Synthesis, thermal, electrochemical, and photophysical characterization of 1,5-bis(diarylamino)naphthalene derivatives as potential hole transport OLED materials

Novel 1,5-bis(diarylamino)naphthalene derivatives (1-9), which have potential as hole-transporting materials for electroluminescent devices, were obtained through palladium-catalyzed coupling of diarylamines and 1,5-dibromonaphthalene. The thermal, electrochemical, and photophysical properties of these compounds were examined and the effects of the N-aryl substituents on these properties were investigated. These materials possess glass transition temperatures ([T.sub.g]) that range from 70-131 [degrees]C and these values are related to the identity of the aryl substituents. Cyclic voltammetric measurements demonstrated that these compounds possess two reversible oxidation processes and were further used to estimate the HOMO energy levels of these materials by comparison with the ferrocene/ferrocenium couple. The intramolecular charge mobility, as gauged by the difference between the two oxidation potentials, indicates that compounds 1-8 have a similar degree of delocalization as meta-diaminobenzene derivatives while that of 9 is similar to TPD. Compounds 1-9 emit in the blue-green region and optical absorption and emission data for these materials can be rationalized in terms of the electronic donating properties of the aryl substituents. This data when combined with the electrochemically determined HOMO energies allowed estimation of the LUMO energy levels. Key words: hole transport materials, diaminonaphthalene, thermal analysis, palladium-catalyzed arylation. Faisant appel a un couplage catalyse par le palladium de diarylamines et de 1,5-dibromonaphtalene, on a prepare des 1,5-bis(diarylamino)naphtalenes (1-9), qui ont le potentiel de transporter des trous pour les appareils electroluminescents. On en a examine les proprietes thermiques, electrochimiques et photophysiques et on a etudie les effets des substituants N-aryles sur ces proprietes. Ces materiaux possedent des temperatures de transition de verre ([T.sub.g]) qui s'etalent de 70 a 131 [degrees]C et on a pu etablir une correlation entre cette propriete et l'identite des substituants aryles. Des mesures de voltamperometrie cyclique demontrent que ces composes possedent deux processus d'oxydations reversibles qui ont, de plus, ete utilisees pour evaluer les niveaux d'energie de l'orbitale moleculaire haute occupee de ces composes par comparaison avec le couple ferrocene/ferrocenium. La mobilite de la charge intramoleculaire, telle qu'evaluee par la difference entre les deux potentiels d'oxydation, indique que les composes 1-8 possedent un degre de delocalisation semblable a celui des derives du meta-diaminobenzene alors que celle du compose 9 est semblable a celle du TDE Les composes 1-9 emettent dans la region du bleu-vert et les donnees d'absorption et emission optique de ces composes peuvent etre rationalisees en termes du caractere electrodonneur des substituants aryles. Lorsque ces donnees sont combinees avec les energies de l'orbitale moleculaire haute occupee determinee electrochimiquement, il est possible d'evaluer les niveaux d'energie de l'orbitale moleculaire basse vacante. Mots cles : materiaux pouvant transporter des trous, diaminonaphtalene, analyse thermique, arylation catalysee par le palladium. [Traduit par la Redaction]