1,3,5,7,9-五吡唑心环烯的合成及配位自组装OACSTPCD

[Objective]Functional group modification is one of the important means to provide coordination sites for the self-assembly of corannulene.The self-assembled structures of corannulene derivatives have potential applications in catalysis,materials and biomedicine.In 2019,we reported on the synthesis and characterization of 1,3,5,7,9-pentapyrrolylcorannulene and decapyrrolylcorannulene.To obtain corannulene derivatives with coordination function,herein we synthesized the 1,3,5,7,9-pentapyrazolylcorannulene molecule by modifying the perimeter of corannulene with pyrazolyl groups and studied its supramolecular coordination self-assembly with C60 and AgSO3CF3,respectively.[Methods]Pyrazolyl functional groups were successfully modified at the perimeter of corannulene by one step five-fold nucleophilic substitution reaction.The molecular structure of the modified corannulene derivatives was characterized by matrix-assisted laser desorption ionization time-of-flight mass spectrometry(MALDI-TOF-MS)and nuclear magnetic resonance(NMR)spectroscopy.The photophysical properties were studied using UV-Vis absorption spectrum and fluorescence emission spectrum.The supramolecular coordination self-assembly of 1,3,5,7,9-pentapyrazolylcorannulene with fullerene C60 or AgSO3CF3 was investigated by means of NMR titration.[Results]Through a regioselective chlorination reaction,the synthon of 1,3,5,7,9-pentachloro corannulene with C5 symmetry was synthesized,and then the five chloro groups of the synthon were substituted by pyrazolyl groups to obtain 1,3,5,7,9-pentapyrazolylcorannulene(1).The structure of compound 1 was characterized by MS and NMR.The UV-Vis absorption spectrum shows that the longest absorption wavelength of 1,3,5,7,9-pentapyrazolylcorannulene is 323 nm.Compared with unmodified corannulene and pentaphenyl corannulene,compound 1 shows a significant redshift.The energy level difference between the highest occupied molecular orbital(HOMO)and the lowest unoccupied molecular orbital(LUMO)of compound 1 is 3.28 eV,which is calculated from the sideband absorption wavelength of the UV-Vis absorption spectrum of compound 1.The large molecular energy level difference indicates that compound 1 is relatively stable.The maximum emission peak of compound 1 is located at 463 nm,and the Stoke shift is calculated as 140 nm.Compound 1 exhibits pronounced blue fluorescence,which is significantly enhanced compared to unmodified corannulene and the previously reported decapyrrolylcorannulene.The NMR titration of compound 1 and C60 shows that with the increase of C60 concentration,the chemical shift of the hydrogen atoms on the corannulene remains unchanged.However,the NMR titration of compound 1 and AgSO3CF3 shows that with the increase of Ag+concentration,the hydrogen peak of compound 1 widen,and the chemical shift changes gradually due to the deshielding effect of metal ions.When a(AgSO3CF3)∶a(compound 1)＞2.5∶1,the peak of hydrogen atoms become narrower,and the chemical shift does not change basically.Electrospray ionization mass spectrometry(ESI-MS)characterization shows that a mass spectrum peak of the formed complex is m/z=2 445.557 8(theoretical value m/z=2 445.661 0),indicating the molecular composition of Ag-L2(SO3CF3)5.Therefore,it is speculated that compound 1 and Ag+exhibit self-assembly site behavior,and may eventually form a cage structure of M5L2(M for metal,L for ligand).[Conclusion]1,3,5,7,9-pentapyrazolylcorannulene with C5 symmetry and five sp2 hybrid nitrogen atoms is synthesized by five-fold nucleophilic substitution reactions.Its molecular structure and photophysical property were characterized by MS,NMR,UV-Vis absorption spectrum and fluorescence spectrum.The introduction of pyrazolyl group improves the fluorescence property of pristine corannulene.In addition,through NMR titration and ESI-MS characterization,it is found that 1,3,5,7,9-pentapyrazolylcorannulene might form coordination self-assembly with Ag in the liquid phase with a supramolecular cage structure of M5L2.This study offers valuable references for the subsequent design and synthesis of corannulene derivative ligands for coordination self-assembly.