Journal of Colloid and Interface Science, Vol.301, No.2, 441-445, 2006
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 angstrom 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 nm(2). Finally, as evidenced by XPS, excellent yields (similar to 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. (c) 2006 Elsevier Inc. All rights reserved.
Keywords:tripod films;hydrogen-terminated silicon surfaces;Suzuki coupling reactions;thermally induced surface hydrosilylation;X-ray photoelectron spectroscopy