Marcus Theory Of Electron Transfer Research Articles

Cage escape governs photoredox reaction rates and quantum yields.

Photoredox catalysis relies on light-induced electron transfer leading to a radical pair comprising an oxidized donor and a reduced acceptor in a solvent cage. For productive onward reaction to occur, the oxidized donor and the reduced acceptor must escape from that solvent cage before they undergo spontaneous reverse electron transfer. Here we show the decisive role that cage escape plays in three benchmark photocatalytic reactions, namely, an aerobic hydroxylation, a reductive debromination and an aza-Henry reaction. Using ruthenium(II)- and chromium(III)-based photocatalysts, which provide inherently different cage escape quantum yields, we determined quantitative correlations between the rates of photoredox product formation and the cage escape quantum yields. These findings can be largely rationalized within the framework of Marcus theory for electron transfer.

DFT study on the Ciclopirox anticancer drug interaction with AlN nanostructures: analysed by AIM, UV-Vis and Marcus theory of electron-transfer

This study's main focus was on the process by which Ciclopirox adhered to AlN nanostructures, Calculations using the density functional theory were done to reach this goal. The calculations encompassed the assessment of Ciclopirox's adsorption energy, the evaluation of the energy band gap, the analysis of variations in the energy band gap, the examination of charge transfers, and the characterisation of the types of interactions that arise from Ciclopirox's adsorption onto AlN nanostructures. We carried out an investigation using the AIM method to explore deeper into the binding properties between the studied AlN nanostructures and Ciclopirox. Our discoveries provide light on the Ciclopirox/AlN nanosheet interaction's electrostatic characteristics. Moreover, the presence of Ciclopirox led to an augmentation in the electrical conductivity of the AlN nanostructures. This intriguing outcome suggests the potential application of these AlN nanomaterials as chemical sensors, capable of generating an electronic signal upon detection of this chemically modified amino acid. The observed sensitivity sequence indicated that the AlN nanosheet exhibited the highest sensitivity, followed by the AlN nanotube and the AlN nanocluster. In conclusion, our study provides compelling evidence supporting the AlN nanosheet as an excellent choice for the detection of Ciclopirox compared to other AlN nanostructures.

Unveiling Mechanistic Insights and Photocatalytic Advancements in Intramolecular Photo-(3 + 2)-Cycloaddition: A Comparative Assessment of Two Paradigmatic Single-Electron-Transfer Models.

The synthesis of 1-aminonorbornane (1-aminoNB), a potential aniline bioisostere, through photochemistry or photoredox catalysis signifies a remarkable breakthrough with implications in organic chemistry, pharmaceutical chemistry, and sustainable chemistry. However, an understanding of the underlying mechanisms involved in these reactions remains limited and ambiguous. Herein, we employ high-precision CASPT2//CASSCF calculations to elucidate the intricate mechanisms regulating the intramolecular photo-(3 + 2)-cycloaddition reactions for the synthesis of 1-aminoNB in the presence or absence of the Ir-complex-based photocatalyst. Our investigations delve into radical cascades, stereoselectivity, particularly single-electron-transfer (SET) events, etc. Furthermore, we innovatively introduce and compare two SET models integrating Marcus electron-transfer theory and transition-state theory. These models combined with kinetic data contribute to recognizing the critical control factors in diverse photocatalysis, thereby guiding the design and manipulation of photoredox catalysis as well as the improvement and modification of photocatalysts.

A computational study on the mercaptopurine drug interaction with aluminum nitride nanostructures: analyzed by Marcus theory of electron-transfer

