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Quantum Dots as Redox Photocatalysts for Organic Synthesis (PhotoRedoQs)

English title Quantum Dots as Redox Photocatalysts for Organic Synthesis (PhotoRedoQs)
Applicant Renaud Philippe
Number 182078
Funding scheme Project funding (Div. I-III)
Research institution Departement für Chemie und Biochemie Universität Bern
Institution of higher education University of Berne - BE
Main discipline Organic Chemistry
Start/End 01.04.2019 - 31.03.2023
Approved amount 650'018.00
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All Disciplines (2)

Discipline
Organic Chemistry
Physical Chemistry

Keywords (6)

radical reactions; quantum dots; organic synthesis; photocatalysis; photoredox catalysis; semiconductors

Lay Summary (French)

Lead
Les points quantiques colloïdaux comme photocatalyseurs redox pour la synthèse organique
Lay summary

Introduction
Au cours de la dernière décennie, l'émergence de la catalyse photoredox utilisant de la lumière visible a révolutionné le domaine de la chimie organique synthétique. La conception des catalyseurs a été stimulée par le développement de catalyseurs pour la conversion de l'énergie solaire. Les complexes de coordination de platinoïdes tels que le ruthénium et de l'iridium ont joué un rôle majeur dans ce développement. Les points quantiques colloïdaux (PQCs, quantum dots QDs en anglais) sont des nanocristaux de matériaux semi-conducteurs qui ont le potentiel de remplacer les platinoïdes en catalyse photoredox. Ces catalyseurs nanocristallins sont très attrayants car ils combinent certains des avantages des catalyseurs homogènes, tels qu'un grand coefficient d'extinction dans le spectre visible, et conservent la possibilité d'être éliminés par ultrafiltration ou centrifugation après réaction. Leurs propriétés redox peuvent être affinées en modifiant leur composition (CdS, CdSe, ZnO, ZnSe), leur taille et la nature des ligands utilisés pour leur stabilisation.

Objectifs
Le projet est divisé en deux thèmes étroitement liés : 1) l'utilisation de PQCs pour engendrer dans des conditions douces des radicaux hautement réactifs utile en synthèse organique; 2) le développement d'une nouvelle classe de photocatalyseurs combinant des PQCs et des nanoparticules d'argent (PQC-Ag) afin d'améliorer leurs propriétés photocatalytiques.

Contexte
Grâce à leur coût modéré et leur nature nanocrystalline, de tels catalyseurs sont particulièrement attractifs pour les applications industrielles de la catalyse photoredox.

Direct link to Lay Summary Last update: 01.03.2019

Responsible applicant and co-applicants

Employees

Name Institute

Associated projects

Number Title Start Funding scheme
172621 Synthetic Methods for Total Synthesis of Natural Products 01.04.2017 Project funding (Div. I-III)

Abstract

In the last decade, the emergence of photoredox catalysis has revolutionized the field of synthetic organic chemistry. Catalyst design has been boosted by development of catalysts for solar energy conversion. Ruthenium and iridium coordination complexes are playing a major role in this development. Besides these homogeneous catalysts, the use of heterogenous semiconductor photoredox catalysts for synthesis is still in his infancy. We propose here a research program dedicated to the investigation of semiconductor colloidal quantum dots (QDs) as photoredox catalysts for synthetic organic chemistry. These nanocrystalline catalysts are highly attractive since they combine some of the advantages of the homogeneous catalysts, such as large extinction coefficient in the visible spectrum, and retain the ability to be removed by ultra-filtration or centrifugation. Moreover, QDs are very resistant to photobleaching and their redox properties may be fine-tuned by changing their composition (CdS, CdSe, ZnO, ZnSe), controlling their size and modifying the ligands used to stabilize them. Finally, finding substitutes to the costly ruthenium and particularly iridium catalysts, will open new perspective for industrial application of photoredox catalysis.The project is divided in two closely related topics: 1) the use of QD-photocatalysts to generate alkoxyl radicals; 2) the development of a new class of photocatalysts combining QDs and Ag nanoparticles (QD-Ag).Generation of alkoxyl radicals using QD-photocatalysts. Alkoxyl radicals are well-known species that possess a truly unique reactivity. However, due to the lack of efficient and mild methods to generated them, their rich chemistry is underutilized in synthesis. We propose to investigate the use and optimization of classical QDs as photocatalysts to develop several innovative methods to generate alkoxyl radicals. For instance, the oxidation of stable and easily prepared borate complexes will be examined.Development of QD-Ag composite catalysts. In order to enhance QD-photocatalyst quantum efficiency, the grafting of Ag-nanoparticles (Ag-NPs) to the QDs will be examined. This modification is expected to favor the charge separation step after light absorption by the QD by electron transfer to the Ag-NP. Furthermore, this will enhance the reactivity of holes that stay in the QD after charge separation by delaying their recombination with electrons lying in the Ag-NP. The photocatalytic behavior of this new class of QDs will be tested with more established synthetic transformations such as the generation of radicals via oxidative decarboxylation of carboxylic acids and oxidation of tertiary amines.
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