Synthesis Of Hosts Based On Corannulene And Its Recognition Of Fullerenes

Fullerene molecules have attracted considerable interest because of the unique curved aromatic?-conjugated systems.However,the complicated and costly technologies for purification of highly pure fullerenes hamper easy access to these attractive molecules and consequently limit most of fullerene applications.The search of synthetic hosts able to encapsulate fullerenes with high stability and selectivity in solution so as to achieve their purifications has attracted great attentions.Although significant advances on selective encapsulation of C₆₀/C₇₀ have been made,purification of C₆₀/C₇₀ mixtures using synthetic hosts still represents a great challenge because most of methods based on synthetic hosts for fullerene purification are mainly selective for C₆₀ but less for C₇₀.In this thesis,a series of host molecules based on corannulene were designed and synthesized.Their properties related to self-assembly and molecular recognition were studied.1.Two pentasubstituted corannulene derivatives were designed and synthesized,and molecular cages with different size cavities were constructed through metal directed self-assembly.Molecular cage COPY1-Pd can quantitatively encapsulates fullerenes C₆₀ and C₇₀ with unprecedentedly thermodynamic stability due to the small crevice sizes,multiple favorable CH-?interactions and concave-convex aromatic interaction between fullerenes and cage.More importantly,the cage displays a temperature-dependent selective binding preference for C₆₀ over C_70.These unique properties enable us to develop an easy and efficient procedure for separation and purification of C₆₀ and C₇₀ in high purity from fullerene soot,without the help of recrystallization or HPLC.It appears that the procedure based on our host is an attractive methodology for separating and purifying fullerenes C₆₀ and C₇₀ in comparison with the traditional chromatographic technique,which is a tedious,energy-and time-consuming process.2.Two tetrasubstituted corannulene derivatives with different substitution sites were designed and synthesized.Expected molecular cages that self-assembled of COPY3 or COPY4 in the presence of Pd?CH₃CN?₂Cl₂ were not formed,while the molecular cages formed exclusively with fullerens as stabilizing templates.Ligand COPY3 and Pd?CH₃CN?₂Cl₂ can self-assemble with fullerenes to form molecular cage because the molecular cage has a large gap,which provides a spacious channel for fullerenes to enter.Ligand COPY3 shows stronger complexation ability to bind C₆₀according to the fullerene replacement experiment and fullerene mixture competitive complexation experiment.4-Dimethylaminopyridine?DMAP?is able to dissociate the cages in order to release fullerenes and ligand.Therefore,the ligand COPY3 can be used to the collection of C₆₀ at room temperature.3.Two kinds of molecular tweezers T1 and T2 with different sizes were designed and synthesized.By using the fluorescence titrations,the Job's plot analysis show that the complexations of both receptor T1 or T2 with C₆₀ and C₇₀ is 1:1.The association constants of receptor T1 to C₆₀ and C₇₀ are?1.63±0.12?×10⁵ and?1.32±0.08?×10⁵respectively,and the association constants of receptor T2 to C₆₀ and C₇₀ are?2.82±0.12?×10⁵ and?8.26±0.70?×10⁵ respectively.Receptor T2 has slightly stronger ability to complex fullerenes than T1.Receptor T2 showed strong complexation towards C₇₀ over C₆₀.The ¹HNMR measurements of spin–spin?T2?relaxation times of receptors T1 and T2 decreased obviously with the addition of C₆₀ and C₇₀,which indicated that complex structures were formed.This is consistent with the DFT theoretical calculation results.The receptors have potential applications in fluorescence detection of fullerenes since the complexes formed by receptors T1 or T2 and C₆₀ and C₇₀ have obvious fluorescence quenching phenomena.