Arylmethyl films have been grafted to glassy carbon surfaces and to pyrolyzed photoresist films (PPFs) by electrochemical oxidation of 1-naphthylmethylcarboxylate and 4-methoxybenzylcarboxylate. Atomic force microscopy (AFM) and electrochemistry were used to characterize the as-prepared films and to monitor changes induced by post-preparation treatments. Film thickness was measured by depth profiling using an AFM tip to remove film from the PPF surface. Surface coverage of electroactive modifiers was estimated from cyclic voltammetry, and monitoring the response of a solution-based redox probe at grafted surfaces gave a qualitative indication of changes in film properties. For preparation of the films, the maximum film thickness increased with the potential applied during grafting, and all films were of multilayer thickness. The apparent rate of electron transfer for the Fe(CN)(6)3-/Fe(CN)(6)4- couple was very low at as-prepared films. After film-grafted electrodes were transferred to pure acetonitrile-electrolyte solution and subjected to negative potential excursions, the response of the Fe(CN)(6)3-/Fe(CN)(6)4- couple changed and was consistent with faster electron-transfer kinetics, the film thickness decreased and the surface roughness increased substantially. Applying a positive potential to the treated film reversed changes in film thickness, but the voltammetric response of the Fe(CN)(6)3-/Fe(CN)(6)4- couple remained kinetically fast. After as-prepared films were subjected to positive applied potentials in acetonitrile-electrolyte solution, the apparent rate of electron transfer for the Fe(CN)(6)3-/Fe(CN)(6)4- couple remained very slow and the measured film thickness was the same or greater than that before treatment at positive potentials. Mechanisms are considered to explain the observed effects of applied potential on film characteristics.

Equilibrium constants are reported for the aluminum(III) complexes with four ligands that contain the 1,2-dihydroxyaryl group: trans-3-(3′,4′-dihydroxyphenyl)propenoic acid (caffeic acid), 3-(3′,4′-dihydroxycinnamoyl)-1,3,4,5-tetrahydroxycyclohexanecarboxylic acid (chlorogenic acid), 3,4-dihydroxybenzylamine (DHB), and 1,2-dihydroxyanthraquinone-3-sulfonic acid (DASA). The protonation and complexation reactions were studied by potentiometric and spectrophotometric titrations in aqueous solution at 25 °C (I ) 0.10 M KCl). The complexation reactions were studied for ligand/metal ratios in the range from 1.3 to 5.9. For caffeic and chlorogenic acids (H 3 L), the experimental data were consistent with the formation of six mononuclear Al-ligand species, each involving catecholate coordination: AlHL + , AlL, Al(OH)L -, AlL 2 3-, Al(OH)L 2 4-, and AlL 3 6-. For DHB (H 2 L), the data were consistent with the formation of six monomeric and one dimeric Al species: AlHL 2+ , Al(HL) 2 + , Al(HL) 3 0 , Al(HL) 2 L -, Al(HL)L 2 2-, AlL 3 3-, and (OH) 2 Al 2 (HL) 2 2+ , in which HL has a protonated amino group. On the basis of the DASA (H 2 L -) titration data, three monomeric and one dimeric Al-ligand species were proposed: AlL 0 , AlL 2 3-, Al(OH)L 2 4-, and Al 2 (OH) 2 L 4 8-. The relative stability of the 1:1 complexes, AlL, was DASA > chlorogenic acid > caffeic acid > DHB. This indicates the progressive electron-withdrawing effects of the ring substituents -SO 3 -< -CHdCH‚CO‚O‚(C 6 H 10 O 3 )‚COOH < -CHdCH‚COOH < -NH 3 + .

Here we report a versatile ring-closing metathesis-based approach to 5-, 6-, and 7-membered cyclic beta-amino esters starting with simple and readily available building blocks-methionine, allylglycine, and serine-where the nature of the amino acid determines the size of the carbocyclic ring.

Self-assembled thiol monolayers bound to single-crystal Au(111) surfaces containing a terminal olefin have been prepared and used to monitor electrochemically the cross-metathesis (CM) between the surface and an olefin-terminated ferrocenyl (Fc) derivative from solution over time. Mixed SAM surfaces were prepared by first adsorbing a diluent for 2 days followed by the olefinic alkanethiol for known adsorption time intervals; three diluents of varying length were used. The oxidation peak areas from the voltammetry show the CM reaction yields a maximum amount of product at 100-150 min. Beyond this time, thiol desorption is apparent and the Fc oxidation peaks diminished. A kinetic simulation of the interfacial reactions involving CM and desorption reactions are described and aided in the interpretation of the voltammetric responses. The length of the diluent and the coverage of surface olefins were important factors in limiting undesirable self-CM reactions on the surface, and a model of the relationship between the diluent and surface concentration of olefin is described. This study shows that attention to monolayer formation and reaction conditions are important parameters when maximizing CM yields on surfaces.