Fluorenyl-substituted silole molecules: geometric, electronic, optical, and device properties
作者:Xiaowei Zhan、Andreas Haldi、Chad Risko、Calvin K. Chan、Wei Zhao、Tatiana V. Timofeeva、Aleksander Korlyukov、Mikhail Yu. Antipin、Sarah Montgomery、Evans Thompson、Zesheng An、Benoit Domercq、Stephen Barlow、Antoine Kahn、Bernard Kippelen、Jean-Luc Brédas、Seth R. Marder
DOI:10.1039/b803470b
日期:——
A series of silole molecules with fluorenyl substituents at varying positions—1-(9,9-dimethylfluoren-2-yl)-1,2,3,4,5-pentaphenylsilole, 1-(fluoren-9-yl)-1,2,3,4,5-pentaphenylsilole, 1,1,3,4-tetraphenyl-2,5-bis(9,9-dimethylfluoren-2-yl)silole, and 1,1-diphenyl-2,3,4,5-tetrakis(9,9-dimethylfluoren-2-yl)silole—has been synthesized and compared to the previously reported compounds, 1,1,2,3,4,5-hexaphenylsilole and 1,1-bis(9,9-dimethylfluoren-2-yl)-2,3,4,5-tetraphenylsilole. The effect of fluorenyl substitution pattern on the geometric, thermal, electronic, optical, and electroluminescence properties was investigated both experimentally and theoretically. Analysis of the X-ray crystal packing diagrams for two new fluorenyl-substituted siloles indicates the presence of π–π stacking and CH⋯π interactions in the solid state. Across the series, excellent thermal and morphological stabilities are displayed. Photoelectron/inverse-photoelectron spectroscopy measurements and density functional theory (DFT) calculations suggest that increased conjugation length through substitution at the 2- and 5-positions plays a more significant role in tuning the ionization potentials and electron affinities of these siloles than do inductive effects through substitution of the silicon. The electronic structure (e.g., HOMO–LUMO gap) and, hence, the optical absorption and fluorescence properties are also sensitive to the positions at which the fluorenyl groups are introduced, with substitution at the 2,5-positions having the largest effect. Solution-processed electroluminescent devices fabricated with the fluorenyl-substituted siloles as the emissive layer have luminous efficiencies as high as 3.6 cd A−1.
一系列在不同位置具有萘基取代基的硅烯分子——1-(9,9-二甲基萘-2-基)-1,2,3,4,5-五苯基硅烯、1-(萘-9-基)-1,2,3,4,5-五苯基硅烯、1,1,3,4-四苯基-2,5-双(9,9-二甲基萘-2-基)硅烯,以及1,1-双苯基-2,3,4,5-四(9,9-二甲基萘-2-基)硅烯——已被合成,并与之前报道的化合物1,1,2,3,4,5-六苯基硅烯和1,1-双(9,9-二甲基萘-2-基)-2,3,4,5-四苯基硅烯进行了比较。研究了萘基取代模式对几何、热、电子、光学及电致发光特性的影响,既进行了实验也进行了理论分析。对两个新型萘基取代硅烯的X射线晶体堆积图进行分析,表明在固态中存在π-π堆积和CH⋯π相互作用。在整个系列中,表现出优良的热稳定性和形态稳定性。光电子/反光电子光谱测量和密度泛函理论(DFT)计算表明,通过在2位和5位的取代增加共轭长度,对于调控这些硅烯的电离电位和电子亲和力的作用比硅的诱导效应更为显著。电子结构(例如,HOMO-LUMO间隙)以及光学吸收和荧光特性也对萘基团引入的位置敏感,其中在2,5位的取代效果最大。利用萘基取代硅烯作为发光层制造的溶液处理电致发光器件,发光效率高达3.6 cd A−1。