Toward control of electron transfer in donor-acceptor molecules by bond-specific infrared excitation

Delor, Milan; Scattergood, Paul A.; Sazanovich, Igor V.; Parker, Anthony W.; Greetham, Gregory M.; Meijer, Anthony J. H. M.; Towrie, Michael; Weinstein, Julia A.

doi:10.1126/science.1259995

Cited by 172 publications

(186 citation statements)

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“…In the superexchange ET mechanism, vibrations can affect the interferences between various ET pathways, so that some ET pathways could be totally switched off (9). Similar experimental observations have been reported, but for the sequential ET mechanisms (12). IR pulses only weakly perturb the electronic structure and the molecular geometry, which facilitates their application for biomolecular ET coherent control.…”

Section: Discussionsupporting

confidence: 57%

“…Infrared (IR) pulses have been used recently to excite selected vibrational modes after triggering ET by UV pulses (11,12). In the superexchange ET mechanism, vibrations can affect the interferences between various ET pathways, so that some ET pathways could be totally switched off (9).…”

Section: Discussionmentioning

confidence: 99%

“…Using lasers to precisely control ET pathways and rates has been a long-term goal of chemists (8). The manner in which infrared light can excite molecular vibrations to affect ET in donor-bridge-acceptor (DBA) systems has been studied theoretically (9, 10) and experimentally (11)(12)(13)(14).The rapid development of bright X-ray lasers and high harmonic sources has opened up new opportunities for X-ray spectroscopy (15). We have recently demonstrated that stimulated X-ray Raman spectroscopy (16, 17) with broadband X-ray pulses can reveal the time-evolving oxidation states of various species in the long-range ET process of the protein azurin (18).…”

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confidence: 99%

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Coherent control of long-range photoinduced electron transfer by stimulated X-ray Raman processes

Dorfman

Zhang

Mukamel

2016

Proc. Natl. Acad. Sci. U.S.A.

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We show that X-ray pulses resonant with selected core transitions can manipulate electron transfer (ET) in molecules with ultrafast and atomic selectivity. We present possible protocols for coherently controlling ET dynamics in donor-bridge-acceptor (DBA) systems by stimulated X-ray resonant Raman processes involving various transitions between the D, B, and A sites. Simulations presented for a Ru(II)-Co(III) model complex demonstrate how the shapes, phases and amplitudes of the X-ray pulses can be optimized to create charge on demand at selected atoms, by opening up otherwise blocked ET pathways.L ong-range electron transfer (ET) over tens of angstroms in molecular assemblies plays an essential role in many biological processes, artificial light-harvesting schemes, and sensor applications (1-7). Using lasers to precisely control ET pathways and rates has been a long-term goal of chemists (8). The manner in which infrared light can excite molecular vibrations to affect ET in donor-bridge-acceptor (DBA) systems has been studied theoretically (9, 10) and experimentally (11)(12)(13)(14).The rapid development of bright X-ray lasers and high harmonic sources has opened up new opportunities for X-ray spectroscopy (15). We have recently demonstrated that stimulated X-ray Raman spectroscopy (16, 17) with broadband X-ray pulses can reveal the time-evolving oxidation states of various species in the long-range ET process of the protein azurin (18). Here we show that by coupling to core-excited states, resonant X-ray pulses can precisely target either the donor, bridge, or the acceptor site in an ET process by altering the valence electronic states in its vicinity by triggering the bridge-to-acceptor (BA), the donor-to-bridge (DB), or the bridgeto-bridge (BB) ET transfer. We show how the ET pathways in a model DBA system ([(CN) 4 Ru II (tpphz)Co III (CN) 4 ] 3− ) can be coherently manipulated by X-ray pulses resonant with the acceptor.Application is made to a Ru-Co light-harvesting complex (shown in Fig. 1 A and B) where an electron is transferred from the donor Ru II to the acceptor Co III to create Ru III /Co II . X-ray pulses can create valence excitations via a Raman process (19), thus altering the occupied molecular orbitals (MOs). We shall focus on the BA ET coherent control scheme illustrated in Fig. 2A. In a stimulated Raman process a core hole created by the X-ray pulse on the acceptor is instantaneously filled by a valence electron on the bridge, resulting in a B→A ET. Such an ET process is analogous to the valence-to-core X-ray spontaneous emission observed in transition metal complexes with ligand-to-metal charge transfer (20). (Fig. 1 A and B) where the bpy ligands are replaced with (CN) − . This eliminates the complicated spin crossover transition at the Co center (23), because the strong ligands (CN) − favor the low-spin state.The relevant ET parameters were obtained from electronic structure calculations. Because the Ru and Co centers are far apart, electronic structure calculations can be carried out for ...

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Section: Discussionsupporting

confidence: 57%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

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Coherent control of long-range photoinduced electron transfer by stimulated X-ray Raman processes

Dorfman

Zhang

Mukamel

2016

Proc. Natl. Acad. Sci. U.S.A.

