Medium Diradical Character, Small Hole and Electron Reorganization Energies and Ambipolar Transistors in Difluorenoheteroles

Four difluorenoheteroleshavinga centralquinoidalcore with the heteroringvaryingas furan,thiophene,its dioxidederivativeand pyrrolehave shownto be mediumcharacterdiradicals.Solid-statestructures,optical,photophysical,magnetic,and electrochemicalpropertieshave been discussedin termsof diradicalcharacter,variationof aromaticcharacterand captoda-tive effects(electronaffinity).Organicfield-effecttran-sistors(OFETs)have been prepared,showingbalancedholeand electronmobilitiesof the orderof103cm2V1s1or ambipolarchargetransportwhichisfirst inferredfrom their redoxamphoterism.Quantumchemicalcalculationsshow that the electricalbehaviorisoriginatedfrom the mediumdiradicalcharacterwhichproducessimilarreorganizationenergiesfor hole andelectrontransports.The visionof a diradicalas simulta-neouslybearingpseudo-holeand pseudo-electronde-fects might justifythe reducedvaluesof reorganizationenergiesfor both regimes.Structure-functionrelation-ships betweendiradicaland ambipolarelectricalbehav-ior are revealed.The authorsthankthe SpanishMinistryof ScienceandInnovation(projectsMINECO/FEDERPGC2018-098533-B-100,and PID2019-110305GB-I00),the Junta de Andalucíaand GeneralidadValenciana,Spain (UMA18FEDERJA057,P18-FR-4549and Prometeo/2019/076)and JSPS KAKENHIgrant (JP21K05042for S.-i.K.,JP21K04995and JP21H05489for R.K., JP21H01887and JP20K21173for M.N.).S.-i.K.gratefullyacknowledgesthe AsahiGlassFoundationforfinancialsupport.We also thankthe ResearchCentralServices(SCAI)of the Universityof Málaga,UnidaddeEspectroscopíaVibracional(Dra. Capely Dr. Zafra)andUnidadde OpticaNo-Linealy EspectroscopíaUltrarápida(Dr. Román).This work was partiallysupportedby theCooperativeResearchProgram“NetworkJoint ResearchCenterfor Materialsand Devices”(KyushuUniversity).WethankProf. ShuheiHigashibayashi(KeioUniversity)forassistancewith synthesis.Mass spectrometricdata werecollectedat HiroshimaUniversity(N-BARD:Ms. TomokoAmimoto).Theoreticalcalculationswere partlyperformedusing ResearchCenterfor ComputationalScience(R-CCS),Okazaki,Japan.F.N and Y.D. acknowledgesupportfrom“Valutazionedella Ricercadi Ateneo”(VRA)—Universityof Bologna.Y.D. acknowledgesMinisterodell’Universitàedella Ricerca(MUR)for her Ph.D. fellowship. Funding for open access charge: Universidad de Málaga / CBU