Cyclophanes crown-like

Tschierske synthesized the butterfly mesogens 132-134 (Scheme 72, Table 9). These compounds are based on a macrocyclic crown-like para-cyclophane ring containing two 2-phenylpyrimidine units. Of/to-palladation and subsequent treatment with substituted half-disks like (5-diketones gave the desired dinuclear palladium complexes with 4 (132), 8 (133), and 12 (134) peripheral alkyl chains [127]. 

Introduction of cyclophane unit, as an integral part of the crown ether, instilled unique properties. Stoddart and co-workers prepared the oxa-thiacrown ether incorporating a rigid horseshoe-shaped aromatic moiety 108 in two steps from hydro-quinone and an excess of l,4-bis(bromomethyl)benzene < 1997JCD1496>. Yields of the first intermediate and 108 were 40% and 61%, respectively. The Cul complex with 108 was a 2 1 (Cu+/108) complex, as a one-dimensional infinite array of cubane-like units consisting of four Cu, four iodine, and four sulfur atoms from four different macrocycles (Scheme 15). 

The consequences of increasing the size of the polyether macrocycle to 68 members (that is, by a factor of two over the small ring system) was investigated. Accordingly, the synthesis of tetrakis-/ -phenylene-68-crown-20 was achieved in dimethylformamide at room temperature in excellent yield and this, in turn, was initially used to produce the [2]-catenane 22 (Figure 5.13). From the temperature dependence of the H NMR spectrum, 22 appears to behave like a molecular train - with the tetracationic cyclophane travelling from station to station around the... 

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