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Polycyclic, highly-conjugated, and ortho-fused aromatic compound, 9-tetraethyleneglycoxy-11-oxa[9]helicene (TO9H), was synthesized and used to explore the feasibility of fabricating thin films and the photoelectrochemical properties of resultant films. Since TO9H has both the hydrophobic helicene part and the hydrophilic tetraethyleneglycoxy (TEG) chain, it behaved as a water-insoluble amphiphile and hence formed a stable Langmuir monolayer at the air–water interface. Homogeneous films with thickness up to a few hundred angstroms were deposited by using a spin-coating method. Both of the monolayers and the spin-coated films were characterized by several methods. Brewster angle microscopic (BAM) images and atomic force microscopic (AFM) topographic images revealed the homogeneous surface of the TO9H monolayer at the air–water interface and of the deposited monolayer and films on solid substrates, respectively. By using an X-ray reflectivity (XR) technique, the thickness, roughness, and electron density of layers or films were determined. The photocurrent evolution was measured using conventional three-electrode systems with light irradiation from a xenon lamp and obtained results showed that the compound TO9H generated a substantial amount of photocurrent under illumination of light.

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Enantiomerically pure 9-substituted 11-oxa[9]helicene derivatives have been synthesized through furan-ring formation by a nucleophilic cyclodehydration reaction of enantiomerically pure helical polycondensed 2,2′-diphenoquinone derivatives (1,1′-bibenzo[c]phenanthrenylidene-2,2′-diones). (P)-2,2′-diphenoquinone derivatives afforded (P)-oxa[9]helicenes, whereas (M)-2,2′-diphenoquinone derivatives afforded the corresponding (M)-oxa[9]helicenes. Therefore, the ring-closing reaction afforded the corresponding enantiomerically pure products without decreasing the enantiomeric excess, and it proceeded stereospecifically with retention of the configuration. The thermal stability of an oxa[9]helicene was studied by determining the decrease in its enantiomeric excess at various temperatures, and its racemization barrier was found to be 165.6 kJ/mol.