Control of surface alkyl catalysis with thiolate monolayers

Pang, Simon H.; Lien, Chih-Heng; Medlin, J. Will

doi:10.1039/c5cy01831e

Cited by 11 publications

(11 citation statements)

References 37 publications

(47 reference statements)

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“…Modification of the catalyst by AT did not appreciably affect selectivity, whereas the C18 modifier lowered the selectivity to ~80%. Previous studies have found that dense C18 SAMs decrease the rate of double bond migration reactions less than other reactions [29], consistent with the dense C18 coating allowing more facile isomerization compared to oxidation. catalysts over the course of a two-hour reaction.…”

Section: Liquid-phase Catalytic Studiessupporting

confidence: 74%

Application of thiolate self-assembled monolayers in selective alcohol oxidation for suppression of Pd catalyst deactivation

Hao

Pylypenko

Schwartz

et al. 2016

Journal of Catalysis

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Rapid deactivation often reduces the effectiveness of Pt-group catalysts in the lowtemperature aerobic oxidation of alcohols. Here, we report the use of thiolate selfassembled monolayers (SAMs) as activity promoters in the liquid-phase oxidation of trans-2-hexen-1-ol (HOL) under low air pressure; the oxidation rate was significantly improved, particularly at high conversion, in contrast to frequently observed activity decrease induced by SAM modification in hydrogenation reactions. Reaction studies indicated that in the regime of low air pressure, catalyst deactivation was mainly caused by the carbonaceous poisons generated from the reaction product 2-hexenal (HAL). Infrared spectroscopy revealed that HAL produced surface residues on Pd that poisoned the catalyst, hypothetically through decarbonylation and dimerization. This poisoning can be suppressed

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Section: Liquid-phase Catalytic Studiessupporting

confidence: 74%

Application of thiolate self-assembled monolayers in selective alcohol oxidation for suppression of Pd catalyst deactivation

Hao

Pylypenko

Schwartz

et al. 2016

Journal of Catalysis

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“…Enoate 2 was envisioned to be synthesized via modification of Marquez's optimized DAG lactone route. 34 Known epoxy alcohol 7 was accessed by the route reported by Marquez and co-workers. 34 BOM protection of epoxy alcohol 7 gave epoxide 8 in moderate yield.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…34 Known epoxy alcohol 7 was accessed by the route reported by Marquez and co-workers. 34 BOM protection of epoxy alcohol 7 gave epoxide 8 in moderate yield. Epoxide 8 was treated with lithium acetylide ethylenediamine complex, 34 producing homopropargylic alcohol 9.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Synthesis and Biological Evaluation of Several Bryostatin Analogues Bearing a Diacylglycerol Lactone C-Ring

et al. 2016

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As an initial step in designing a simplified bryostatin hybrid molecule, three bryostatin analogues bearing a diacylglycerol lactone-based C-ring, which possessed the requisite pharmacophores for binding to protein kinase C (PKC) together with a modified bryostatin-like A- and B-ring region, were synthesized and evaluated. Merle 46 and Merle 47 exhibited binding affinity to PKC alpha with Ki values of 7000 ± 990 and 4940 ± 470 nM, respectively. Reinstallation of the trans-olefin and gem-dimethyl group present in bryostatin 1 in Merle 48 resulted in improved binding affinity, 363 ± 42 nM. While Merle 46 and 47 were only marginally active biologically, Merle 48 showed sufficient activity on the U937 cells to confirm that it was PMA-like for growth and attachment, as predicted by the substitution pattern of its A- and B-rings.

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“…The relative CO affinity on Al 2 O 3 -supported Pd catalysts modified with different thiols was experimentally measured using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). 1-Adamantane (AT), 1-hexanethiol (C 6 ), and 1-octadecanethiol (C 18 ) were deposited onto a Pd/Al 2 O 3 catalyst using an established procedure. − Samples were reduced for 1 h at 160 °C in 25% H 2 /Ar and then cooled to 50 °C before pure CO was introduced into the reactor system. After a 5 min exposure, CO was evacuated with a vacuum pump to a base pressure of <200 mTorr.…”

Section: Methodsmentioning

confidence: 99%

Thermodynamics of Alkanethiol Self-Assembled Monolayer Assembly on Pd Surfaces

et al. 2018

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We investigate the structure and binding energy of alkanethiolate self-assembled monolayers (SAMs) on Pd (111), Pd (100), and Pd (110) facets at different coverages. Dispersion-corrected density functional theory calculations are used to correlate the binding energy of alkanethiolates with alkyl chain length and coverage. The equilibrium coverage of thiolate layers strongly prefers 1/3 monolayer (ML) on the Pd (111) surface. The coverage of thiolates varies with chemical potential on Pd (100) and Pd (110), increasing from 1/3 to 1/2 ML on (100) and from 1/4 to 1/2 ML on (110) as the thiol chemical potential is increased. Higher coverages are driven by attractive dispersion interactions between the extended alkyl chains, such that transitions to higher coverages occur at lower thiol chemical potentials for longer chain thiolates. Stronger adsorption to the Pd (100) surface causes the equilibrium Wulff construction of Pd particles to take on a cubic shape upon saturation with thiols. The binding of H, O, and CO adsorbates is weakened as the thiolate coverage is increased, with saturation coverages causing unfavorable binding of O and CO on Pd (100) and weakened binding on other facets. Temperature-dependent CO diffuse reflectance infrared Fourier transform spectroscopy experiments are used to corroborate the weakened binding of CO in the presence of thiolate SAMs of varying surface density. Preliminary results of multiscale modeling efforts on the Pd-thiol system using a reactive force field, ReaxFF, are also discussed.

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Control of surface alkyl catalysis with thiolate monolayers

Abstract: Pd surface modification by thiolate SAMs resulted in preferential terminal-to-internal olefin isomerization instead of hydrogenation, particularly at high conversion.

Cited by 11 publications

References 37 publications

Application of thiolate self-assembled monolayers in selective alcohol oxidation for suppression of Pd catalyst deactivation

Application of thiolate self-assembled monolayers in selective alcohol oxidation for suppression of Pd catalyst deactivation

Synthesis and Biological Evaluation of Several Bryostatin Analogues Bearing a Diacylglycerol Lactone C-Ring

Thermodynamics of Alkanethiol Self-Assembled Monolayer Assembly on Pd Surfaces

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