Self-assembled monolayers reduction

Collman JP, Ennis MS, Offord DA, Chng LL, Griffin JH. 1996. Electrocatal)4ic reduction of dioxygen by diruthenium cofacial diporphyrins axiaUy-bound to a gold-supported, self-assembled monolayer. Inorg Chem 35 1751. 

The first surface-initiated enzymatic polymerization reported was the synthesis of amylose brushes on planar and spherical surfaces [145]. For this, silica or silicone surfaces were modified with self-assembled monolayers of (3 amino-propyl)trimethoxysilane or chlorodimethylsilane, respectively. To these functionalities, oligosaccharides were added via (a) reductive amidation of the oligosaccharides to surface-bound amines, (b) conversion of the oiigosaccharide to the according aldonic acid lactone and reaction with surface bound amines, and (c) incorporation... 

Ex situ measurements in the presence of dissolved oxygen have proved that the mixed monolayer was stable in the solution free of 6TG and guanine. Madueno etal. [Ill] have also studied adsorption and phase formation of 6TG on mercury electrode. At high potentials, the molecules were chemisorbed and were able to form a self-assembled monolayer. When the potential was scanned to more negative values, reductive desorption of the monolayer was observed. Cathodic voltam-metric peaks, which are typical of a 2D condensed phase transition, divided the potential window into two regions one, in which self-assembled monolayer was stable, and the second, in which a physisorbed state existed. 

UPD on Pt(lll) displays inhibited activity in acidic solutions even when small quantities of Cu were deposited, suggesting that this surface lacks sufficient Pt active sites. " Although not involving Pt, Ag-UPD on Au(lll) coated with a self-assembled monolayer (SAM) of decanethiol displayed island size effects. HMRD measurements and STM images found two-electron reductions dominate on islands with 750 Ag atoms and four-electron reductions dominate on islands consisting of 4000 Ag atoms. 

Electrochemical data indicate that self-assembled monolayers of 5 and 6 catalyze the two-electron reduction of O2 to H2O2. The monolayer from 6 is a more effective electrocatalyst for the reduction of O2 than that from 5 [300]. The different reactivity results from different interfacial architecture this is confirmed by infrared, X-ray photoelectron, and visible spectroscopic measurements [300] which revealed coplanar, inclined t -7z stacking of the porphyrin ring in the monolayer of 5 and head-to-tail orientation of the porphyrin ring in the monolayer of 6. Treatment of the monolayer of 8 with Co(OAc)2 in methanol resulted in electrocatalytic activity in the reduction of O2 [300]. In contrast, a monolayer of 7 treated similarly failed to catalyze dioxygen reduction [300], although treatment of a mixed monolayer of 7 and CH3(CH2)3SH with Co(OAc)2 results in electrocatalytic activity similar to that of 6. 

The extent of metal insertion is strongly dependent on the type of metal ion. Cobalt (II), nickel (II), and zinc (II) are readily incorporated into the porphyrin ring, whereas manganese (II), iron (II), and copper (II) are difficult to insert under the same experimental conditions [335]. Self-assembled monolayers of 12 and 13 have electro-catalytic activity in the reduction of O2 to H2O and H2O2, respectively. 

Fluoride is trapped as NaF and under certain conditions the yield of per-florotetralin can be maximized. Lewis acidic sites in crystal surface defects are thought to assist in the C-F activation process and at 470°C the system is active for demineralization of chlorofluorocarbons to afford NaF, NaCl and carbon [76]. Detailed electrochemical studies of the reduction of C-F bonds in aryltrif-luoromethanes and fluoroalkoxyarenes have been reported [77]. Free radicals cleave C-F bonds of fluorinated self-assembled monolayer surfaces [78]. 

Srinivasan, U. Houston, M.R. Howe, R.T. Maboudian, R. Alkyltrichlorosilane-based self assembled monolayer films for stiction reduction in silicon micromachines. J. Microelectromechan. Syst. 1998, 7 (2), 252-260. 

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