Watson Mark D, Debije Michael G, Warman John M, Müllen Klaus
Max-Planck-Institute for Polymer Research, Postfach 3148, D-55021 Mainz, Germany.
J Am Chem Soc. 2004 Jan 28;126(3):766-71. doi: 10.1021/ja037522+.
A remarkable, regiospecific hydrogenation zips around the approximately 4 nm perimeter of hexa-peri-hexabenzocoronenes (HBC) adding 18 hydrogen atoms, leading to the first peralkylated coronenes, in quantitative yields in some cases. Increasing steric bulk of side chains was found to hinder the reaction, while unsubstituted HBC could be converted to a modest extent despite its vanishing solubility. The structures of the novel coronenes are unequivocally confirmed by MALDI-TOF, 1H, 13C, and heteronuclear correlation NMR, and UV-vis absorption spectroscopy. The puckered-ring periphery of these discotics does not prohibit self-assembly to columnar structures in a fashion similar to that of the planar precursors, as determined from wide-angle X-ray diffraction, but decreases the isotropization temperature by approximately 300 degrees C relative to the latter. Branching in the alkyl chains frustrates nucleation from the melt, resulting in clear polymorphism depending on the thermal treatment. Nonetheless, preliminary measurements indicate high charge-carrier mobilities and lifetimes within the bulk material, on the same order as those previously found for HBCs.
一种引人注目的区域特异性氢化反应沿着六并六苯并蔻（HBC）约4纳米的周长进行，添加18个氢原子，在某些情况下可定量生成首个全烷基化的蔻烯。研究发现，侧链空间位阻的增加会阻碍反应，而未取代的HBC尽管溶解度极低，但仍能在一定程度上发生转化。通过基质辅助激光解吸电离飞行时间质谱（MALDI - TOF）、氢核磁共振（¹H）、碳核磁共振（¹³C）以及异核相关核磁共振和紫外 - 可见吸收光谱，明确证实了新型蔻烯的结构。由广角X射线衍射测定可知，这些盘状化合物的褶皱环周边并不妨碍其以类似于平面前体的方式自组装成柱状结构，但相对于后者，其各向同性温度降低了约300摄氏度。烷基链中的支化阻碍了熔体中的成核过程，根据热处理方式的不同会产生明显的多晶型现象。尽管如此，初步测量表明块状材料内部具有较高的电荷载流子迁移率和寿命，与之前在HBC中发现的数值处于同一量级。
