Supramolecular Assembly And Chiral Regulation Based On ?-Conjugated System

Perylene 3,4:9,10-tetraparboxylate diimide,namely perylene imide(PBI),belong to n-type organic semiconductor,has been widely used in photoelectric materials,dyes and electronic devices due to its easy modification of chemical structure and excellent photoelectric properties.The research and exploration of the assembly behavior of organic semiconductor molecules at the two-dimensional interface provides guidance for the design of optoelectronic devices and organic semiconductor materials with good performance.By modifying the structure of the perylene imide molecule,the multifunction of the molecule can be realized.In this paper,using scanning tunneling microscope technology(STM)and computational chemistry methods,the effect of alkyl chain length and solvent effect on the two-dimensional crystallization behavior of PMIs molecules were studied at the liquid-highly oriented pyrolytic graphite interface.The main research contents of this paper are as follows:1.The effect of achiral flexible alkyl chains of different lengths on the two-dimensional crystallization of PMIs molecules was studied.We designed three molecules with the same conjugated bone and geometric symmetry,but different lengths of the branched substituted alkyl groups,the supramolecular assembly behavior of three perylene imide derivatives based on n-type semiconductors on liquid-solid surfaces was explored using scanning tunneling microscopy and computational chemistry methods.It was found that the nanopatterns formed by the assembly of the three molecules belong to the p2 mg achiral plane group.Molecules modified with alkyl chains of different lengths show different degrees of two-dimensional chiral expression.As the length of the substituted alkyl chain increases,the expression of local layer chirality increases gradually,indicating that by simply changing the length of the achiral branched alkyl chain on the perylene imide core,can be manipulated torsion angle between the adsorption layer and the underlying substrate,to control the expression of the two-dimensional chiral.This research provides a new idea for the two-dimensional chiral control of achiral molecules on the two-dimensional interface.2.The effect of solvent effect on the structure and chirality of N-type semiconductor perylene imide at the solid-liquid interface was investigated.It was found that the molecules self-assembled in solvents with different polarities and formed long range ordered banded nanostructures.The monolayer was composed of microregions with different chirality.In1-Octanoic acid or phenyloctane,h-PMI and p-PMI molecules are assembled in an arrangement of achiral P2 mg,and the orientation angle between the monolayer and the substrate does not change.h-PMI molecules locally form a two-dimensional lamellar chiral structure,and the whole membrane assembled by p-PMI has lamellar chirality.The results showed that the change of solvent had no significant effect on the nanoscale patterns and chirality of PMIS molecules assembled at the solid-liquid interface.The results showed that the two-dimensional graphic interface could be realized by designing specific supramolecular structures and introducing different lengths of alkyl chains,which provided a theoretical basis for the preparation of valuable perylene imide derivatives.