We analyzed the mercaptopurine adsorption on AlN nanostructures consisting of zero-dimensional nanoclusters, one-dimensional nanotubes, and two-dimensional nanosheets using calculations based on density functional theory (DFT). The adsorption energy, energy band gap, fluctuations in the energy band gap, charge transfers, and types of interactions that take place after mercaptopurine is adsorbed on the AlN nanostructures have all been calculated using DFT. The results show MP adsorption energies on AlN nanoparticles are −4.22, −5.95, and −8.70 eV. In this situation, MP molecules have been drawn to the surface due to the higher adsorption energies available on the AlN nanosheet (a process known as chemisorption). The Atoms in Molecules inquiry was conducted to learn more about and better comprehend the binding properties of the investigated AlN nanostructures utilizing mercaptopurine. Our findings indicate the mercaptopurine/AlN nanosheet bonding’s electrostatic properties. Additionally, the electrical conductivity of the AlN nanostructures increases whenever mercaptopurine is adsorbed on them. This shows that the AlN nanoparticles might function as chemical sensors and offer an electrical signal in mercaptopurine. The following is the order of sensitivity: AlN nanosheet > AlN nanotube > AlN nanocluster. The outcomes indicate that the nanosheet has the most potential for mercaptopurine detection among the AlN nanostructures. Communicated by Ramaswamy H. Sarma

The calculation of D-A-π-A-D hole transfer materials containing fluoranthene core for efficient perovskite solar cells

In this work, an inexpensive, effective, and dopant-free hole transport material (HTM) of D-A-π-A-D (D=donor, A=acceptor) molecular configuration, called DTB-FL was selected as the basis and then different substitutes were introduced (SO3H, SiCl3, PO3H2, OC2F3, F, CO2H, CH2OH and H) on its central five-membered ring to replace C8H17 alkyl groups. These materials were applied as HTMs for ammonium-free Cs0.05FA0.95PbI3 perovskite solar cells (PSCs). Several properties of the designed HTMs were explored by density functional theory (DFT) and time-dependent DFT (TD-DFT) computations combined with Marcus theory for electron transfer, such as absorption and emission spectra, solubility, stability, reorganization energy, and hole mobility. Results showed that each designed HTM had a higher HOMO level than the perovskite valence band, allowing holes to be successfully injected into the HTM from perovskite. Moreover, theoretical results proved that all HTMs had LUMO energies very upper compared to perovskite conduction band, guaranteeing blocked electron flow effect from CsPbI3−xBrx towards cathode. In terms of VOC amounts, DTB-PO3H2 and DTB-SO3H were found to have the highest power conversion efficiency (PCE), open-circuit voltage (VOC), and fill factor (FF) amounts, which verified they were promising HTMs for the fabrication of PSC devices. Overall, it could be concluded that the designed HTMs had great potentials for PSC fabrication.

Co-function Mechanisms of Chlorine and Alkoxy Radicals in Cerium-Catalyzed C-H Functionalization of Alkane Mediated by Visible Light.

Identification of radical intermediates for the catalytic functionalization of alkanes offers a number of unique challenges and has recently raised a controversial issue concerning the subtle role of chlorine versus alkoxy radicals in cerium photocatalysis. This study is an attempt to settle the controversy within the theoretical frameworks of Marcus electron transfer and transition state theory. Co-function mechanisms were proposed together with a scheme of kinetic evaluations to account for ternary dynamic competition among photolysis, back electron transfer, and hydrogen atom transfer (HAT). Cl•-based HAT has been proven to initially control the early dynamics of the photocatalytic transformation on the picosecond to nanosecond time scale, which is subsequently taken over by a postnanosecond event of alkoxy radical-mediated HAT. The theoretical models developed herein provide a uniform understanding of the continuous time dynamics of photogenerated radicals to address some paradoxical arguments in lanthanide photocatalysis.

Three-Dimensional Anisotropic Carrier Mobility and Structure–Property Relationships for [1]Benzothieno[3,2-b][1]benzothiophene Derivatives: A Theoretical Study

