Sazanovich, I.V., Best, J., Scattergood, P.A. et al. (5 more authors) (2014) Ultrafast photoinduced charge transport in Pt(II) donor-acceptor assembly bearing naphthalimide electron acceptor and phenothiazine electron donor. Physical Chemistry Chemical Physics, 16 (47). 25775 - 25788. ISSN 1463-9076
Abstract
Visible light-induced charge transfer dynamics were investigated in a novel transition metal triad acceptor–chromophore–donor, (NDI–phen)Pt(II)(–C[triple bond, length as m-dash]C–Ph–CH2–PTZ)2 (1), designed for photoinduced charge separation using a combination of time-resolved infrared (TRIR) and femtosecond electronic transient absorption (TA) spectroscopy. In 1, the electron acceptor is 1,4,5,8-naphthalene diimide (NDI), and the electron donor is phenothiazine (PTZ), and [(phen)Pt(–C[triple bond, length as m-dash]C–Ph–)], where phen is 1,10-phenanthroline, represents the chromophoric core. The first excited state observed in 1 is a 3MLCT/LL′CT, with {Pt(II)–acetylide}-to-phen character. Following that, charge transfer from the phen-anion onto the NDI subunit to form NDI−–phen–[Pt–(C[triple bond, length as m-dash]C)2]+–PTZ2 occurs with a time constant of 2.3 ps. This transition is characterised by appearance of the prominent NDI-anion features in both TRIR and TA spectra. The final step of the charge separation in 1 proceeds with a time constant of [similar]15 ps during which the hole migrates from the [Pt–(C[triple bond, length as m-dash]C)2] subunit to one of the PTZ groups. Charge recombination in 1 then occurs with two distinct time constants of 36 ns and 107 ns, corresponding to the back electron transfer to each of the two donor groups; a rather rare occurrence which manifests that the hole in the final charge-separated state is localised on one of the two donor PTZ groups. The assignment of the nature of the excited states and dynamics in 1 was assisted by TRIR investigations of the analogous previously reported ((COOEt)2bpy)Pt(C[triple bond, length as m-dash]C–Ph–CH2–PTZ)2 (2), (J. E. McGarrah and R. Eisenberg, Inorg. Chem., 2003, 42, 4355; J. E. McGarrah, J. T. Hupp and S. N. Smirnov, J. Phys. Chem. A, 2009, 113, 6430) as well as (bpy)Pt(C[triple bond, length as m-dash]C–Ph–C7H15)2, which represent the acceptor-free dyad, and the chromophoric core, respectively. Thus, the step-wise formation of the full charge-separated state on the picosecond time scale and charge recombination via tunnelling have been established; and the presence of two distinct charge recombination pathways has been observed.
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Copyright, Publisher and Additional Information: | © 2014 The Author(s). This is an Open Access article distributed under the terms of the Creative Commons Attribution Licence (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. | ||||
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Institution: | The University of Sheffield | ||||
Academic Units: | The University of Sheffield > Faculty of Science (Sheffield) > Department of Chemistry (Sheffield) | ||||
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Depositing User: | Symplectic Sheffield | ||||
Date Deposited: | 03 Mar 2015 14:43 | ||||
Last Modified: | 03 Mar 2015 14:43 | ||||
Published Version: | http://dx.doi.org/10.1039/c4cp03995e | ||||
Status: | Published | ||||
Publisher: | Royal Society of Chemistry | ||||
Refereed: | Yes | ||||
Identification Number: | https://doi.org/10.1039/c4cp03995e |