作者:Jin-Sung Seo、Yong-Sik Yoo、Moon-Gun Choi
DOI:10.1039/b008904o
日期:——
The preparation and characterization of ferrocene containing
hexacatenar metallomesogens 4aâh based on alkoxy terminal groups with hexyloxy (4a), octyloxy (4b),
decyloxy (4c), dodecyloxy (4d), tetradecyloxy (4e),
hexadecyloxy (4f), octadecyloxy (4g) and eicosyloxy (4h)
chains are described. The introduction of alkyl chains of different lengths
induces a rich variety of self-assembled liquid crystalline structures. In
the crystalline state, the ferrocene containing hexacatenar metallomesogens 4aâh organize into a microphase-separated monolayer
lamellar structure. In contrast, a dramatic phase change after crystalline
melting of the metallomesogens is observed with variation of the chain length.
The ferrocene containing hexacatenar metallomesogens 4b
and c display a bicontinuous cubic
mesophase with Ia3d symmetry, while the ferrocene containing
hexacatenar metallomesogens 4dâg exhibit a hexagonal columnar mesophase. Further
increasing the length of the alkyl chain as in the case of 4h
suppresses liquid crystallinity and induces only a crystalline phase. This
unique behavior in the ferrocene containing metallomesogenic molecules can
be understood to originate from the anisotropic aggregation of ferrocene containing
aromatic segments and consequent entropic penalties associated with chain
stretching.
本研究介绍了基于烷氧基末端基团的含二茂铁六碳烯金属异构体 4aâh 的制备和特性,这些烷氧基末端基团包括己氧基 (4a)、辛氧基 (4b)、癸氧基 (4c)、十二氧基 (4d)、十四氧基 (4e)、十六氧基 (4f)、十八氧基 (4g) 和二十四氧基 (4h)。引入不同长度的烷基链后,可产生丰富多样的自组装液晶结构。在结晶状态下,含有二茂铁的六碳烯金属异构体 4aâh 组织成微相分离的单层片状结构。相反,随着链长的变化,金属诱导体结晶熔化后出现了显著的相变:含有六碳烯的二茂铁金属诱导体 4b 和 c 显示出具有 Ia3d 对称性的双连续立方介相,而含有六碳烯的二茂铁金属诱导体 4dâg 则显示出六方柱状介相。进一步增加烷基链的长度(如 4h 的情况)会抑制液态结晶性,而只产生结晶相。含有二茂铁的金属茂金属分子的这种独特行为可以理解为是由于含有芳香族段的二茂铁的各向异性聚集以及由此产生的与链伸展相关的熵罚。