Theoretical Study On The Investigation And Regulation Of Bonding Characteristics In The Dimers Of PLY And OLY Radicals

Polycyclic Odd Alternant Hydrocarbons（POAHs）consist of three or more aromatic hydrocarbon rings with an odd number of carbon atoms,which exhibit the radical characteristic in their neutral system.Among them,the three-ring-fused system,Phenalenyl（PLY）radical,and five-ring-fused system,Olympicenyl（OLY）radical,which can be widely used in many fields,such as organic conductive materials,chemical sensors,spintronics,magnetic functional materials,catalytic reactions and energy storage materials due to their unique bonding and electronic properties.In this paper,we designed a series of PLY and OLY radicals-based dimers.The structure,interlayer interaction and bonding characteristics in the dimer derivatives of PLY and OLY radical were calculated and analyzed by density functional theory,which revealed the microscopic mechanism of interlayer interaction and could provid a theoretical basis for the synthesis of high-performance multifunctional materials.Specific work contents are as follows:（1）Firstly,two plane-like molecules 1 and 2 of the PLY radical modified by BNB/NBN groups were designed,and we further discussed the geometric structure,bonding properties,orbital interaction and energy decomposition analysis of the heteroatomic-modified dimers（heteropolymers and homopolymers）.Results showed that three 2e/4c bonds in the“hamburger”hetero-dimer（1-2）which has a large distance between the central atoms.While the homo-dimers（1₂ and 2₂）have a"waffle"structure due to the formation of fourσbonds within the molecule.Compared with pure PLY₂,the layer interaction energy of all dimers is enhanced significantly,in particular,the interaction energy of 2₂ reaches-414.84 kcal/mol.（2）An external electric field with a strength of 0-190×10^-4 au was applied along the bonding direction of the OLY dimer.The results showed that with the increase of the external electric field strength,the distance between molecular layers was lengthened gradually,and the2e/20c bonds were weakened or even completely broken.Moreover,the increased external electric field strength caused interlayer charge transfer.The electrostatic interaction between layers is gradually enhanced.Therefore,the external electric field not only regulated the interlayer interactions of molecules,but also caused the symmetric molecules to produce strong polarity.Furthermore,we found that the external electric field induces the system to produce a large nonlinear optical response.（3）We constructed a series of PLY-OLY dimers using two strategies（Substituent or Heteroatomic Modification）and investigated their structures and the mechanism of their bonding mode conversion（σ-type toπ-type dimer）.The results showed that the substituent effect exhibits a certain regulatory trend:the energy barrier of unilateral reaction is increased,and the energy barrier of bond reaction process is decreased.The exciting thing is that the substitution effect of heteroatoms can significantly change the electronic properties of the radical systems leading to the change of interaction energy in the dimers.This strategy successfully regulated the bonding conversion of the dimers:the dominant configuration changed fromσ-type toπ-type dimer.In this paper,we studied the photoelectric properties and bonding characteristics of dimers and its derivatives based on PLY and OLY radicals.We hope that this work can provide new research ideas for designing functional molecular materials with excellent properties.