The DFT Study On Second-order NLO Properties Of A Series Of Buckybowl Complexes Of C₂₀H₁₀

The study of nonlinear optical(NLO)material has attracted significant interests both from experimental and theoretical scientific communities due to its potential application in organic electronics,optoelectronics,and conductors.Buckybowls,bowl-shaped polycyclic aromatic hydrocarbons with carbon networks.They retain the structural stabilities,having noteworthy electro-acceptor ability and the convex and concave ?-faces which are available for coordination with cations and anions.Therefore,the electronic structures,the position of coordination and the NLO response of buckybowl compounds have become a new research direction in recent years.We evaluate the NLO properties of ion-buckybowl complexes and ferrocenyl-?bridge-corannulenyl(D-?-A)compounds employing density functional theory(DFT),it has the following results:(1)Using DFT theory to calculate the geometical structure,binding interactions,dipole moments and the first hyperpolarizabilities(?tot)of ion-buckybowl complexes.It is found that the stabilities of ion-buckybowl compounds primarily originate from the interaction energy,which was proved by a new isomerization energy decomposition analysis approach.Plots of reduced density gradient mirror the ion-? weak interaction has been formed between the ions and buckybowls.Significantly,the buckybowl subunits cannot effectively impact the NLO,but the kind of ion has marked influence on the second-order NLO responses.The ?tot values of Cl--buckybowl complexes are all larger as compared to that of Na+-buckybowl complexes,which is attributed to the large charge-transfer from Cl-to buckybowl.(2)By calculating the electronic structures,UV-visible absorbance spectra and first hyperpolarizabilities of ferrocenyl-? bridge-corannulenyl compounds using DFT,we found that the stabilities of the endo and exo conformers are almost the same.Two conformers are easy to convert.Furthermore,the maximum absorption wavelength of heterocyclic compounds show apparent red-shift compared with the compound with phenyl as ? bridge.This trend indicates that the heterocyclic compounds posses the smaller crucial transition energy,which might lead to a larger NLO response.Interestingly,the first hyperpolarizabilities values of exo conformers are all larger than that of endo conformers because of the larger degree of charge transfer transition of exo conformers compared to that of the corresponding endo conformers.Our research provides important evidence for using five-membered heterocycle as ? bridge in enhancing the NLO properties of D-?-A type compounds.Therefore,controlling the kinds of ? bridges is an important way for the designof new appealing NLO compounds.