Triplet excited state properties in variable gap π-conjugated donor–acceptor–donor chromophores

Handle URI:
http://hdl.handle.net/10754/617306
Title:
Triplet excited state properties in variable gap π-conjugated donor–acceptor–donor chromophores
Authors:
Cekli, Seda; Winkel, Russell W.; Alarousu, Erkki; Mohammed, Omar F. ( 0000-0001-8500-1130 ) ; Schanze, Kirk S.
Abstract:
A series of variable band-gap donor–acceptor–donor (DAD) chromophores capped with platinum(II) acetylide units has been synthesized and fully characterized by electrochemical and photophysical methods, with particular emphasis placed on probing triplet excited state properties. A counter-intuitive trend of increasing fluorescence quantum efficiency and lifetime with decreasing excited state energy (optical gap) is observed across the series of DAD chromophores. Careful study of the excited state dynamics, including triplet yields (as inferred from singlet oxygen sensitization), reveals that the underlying origin of the unusual trend in the fluorescence parameters is that the singlet–triplet intersystem crossing rate and yield decrease with decreasing optical gap. It is concluded that the rate of intersystem crossing decreases as the LUMO is increasingly localized on the acceptor unit in the DAD chromophore, and this result is interpreted as arising because the extent of spin–orbit coupling induced by the platinum heavy metal centers decreases as the LUMO is more localized on the acceptor. In addition to the trend in intersystem crossing, the results show that the triplet decay rates follow the Energy Gap Law correlation over a 1.8 eV range of triplet energy and 1000-fold range of triplet decay rates. Finally, femtosecond transient absorption studies for the DAD chromophores reveals a strong absorption in the near-infrared region which is attributed to the singlet excited state. This spectral band appears to be general for DAD chromophores, and may be a signature of the charge transfer (CT) singlet excited state.
KAUST Department:
Solar and Photovoltaic Engineering Research Center (SPERC); Physical Sciences and Engineering (PSE) Division
Citation:
Triplet excited state properties in variable gap π-conjugated donor–acceptor–donor chromophores 2016, 7 (6):3621 Chem. Sci.
Publisher:
Royal Society of Chemistry (RSC)
Journal:
Chem. Sci.
Issue Date:
12-Feb-2016
DOI:
10.1039/C5SC04578A
Type:
Article
ISSN:
2041-6520; 2041-6539
Sponsors:
This work was supported by the National Science Foundation (Grant No. CHE-115164 and CHE-1504727). The authors acknowledge the University of Florida Research Computing (http://researchcomputing.ufl.edu) for providing computational resources and support that have contributed to the research results reported in this publication.
Additional Links:
http://xlink.rsc.org/?DOI=C5SC04578A
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Articles

Full metadata record

DC FieldValue Language
dc.contributor.authorCekli, Sedaen
dc.contributor.authorWinkel, Russell W.en
dc.contributor.authorAlarousu, Erkkien
dc.contributor.authorMohammed, Omar F.en
dc.contributor.authorSchanze, Kirk S.en
dc.date.accessioned2016-07-21T10:16:56Z-
dc.date.available2016-07-21T10:16:56Z-
dc.date.issued2016-02-12-
dc.identifier.citationTriplet excited state properties in variable gap π-conjugated donor–acceptor–donor chromophores 2016, 7 (6):3621 Chem. Sci.en
dc.identifier.issn2041-6520-
dc.identifier.issn2041-6539-
dc.identifier.doi10.1039/C5SC04578A-
dc.identifier.urihttp://hdl.handle.net/10754/617306-
dc.description.abstractA series of variable band-gap donor–acceptor–donor (DAD) chromophores capped with platinum(II) acetylide units has been synthesized and fully characterized by electrochemical and photophysical methods, with particular emphasis placed on probing triplet excited state properties. A counter-intuitive trend of increasing fluorescence quantum efficiency and lifetime with decreasing excited state energy (optical gap) is observed across the series of DAD chromophores. Careful study of the excited state dynamics, including triplet yields (as inferred from singlet oxygen sensitization), reveals that the underlying origin of the unusual trend in the fluorescence parameters is that the singlet–triplet intersystem crossing rate and yield decrease with decreasing optical gap. It is concluded that the rate of intersystem crossing decreases as the LUMO is increasingly localized on the acceptor unit in the DAD chromophore, and this result is interpreted as arising because the extent of spin–orbit coupling induced by the platinum heavy metal centers decreases as the LUMO is more localized on the acceptor. In addition to the trend in intersystem crossing, the results show that the triplet decay rates follow the Energy Gap Law correlation over a 1.8 eV range of triplet energy and 1000-fold range of triplet decay rates. Finally, femtosecond transient absorption studies for the DAD chromophores reveals a strong absorption in the near-infrared region which is attributed to the singlet excited state. This spectral band appears to be general for DAD chromophores, and may be a signature of the charge transfer (CT) singlet excited state.en
dc.description.sponsorshipThis work was supported by the National Science Foundation (Grant No. CHE-115164 and CHE-1504727). The authors acknowledge the University of Florida Research Computing (http://researchcomputing.ufl.edu) for providing computational resources and support that have contributed to the research results reported in this publication.en
dc.language.isoenen
dc.publisherRoyal Society of Chemistry (RSC)en
dc.relation.urlhttp://xlink.rsc.org/?DOI=C5SC04578Aen
dc.rightsThis article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence. http://creativecommons.org/licenses/by-nc/3.0/en
dc.titleTriplet excited state properties in variable gap π-conjugated donor–acceptor–donor chromophoresen
dc.typeArticleen
dc.contributor.departmentSolar and Photovoltaic Engineering Research Center (SPERC)en
dc.contributor.departmentPhysical Sciences and Engineering (PSE) Divisionen
dc.identifier.journalChem. Sci.en
dc.eprint.versionPublisher's Version/PDFen
dc.contributor.institutionDepartment of Chemistry and Center for Macromolecular Science and Engineering, University of Florida, Gainesville, USAen
dc.contributor.affiliationKing Abdullah University of Science and Technology (KAUST)en
kaust.authorAlarousu, Erkkien
kaust.authorMohammed, Omar F.en
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