Grafting of Monocarboxylic Substituted Polychlorotriphenylmethyl Radicals onto a COOH-Functionalized Self-Assembled Monolayer through Copper (II) Metal Ions

• Published in: Langmuir 2008-07, Vol.24 (13), p.6640-6648
• Main Authors: Shekhah, O, Roques, N, Mugnaini, V, Munuera, C, Ocal, C, Veciana, J, Wöll, C
• Format: Article
• Language: English
• Subjects: Chemistry; Colloidal state and disperse state; Exact sciences and technology; General and physical chemistry; Interfaces: Adsorption, Reactions, Films, Forces; Surface physical chemistry
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la800771q

A monocarboxylic substituted polychlorotriphenylmethyl radical (PTMCOOH) has been grafted onto a COOH-functionalized SAM (mercaptohexadecanoic acid, MHDA SAM), using copper (II) metal ions as linkers between the carboxyl groups of the SAM and the ligand. The metal-radical adlayer has been characterized thoroughly using different surface analysis techniques, such as contact angle, IRRAS, XPS, SPR, ToF-SIMS, SFM, and NEXAFS. The magnetic character was confirmed by EPR. The density of unoccupied states was investigated using X-ray absorption spectroscopy. A low-energy peak in the NEXAFS spectrum directly revealed the presence of partially occupied electronic levels, thus proving the open-shell character of the grafted ligands. SEM measurements on a laterally patterned sample prepared by μCP of MHDA in a matrix of hexadecane thiolate (a CH3-terminated SAM) was performed to demonstrate that the metal-assisted anchoring of the open-shell ligand occurs selectively on the COOH terminated SAM. These results represent an easy and new approach to anchor organic radicals on surfaces and constitute a first step toward the growth of magnetic metal-organic radical-based frameworks on solid substrates.