Cyclophane host-guest interaction

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 luminescence of a thin film coated with [Re(CO)3(/u.-4,4 -bipyridine)Cl]4 was quenched by nitrobenzene vapor because of electron transfer. Recently, mesoporous thin films of [Re(CO)3(/u.-L)Cl]4 (L = 4,4 -pyrazine or 4,4 -bipyridine) have been utilized as sensors for volatile organic compounds (VOCs). The host-guest interaction between the rhenium cyclophanes and VOCs was confirmed by quartz crystal microbalance studies. 

Elemental analyses were performed at the Microanalysis Center of Kyushu University. Fluorescence and electronic absorption spectra were taken on a Hitachi 650-40 fluorescence spectrometer and a Hitachi 220A spectrophotometer, respectively. The critical aggregate concentration (cac) was determined by surface tension measurements on a Shimadzu ST-1 surface tensometer assembled by the Wilhelmy principle 2.5 X 10 " moldm for 1 in aqueous media at room temperature. Thus, the cyclophane concentration was maintained in a range below the cac value for all measurements on the host-guest interactions. 

HOST-GUEST INTERACTIONS WITH HYDROPHOBIC CYCLOPHANES IN AQUEOUS MEDIA... 

In the past decade, we have prepared various [20]- and [lO.lOJpara-cyclophanes to explore novel host-guest interaction systems and found that these host molecules demonstrate two different incorporation modes, penetration and face-to-face, toward various hydrophobic guest mole-... 

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