10.1021/jacs.6b06877.s003 Yuji Yamaguchi Yuji Yamaguchi Maki Takubo Maki Takubo Keisuke Ogawa Keisuke Ogawa Ken-ichi Nakayama Ken-ichi Nakayama Tomoyuki Koganezawa Tomoyuki Koganezawa Hiroshi Katagiri Hiroshi Katagiri Terazulene Isomers: Polarity Change of OFETs through Molecular Orbital Distribution Contrast American Chemical Society 2016 Molecular Orbital Distribution Contrast Intermolecular π- conjugation system LUMO HOMO terazulene n-type transistor behavior FET TAz 4 exhibits TAz 3 exhibit ambipolar characteristics OFET TAz 2 azulene unit TAz 4 2016-08-11 00:00:00 Dataset https://acs.figshare.com/articles/dataset/Terazulene_Isomers_Polarity_Change_of_OFETs_through_Molecular_Orbital_Distribution_Contrast/3776550 Intermolecular orbital coupling is fundamentally important to organic semiconductor performance. Recently, we reported that 2,6′:2′,6″-terazulene (<b>TAz1</b>) exhibited excellent performance as an n-type organic field-effect transistor (OFET) via molecular orbital distribution control. To validate and develop this concept, here we present three other terazulene regioisomers, which have three azulene molecules connected at the 2- or 6-position along the long axis of the azulene, thus constructing a linear expanded π-conjugation system: 2,2′:6′,2″-terazulene (<b>TAz2</b>), 2,2′:6′,6″-terazulene (<b>TAz3</b>), and 6,2′:6′,6″-terazulene (<b>TAz4</b>). <b>TAz2</b> and <b>TAz3</b> exhibit ambipolar characteristics; <b>TAz4</b> exhibits clear n-type transistor behavior as an OFET. The lowest unoccupied molecular orbitals (LUMOs) of all terazulenes are fully delocalized over the entire molecule. In contrast, the highest occupied molecular orbitals (HOMOs) of <b>TAz2</b> and <b>TAz3</b> are delocalized over the 2,2′-biazulene units; the HOMOs of <b>TAz4</b> are localized at one end of the azulene unit. These findings confirm that terazulene isomers which are simple hydrocarbon compounds are versatile materials with a tunable-polarity FET characteristic that depends on the direction of the azulene unit and the related contrast of the molecular orbital distribution in the terazulene backbone.