Through the Marcus electron-transfer theory combined with the random walk technique for the charge-carrier diffusion process, we simulated the three-dimensional (3D) distributions of hole and electron mobilities for [1]benzothieno[3,2-b][1]benzothiophene (BTBT) and its derivatives. Our predicted mobility ranges agree well with the measured field-effect mobility of the BTBT derivatives. We further analyzed the charge-transfer mobility anisotropy of the studied compounds, and the optimum conducting-channel direction relative to the crystal axis was determined, which provides a reliable reference to assist in the performance optimization of field-effect transistors (FETs). Moreover, we analyzed in detail the influences of different substituents on the reorganization energies, ionization energies, electron affinities, frontier molecular orbital charge distributions, and solid-state packing motifs of the BTBT. It was found that the reorganization energies and energy barrier of charge injection effectively decreased with the fusion of the thiophene ring. However, the herringbone packing of BTBT is transformed to π stacking at a local site; as a result, the hole and electron mobilities of BTBT decreased slightly. In comparison, attaching electron-withdrawing −COPhF to BTBT not only increases the electron affinities significantly but also increases the electronic couplings and decreases the reorganization energy related to the electron transfer. It provides a promising way to design n-type or ambipolar organic semiconducting materials.

Calculation of Excited State Internal Conversion Rate Constant Using the One-Effective Mode Marcus-Jortner-Levich Theory.

In this article, the one-effective mode Marcus-Jortner-Levich (MJL) theory and the classical Marcus theory for electron transfer were applied to estimate the internal conversion rate constant, kIC, of organic molecules and a Ru-based complex, all belonging to the Marcus inverted region. For this, the reorganization energy was calculated using the minimum energy conical intersection point to account for more vibrational levels, correcting the density of states. The results showed good agreement with experimental and theoretically determined kIC, with a small overestimation by the Marcus theory. Also, molecules less dependent on the solvent effects, like benzophenone, presented better results than molecules with an expressive dependence, like 1-aminonaphthalene. Moreover, the results suggest that each molecule possesses unique normal modes leading to the excited state deactivation that does not necessarily match the X-H bond stretching, as previously suggested.

Side-chain engineering on triphenylamine derivative-based hole-transport materials for perovskite solar cells: Theoretical simulation and experimental exploration

The development of hole-transport materials (HTMs) is a significant approach to promote the power conversion efficiency (PCE) of perovskite solar cells (PSCs). Here, based on the triphenylamine (TPA) derivatives and patulous TPA derivatives as side-chains, WR1 and WR2 are designed and explored by density functional theory (DFT), time-dependent DFT (TD-DFT) in combination with Marcus electron transfer theory. The calculated results show that the WR1 exhibits matching energy levels with perovskite and better hole transporting ability in comparison with these of WR2 can save as a potential HTM for PSCs applications. In order to confirm screening results of molecular design, the WR1 as HTM in PSC device reveals that the WR1-based PSC device obtained the PCE of 20.04% higher than that of the typical Spiro-OMeTAD-based device (18.84%). Moreover, the experimental results can well verify the data of theoretical simulations. The strategy of side-chain modification on TPA derivatives-based materials is a viable method to exploit new HTMs.

Ambipolar Charge Transport of PCNTC-O and PCNTC-R Cocrystals Obtained Under 1:2 and 1:1 Ratios of Donor and Acceptor

The efficiency of microelectronic devices depends greatly on the charge transport performance of organic semiconductors. The purpose of this work is to analyze the effect of donor-acceptor (D-A) cocrystals on the charge transport characteristics of organic semiconductors using the Marcus theory of electron transfer combined with kinetic Monte Carlo simulations. For two different cocrystals, sesquikis (benzene-1,2,4,5-tetracarbonitrile) 2-(1,3-benzothiazol-2-yl)-3-(pyren-1-yl)prop-2-eneni-trile(PCNTC-O) and ben-zene-1,2,4,5-tetracarbonitrile 2-(1,3-benzothiazol-2-yl)-3-(pyren-1-yl)pr-op-2-enenitrile(PCNTC-R) cocrystals, were investigated using 2-(benzo[d]-thiazol-2-yl)-3-(pyren-1-yl)acrylonitrile (Py-BZTCN) as the donor and 1,2,4,5-tetracyanobenzene (TCNB) as the acceptor mixed at 1:2 and 1:1 ratios, respectively. According to our calculations, PCNTC-O and PCNTC-R both exhibit bipolar charge transport behaviour with mobilities electron/hole attaining 0.0104/0.1252 and 0.0241/0.0598 cm2/Vs, respectively.

