Complex Formation with Surfactants other than Quaternary Alkylammonium Salts

12 Complex Formation with Surfactants other than Quaternary Alkylammonium Salts [81] 

The crystal structure of CPB itself was already reported by Ballirano et al [82]. If the CPB only and the complex structures are compared, a mechanism of formation of the latter may be envisaged. Thus, the complex structures are formed as the alkyl chains 

For the CTAB complexes, the A, B and C values are less than 10.29, 7.48 and 5.60 A, respectively. Along the q direction the void space is connected as a column. This means that the value of C corresponds to the molar ratio between the smfactant and the aromatic compound. However, the A and B values indicate the size of the molecule included in the void space. The A and B values in the CPB complexes, especially in XXXIV, are larger than the threshold values of the CTAB complexes. This indicates that CPB can accommodate bulkier aromatic compounds than CTAB. All efforts to make a complex between CTAB and 9-anthracenecarboxyloc acid were in vain, probably because 9-anthracenecarboxylic acid is too bulky for the void space available in the CTAB complex, although a guaiacol complex with CTAB was made. These results suggest that it is possible to discriminate aromatic compounds by making complexes with different surfactants. 

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There are a variety of cationic surfactants other than quaternary alkylammonium salts. Accordingly, complex formation of 1-hexadecylpyridinium bromide (CPB) was attempted (Figure 4.44). After many trials, ten complex crystals were obtained, two of which were suitable for X-ray analysis, i.e. with guaiacol (XXXIII) and 9-anthracenecarboxylic acid (XXXTV) (Figure 4.44). The two crystals are isostructural. 

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