Thin films derived from giant, tripod-shaped oligophenylenes end-capped with triallylsilyl groups on hydrogen-terminated Si(111) surfaces

Monolayers of giant, tripod-shaped molecules 1 with each tripod leg composed of seven phenylene units end-capped with a triallylsilyl group were prepared on hydrogen-terminated silicon surfaces (H–Si(111)) via thermally induced surface hydrosilylation. The films were characterized by ellipsometry, contact-angle goniometry, and X-ray photoelectron spectroscopy (XPS). The measured ellipsometric thickness of 24 Å of the films suggests anchoring of 1 on the substrate surface with a tripod orientation of high coverage. By measuring the contact angle hysteresis of a series of probe liquids with systematically varied sizes, the molecular pores present on the films consisting of the intercalated molecules of 1 are similar to the cross sectional areas of glycerol and decalin of 0.32–0.49 nm2. Finally, as evidenced by XPS, excellent yields (∼90%)(∼90%) of Suzuki coupling reactions with arylboronic acid derivatives on the films was achieved, suggesting that the desired tripod orientation of such giant molecules as 1 helps to eliminate the steric hindrance for the reaction.

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