A Contrasting Effect of Acid in Electron Transfer, Oxygen Atom Transfer, and Hydrogen Atom Transfer Reactions of a Nickel(III) Complex.

There have been many examples of the accelerating effects of acids in electron transfer (ET), oxygen atom transfer (OAT), and hydrogen atom transfer (HAT) reactions. Herein, we report a contrasting effect of acids in the ET, OAT, and HAT reactions of a nickel(III) complex, [NiIII(PaPy3*)]2+ (1) in acetone/CH3CN (v/v 19:1). 1 was synthesized by reacting [NiII(PaPy3*)]+ (2) with magic blue or iodosylbenzene in the absence or presence of triflic acid (HOTf), respectively. Sulfoxidation of thioanisole by 1 and H2O occurred in the presence of HOTf, and the reaction rate increased proportionally with increasing concentration of HOTf ([HOTf]). The rate of ET from diacetylferrocene to 1 also increased linearly with increasing [HOTf]. In contrast, HAT from 9,10-dihydroanthracene (DHA) to 1 slowed down with increasing [HOTf], exhibiting an inversely proportional relation to [HOTf]. The accelerating effect of HOTf in the ET and OAT reactions was ascribed to the binding of H+ to the PaPy3* ligand of 2; the one-electron reduction potential (Ered) of 1 was positively shifted with increasing [HOTf]. Such a positive shift in the Ered value resulted in accelerating the ET and OAT reactions that proceeded via the rate-determining ET step. On the other hand, the decelerating effect of HOTf on HAT from DHA to 1 resulted from the inhibition of proton transfer from DHA•+ to 2 due to the binding of H+ to the PaPy3* ligand of 2. The ET reactions of 1 in the absence and presence of HOTf were well analyzed in light of the Marcus theory of ET in comparison with the HAT reactions.

Aliphatic and Aromatic C–H Bond Oxidation by High-Valent Manganese(IV)-Hydroxo Species

The strong C-H bond activation of hydrocarbons is a difficult reaction in environmental and biological chemistry. Herein, a high-valent manganese(IV)-hydroxo complex, [MnIV(CHDAP-O)(OH)]2+ (2), was synthesized and characterized by various physicochemical measurements, such as ultraviolet-visible (UV-vis), electrospray ionization-mass spectrometry (ESI-MS), electron paramagnetic resonance (EPR), and helium-tagging infrared photodissociation (IRPD) methods. The one-electron reduction potential (Ered) of 2 was determined to be 0.93 V vs SCE by redox titration. 2 is formed via a transient green species assigned to a manganese(IV)-bis(hydroxo) complex, [MnIV(CHDAP)(OH)2]2+ (2'), which performs intramolecular aliphatic C-H bond activation. The kinetic isotope effect (KIE) value of 4.8 in the intramolecular oxidation was observed, which indicates that the C-H bond activation occurs via rate-determining hydrogen atom abstraction. Further, complex 2 can activate the C-H bonds of aromatic compounds, anthracene and its derivatives, under mild conditions. The KIE value of 1.0 was obtained in the oxidation of anthracene. The rate constant (ket) of electron transfer (ET) from N,N'-dimethylaniline derivatives to 2 is fitted by Marcus theory of electron transfer to afford the reorganization energy of ET (λ = 1.59 eV). The driving force dependence of log ket for oxidation of anthracene derivatives by 2 is well evaluated by Marcus theory of electron transfer. Detailed kinetic studies, including the KIE value and Marcus theory of outer-sphere electron transfer, imply that the mechanism of aromatic C-H bond hydroxylation by 2 proceeds via the rate-determining electron-transfer pathway.

Investigation of the Failure of Marcus Theory for Hydrated Electron Reactions.

