New Curved/Heterocyclic Aromatics And Corresponding Ionic Radicals Based On The Perylene Building Block

Organic curved/heterocyclic conjugated systems possess the diversified structure and tunable physical properties.Their corresponding radical ions have both electron and spin properties while maintaining the characteristics ofπ-conjugated molecules,which are a class of organic functional materials with unique optical,electronic and magnetic properties.The research of these molecular materilas not only has important scientific significance,but also huge application prospects in organic spintronic devices,organic optoelectronic device and organic storage material.The oxidation or reduction radicals of curved/heterocyclic conjugated molecules are also one of the frontiers of multidisciplinary research.In this thesis,using twisted perylene as the building block of conjugated extension,we have designed and synthesized theπ-extended new twisted/heterocyclic conjugated molecules and corresponding radical ions.And the intrinsic properties of the conjugated molecule have been studied,followed by focused investigation of the relationship among electronic structure,physical properties and structure-activity relationship.The specific research contents are as follows:1.We have designed and synthesized the heterocyclic conjugated molecule TTP,in which four benzothiophene units diagonally fused to a twisted perylene at both ortho-and peri-positions and spatially arranged in a double helical-like structure.We succeeded in optical resolution of two chiral enantiomers,which exhibited intriguing CD and CPL properties(g_lum≈1.09×10^-3).In the crystalline state of racemate TTP,the unique extensiveπ-πstacking as J-aggregations crossed with H-aggregations provided an ordered supramolecular network.Interestingly,the racemate showed strong photoluminescence both in solution（Φ_f=68%）and at the solid state（Φ_f=57%）,meanwhile,possessed the charge-carrier transport property with a hole mobility（μ_h）up to 0.02 cm²V^-1s^-1 by the thin-film based OFET measurements（Chapter 2）.2.Radical cation(TTP^·+)was obtained by one-electron chemical oxidation of above-mentioned TTP molecules,which can be prepared in large quantities.It exhibits unusual stability in the air,even exposing to the moisture.The crystalline radical cation possessed antiferromagnetic coupling,showing a Néel temperature of108.5 K(J=-101.8 cm^-1),while its crystal demonstrated weak electrical conductivity（ζ=0.006 S/cm）at room temperature.In addition,the radical can also be used as device dopants to increase the conductivity of the semiconductor polymer P3HT to 8.5S/cm.It also has shown p-type thermoelectric performance,with power factor PF of0.5μWm^-1K^-2（Chapter 3）.3.The evolution of the electronic structure of the conjugated TTP at various oxidation states was studied.Both experimental and theoretical results revealed that dication is open-shell singlet diradcial dication.Interestingly,the packing order of this three-dimensional diradical became ordered as temperature increasing due to the rise of biradical character and therefore increase of intermolecular spin-spin interaction.Besides,this thermal behavior is reflected by improved device performance in electrical conductivity.For example,the conductivity of dication TTP²⁺·2[Sb F₆]^-is 1×10^-4 S/cm at room temperature,and increased to 0.064 S/cm at50 ^oC（Chapter 4）.4.The electronic structure of the curved conjugated molecule bisdibenzocorannulene（BDBC）at the redox states was studied.The corresponding anions and cations can be easily obtained by chemical reduction and oxidation,respectively.Our research leads to the following conclusions:（1）both radical anion and dianion possessed interesting global aromat icity.（2）Due to the electron-withdrawing properties of curved molecules,the anionic radicals of BDBC present rare"naked"state,that is,there is no need for electrostatic stability with ions or polar molecule,indicating a high thermodynamic stability.（3）The radical cation of BDBC invariably converts to stable dication through chemical oxidation.Interestingly,the dication had an unusual open-shell singlet diradical in the ground state,named as(BDBC^··)²⁺.With the help of experiments and theoretical calculations,we proposed a new mechanism of the formation of diradical,that is,delocalized non-bondedπelectron induced by strong localized antiaromaticity（Chapter 5）.