the Scholl reaction.The reaction can occur selectively to produce large π-extended carbon nanoring.Diels-Alder reaction was performed to construct the precursor with two peripheral C-C bonds that are readily incorporated into the extended aromatic moiety to overcome strain-induced side reactions,such as 1,2-phenyl shift.Compared to its precursor,a significant redshift(～100 nm for absorption)was observed for the prepared large π-extended carbon nanoring.This synthetic strategy can open up a feasible path for the π-extension of small strained conjugated macrocycles.