Reactions of the hydrated electron with a wide variety of substrates have been found to exhibit unusually similar activation energies in a manner incompatible with Marcus electron transfer theory. Given the fundamental linear response assumption of Marcus theory, one possible explanation for this apparent failure is that the underlying free energy surfaces governing the reactions are not harmonic; i.e., hydrated electron structural fluctuations exhibit non-Gaussian behavior. In this work, we test this hypothesis by using simulations to calculate the hydrated electron vertical detachment energy distribution. We consider both cavity and noncavity models for the hydrated electron, between which the actual hydrated electron behavior is expected to lie. Our results identify a possible origin for non-Gaussian behavior of the hydrated electron but show that it is not of sufficient magnitude to explain the failure of Marcus theory to describe its reactions. Thus, other explanations must be sought.

Spin Orbit Coupling in Orthogonal Charge Transfer States: (TD-)DFT of Pyrene-Dimethylaniline.

The conformational dependence of the matrix element for spin–orbit coupling and of the electronic coupling for charge separation are determined for an electron donor–acceptor system containing a pyrene acceptor and a dimethylaniline donor. Different kinetic and energetic aspects that play a role in the spin–orbit charge transfer intersystem crossing (SOCT-ISC) mechanism are discussed. This includes parameters related to initial charge separation and the charge recombination pathways using the Classical Marcus Theory of electron transfer. The spin–orbit coupling, which plays a significant role in charge recombination to the triplet state, can be probed by (TD)-DFT, using the latter as a tool to understand and predict the SOCT-ISC mechanism. The matrix elements for spin–orbit coupling for acetone and 4-thio-thymine are used for benchmarking. (Time Dependent-) Density Functional Theory (DFT and TD-DFT) calculations are applied using the quantum chemical program Amsterdam Density Functional (ADF).

Tuning the electron transfer rates in near-infrared PbS quantum dots-anthraquinones complex by different chlorine-substituted

The electron transfer (ET) from photoinduced quantum dot (QDs) to electron acceptors through a nanoscale interface plays a crucial part in the functionality and efficiency of QDs-photonic device. The driving force play a crucial part in the ET process of most QD-based system relying on the Marcus ET theory. However, there has rarely reports about tuning the driving force with substituents in acceptor molecules. Here, the ET process between near-infrared (NIR) PbS quantum dot (QDs) and different chlorine-substituted Anthraquinone (AQ) derivatives was studied via the femtosecond transient absorption spectroscopy. The ET process was gradually accelerated by adding chlorine atoms in these AQ molecules. Through the calculation of Marcus ET theory, the driving force of the complexes was gradually increased with the number of chlorine atoms substituted in AQ molecules, thus facilitating ET process. Our findings broaden the application of NIR PbS-organic compounds in photovoltaic devices.

Reaction Rate Theory-Based Mathematical Approximation for the Amount of Time it Takes For Cellular Respiration to Occur

Abstract The venerable process of cellular respiration is essential for cells to produce energy from glucose molecules, in order to carry out cellular work. The process is responsible for producing molecules of ATP, a molecule which is thermodynamically coupled with other biochemical and biophysical processes in order to provide energy for such processes to occur. While the process of cellular respiration is essential to biology, one cycle of the process occurs only in a matter of milliseconds, and so, it would be impractical to measure the time it takes for the process to occur through conventional means. Therefore, using concepts from reaction rate theory, particularly Marcus Theory of electron transfer, Michaelis-Menten kinetics for enzymatic catalysis, and the hard-sphere model of collision theory, I formulate and propose a mathematical approximation for the amount of time it takes for cellular respiration to occur. Through this heuristic approach, quantitatively knowing the amount of time it takes for one cycle of cellular respiration to occur could potentially have future applications in biological research.

Insightful understanding of charge transfer processes in metalated phthalocyanines.

Marcus electron transfer theory coupling with quantum-mechanics (QM) calculations was applied to study the hole mobilities of a series of metalated phthalocyanine molecular crystals. The effect of metals on the frontier occupied molecular orbitals is discussed according to their eigenvalues and distributions. Temperature-dependent mobilities are rationalized by considering intermolecular interactions. Our results reveal that the central metal atoms have limited impacts on the properties of phthalocyanines. This discovery is demonstrated by their almost identical distributions and energy order of the highest occupied molecular orbitals of phthalocyanine compounds and slightly deceased internal reorganization energy and increased electron coupling compared with those of metal-free phthalocyanine. Our results reveal that the weak intermolecular interaction is mainly responsible for the notable temperature-dependent conductivity. The findings of this paper are expected to benefit the molecular design of novel phthalocyanine-based electronic devices.

