Laboratory-scale photoredox catalysis using hydrated electrons sustainably generated with a single green laser

Abstract

<p>A combined photokinetical approach helped develop and optimize a green-light driven photoredox catalytic system that generates a “super-reductant” with simple instrumentation, consumes only a bioavailable donor, and provides very high turnover numbers.</p>

Autoren

Robert Naumann
Christoph Kerzig
Martin Goez

DOI

10.1039/c7sc03514d

eISSN

2041-6539

ISSN

2041-6520

Ausgabe der Veröffentlichung

11

Zeitschrift

Chem. Sci.

Sprache

en

Online publication date

2017

Paginierung

7510 - 7520

Status

Published online

Herausgeber

Royal Society of Chemistry (RSC)

Herausgeber URL

http://dx.doi.org/10.1039/c7sc03514d

Datum der Datenerfassung

2024

Titel

Laboratory-scale photoredox catalysis using hydrated electrons sustainably generated with a single green laser

Ausgabe der Zeitschrift

8

Datenquelle: Crossref

Abstract

The ruthenium-tris-bipyridyl dication as catalyst combined with the ascorbate dianion as bioavailable sacrificial donor provides the first regenerative source of hydrated electrons for chemical syntheses on millimolar scales. This electron generator is operated simply by illumination with a frequency-doubled Nd:YAG laser (532 nm) running at its normal repetition rate. Much more detailed information than by product studies alone was obtained by photokinetical characterization from submicroseconds (time-resolved laser flash photolysis) up to one hour (preparative photolysis). The experiments on short timescales established a reaction mechanism more complex than previously thought, and proved the catalytic action by unchanged concentration traces of the key transients over a number of flashes so large that the accumulated electron total surpassed the catalyst concentration many times. Preparative photolyses revealed that the sacrificial donor greatly enhances the catalyst stability through quenching the initial metal-to-ligand charge-transfer state before destructive dd states can be populated from it, such that the efficiency of this electron generator is no longer limited by catalyst decomposition but by electron scavenging by the accumulating oxidation products of the ascorbate. Applications covered dechlorinations of selected aliphatic and aromatic chlorides and the reduction of a model ketone. All these substrates are impervious to photoredox catalysts exhibiting lower reducing power than the hydrated electron, but the combination of an extremely negative standard potential and a long unquenched life allowed turnover numbers up to 1400 with our method.

Addresses

Martin-Luther-Universität Halle-Wittenberg , Institut für Chemie , Kurt-Mothes-Str. 2 , D-06120 Halle (Saale) , Germany . Email: martin.goez@chemie.uni-halle.de.

Autoren

Robert Naumann
Christoph Kerzig
Martin Goez

DOI

10.1039/c7sc03514d

eISSN

2041-6539

Externe Identifier

PubMed Identifier: 29163905
PubMed Central ID: PMC5676201

Open access

true

ISSN

2041-6520

Ausgabe der Veröffentlichung

11

Zeitschrift

Chemical science

Sprache

eng

Medium

Print-Electronic

Online publication date

2017

Open access status

Open Access

Paginierung

7510 - 7520

Datum der Veröffentlichung

2017

Status

Published

Publisher licence

CC BY-NC

Datum der Datenerfassung

2017

Titel

Laboratory-scale photoredox catalysis using hydrated electrons sustainably generated with a single green laser.

Sub types

research-article
Journal Article

Ausgabe der Zeitschrift

8

Files

https://pubs.rsc.org/en/content/articlepdf/2017/sc/c7sc03514d https://europepmc.org/articles/PMC5676201?pdf=render

Datenquelle: Europe PubMed Central

Abstract

The ruthenium-tris-bipyridyl dication as catalyst combined with the ascorbate dianion as bioavailable sacrificial donor provides the first regenerative source of hydrated electrons for chemical syntheses on millimolar scales. This electron generator is operated simply by illumination with a frequency-doubled Nd:YAG laser (532 nm) running at its normal repetition rate. Much more detailed information than by product studies alone was obtained by photokinetical characterization from submicroseconds (time-resolved laser flash photolysis) up to one hour (preparative photolysis). The experiments on short timescales established a reaction mechanism more complex than previously thought, and proved the catalytic action by unchanged concentration traces of the key transients over a number of flashes so large that the accumulated electron total surpassed the catalyst concentration many times. Preparative photolyses revealed that the sacrificial donor greatly enhances the catalyst stability through quenching the initial metal-to-ligand charge-transfer state before destructive dd states can be populated from it, such that the efficiency of this electron generator is no longer limited by catalyst decomposition but by electron scavenging by the accumulating oxidation products of the ascorbate. Applications covered dechlorinations of selected aliphatic and aromatic chlorides and the reduction of a model ketone. All these substrates are impervious to photoredox catalysts exhibiting lower reducing power than the hydrated electron, but the combination of an extremely negative standard potential and a long unquenched life allowed turnover numbers up to 1400 with our method.

Date of acceptance

2017

Autoren

Robert Naumann
Christoph Kerzig
Martin Goez

Autoren-URL

https://www.ncbi.nlm.nih.gov/pubmed/29163905

DOI

10.1039/c7sc03514d

Externe Identifier

PubMed Central ID: PMC5676201

ISSN

2041-6520

Ausgabe der Veröffentlichung

11

Zeitschrift

Chem Sci

Sprache

eng

Country

England

Paginierung

7510 - 7520

PII

c7sc03514d

Datum der Veröffentlichung

2017

Status

Published

Titel

Laboratory-scale photoredox catalysis using hydrated electrons sustainably generated with a single green laser.

Sub types

Journal Article

Ausgabe der Zeitschrift

8

Datenquelle: PubMed

Laboratory-scale photoredox catalysis using hydrated electrons sustainably generated with a single green laser

Files

Werkzeuge