Excited state decay of cyclometalated polypyridine ruthenium complexes: insight from theory and experiment

Abstract

<p>This perspective article tackles the open question why cyclometalated polypyridine ruthenium(<sc>ii</sc>) complexes typically only emit very weakly at room temperature and delivers answers beyond the standard schemes involving <sup>3</sup>MC and tunneling decay channels.</p>

Autoren

Christoph Kreitner
Katja Heinze

DOI

10.1039/c6dt01989g

eISSN

1477-9234

ISSN

1477-9226

Ausgabe der Veröffentlichung

35

Zeitschrift

Dalton Transactions

Sprache

en

Online publication date

2016

Paginierung

13631 - 13647

Status

Published online

Herausgeber

Royal Society of Chemistry (RSC)

Herausgeber URL

http://dx.doi.org/10.1039/c6dt01989g

Datum der Datenerfassung

2024

Titel

Excited state decay of cyclometalated polypyridine ruthenium complexes: insight from theory and experiment

Ausgabe der Zeitschrift

45

Datenquelle: Crossref

Abstract

Deactivation pathways of the triplet metal-to-ligand charge transfer ((3)MLCT) excited state of cyclometalated polypyridine ruthenium complexes with [RuN5C](+) coordination are discussed on the basis of the available experimental data and a series of density functional theory calculations. Three different complex classes are considered, namely with [Ru(N^N)2(N^C)](+), [Ru(N^N^N)(N^C^N)](+) and [Ru(N^N^N)(N^N^C)](+) coordination modes. Excited state deactivation in these complex types proceeds via five distinct decay channels. Vibronic coupling of the (3)MLCT state to high-energy oscillators of the singlet ground state ((1)GS) allows tunneling to the ground state followed by vibrational relaxation (path A). A ligand field excited state ((3)MC) is thermally accessible via a (3)MLCT →(3)MC transition state with the (3)MC state being strongly coupled to the (1)GS surface via a low-energy minimum energy crossing point (path B). Furthermore, a (3)MLCT →(1)GS surface crossing point directly couples the triplet and singlet potential energy surfaces (path C). Charge transfer states either with higher singlet character or with different orbital parentage and intrinsic symmetry restrictions are thermally populated which promote non-radiative decay via tunneling to the (1)GS state (path D). Finally, the excited state can decay via phosphorescence (path E). The dominant deactivation pathways differ for the three individual complex classes. The implications of these findings for isoelectronic iridium(iii) or iron(ii) complexes are discussed. Ultimately, strategies for optimizing the emission efficiencies of cyclometalated polypyridine complexes of d(6)-metal ions, especially Ru(II), are suggested.

Addresses

Institute of Inorganic and Analytical Chemistry, Johannes Gutenberg University, Duesbergweg 10-14, D-55128 Mainz, Germany. katja.heinze@uni-mainz.de.

Autoren

Christoph Kreitner
Katja Heinze

DOI

10.1039/c6dt01989g

eISSN

1477-9234

Externe Identifier

PubMed Identifier: 27334798

Funding acknowledgements

Deutsche Forschungsgemeinschaft: GSC 266

Open access

false

ISSN

1477-9226

Ausgabe der Veröffentlichung

35

Zeitschrift

Dalton transactions (Cambridge, England : 2003)

Sprache

eng

Medium

Print-Electronic

Online publication date

2016

Paginierung

13631 - 13647

Datum der Veröffentlichung

2016

Status

Published

Datum der Datenerfassung

2016

Titel

Excited state decay of cyclometalated polypyridine ruthenium complexes: insight from theory and experiment.

Sub types

Journal Article

Ausgabe der Zeitschrift

45

Datenquelle: Europe PubMed Central

Abstract

Deactivation pathways of the triplet metal-to-ligand charge transfer ((3)MLCT) excited state of cyclometalated polypyridine ruthenium complexes with [RuN5C](+) coordination are discussed on the basis of the available experimental data and a series of density functional theory calculations. Three different complex classes are considered, namely with [Ru(N^N)2(N^C)](+), [Ru(N^N^N)(N^C^N)](+) and [Ru(N^N^N)(N^N^C)](+) coordination modes. Excited state deactivation in these complex types proceeds via five distinct decay channels. Vibronic coupling of the (3)MLCT state to high-energy oscillators of the singlet ground state ((1)GS) allows tunneling to the ground state followed by vibrational relaxation (path A). A ligand field excited state ((3)MC) is thermally accessible via a (3)MLCT →(3)MC transition state with the (3)MC state being strongly coupled to the (1)GS surface via a low-energy minimum energy crossing point (path B). Furthermore, a (3)MLCT →(1)GS surface crossing point directly couples the triplet and singlet potential energy surfaces (path C). Charge transfer states either with higher singlet character or with different orbital parentage and intrinsic symmetry restrictions are thermally populated which promote non-radiative decay via tunneling to the (1)GS state (path D). Finally, the excited state can decay via phosphorescence (path E). The dominant deactivation pathways differ for the three individual complex classes. The implications of these findings for isoelectronic iridium(iii) or iron(ii) complexes are discussed. Ultimately, strategies for optimizing the emission efficiencies of cyclometalated polypyridine complexes of d(6)-metal ions, especially Ru(II), are suggested.

Autoren

Christoph Kreitner
Katja Heinze

Autoren-URL

https://www.ncbi.nlm.nih.gov/pubmed/27334798

DOI

10.1039/c6dt01989g

eISSN

1477-9234

Ausgabe der Veröffentlichung

35

Zeitschrift

Dalton Trans

Sprache

eng

Country

England

Paginierung

13631 - 13647

Datum der Veröffentlichung

2016

Status

Published

Datum, an dem der Datensatz öffentlich gemacht wurde

2018

Titel

Excited state decay of cyclometalated polypyridine ruthenium complexes: insight from theory and experiment.

Sub types

Journal Article

Ausgabe der Zeitschrift

45

Datenquelle: PubMed

Excited state decay of cyclometalated polypyridine ruthenium complexes: insight from theory and experiment

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