Synthesis and FET characterization of novel ambipolar and low‐bandgap naphthalene‐diimide‐based semiconducting polymers

A novel series of naphthalene‐diimide‐based semiconducting polymers ( P1–P4 ) containing benzodithiophene or dithienopyrrole were successfully synthesized for ambipolar semiconducting materials showing near infrared absorptions. The incorporation of a 3‐hexylthiophene (3HT) spacer extended the intramolecular charge‐transfer (ICT) peak from λ_onset = 739 nm ( P1 ) to 785 nm ( P3 ). Moreover, about 250 nm red‐shift of the ICT peaks was observed in P2 and P4 compared to P1 and P3 due to the increased high‐lying HOMO energy levels. The grazing incidence X‐ray scattering of the P3 and P4 films proved the slightly improved crystalline order in the π?π stacking direction, indicating that the planar backbone is probably due to the introduced 3HT. The P1–P4 ‐based field‐effect transistor showed n‐type dominant ambipolar characteristics. The P2 and P4 showed higher electron mobilities up to 1.5 × 10^?2 cm² V^?1 s^?1 than P1 and P3 , which might be influenced by the orientation of the polymer backbone and the intermolecular orbital overlap. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 359–367     

Crystal Structures and Phase‐Transition Dynamics of Cobaltocenium Salts with Bis(perfluoroalkylsulfonyl)amide Anions: Remarkable Odd–Even Effect of the Fluorocarbon Chains in the Anion

Crystal structures and thermal properties of cobaltocenium salts with bis(perfluoroalkylsulfonyl)amide (C_nF_2n+1SO₂)₂N anions [n=0 ( 1 ), 1 ( 1 a ), 2 ( 1 b ), 3 ( 1 c ), and 4 ( 1 d )] and the 1,1,2,2,3,3‐hexafluoropropane‐1,3‐disulfonylamide anion ( 2 ) were investigated. In these solids, the cations are surrounded by four anions around their C₅ axis, and stacking of these local structures forms two kinds of assembled structures. In the salts with even n ( 1 , 1 b , and 1 d ), the cation and anion are arranged alternately to form mixed‐stack columns in the crystal. In contrast, in the salts with odd n ( 1 a and 1 c ), the cations and anions independently form segregated‐stack columns. An odd–even effect was also observed in the sum of the phase‐change entropies from crystal to melt. All of the salts exhibited phase transitions in the solid state. The phase transitions to the lowest‐temperature phase in 1 , 1 a , and 2 are accompanied by order–disorder of the anions and symmetry lowering of the space group, which results in the formation of an ion pair. Solid‐state ¹³C NMR measurements on 1 a and 1 b revealed enhanced molecular motions of the cation in the higher‐temperature phases.