Temperature-Mediated Polymorphism in Molecular Crystals: The Impact on Crystal Packing and Charge Transport

详细信息    查看全文

• 作者：Loah A. Stevens ; Katelyn P. Goetz ; Alexandr Fonari ; Ying Shu ; Rachel M. Williamson ; Jean-Luc Br茅das ; Veaceslav Coropceanu ; Oana D. Jurchescu ; Gavin E. Collis
• 刊名：Chemistry of Materials
• 出版年：2015
• 出版时间：January 13, 2015
• 年：2015
• 卷：27
• 期：1
• 页码：112-118
• 全文大小：325K
• ISSN：1520-5002

文摘

We report a novel synthesis to ultra high purity 7,14-bis((trimethylsilyl)ethynyl)dibenzo[b,def]-chrysene (TMS-DBC) and the use of this material in the growth of single crystals by solution and vapor deposition techniques. We observe that the substrate temperature has a dramatic impact on the crystal growth, producing two distinct polymorphs of TMS-DBC; low temperature (LT) fine red needles and high temperature (HT) large yellow platelets. Single crystal X-ray crystallography confirms packing structures where the LT crystals form a 1D slipped-stack structure, while the HT crystals adopt a 2D brickwork motif. These polymorphs also represent a rare example where both are extremely stable and do not interconvert to the other crystal structure upon solvent or thermal annealing. Single crystal organic field-effect transistors of the LT and HT crystals show that the HT 2D brickwork motif produces hole mobilities as high as 2.1 cm² V^鈥? s^鈥?, while the mobility of the 1D structure is significantly lower, at 0.028 cm² V^鈥? s^鈥?. Electronic-structure calculations indicate that the superior charge transport in the brickwork polymorph in comparison to the slipped-stack polymorph is due to the presence of an increased dimensionality of the charge migration pathways.