| Abstract
| - The cholesteryl esters (3b and 3a) of5-carboxy-1,3-phenylene-16-crown-5 and5-carboxy-4,6-dichloro-1,3-phenylene-16-crown-5 show cholesteric liquid crystalline behaviorbut only upon heating samplesthat were rapidly cooled from the isotropic melt in the case of3a and a monotropic phase for 3b.The dichloro compound 3a was formed by treatment of thecorresponding acid 2 with SOCl2firstand then cholesterol; it is believed that the SOCl2 wascontaminated with SO2Cl2, leading tothechlorination of the aromatic ring. The dichloro compound3a was structurally characterized usingsingle crystal X-ray diffraction. 3a crystallizes inthe orthorhombic space groupP212121 withunitcell parameters of a = 12.76(4) Å, b =17.511(5) Å, and c = 18.213 Å. Use of freshlyopened SOCl2produced 3b. The reaction of the acid 2 andcholesterol in the presence of dicyclohexylcarbodiimideyielded the acylisourea 4 as the major product (64%) alongwith 3b (36%) upon treatment withcholesterol. The dicholesteryl ester 9 ofbis(5-carboxy-1,3-phenylene)-32-crown-10 (8a) wasalsosynthesized, and by differential scanning calorimetry (DSC) andpolarized optical microscopy noliquid crystalline behavior was observed with this system.Apparently the presence of the semirigidcrown in the molecule prevents the two cholesteryl moieties fromorganizing in independent helices.The complexation ability of this cholesteryl crown (9)with methyl viologen bis(hexafluorophosphate)([paraquat]·2[PF6]) (12) in acetonehas been examined by 1H NMR spectroscopy; it showedweakerbinding than its simple dimethyl ester analog8b.
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