scholarly journals Mimicking Natural Photosynthesis: Designing Ultrafast Photosensitized Electron Transfer into Multiheme Cytochrome Protein Nanowires

Nanomaterials ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 2143
Author(s):  
Daniel R. Marzolf ◽  
Aidan M. McKenzie ◽  
Matthew C. O’Malley ◽  
Nina S. Ponomarenko ◽  
Coleman M. Swaim ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Charge Transfer ◽  
Model Systems ◽  
Covalent Attachment ◽  
Chemical Labeling ◽  
Covalent Bonds ◽  
Time Resolved ◽  
Redox Active ◽  
Dynamics Simulations ◽  
Ultrafast Charge Transfer

Efficient nanomaterials for artificial photosynthesis require fast and robust unidirectional electron transfer (ET) from photosensitizers through charge-separation and accumulation units to redox-active catalytic sites. We explored the ultrafast time-scale limits of photo-induced charge transfer between a Ru(II)tris(bipyridine) derivative photosensitizer and PpcA, a 3-heme c-type cytochrome serving as a nanoscale biological wire. Four covalent attachment sites (K28C, K29C, K52C, and G53C) were engineered in PpcA enabling site-specific covalent labeling with expected donor-acceptor (DA) distances of 4–8 Å. X-ray scattering results demonstrated that mutations and chemical labeling did not disrupt the structure of the proteins. Time-resolved spectroscopy revealed three orders of magnitude difference in charge transfer rates for the systems with otherwise similar DA distances and the same number of covalent bonds separating donors and acceptors. All-atom molecular dynamics simulations provided additional insight into the structure-function requirements for ultrafast charge transfer and the requirement of van der Waals contact between aromatic atoms of photosensitizers and hemes in order to observe sub-nanosecond ET. This work demonstrates opportunities to utilize multi-heme c-cytochromes as frameworks for designing ultrafast light-driven ET into charge-accumulating biohybrid model systems, and ultimately for mimicking the photosynthetic paradigm of efficiently coupling ultrafast, light-driven electron transfer chemistry to multi-step catalysis within small, experimentally versatile photosynthetic biohybrid assemblies.

scholarly journals Choosing sides: unusual ultrafast charge transfer pathways in an asymmetric electron-accepting cyclophane that binds an electron donor

2019 ◽  
Vol 10 (15) ◽  
pp. 4282-4292 ◽  
Author(s):  
Jiawang Zhou ◽  
Yilei Wu ◽  
Indranil Roy ◽  
Avik Samanta ◽  
J. Fraser Stoddart ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Charge Transfer ◽  
Electron Donor ◽  
Ultrafast Charge Transfer

Photo-driven electron transfer is faster from an electron donor guest to the harder to reduce acceptor in an asymmetric cyclophane host.

scholarly journals Time-Resolved Spectroscopy of Photo-Induced Electron Transfer in Dinuclear and Tetranuclear Fe/Co Prussian Blue Analogues

2020 ◽  
Author(s):  
Jennifer Zimara ◽  
Hendrik Stevens ◽  
Rainer Oswald ◽  
Serhiy Demeshko ◽  
Sebastian Dechert ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Charge Transfer ◽  
Prussian Blue ◽  
Variable Temperature ◽  
Spin Transition ◽  
Acetonitrile Solution ◽  
Time Resolved ◽  
Thermally Induced ◽  
Prussian Blue Analogues ◽  
Charge Transfer Dynamics

The dynamics of photo-driven charge transfer-induced spin transition (CTIST) in two Fe/Co Prussian Blue Analogues (PBAs) is revealed by femtosecond IR and UV/vis pump-probe spectroscopy. Depending on temperature the known tetranuclear square-type complex [Co<sub>2</sub>Fe<sub>2</sub>(CN)<sub>6</sub>(tp*)<sub>2</sub>(4,4’-dtbbpy)<sub>4</sub>](PF<sub>6</sub>)<sub>2</sub> (<b>1</b>) exists in two electronic states. In acetonitrile solution at <240 K the low temperature (<b>LT</b>) phase is prevalent consisting of low-spin Fe(II) and low-spin Co(III), [Fe<sup>II</sup><sub>LS</sub>Co<sup>III</sup><sub>LS</sub>]<sub>2</sub>. Temperature rise causes thermally induced CTIST towards the high temperature (<b>HT</b>) phase consisting of low-spin Fe(III) and high-spin Co(II), [Fe<sup>III</sup><sub>LS</sub>Co<sup>II</sup><sub>HS</sub>]<sub>2</sub>, being prevalent at >300 K. Photo-excitation into the intervalence charge transfer (IVCT) band of the <b>LT</b> phase at 800 nm induces electron transfer in one Fe-Co edge of PBA <b>1</b> and produces a [Fe<sup>III</sup><sub>LS</sub>Co<sup>II</sup><sub>LS</sub>] intermediate which by spin crossover (SCO) is stabilized within 400 fs to a long-lived (>1 ns) [Fe<sup>III</sup><sub>LS</sub>Co<sup>II</sup><sub>HS</sub>]. In contrast, IVCT excitation of the <b>HT</b> phase at 400 nm generates a [Fe<sup>II</sup><sub>LS</sub>Co<sup>III</sup><sub>HS</sub>] species with a lifetime of 3.6 ps. Subsequent back-electron transfer populates the vibrationally hot ground state, which thermalizes within 8 ps. The newly synthesized dinuclear PBA, [CoFe(CN)<sub>3</sub>(tp*)(pz*<sub>4</sub>Lut)]ClO<sub>4</sub> (<b>2</b>), provides a benchmark of the <b>HT</b> phase of <b>1</b>, i.e. [Fe<sup>III</sup><sub>LS</sub>Co<sup>II</sup><sub>HS</sub>], as verified by variable temperature magnetic susceptibility measurements and <sup>57</sup>Fe Mößbauer spectroscopy. The photo-induced charge transfer dynamics of PBA <b>2</b> indeed is almost identical to that of the <b>HT</b> phase of phase of PBA <b>1</b> with a lifetime of the excited [Fe<sup>II</sup><sub>LS</sub>Co<sup>III</sup><sub>HS</sub>] species of 3.8 ps.

