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Excited State Evolution towards Ligand Loss and Ligand Chelation at Group 6 Metal Carbonyl Centres

Overview of attention for article published in Dalton Transactions: An International Journal of Inorganic Chemistry, November 2014
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Title
Excited State Evolution towards Ligand Loss and Ligand Chelation at Group 6 Metal Carbonyl Centres
Published in
Dalton Transactions: An International Journal of Inorganic Chemistry, November 2014
DOI 10.1039/c4dt01544d
Pubmed ID
Authors

Mary Pryce, Conor Long, Jenifer Manton, Suzanne McMahon, Gregory M Greetham, ian Clarke, Wybren Jan Buma, Sander Woutersen, Saeed Amirjalayer, Emma Harvey, Anthony Coleman, Jennifer C. Manton, Anthony C. Coleman, Emma C. Harvey, Gregory M. Greetham, Ian P. Clark, Mary T. Pryce

Abstract

The photochemistry and photophysics of three model "half-sandwich" complexes (η(6)-benzophenone)Cr(CO)3, (η(6)-styrene)Cr(CO)3, and (η(6)-allylbenzene)Cr(CO)3 were investigated using pico-second time-resolved infrared spectroscopy and time-dependent density functional theory methods. The (η(6)-benzophenone)Cr(CO)3 complex was studied using two excitation wavelengths (470 and 320 nm) while the remaining complexes were irradiated using 400 nm light. Two independent excited states were detected spectroscopically for each complex, one an unreactive excited state of metal-to-arene charge-transfer character and the other with metal-to-carbonyl charge transfer character. This second excited state leads to an arrested release of CO on the pico-second time-scale. Low-energy excitation (470 nm) of (η(6)-benzophenone)Cr(CO)3 populated only the unreactive excited state which simply relaxes to the parent complex. Higher energy irradiation (320 nm) induced CO-loss. Irradiation of (η(6)-styrene)Cr(CO)3, or (η(6)-allylbenzene)Cr(CO)3 at 400 nm provided evidence for the simultaneous population of both the reactive and unreactive excited states. The efficiency at which the unreactive excited state is populated depends on the degree of conjugation of the substituent with the arene π-system and this affects the efficiency of the CO-loss process. The quantum yield of CO-loss is 0.50 for (η(6)-allylbenzene)Cr(CO)3 and 0.43 for (η(6)-styrene)Cr(CO)3. These studies provide evidence for the existence of two photophysical routes to CO loss, a minor ultrafast route and an arrested mechanism involving the intermediate population of a reactive excited state. This reactive excited state either relaxes to reform the parent species or eject CO. Thus the quantum yield of the CO-loss is strongly dependent on the excitation wavelength. Time-dependent density functional theory calculations confirm that the state responsible for ultrafast CO-loss has significant metal-centred character while the reactive state responsible for the arrested CO-loss has significant metal-to-carbonyl charge-transfer character. The CO-loss product (η(6)-allylbenzene)Cr(CO)2 formed following irradiation of (η(6)-allylbenzene)Cr(CO)3 reacts further with the pendent alkenyl group to form the chelate product (η(6),η(2)-allylbenzene)Cr(CO)2.

Twitter Demographics

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Mendeley readers

The data shown below were compiled from readership statistics for 6 Mendeley readers of this research output. Click here to see the associated Mendeley record.

Geographical breakdown

Country Count As %
United Kingdom 1 17%
Unknown 5 83%

Demographic breakdown

Readers by professional status Count As %
Student > Ph. D. Student 2 33%
Student > Bachelor 1 17%
Student > Master 1 17%
Researcher 1 17%
Unspecified 1 17%
Other 0 0%
Readers by discipline Count As %
Chemistry 5 83%
Unspecified 1 17%

Attention Score in Context

This research output has an Altmetric Attention Score of 1. This is our high-level measure of the quality and quantity of online attention that it has received. This Attention Score, as well as the ranking and number of research outputs shown below, was calculated when the research output was last mentioned on 12 November 2014.
All research outputs
#3,452,116
of 4,497,175 outputs
Outputs from Dalton Transactions: An International Journal of Inorganic Chemistry
#6,735
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Outputs of similar age
#82,165
of 109,478 outputs
Outputs of similar age from Dalton Transactions: An International Journal of Inorganic Chemistry
#9
of 9 outputs
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