title: Steric effects in the reaction of aryl radicals on surfaces.
abstract: Steric effects are investigated in the reaction of aryl radicals with surfaces. The electrochemical reduction of 2-, 3-, 4-methyl, 2-methoxy, 2-ethyl, 2,6-, 2,4-, and 3,5-dimethyl, 4-tert-butyl, 3,5-bis-tert-butyl benzenediazonium, 3,5-bis(trifluoromethyl), and pentafluoro benzenediazonium tetrafluoroborates is examined in acetonitrile solutions. It leads to the formation of grafted layers only if the steric hindrance at the 2- or 2,6-position(s) is small. When the 3,5-positions are crowded with tert-butyl groups, the growth of the organic layer is limited by steric effects and a monolayer is formed. The efficiency of the grafting process is assessed by cyclic voltammetry, X-ray photoelectron spectroscopy, infrared, and ellipsometry. These experiments, together with density functional computations of bonding energies of substituted phenyl groups on a copper surface, are discussed in terms of the reactivity of aryl radicals in the electrografting reaction and in the growth of the polyaryl layer.
authors.affiliation: Laboratoire Environnement et Chimie Analytique, UMR 7121, CNRS-ESPCI Paris Tech, 10 rue Vauquelin, 75231 Paris Cedex 05, France.
authors.forename: Catherine
authors.initials: C
authors.lastname: Combellas
authors.forename: De-en
authors.initials: DE
authors.lastname: Jiang
authors.forename: Frédéric
authors.initials: F
authors.lastname: Kanoufi
authors.forename: Jean
authors.initials: J
authors.lastname: Pinson
authors.forename: Fetah
authors.initials: F
authors.lastname: Podvorica