Iritani Kohei, Takeda Hiroshi, Kather Michael, Yokoi Masahiko, Moeglen Magali, Ikeda Motoki, Otsubo Yusuke, Ozawa Yu, Tahara Kazukuni, Hirose Keiji, De Feyter Steven, Tobe Yoshito
Department of Applied Chemistry, School of Engineering , Tokyo University of Technology , Hachioji, Tokyo 192-0982 , Japan.
Department of Applied Chemistry, School of Science and Technology , Meiji University , Kawasaki , Kanagawa 214-8571 , Japan.
Langmuir. 2019 Nov 26;35(47):15051-15062. doi: 10.1021/acs.langmuir.9b02748. Epub 2019 Nov 13.
We present here the construction of a self-assembled two-dimensional network at the liquid/solid interface using a hexagonal pyridine macrocycle which binds an organic cation in its intrinsic porous space by electrostatic interactions. For this purpose, a hexagonal pyridinylene-butadiynylene macrocycle (PyBM) having six octyloxymethyl groups, , was synthesized. As guests, tropylium () tetrafluoroborate and trioxatriangulenium () hexafluorophosphate were used. In this study, we focused on (i) the network patterns of which change in response to its concentration and (ii) the position of the guest immobilized in the porous space of the macrocycle. Scanning tunneling microscopy (STM) observations at the interface of 1,2,4-trichlorobenzene (TCB) and highly oriented pyrolytic graphite (HOPG) revealed that formed four different polymorphs, oblique, loose hexagonal, linear, and rectangular, depending on the solute concentration and annealing treatment. Solvent TCB molecules are likely coadsorbed to not only the intrinsically porous space of (internal TCB) but also the space outside of the macrocycle between its alkyl chains (external TCB) in most of the cases. Upon adding the guest cation, whereas small was not visualized in the pore due to size mismatching, larger was clearly observed in each pore. In addition, based on high-resolution STM images of the rhombus packing pattern of , we revealed experimentally that was placed at an off-center position of the deformed hexagonal macrocyclic core in the rhombus pattern. On the basis of the molecular mechanics calculations, we hypothesize that the off-center location of is due to deformation of the hexagonal macrocycle through interaction with two external TCB molecules located at opposite edges of the macrocyclic core. Symmetry breaking of the macrocyclic host framework induced by coadsorbed surrounding solvent molecules thus plays a significant role in host-guest complexation at the liquid/solid interface.
我们在此展示了一种在液/固界面使用六方吡啶大环构建的自组装二维网络，该大环通过静电相互作用在其固有孔隙空间中结合有机阳离子。为此，合成了具有六个辛氧基甲基的六方吡啶撑 - 丁二炔撑大环（PyBM）。作为客体，使用了四氟硼酸䓬盐（）和六氟磷酸三氧杂三角烯盐（）。在本研究中，我们关注（i）随浓度变化的的网络模式，以及（ii）固定在大环孔隙空间中的客体的位置。在1,2,4 - 三氯苯（TCB）与高度取向热解石墨（HOPG）的界面处进行的扫描隧道显微镜（STM）观察表明，根据溶质浓度和退火处理，形成了四种不同的多晶型物，即斜方、松散六方、线性和矩形。在大多数情况下，溶剂TCB分子可能不仅共吸附到的固有孔隙空间（内部TCB），还吸附到大环烷基链之间的大环外部空间（外部TCB）。加入客体阳离子后，由于尺寸不匹配，小孔中的小分子未被观察到，而在每个孔中都清楚地观察到了较大的分子。此外，基于的菱形堆积模式的高分辨率STM图像，我们通过实验揭示了在菱形模式中位于变形的六方大环核心的偏心位置。基于分子力学计算，我们推测的偏心位置是由于六方大环与位于大环核心相对边缘的两个外部TCB分子相互作用而变形所致。因此，共吸附的周围溶剂分子引起的大环主体框架的对称性破缺在液/固界面的主客体络合中起着重要作用。
