Wang Chao, Hao Hua, Tajima Keisuke
RIKEN Center for Emergent Matter Science (CEMS), 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan.
Adv Sci (Weinh). 2022 May;9(16):e2201045. doi: 10.1002/advs.202201045. Epub 2022 Mar 28.
A diradicaloid molecule with high semiconducting performance is synthesized based on the quinoidal benzo[1,2-b:4,5-b']dithiophene structure. The diradical character is investigated by quantum chemical calculations and variable temperature electron spin resonance. The diode devices based on this molecule show a large change in electric current in magnetic fields below 100 mT with a strong dependence on the measurement temperatures; as the population of the triplet diradicals increases at high temperatures, the magnetoconductance (MC) values increase. As a result, a MC of -19.4% is achieved at 120 °C, which is the largest negative MC observed for organic molecules to date. In contrast, a smaller diradicaloid molecule based on quinoidal thieno[3,2-b]thiophene without thermally accessible triplet state shows no MC, indicating the essential role of the triplet diradicals. The strong correlation between the MC and the triplet diradical concentrations suggests that the charge conduction in the diradicaloid is suppressed through a spin-blocking mechanism, which can be controlled through the magnetic modulation of the hyperfine fields. The compound forms high-crystallinity thin films and has high monopolar electron transport in organic field-effect transistors, with an average mobility of 1.01 cm V s for edge-cast films.
基于醌型苯并[1,2 - b:4,5 - b']二噻吩结构合成了一种具有高半导体性能的双自由基类分子。通过量子化学计算和变温电子自旋共振研究了其双自由基特性。基于该分子的二极管器件在低于100 mT的磁场中电流有很大变化，且强烈依赖于测量温度；随着高温下三重态双自由基数量的增加，磁电导（MC）值增大。结果，在120°C时实现了-19.4%的磁电导，这是迄今为止有机分子中观测到的最大负磁电导。相比之下，基于醌型噻吩并[3,2 - b]噻吩且没有可热激发三重态的较小双自由基类分子则没有磁电导，这表明三重态双自由基的重要作用。磁电导与三重态双自由基浓度之间的强相关性表明，双自由基类中的电荷传导通过自旋阻挡机制受到抑制，这可以通过超精细场的磁调制来控制。该化合物形成高结晶度薄膜，在有机场效应晶体管中具有高单极性电子传输，边缘浇铸薄膜平均迁移率为1.01 cm² V⁻¹ s⁻¹。