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“…Another important component in our system is the metal centre which acts as a vibrational energy transfer bottleneck that contributes to the localization of injected quanta of energy on either arm of the molecule. [38][39][40][41][42] Furthermore, the presence of the metal offering a two-step charge-separation process starting from a metal-to-acceptor charge transfer followed by reductive quenching from the donor is a particularly effective design strategy to achieve IR-control: 15,16,35,36 it allows the rapid population of a far-fromequilibrium gateway state where an IR pump can be introduced, and in this way perturb an otherwise symmetrical system in a spatially selective manner at a crucial crossroad where small structural and energetic fluctuations dictate the chosen electronic pathway. 43 Complementary to such excited state evolution is the ability to delay the control pulse with respect to actinic excitation, thus influencing reactivity at the decisive moments of light-induced molecular function [44][45][46][47] and circumventing the myriad of processes occurring immediately after electronic excitation, which would rapidly scramble the selectivity of mode-specific excitation.…”

Section: Control Of Et Pathways Using Targeted Vibrational Excitationmentioning

confidence: 99%

Directing the path of light-induced electron transfer at a molecular fork using vibrational excitation

et al. 2017

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Ultrafast electron transfer in condensed-phase molecular systems is often strongly coupled to intramolecular vibrations that can promote, suppress and direct electronic processes. Recent experiments exploring this phenomenon proved that light-induced electron transfer can be strongly modulated by vibrational excitation, suggesting a new avenue for active control over molecular function. Here, we achieve the first example of such explicit vibrational control through judicious design of a Pt(II)-acetylide charge-transfer Donor-Bridge-Acceptor-Bridge-Donor "fork" system: asymmetric 13 C isotopic labelling of one of the two -C≡C-bridges makes the two parallel and otherwise identical Donor→Acceptor electron-transfer pathways structurally distinct, enabling independent vibrational perturbation of either. Applying an ultrafast UV pump (excitation)-IR pump (perturbation)-IR probe (monitoring) pulse sequence, we show that the pathway that is vibrationally perturbed during UV-induced electron-transfer is dramatically slowed down compared to its unperturbed counterpart. One can thus choose the dominant electron transfer pathway. The findings deliver a new opportunity for precise perturbative control of electronic energy propagation in molecular devices. Main TextControlling the function of future advanced materials demands a profound understanding of energymatter interactions in molecular systems at the quantum level. 1 There is a growing consensus that energy-and electron-transfer processes occurring far away from equilibrium in condensed-phase systems on femto-to-picosecond timescales do not conform to the Born-Oppenheimer approximation. Indeed, nuclear and electronic wave functions often strongly interact with each other, leading to exotic phenomena whereby vibrational motion can mediate and dictate the rate and efficiency of electronic transitions. [2][3][4][5] With overwhelming evidence that nuclear-electronic (vibronic) interactions play a crucial role in a broad range of systems, including light harvesting and conversion in photosynthetic organisms, 6-11 this phenomenon represents a tremendous opportunity to acquire deeper knowledge and control over the structural traits that govern molecular function and reactivity.Recent efforts led by Rubtsov et al.,12,13 Bakulin et al., 14 and our group 15,16 have shown that one way to experimentally exploit vibronic coupling to modulate molecular function is to introduce targeted vibrational excitation along specific reaction co-ordinates using ultrafast mid-infrared (IR) pulses. This approach enables promoting or suppressing electronic transitions, notably photo-induced electron transfer (ET), an elementary process that pervades the natural world. Although the demonstrated excited state modulations have been remarkably efficient, up to 100% suppression in one case, 15 predictive and directive control of electron transfer in the condensed phase has not been achieved yet.

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“…Secondly, we have demonstrated that exciting bridge vibrations in the branching CT state with an IR pulse led to a radical change in the reaction pathways, probably due to perturbation of vibronic interactions between the CT state and potential product states. 38 Specifically, one of the 3 pathways of the CT state decay in % & has been switched off, as illustrated in Scheme 1B. These experiments require firstly collecting the data in a standard pump$probe configuration, where UV/Vis excitation pulse is followed by the probing IR pulse over a series of time delays {UV/Vis pump $IR probe } = ) (Scheme 1A).…”

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Ultrafast charge transfer dynamics in supramolecular Pt(ii) donor–bridge–acceptor assemblies: the effect of vibronic coupling

et al. 2015

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Toward control of electron transfer in donor-acceptor molecules by bond-specific infrared excitation

Cited by 172 publications

References 50 publications

Coherent control of long-range photoinduced electron transfer by stimulated X-ray Raman processes

Coherent control of long-range photoinduced electron transfer by stimulated X-ray Raman processes

Directing the path of light-induced electron transfer at a molecular fork using vibrational excitation

Ultrafast charge transfer dynamics in supramolecular Pt(ii) donor–bridge–acceptor assemblies: the effect of vibronic coupling

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