Study On Supramolecular Chemistry System Based On Cycloparaphenylenes

A fundamental challenge in chemistry and materials science is to create new carbon nanomaterials with novel structures and intriguing properties.A promising strategy is to assemble structurally unique carbon building blocks,such as non-planar?-conjugated cyclic molecules.Currently,the ?-conjugated nanocarbon materials,including fullerenes,carbon nanotubes,graphenes,and polycyclic aromatic hydrocarbons have shown extraordinary electronic and optical properties and significant applications in electronics,photonics and biomedical areas.The controllable self-assembly of the ?-conjugated building blocks via non-covalent interactions between adjacent units can meet the continuously increasing demands for high-performance optoelectronics and biomedical materials through rational supramolecular design,and offers abundant opportunity to tailor device performance.However,self-assembly of such cyclic ?-molecules to form organized nanostructures has been rarely explored and still remains a great challenge.This is in part due to the difficulty of the synthesis of pure carbon-or benzene-based building blocks with unique structures,and also in part due to the lack of capability to organize these building blocks with highly sophisticated and precisely regulated strategy.Thus,supramolecular architectures that combined crystalline order,oriented arrangement of small ?-conjugated cycles,controllable morphology and photoluminescence are expected to give rise to a new class of functional materials displaying unique photonic,electronic and biological functions.In this thesis,we synthesized a family of cycloparaphenylenes and discovered that these non-planar rigid cyclic ?-molecules could self-assemble into structurally distinct two-dimensional crystalline nanosheets and nanoscale multiwalled crystalline vesicles in solution.The application of these materials in biomedical area has also been evaluated.The main contents are described as below:(1)We designed and synthesized five kinds of cycloparaphenylenes(CPP)and their derivatives,which are referred to[8]CPP,[10]CPP,[8]CPP-pyrene,[8]CPP-TPE and[8]CPP-COOH.The spatial structures of these cycloparaphenylenes were determined by density functional theory(DFT)methods using RB3LYP/6-31G(d).(2)The spectra and self-assembly properties of cycloparaphenylene and its derivatives were systematically studied.The self-assembly behaviors of these cycloparaphenylenes in solution were initially investigated by fluorescence spectra.A gradually enlarging red shift of excitation spectra was found when the concentration increased.The significant spectral red-shift in fluorescence excitation spectra of the samples indicates that these non-planar cyclic conjugated molecules form aggregates at high concentration.We further discovered the first example of cycloparaphenylene molecules as building blocks to self-assemble structurally distinct ultrathin crystalline nanosheets and nanoscale multiwalled crystalline vesicles in solution.Cycloparaphenylene molecules can precisely stack together to form highly ordered structures in an obliquely standing fashion.The key driving force for the formation of nanoscale sheets and vesicles is crystallization of non-planar cyclic ?-molecules and?-? interaction in selective solvents,which is robust enough to maintain the curved structure of the vesicles.The size of the self-assembled CPP vesicles can be controlled by changing the CPP concentration in a THF/H2O mixed solvent,temperature and THF to H2O ratio of the mixed solvent.(3)The biological properties of cycloparaphenylene and its derivatives were studied.The interaction of these nanoscale materials with cells was examined.It was found that the cyclic benzenoid-based vesicles had extraordinary capability to penetrate cell membranes.The nanoscale cycloparaphenylene vesicles can be internalized by cancer cells through an energy-or temperature-independent process.