Synthesis Of C-HBC Derivatives And Study Of Their Single Molecular Conductivity

The Moore’s Law,proposed by Gordon Moore in 1965,has guided and influenced the rapid progress of the semiconductor and information industry for decades.However,with the decreasing size of semiconductor devices,the conventional method for preparing device has been challenged,while molecular electronics research on molecular devices from the microscopic molecular level is gradually emerging.Research on molecular devices,focusing on molecular junction-based test methods to explore molecular conductivity,lays the foundation for molecular electronics to bridge the gap from theoretical research to practical applications.Mechanically controlled break junction(MCBJ)test technology has been rapidly developed into a widely used test method because of its clean face-to-face electrode,stable temperature range,strong anti-interference factors,and wide application of technology.Therefore,it is used as the test basis for the research of this thesis.Most of the studies on the conductivity of current molecules focus on traditional chain olefins,alkynes and other molecules,while the conductance properties of relatively large fused ring compounds,especially non-planar fused aromatic hydrocarbons,such as c-HBC,are underexplored.Due to its unique twist structure,such molecules have shown excellent charge transport properties in organic materials,exhibited excellent photoelectric conversion performance in organic photovoltaic devices,and unique self-assembly properties,and is expected to show promising potential application scenarios in molecular semiconductor devices.Therefore,this thesis takes c-HBC as the research object,and uses MCBJ test technology as the molecular conductivity test method to explore the characteristics of c-HBC conductance,mainly from the following aspects:Firstly,based on the design of conformational level and combined with the classical two-step Barton-Kellogg synthesis method,three bis-methyl substituted cHBC derivatives with different twist angles were synthesized to explore the difference in conductivity of molecules with different angles.NMR and other methods were used to characterize the molecular structure.MCBJ was used as a test platform for conductance testing.The results showed that there were double conductance values in one of the groups,and it was postulated that there might be conduction through intermolecular π-π interaction.Secondly,the mono-methyl substituted c-HBC derivative was designed and synthesized.MCBJ conductance test also showed a conductive platform,confirming the existence of a conductive pathway between the molecules,and found that the intermolecular charge transfer effect is better than the intramolecular transport.Finally,bis-methylthio substituted [4]-helicene was designed and synthesized.Investigation of the conductivity of bis-methylthio substituted [4]-helicene suggested that the conductivity of the [4]-helicene skeleton is not constant,that is,its standalone conductivity is superior to its presence in c-HBC molecules.This may be attributed to the larger twist angle of the [4]-helicene skeleton within c-HBC,which causes the conjugation to be weakened.In summary,the overall observations and conclusions of this thesis provide a reference for the subsequent electrical performance testing of other fused-ring compounds.The experimental results provide a molecular direction for the design of molecular circuits without the need for a double-point molecular link.This also provides a new research idea for research methods with low electrode distance tolerance.