Bridge-Length- and Solvent-Dependent Charge Separation and Recombination Processes in Donor-Bridge-Acceptor Molecules.

The photoinduced intramolecular charge separation (CS) and charge recombination (CR) phenomena in a series of donor-bridge-acceptor (D-B-A) molecules are intensively investigated as a means of understanding electron transport through the π-B. Pyrene (Pyr) and triarylamine (TAA) moieties connected via phenylene Bs of various lengths are studied because their CS and CR behaviors can be readily monitored in real time by femtosecond transient absorption (fs-TA) spectroscopy. By combining the steady-state and fs-TA spectroscopic measurements in a variety of solvents together with chemical calculations, the parameters that govern the CS behaviors of these dyads were obtained, such as the solvent effects on free energy and the B-length-dependent electronic coupling (VDA) between D and A. We observed the sharp switch of the CS behavior with the increase of the solvent polarity and B-linker lengths. Furthermore, in the case of the shortest distance between D and A when the electron coupling is sufficiently large, we observed that the CS phenomenon occurs even in low-polar solvents. Upon increasing the length of B, CS occurs only in strong polar solvents. The distance-dependent decay constant of the CS rate is determined as ∼0.53 Å-1, indicating that CS is governed by superexchange tunneling interactions. The CS rate constants are also approximately estimated using Marcus electron transfer theory, and the results imply that the VDA value is the key factor dominating the CS rate, while the facile rotation of the phenylene B is important for modulating the lifetime of the charge-separated state in these D-B-A dyads. These results shed light on the practical strategy for obtaining a high CS efficiency with a long-lived CS state in TAA-B-Pyr derivatives.

Heat transport induced by electron transfer: A general temperature quantum calculation.

Electron transfer dominates chemical processes in biological, inorganic, and material chemistry. Energetic aspects of such phenomena, in particular, the energy transfer associated with the electron transfer process, have received little attention in the past but are important in designing energy conversion devices. This paper generalizes our earlier work in this direction, which was based on the semiclassical Marcus theory of electron transfer. It provides, within a simple model, a unified framework that includes the deep (nuclear) tunneling limit of electron transfer and the associated heat transfer when the donor and acceptor sites are seated in environments characterized by different local temperatures. The electron transfer induced heat conduction is shown to go through a maximum at some intermediate average temperature where quantum effects are already appreciable, and it approaches zero when the average temperature is very high (the classical limit) or very low (deep tunneling).

Photoinduced electron transfer reactions in mixed micelles of a star block copolymer and surface active ionic liquids: Role of the anion

This work investigates the effect of different counter anions of ionic liquid (IL) co-surfactants, viz. [NTf2]−, [DCN]−, [PF6]−, [BF4]−, [Br]−, associated with the common cation (1-decyl-3-methylimidazolium, [DMIm]+), on the microenvironments of mixed micelles formed with a star block copolymer, T1304, through spectrofluorometric studies. The role of IL anions has been explored for modulating photoinduced electron transfer (PET) reactions between a series of coumarin dyes as the electron acceptors and N,N-dimethylaniline (DMAN) as the electron donor in different T1304-IL mixed micelles. It is revealed that IL co-surfactants increase the polarity in the corona region of micelles to different extents, depending on the nature of the IL anion. The PET reactions in all micellar systems follow the Marcus Inversion (MI) behavior, as predicted by Marcus electron transfer theory, but the rate constant of electron transfer and the onset of the MI along the reaction exergonicity scale, (−ΔG°)onset, varies with the IL anion. It is observed that rather than being correlated with their chaotropic/kosmotropic nature, the effect of the IL in T1304 micelles can be correlated with the hydrophobicity/hydrophilicity, and the steric bulkiness of the IL anions.