scholarly journals Vibrational Mode Coupling to Reverse Electron Transfer in (CN)5FeCNRu(NH3)5− in Solution

1999 ◽  
Vol 19 (1-4) ◽  
pp. 385-387
Author(s):  
Chengfei Wang ◽  
Boris Akhremitchev ◽  
Gilbert C. Walker
Keyword(s):  
Electron Transfer ◽  
Charge Transfer ◽  
Spectral Data ◽  
Infrared Spectra ◽  
High Frequency ◽  
Mode Coupling ◽  
Vibrational Mode ◽  
Time Resolved ◽  
Reverse Electron Transfer ◽  
Infrared Spectral

We present charge transfer absorption, resonance Raman and time-resolved infrared spectral data for (CN)5FeCNRu(NH3)5− in various solvents. The transient infrared spectra and anisotropies reveal both non-equilibrium vibrational populations of high frequency modes and local solvent heating.

Binary small molecule organic nanoparticles exhibit both direct and diffusion-limited ultrafast charge transfer with NIR excitation

Nanoscale ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 2385-2392 ◽  
Author(s):  
Bryan Kudisch ◽  
Margherita Maiuri ◽  
Leon Wang ◽  
Tristan Lim ◽  
Hoang Lu ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Charge Transfer ◽  
Small Molecules ◽  
Photoinduced Electron Transfer ◽  
Ultrafast Spectroscopy ◽  
Facile Synthesis ◽  
Organic Nanoparticles ◽  
Diffusion Limited ◽  
Ultrafast Charge Transfer ◽  
And Diffusion

We report the facile synthesis on new binary organic nanoparticles composed of NIR absorbing small molecules, which we show using ultrafast spectroscopy undergo photoinduced electron transfer.

Photoinduced electron transfer (PET) versus excimer formation in supramolecular p/n-heterojunctions of perylene bisimide dyes and implications for organic photovoltaics

2015 ◽  
Vol 185 ◽  
pp. 507-527 ◽  
Author(s):  
Agnieszka Nowak-Król ◽  
Benjamin Fimmel ◽  
Minjung Son ◽  
Dongho Kim ◽  
Frank Würthner
Keyword(s):  
Electron Transfer ◽  
Organic Solar Cells ◽  
Photoinduced Electron Transfer ◽  
Transient Absorption ◽  
Model Systems ◽  
Transient Absorption Spectroscopy ◽  
Time Resolved ◽  
Perylene Bisimide ◽  
Excimer Formation ◽  
Molecular Semiconductor

Foldamer systems comprised of two perylene bisimide (PBI) dyes attached to the conjugated backbones of 1,2-bis(phenylethynyl)benzene and phenylethynyl-bis(phenylene)indane, respectively, were synthesized and investigated with regard to their solvent-dependent properties. UV/Vis absorption and steady-state fluorescence spectra show that both foldamers exist predominantly in a folded H-aggregated state consisting of π–π-stacked PBIs in THF and in more random conformations with weaker excitonic coupling between the PBIs in chloroform. Time-resolved fluorescence spectroscopy and transient absorption spectroscopy reveal entirely different relaxation pathways for the photoexcited molecules in the given solvents, i.e. photoinduced electron transfer leading to charge separated states for the open conformations (in chloroform) and relaxation into excimer states with red-shifted emission for the stacked conformations (in THF). Supported by redox data from cyclic voltammetry and Rehm–Weller analysis we could relate the processes occurring in these solution-phase model systems to the elementary processes in organic solar cells. Accordingly, only if relaxation pathways such as excimer formation are strictly avoided in molecular semiconductor materials, excitons may diffuse over larger distances to the heterojunction interface and produce photocurrent via the formation of electron/hole pairs by photoinduced electron transfer.

scholarly journals Electron Transfer Pathways and Dynamics in Drosophila Cryptochrome - the Role of Protein Electrostatics

2019 ◽  
Vol 205 ◽  
pp. 10009 ◽  
Author(s):  
Martin Richter ◽  
Benjamin P. Fingerhut
Keyword(s):  
Amino Acids ◽  
Electron Transfer ◽  
Charge Transfer ◽  
Charge Separation ◽  
Quantum Dynamics ◽  
Protein Electrostatics ◽  
Charged Amino Acids ◽  
Electron Transfer Pathways ◽  
Dynamics Simulations

Dissipative quantum dynamics simulations reveal a branching of charge separation dynamics in Drosophila Cryptochrome due to subtle balanced energetics within the enzyme. In silico mutations of charged amino acids provide control over charge transfer directionality.

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