1.6.20.25-tetraaza paracyclophane

The first is a cyclophane-based system reported by Murakami et al. (Fig. 9.12a). [31] The sides of the host consist of tetraaza-[3.3.3.3]paracyclophane units, and its octaprotonated cation has been shown to bind anionic guests. The molecule possesses 48 asymmetric units of [(N/3)-(CH2)- (C6H4)/2 ]/2. 

Both of the tetraaza[3.3.3.3]paracyclophane (1) and tetraaza[n.l.n.l]paracyclo-phane (n = 6, 7, 8 cf. 2) rings have frequently been used as fundamental molecular skeletons for preparation of functionalized macrocyclic hosts [24-36]. Formation of three-dimensionally extended hydrophobic cavities was approached by introducing multiple hydrocarbon branches into the macrocyclic skeletons. Multiple hydrophobic chains thus placed in a macrocycle must be extended in the same direction and undergo mutual association to attain their optimal hydrophobic interactions in aqueous media due to thermodynamic reasons, while in nonaqueous media they presumably assume a free and separated configuration to minimize their mutual steric interactions. Consequently, such hydrophobic branches may provide a large hydrophobic cavity in aqueous media. 

In order to construct a hydrophobic three-dimensional cavity that is in-tramolecularly limited in space, we have prepared cage-type cyclophanes by linking macrocyclic rings. First we prepared a macropolycyclic host, which is constructed with two rigid macrocyclic skeletons of different size, tetraaza[3.3.3.3]paracyclophane as the larger one and tetraazacyclotetradecane as the smaller one, and four flexible hydrocarbon chains that connect the two macrocycles [40]. The flexibility of four hydrocarbon chains connecting the two macrocycles allows the induced-fit host-guest interaction in aqueous media. 

The first is a cyclophane-based system reported by Murakami et al. (Figure 14a). The sides of the host consist of tetraaza-[3.3.3.3]paracyclophane units and... 

The two 5,6,8,9-tetraaza[3.3]paracyclophanes 6a,b exist as chair and boat conformers, the boat form being energetically favored.27 The chair conformer with the propylene bridge arranged anti to the methoxy substituents predominates over the chair conformation with syn arrangement of the bridge. 

R. Hilgenfeld and W. Saenger, Angew. Chem., 94, 788 (1982). An X-ray structure analysis of the adduct of 1,6,19,24-tetraaza-[6.0.6.0]paracyclophane with benzene (the Stetter complex) showed that the benzene molecules are not accommodated in the cavity... 

ABSTRACT. Crystal and molecular structures of (1 1) molecular complexes of N,N, N",N" -tetramethyl-2,ll,20,29-tetraaza[3.3.3.3]paracyclophane(] ) with CHCI3, CH2C12/ CH3CN and CO2 are reported. The macrocycle has square-box structure, giving hydrophobic cavity surrounded by four benzene rings. The guest molecules are included in the cavity. 

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