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Ultrafast excited state dynamics of [Cr(CO)4(bpy)] : Revealing the relaxation between triplet charge-transfer states

Ma, Fei LU ; Jarenmark, Martin LU ; Hedström, Svante LU ; Persson, Petter LU ; Nordlander, Ebbe LU and Yartsev, Arkady LU (2016) In RSC Advances 6(25). p.20507-20515
Abstract

Ultrafast excited state dynamics of [Cr(CO)4(bpy)] upon metal-to-ligand charge-transfer (1MLCT) transition have been studied by pump-probe absorption spectroscopy in CH3CN, pyridine and CH2Cl2 solvents. Intersystem crossing (ISC) was found to be very fast (∼100 fs) and efficient, while the formation of the photoproduct with one axial CO dissociated is significantly less competitive, indicating a barrier along the dissociative coordinate. As a refinement of the previous dynamic model [I. R. Farrell, et al., J. Am. Chem. Soc., 1999, 121, 5296-5301], we show that a conventional downhill energy relaxation concept dominates the observed dynamics. Experimentally, we have identified the... (More)

Ultrafast excited state dynamics of [Cr(CO)4(bpy)] upon metal-to-ligand charge-transfer (1MLCT) transition have been studied by pump-probe absorption spectroscopy in CH3CN, pyridine and CH2Cl2 solvents. Intersystem crossing (ISC) was found to be very fast (∼100 fs) and efficient, while the formation of the photoproduct with one axial CO dissociated is significantly less competitive, indicating a barrier along the dissociative coordinate. As a refinement of the previous dynamic model [I. R. Farrell, et al., J. Am. Chem. Soc., 1999, 121, 5296-5301], we show that a conventional downhill energy relaxation concept dominates the observed dynamics. Experimentally, we have identified the consecutive population of two triplet states as a result of triplet electronic relaxation convoluted with vibrational and solvent relaxation (the overall time is 2.7-6.9 ps depending on solvent), as well as the overall depopulation of the excited state through the lowest triplet state (57-84 ps). Adaptive excitation pulse shaping could not achieve optimization of the photoproduct quantum yield via re-distribution of only low-frequency vibrational modes during excitation, indicating that the two low-lying 1MLCT states, Cr(3d) → π∗bpy and Cr(3d) → π∗CO, are not coupled.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
RSC Advances
volume
6
issue
25
pages
9 pages
publisher
Royal Society of Chemistry
external identifiers
  • Scopus:84959197654
ISSN
2046-2069
DOI
10.1039/c5ra25670d
language
English
LU publication?
yes
id
51e22348-b1e4-4479-babb-f95a3219c0e4
date added to LUP
2016-07-19 07:16:09
date last changed
2016-10-13 05:11:47
@misc{51e22348-b1e4-4479-babb-f95a3219c0e4,
  abstract     = {<p>Ultrafast excited state dynamics of [Cr(CO)<sub>4</sub>(bpy)] upon metal-to-ligand charge-transfer (<sup>1</sup>MLCT) transition have been studied by pump-probe absorption spectroscopy in CH<sub>3</sub>CN, pyridine and CH<sub>2</sub>Cl<sub>2</sub> solvents. Intersystem crossing (ISC) was found to be very fast (∼100 fs) and efficient, while the formation of the photoproduct with one axial CO dissociated is significantly less competitive, indicating a barrier along the dissociative coordinate. As a refinement of the previous dynamic model [I. R. Farrell, et al., J. Am. Chem. Soc., 1999, 121, 5296-5301], we show that a conventional downhill energy relaxation concept dominates the observed dynamics. Experimentally, we have identified the consecutive population of two triplet states as a result of triplet electronic relaxation convoluted with vibrational and solvent relaxation (the overall time is 2.7-6.9 ps depending on solvent), as well as the overall depopulation of the excited state through the lowest triplet state (57-84 ps). Adaptive excitation pulse shaping could not achieve optimization of the photoproduct quantum yield via re-distribution of only low-frequency vibrational modes during excitation, indicating that the two low-lying <sup>1</sup>MLCT states, Cr(3d) → π∗bpy and Cr(3d) → π∗CO, are not coupled.</p>},
  author       = {Ma, Fei and Jarenmark, Martin and Hedström, Svante and Persson, Petter and Nordlander, Ebbe and Yartsev, Arkady},
  issn         = {2046-2069},
  language     = {eng},
  number       = {25},
  pages        = {20507--20515},
  publisher    = {ARRAY(0xae904e0)},
  series       = {RSC Advances},
  title        = {Ultrafast excited state dynamics of [Cr(CO)<sub>4</sub>(bpy)] : Revealing the relaxation between triplet charge-transfer states},
  url          = {http://dx.doi.org/10.1039/c5ra25670d},
  volume       = {6},
  year         = {2016},
}