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Direct Determination of the Rate of Intersystem Crossing in a Near-IR Luminescent Cr(III) Triazolyl Complex

Jones, Robert W. ; Auty, Alexander J. ; Wu, Guanzhi ; Persson, Petter LU ; Appleby, Martin V. ; Chekulaev, Dimitri ; Rice, Craig R. ; Weinstein, Julia A. ; Elliott, Paul I.P. and Scattergood, Paul A. (2023) In Journal of the American Chemical Society 145(22). p.12081-12092
Abstract

A detailed understanding of the dynamics of photoinduced processes occurring in the electronic excited state is essential in informing the rational design of photoactive transition-metal complexes. Here, the rate of intersystem crossing in a Cr(III)-centered spin-flip emitter is directly determined through the use of ultrafast broadband fluorescence upconversion spectroscopy (FLUPS). In this contribution, we combine 1,2,3-triazole-based ligands with a Cr(III) center and report the solution-stable complex [Cr(btmp)2]3+(btmp = 2,6-bis(4-phenyl-1,2,3-triazol-1-yl-methyl)pyridine) (13+), which displays near-infrared (NIR) luminescence at 760 nm (τ = 13.7 μs, φ = 0.1%) in fluid solution. The excited-state... (More)

A detailed understanding of the dynamics of photoinduced processes occurring in the electronic excited state is essential in informing the rational design of photoactive transition-metal complexes. Here, the rate of intersystem crossing in a Cr(III)-centered spin-flip emitter is directly determined through the use of ultrafast broadband fluorescence upconversion spectroscopy (FLUPS). In this contribution, we combine 1,2,3-triazole-based ligands with a Cr(III) center and report the solution-stable complex [Cr(btmp)2]3+(btmp = 2,6-bis(4-phenyl-1,2,3-triazol-1-yl-methyl)pyridine) (13+), which displays near-infrared (NIR) luminescence at 760 nm (τ = 13.7 μs, φ = 0.1%) in fluid solution. The excited-state properties of 13+are probed in detail through a combination of ultrafast transient absorption (TA) and femtosecond-to-picosecond FLUPS. Although TA spectroscopy allows us to observe the evolution of phosphorescent excited states within the doublet manifold, more significantly and for the first time for a complex of Cr(III), we utilize FLUPS to capture the short-lived fluorescence from initially populated quartet excited states immediately prior to the intersystem crossing process. The decay of fluorescence from the low-lying 4MC state therefore allows us to assign a value of (823 fs)-1to the rate of intersystem crossing. Importantly, the sensitivity of FLUPS to only luminescent states allows us to disentangle the rate of intersystem crossing from other closely associated excited-state events, something which has not been possible in the spectroscopic studies previously reported for luminescent Cr(III) systems.

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author
; ; ; ; ; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Journal of the American Chemical Society
volume
145
issue
22
pages
12 pages
publisher
The American Chemical Society (ACS)
external identifiers
  • pmid:37224437
  • scopus:85162001475
ISSN
0002-7863
DOI
10.1021/jacs.3c01543
language
English
LU publication?
yes
id
5a642e93-458b-4228-bf1b-bb6ab768bc5a
date added to LUP
2023-09-18 13:50:54
date last changed
2024-04-19 01:19:51
@article{5a642e93-458b-4228-bf1b-bb6ab768bc5a,
  abstract     = {{<p>A detailed understanding of the dynamics of photoinduced processes occurring in the electronic excited state is essential in informing the rational design of photoactive transition-metal complexes. Here, the rate of intersystem crossing in a Cr(III)-centered spin-flip emitter is directly determined through the use of ultrafast broadband fluorescence upconversion spectroscopy (FLUPS). In this contribution, we combine 1,2,3-triazole-based ligands with a Cr(III) center and report the solution-stable complex [Cr(btmp)<sub>2</sub>]<sup>3+</sup>(btmp = 2,6-bis(4-phenyl-1,2,3-triazol-1-yl-methyl)pyridine) (1<sup>3+</sup>), which displays near-infrared (NIR) luminescence at 760 nm (τ = 13.7 μs, φ = 0.1%) in fluid solution. The excited-state properties of 1<sup>3+</sup>are probed in detail through a combination of ultrafast transient absorption (TA) and femtosecond-to-picosecond FLUPS. Although TA spectroscopy allows us to observe the evolution of phosphorescent excited states within the doublet manifold, more significantly and for the first time for a complex of Cr(III), we utilize FLUPS to capture the short-lived fluorescence from initially populated quartet excited states immediately prior to the intersystem crossing process. The decay of fluorescence from the low-lying <sup>4</sup>MC state therefore allows us to assign a value of (823 fs)<sup>-1</sup>to the rate of intersystem crossing. Importantly, the sensitivity of FLUPS to only luminescent states allows us to disentangle the rate of intersystem crossing from other closely associated excited-state events, something which has not been possible in the spectroscopic studies previously reported for luminescent Cr(III) systems.</p>}},
  author       = {{Jones, Robert W. and Auty, Alexander J. and Wu, Guanzhi and Persson, Petter and Appleby, Martin V. and Chekulaev, Dimitri and Rice, Craig R. and Weinstein, Julia A. and Elliott, Paul I.P. and Scattergood, Paul A.}},
  issn         = {{0002-7863}},
  language     = {{eng}},
  number       = {{22}},
  pages        = {{12081--12092}},
  publisher    = {{The American Chemical Society (ACS)}},
  series       = {{Journal of the American Chemical Society}},
  title        = {{Direct Determination of the Rate of Intersystem Crossing in a Near-IR Luminescent Cr(III) Triazolyl Complex}},
  url          = {{http://dx.doi.org/10.1021/jacs.3c01543}},
  doi          = {{10.1021/jacs.3c01543}},
  volume       = {{145}},
  year         = {{2023}},
}