Solvent-induced configuration mixing and triplet excited-state inversion: Insights from transient absorption and transient dc photoconductivity measurements

Chunxing She, Aaron A. Rachford, Xianghuai Wang, Sébastien Goeb, Ala'A O. El-Ballouli, Felix N. Castellano, Joseph T Hupp

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

Solvent-induced excited-state configuration mixing in a Pt(ii) diimine chromophore with phenylene ethynylene containing acetylide ligands, [Pt( tBu2bpy)(PE3)2] (1), was characterized by nanosecond transient absorption spectroscopy and transient dc photoconductivity (TDCP). The mixing is a result of closely spaced triplet charge transfer ( 3CT) and intraligand-localized (3IL) triplet energy levels that are finely tuned with solvent polarity as ascertained by their parent model chromophores [Pt(tBu2bpy)(PE1)2] (2) and [Pt(P2)(PE3)2] (3), respectively. The absorption difference spectrum of the mixed triplet state is dramatically different from those of the 3CT and 3IL state model chromophores. The 3CT, 3IL and configuration-mixed triplet states led to distinct TDCP signals. The TDCP response is of negative polarity for 3CT excited states but of positive polarity for 3IL excited states. TDCP transients for 1 in mixed solvents are a combination of signals from the 3IL and 3CT states, with the signal magnitude depending on the polarity of solvent composition. The fraction of 3CT state character in the configurationally mixed excited state was quantified by TDCP to be ∼0.24 in pure benzene, while it decreased to ∼0.05 in 20: 80 (v: v) benzene-CH2Cl2. The charge transfer fraction appears to increase slightly to ∼0.11 in the lower polarity 20: 80 n-hexane-CH 2Cl2 medium. TDCP is shown to be a useful tool for the identification of the lowest excited state in electrically neutral metal-organic chromophores.

Original languageEnglish
Pages (from-to)8586-8591
Number of pages6
JournalPhysical Chemistry Chemical Physics
Volume11
Issue number38
DOIs
Publication statusPublished - 2009

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Photoconductivity
Excited states
photoconductivity
inversions
polarity
chromophores
Chromophores
configurations
excitation
atomic energy levels
Benzene
benzene
charge transfer
Charge transfer
absorption spectroscopy
energy levels
Absorption spectroscopy
methylidyne
Electron energy levels
ligands

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Physics and Astronomy(all)

Cite this

Solvent-induced configuration mixing and triplet excited-state inversion : Insights from transient absorption and transient dc photoconductivity measurements. / She, Chunxing; Rachford, Aaron A.; Wang, Xianghuai; Goeb, Sébastien; El-Ballouli, Ala'A O.; Castellano, Felix N.; Hupp, Joseph T.

In: Physical Chemistry Chemical Physics, Vol. 11, No. 38, 2009, p. 8586-8591.

Research output: Contribution to journalArticle

She, Chunxing ; Rachford, Aaron A. ; Wang, Xianghuai ; Goeb, Sébastien ; El-Ballouli, Ala'A O. ; Castellano, Felix N. ; Hupp, Joseph T. / Solvent-induced configuration mixing and triplet excited-state inversion : Insights from transient absorption and transient dc photoconductivity measurements. In: Physical Chemistry Chemical Physics. 2009 ; Vol. 11, No. 38. pp. 8586-8591.
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