Grafting Behavior for the Resonating Variants of Ethynylaniline on Hydrogenated Silicon (100) Surfaces under Thermal Hydrosilylation

Joline Tung; Lih Shin Tew; Carmine Coluccini; Yue-Der Lin; Yit Lung Khung

doi:10.1002/chem.201802003

Grafting Behavior for the Resonating Variants of Ethynylaniline on Hydrogenated Silicon (100) Surfaces under Thermal Hydrosilylation

Chemistry. 2018 Sep 6;24(50):13270-13277. doi: 10.1002/chem.201802003. Epub 2018 Aug 3.

Authors

Joline Tung¹, Lih Shin Tew², Carmine Coluccini³, Yue-Der Lin⁴, Yit Lung Khung⁵

Affiliations

¹ College of Arts and Sciences, University of North Carolina at Chapel Hill (UNC), Chapel Hill, NC, 27514, USA.
² Advanced Medical and Dental Institute (AMDI), Universiti Sains Malaysia, 13200, Kepala Batas Pulau Pinang, Malaysia.
³ Institute of New Drug Development, China Medical University, No.91 Hsueh-Shih Road, Taichung, Taiwan.
⁴ Department of Automatic Control Engineering, Feng Chia University, No. 100, Wenhwa Rd., Seatwen, Taichung, Taiwan.
⁵ Department of Biological Science and Technology, China Medical University, No.91 Hsueh-Shih Road, Taichung, Taiwan.

PMID: 29932257
DOI: 10.1002/chem.201802003

Abstract

This work reports the outcome of thermal grafting of 2-ethynylaniline, 3-ethynylaniline, and 4-ethynylaniline on a hydrogenated Si(100) surface. Using high-resolution XPS and AFM, it was found that the grafting of these compounds could be attributed to resonating structures that arise from the position of an electron-donating NH₂ group and an electron-withdrawing acetylene group. For the ortho- and para-positioned acetylene group, surface reactions were observed to proceed predominantly via the acetylene to form a Si-C bond, whereas the meta-positioned acetylene group was found to have undergone nucleophilic grafting through the NH₂ group onto the silicon surface to form a Si-N bond. Furthermore, a tert-butoxycarbonyl-protected derivative for a meta-positioned ethynylaniline was synthesized to exclusively force the reaction to react with the acetylene group and subsequent analysis confirmed that unprotected 3-ethynylaniline had indeed reacted through the nucleophilic NH₂ group as hypothesized. Thus, for the first time, the interplay between resonance structures and their effects on silicon surface modifications were systematically catalogued.

Keywords: AFM; XPS; ethynylaniline; nucleophilic addition; thermal hydrosilylation.