Rubrene untwisted: common density functional theory calculations overestimate its deviant tendencies
Rubrene untwisted: common density functional theory calculations overestimate its deviant tendencies
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DOI：
10.1039/d0tc05463a
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发表时间：
2021-02-28
影响因子：
6.4
通讯作者：
Beran, Gregory J. O.
中科院分区：
文献类型：
--
作者：
Greenwell, Chandler;Beran, Gregory J. O.
红荧烯的极高载流子迁移率源于其固有的电子特性和促进电荷传输的有利晶体堆积的结合。然而，与红荧烯单晶采用的平面构象不同，许多红荧烯衍生物结晶时具有扭曲的并四苯核，并且表现出较差的载流子迁移率。典型的密度泛函理论（DFT）计算表明，在气相中，扭曲构象是优选的，类似于10-14 kJ mol(-1) 或更多。然而，目前的工作表明，由于密度驱动的离域误差，这些计算高估了扭转能量几个kJ mol(-1)，并且当使用更高级别的相关波函数模型计算时，扭转能量实际上仅类似于典型红荧烯衍生物的8-10 kJ mol(-1)。这一结果对于红荧烯衍生物的晶体工程有两个重要意义：首先，DFT 计算可能会错误地预测包含扭曲红荧烯构象的多晶型物更稳定，而实际上具有平面构象的结构是优选的，正如这里针对全氟红荧烯所证明的那样。其次，较小的扭曲能量使得固体形式筛选更有可能发现红荧烯衍生物的新平面核多晶型物，这些多晶型物以前仅以扭曲构象结晶。这些反过来可能会表现出更好的有机半导体特性。
The exceptionally high carrier mobility of rubrene derives from the combination of its intrinsic electronic properties and favorable crystal packing that facilitates charge transport. Unlike the planar conformations adopted by rubrene single crystals, however, many rubrene derivatives crystallize with a twisted tetracene core and exhibit poor carrier mobility. Typical density functional theory (DFT) calculations suggest that the twisted conformation is preferred by similar to 10-14 kJ mol(-1) or more in the gas phase. However, the present work shows that those calculations overestimate the twisting energy by several kJ mol(-1) due to density-driven delocalization error, and that the twisting energies are actually only similar to 8-10 kJ mol(-1) for typical rubrene derivatives when computed with higher-level correlated wave function models. This result has two significant implications for crystal engineering with rubrene derivatives: first, DFT calculations can erroneously predict polymorphs containing twisted rubrene conformations to be more stable, when in fact structures with planar conformations are preferred, as is demonstrated here for perfluororubrene. Second, the smaller twisting energies make it more likely that solid form screening could discover new planar-core polymorphs of rubrene derivatives that have previously been crystallized only in a twisted conformation. These in turn might exhibit better organic semiconducting properties.