Self-assembly Of Tetraphenylporphyrin Molecules On Metal Substrates And Their Physicochemical Properties

Porphyrin and its related compounds have been the research hotspot in the field of the fields of biology,chemistry and surface science for decades due to their inherent physical and chemical properties.The macrocycle at the center of the porphyrin can coordinate with a single metal ion or two hydrogen atoms,and the adsorption of different atoms in the center of the macrocycle will cause different physical and chemical properties.As a kind of porphyrin-related compounds,the 5,10,15,20-tetraphenyl porphyrin molecule retains the central macrocyclic structure of porphyrin molecule and four benzene rings are introduced in the corners,which makes its electronic properties rather unique.The main research content of this paper is to use the ultra-high vacuum low-temperature scanning tunneling microscope(STM)/atomic force microscope(AFM)produced by German Scienta Omicron company,combined with density functional theory based on first-principles,etc.,to explore the adsorption structure of 5,10,15,20-tetraphenyl porphyrin molecules on precious metal substrates(eg Au,Cu)and configuration of dehydrocyclization products,and characterization of their electrical properties.At the same time,the self-assembly structure of C₁₈H₁₀Br₄ molecule on the surface of different metal substrates was also studied.The specific work is as follows:1.Self-assembly of 5,10,15,20-tetraphenyl porphyrin molecules.At low coverage,5,10,15,20-tetraphenyl porphyrin molecules diffuse freely on gold substrates(Au(111),Au(788)),and preferentially adsorb on the edge of the step and the"elbow"of gold-reconstructed.As the molecular coverage increases,self-assembled islands of 5,10,15,20-tetraphenyl porphyrin molecules are formed.2.Dehydrocyclization of 5,10,15,20-tetraphenyl porphyrin molecules.When annealed at 150?,the 5,10,15,20-tetraphenyl porphyrin molecule just started to undergo dehydrocyclization;when the temperature was raised to 200?,the dehydrocyclization reaction further occurred,and part of the four phenyl groups in the 5,10,15,20-tetraphenyl porphyrin molecule form a covalent bond with the adjacent five-membered ring;after annealing at 300?for 20 min,the 5,10,15,20-tetraphenyl porphyrin molecule undergoes a complete dehydrocyclization reaction and forms four different configurations of cyclization products.Through the analysis of experimental data and theoretical calculation results,it is found that the electronic state structures of the four dehydrocyclization configurations are relatively independent,and the"transfer"of the state density between different configurations can be achieved.3.Adsorption behavior of C₁₈H₁₀Br₄ molecule on the surface of the metal substrate.The adsorption morphology of C₁₈H₁₀Br₄ on gold,silver,and copper single-crystal substrates was studied,and its self-assembled structure on single-crystal Au(111)substrate was analyzed.This provides some references for further exploration of the electrical properties,energy band structure,and reaction mechanism of C₁₈H₁₀Br₄ in the future.