Design,Synthesis And Properties Studies On The Benzene-Bridged Expanded Carbaporphyrin

Expanded porphyrin refers to porphyrin analogues containing more than 4pyrrole units in the molecular structure.Its rich topological structure and electronic properties endow the expanded porphyrin excellent photophysical,electrochemical and coordination properties.As an important supramolecular host,expanded porphyrins have been widely used in materials science,environmental energy and other research fields in recent years,and have shown great promise in near-infrared absorbing dyes,nonlinear optical materials,explosive sensors,and host-guest recognition.Therefore,the design and synthesis of new expanded porphyrins has become a research hotspot in supramolecular chemistry in recent years.By introducing aromatic units such as m-phenylene and p-phenylene into the expanded porphyrin transfer into the expanded carbaporphyrins,the ?-conjugation path of the macrocycle can be effectively extended and its conformational flexibility can be enhanced.Literature research has found that: expanded carbaporphyrins have divergent conformational behaviors,but due to their poor stability,there are few related reports of fully meso-free expanded carbaporphyrins.In this context,this thesis uses a kinetic protection strategy—introducing ?-ethyl protecting group into the pyrrole unit of the expanded carbaporphyrin to design and synthesize a new type of meso-free benzene-bridged expanded carbaporphyrins.The structures of the above compounds were characterized in detail by nuclear magnetic resolution(NMR),high resolution mass spectrometry(HRMS),X-ray single crystal diffraction and other technical means.In addition,this thesis conducts a preliminary discussion on its photophysical and electrochemical properties through ultraviolet-visible(UV-VIS)absorption spectroscopy,cyclic voltammetry(CV),differential pulse voltammetry(DPV)and computational chemistry studies.The main content mainly includes the following aspects:(1)Using monopyrrole dialdehyde and 1,4-benzenedipyrrole as the starting materials,a fully meso-free benzene bridged expanded carbaporphyrin ExPr-1 was successfully obtained by acid-catalyzed condensation and DDQ oxidation.Metal coordination studies have shown that the expanded porphyrin can form a stable coordination complex ExPr-1-Pd with palladium,and ExPr-1-Pd adopts the "NNNC" coordination mode;coordination with palladium can effectively promote the ?-electron delocalization,and the UV-Vis spectrum shows that it has strong absorption in the near-infrared region.In addition,the protonation of ExPr-1 can also promotes the delocalization of the macrocycle,and both trifluoroacetic acid(TFA)and methanesulfonic acid(MSA)will cause the overall red-shift of the absorption of ExPr-1.DFT calculations further confirmed that ExPr-1 has nonaromatic characteristics.Metalization and protonation only caused a conformational change,but did not cause a change in ExPr-1's aromaticity.(2)Using furan-based di-carbinol and 1,4-benzenedipyrrole as starting materials,acid-catalyzed secondary alcohol and pyrrole ?-position condensation,followed by DDQ oxidation,We successfully obtained the meso-aryl substituted benzene-bridged expanded carbaporphyrin ExPr-2.Compared with the compound ExPr-1,large aromatic substituents at the meso-position does not cause a significant change in the degree of delocalization of the ?-electron of the macrocyclic ring.However,the introduction of aromatic substituents at the meso-position can cause configuration changes.X-ray single crystal structure analysis reaveals that ExPr-2has a near-planar conformation.Due to the large cavity of this structure,the coordination with the metal is limited.In addition,ExPr-2 can form a unique supramolecular self-assembly through hydrogen bonding with pyromellitic acid.