Faculty of Agriculture, Meijo University, Shiogamaguchi 1-501 Tempaku-ku, Nagoya 468-8502 (Japan), Fax: (+81) 52-833-7200.
Chemistry. 2013 Sep 9;19(37):12313-24. doi: 10.1002/chem.201300578. Epub 2013 Jul 29.
Ten types of neutral charge transfer (CT) complexes of coronene (electron donor; D) were obtained with various electron acceptors (A). In addition to the reported 7,7,8,8-tetracyanoquinodimethane (TCNQ) complex of 1:1 stoichiometry with a DA-type alternating π column, TCNQ also afforded a 3:1 complex, in which a face-to-face dimer of parallel coronenes (Cor-As) is sandwiched between TCNQs to construct a DDA-type alternating π column flanked by another coronene (Cor-B). Whereas solid-state (2)H NMR spectra of the 1:1 TCNQ complex formed with deuterated coronene confirmed the single in-plane 6-fold flipping motion of the coronenes, two unsynchronized motions were confirmed for the 3:1 TCNQ complex, which is consistent with a crystallographic study. Neutral [Ni(mnt)2] (mnt: maleonitriledithiolate) as an electron acceptor afforded a 5:2 complex with a DDA-type alternating π column flanked by another coronene, similar to the 3:1 TCNQ complex. The fact that the Cor-As in the [Ni(mnt)2] complex arrange in a non-parallel fashion must cause the fast in-plane rotation of Cor-A relative to that of Cor-B. This is in sharp contrast to the 3:1 TCNQ complex, in which the dimer of parallel Cor-As shows inter-column interactions with neighboring Cor-As. The solid-state (1)H NMR signal of the [Ni(mnt)2] complex suddenly broadens at temperatures below approximately 60 K, indicating that the in-plane rotation of the coronenes undergoes down to approximately 60 K; the rotational rate reaches the gigahertz regime at room temperature. Rotational barriers of these CT complexes, as estimated from variable-temperature spin-lattice relaxation time (T1) experiments, are significantly lower than that of pristine coronene. The investigated structure-property relationships indicate that the complexation not only facilitates the molecular rotation of coronenes but also provides a new solid-state rotor system that involves unsynchronized plural rotators.
十种中性电荷转移（CT）配合物的蒄（电子给体；D）与各种电子受体（A）获得。除了报道的 7,7,8,8-四氰基对醌二甲烷（TCNQ）的 1:1 化学计量的配合物与交替π柱的 DA 型，TCNQ 还提供了一个 3:1 配合物，其中平行的蒄（Cor-As）面对面二聚体夹在 TCNQs 之间以构建由另一个蒄（Cor-B）侧翼的 DDA 型交替π柱。虽然固态（2）H NMR 光谱的 1:1 TCNQ 配合物形成氘化的蒄证实了冠的单一面内 6 倍翻转运动，两个不同步的运动被证实为 3:1 TCNQ 配合物，这与晶体学研究一致。中性[Ni（mnt）2]（mnt：马来二硫代二氰胺）作为电子受体提供了一个 DDA 型交替π柱的 5:2 配合物，由另一个蒄侧翼，类似于 3:1 TCNQ 配合物。事实是，在[Ni（mnt）2]配合物中的 Cor-As 以非平行的方式排列，必须导致 Cor-A 相对于 Cor-B 的快速面内旋转。这与 3:1 TCNQ 配合物形成鲜明对比，其中平行 Cor-As 的二聚体与相邻的 Cor-As 显示出柱间相互作用。[Ni（mnt）2]配合物的固态（1）H NMR 信号在低于约 60 K 的温度下突然变宽，表明冠的面内旋转在约 60 K 下进行；在室温下，旋转速率达到千兆赫范围。从变温自旋晶格弛豫时间（T1）实验估算的这些 CT 配合物的旋转势垒明显低于原始冠的旋转势垒。所研究的结构-性质关系表明，配合物不仅促进了冠的分子旋转，而且还提供了一种涉及不同步多个转子的新的固态转子系统。
