Jump to main content
Jump to site search

Issue 47, 2014
Previous Article Next Article

Electron transfer dynamics and excited state branching in a charge-transfer platinum(II) donor–bridge-acceptor assembly

Author affiliations

Abstract

A linear asymmetric Pt(II) trans-acetylide donor–bridge-acceptor triad designed for efficient charge separation, NAP[triple bond, length as m-dash]Pt(PBu3)2[triple bond, length as m-dash]Ph–CH2–PTZ (1), containing strong electron acceptor and donor groups, 4-ethynyl-N-octyl-1,8-naphthalimide (NAP) and phenothiazine (PTZ) respectively, has been synthesised and its photoinduced charge transfer processes characterised in detail. Excitation with 400 nm, ∼50 fs laser pulse initially populates a charge transfer manifold stemming from electron transfer from the Pt-acetylide centre to the NAP acceptor and triggers a cascade of charge and energy transfer events. A combination of ultrafast time-resolved infrared (TRIR) and transient absorption (TA) spectroscopies, supported by UV-Vis/IR spectroelectrochemistry, emission spectroscopy and DFT calculations reveals a self-consistent photophysical picture of the excited state evolution from femto- to milliseconds. The characteristic features of the NAP-anion and PTZ-cation are clearly observed in both the TRIR and TA spectra, confirming the occurrence of electron transfer and allowing the rate constants of individual ET-steps to be obtained. Intriguingly, 1 has three separate ultrafast electron transfer pathways from a non-thermalised charge transfer manifold directly observed by TRIR on timescales ranging from 0.2 to 14 ps: charge recombination to form either the intraligand triplet 3NAP with 57% yield, or the ground state, and forward electron transfer to form the full charge-separated state 3CSS (3[PTZ+–NAP]) with 10% yield as determined by target analysis. The 3CSS decays by charge-recombination to the ground state with ∼1 ns lifetime. The lowest excited state is 3NAP, which possesses a long lifetime of 190 μs and efficiently sensitises singlet oxygen. Overall, molecular donor–bridge-acceptor triad 1 demonstrates excited state branching over 3 different pathways, including formation of a long-distant (18 Å) full charge-separated excited state from a directly observed vibrationally hot precursor state.

Graphical abstract: Electron transfer dynamics and excited state branching in a charge-transfer platinum(ii) donor–bridge-acceptor assembly

Back to tab navigation

Supplementary files

Publication details

The article was received on 06 Jun 2014, accepted on 20 Oct 2014 and first published on 31 Oct 2014


Article type: Paper
DOI: 10.1039/C4DT01682C
Citation: Dalton Trans., 2014,43, 17677-17693
  • Open access: Creative Commons BY license
  •   Request permissions

    Electron transfer dynamics and excited state branching in a charge-transfer platinum(II) donor–bridge-acceptor assembly

    P. A. Scattergood, M. Delor, I. V. Sazanovich, O. V. Bouganov, S. A. Tikhomirov, A. S. Stasheuski, A. W. Parker, G. M. Greetham, M. Towrie, E. S. Davies, A. J. H. M. Meijer and J. A. Weinstein, Dalton Trans., 2014, 43, 17677
    DOI: 10.1039/C4DT01682C

    This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. Material from this article can be used in other publications provided that the correct acknowledgement is given with the reproduced material.

    Reproduced material should be attributed as follows:

    • For reproduction of material from NJC:
      [Original citation] - Published by The Royal Society of Chemistry (RSC) on behalf of the Centre National de la Recherche Scientifique (CNRS) and the RSC.
    • For reproduction of material from PCCP:
      [Original citation] - Published by the PCCP Owner Societies.
    • For reproduction of material from PPS:
      [Original citation] - Published by The Royal Society of Chemistry (RSC) on behalf of the European Society for Photobiology, the European Photochemistry Association, and RSC.
    • For reproduction of material from all other RSC journals:
      [Original citation] - Published by The Royal Society of Chemistry.

    Information about reproducing material from RSC articles with different licences is available on our Permission Requests page.

Search articles by author

Spotlight

Advertisements