Electron Transfer Theory Research Articles

Modelling electrocatalytic reactions with a concerted treatment of multistep electron transfer kinetics and local reaction conditions

A physicochemical model is developed for electrocatalytic reactions involving multiple electron transfer steps occurring in the electric double layer (EDL). The local reaction conditions are calculated using a mean-field EDL model, which is derived from a comprehensive grand potential that considers the steric effects, solvent polarization, and chemisorption-induced surface dipoles. Macroscopic mass transport in the so-called diffusion layer is controlled by the same set of controlling equations of the EDL model, without imposing the electroneutrality assumption as usual. The Gerischer’s formulation of electron transfer theory, corrected with local reaction conditions, is used to describe the kinetics of elementary steps. Multistep kinetics of the electrocatalytic reaction is treated using microkinetics modelling, without resorting to the usual rate-determining step approximation. In formal analysis of the model, we retrieve canonical models with additional assumptions. Self-consistent numerical implementation of the model is demonstrated for oxygen reduction reaction (ORR) at Pt(111) in acidic solution, and the aptness of the model is verified by comparison with experimental data. A comparative study of the full model and its simplified versions allows us to examine how the ORR is influenced by asymmetric steric effects, finite concentration of ions, solvent polarization, surface charge effects, and metal electronic structure effects. We find that the difference in terms of the overpotential between the full model and the simplest model can be up to ∼0.1 V at a current density of −6 mA .

Ligand and solvent effects on the kinetics of the electrochemical reduction of Ni(II) complexes: Experiment and quantum chemical modeling

The two-electron reduction of some Ni(II) complexes with α-diimine ligands ([Ni(bpy)3]2+ and [Ni(pybox)2]2+) at a platinum electrode from acetonitrile (AN) and dimethylformamide (DMF) solutions is investigated by cyclic voltammetry (CV). Digisim simulations are employed to determine kinetic parameters. For [Ni(bpy)3]2+ in AN the first electron transfer (ET) step was found to be rate-controlling. The rate constants of the first and second steps (k1 and k2) are practically the same in the DMF solution. In contrast, the second ET step is rate controlling for the [Ni(pybox)2]2+ complex in AN, while the difference between k1 and k2 for this complex reactant in DMF becomes less noticeable. Molecular modeling based on the quantum mechanical theory of electron transfer and on density functional theory (DFT) calculations is performed for the first time to predict the activation barriers of the two-step heterogeneous redox processes and to elucidate the role of the ligands and solvents in the kinetics of these processes. Three-dimensional reaction free energy surfaces are constructed along the solvent and intramolecular coordinates. The electronic transmission coefficients are estimated as well. The results of model calculations are in qualitative agreement with the experimental data.

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.

Structure-Dependent Electron Transfer Rates for Dihydrophenazine, Phenoxazine, and Phenothiazine Photoredox Catalysts Employed in Atom Transfer Radical Polymerization.

Organic photocatalysts (PCs) are gaining popularity in applications of photoredox catalysis, but few studies have explored their modus operandi. We report a detailed mechanistic investigation of the electron transfer activation step of organocatalyzed atom transfer radical polymerization (O-ATRP) involving electronically excited organic PCs and a radical initiator, methyl 2-bromopropionate (MBP). This study compares nine N-aryl modified PCs possessing dihydrophenazine, phenoxazine, or phenothiazine core chromophores. Transient electronic and vibrational absorption spectroscopies over subpicosecond to nanosecond and microsecond time intervals, respectively, track spectroscopic signatures of both the reactants and products of photoinduced electron transfer in N,N-dimethylformamide, dichloromethane, and toluene solutions. The rate coefficients for electron transfer exhibit a range of values up to ∼1010 M-1 s-1 influenced systematically by the PC structures. These rate coefficients are an order of magnitude smaller for catalysts with charge transfer character in their first excited singlet (S1) or triplet (T1) states than for photocatalysts with locally excited character. The latter species show nearly diffusion-limited rate coefficients for the electron transfer to MBP. The derived kinetic parameters are used to model the contributions to electron transfer from the S1 state of each PC for different concentrations of MBP. Comparisons of singlet and triplet reactivity for one of the phenoxazine PCs reveal that the rate coefficient kET(T1) = (2.7 ± 0.3) × 107 M-1 s-1 for electron transfer from the T1 state is 2 orders of magnitude lower than that from the S1 state, kET(S1) = (2.6 ± 0.4) × 109 M-1 s-1. The trends in bimolecular electron transfer rate coefficients are accounted for using a modified Marcus theory for dissociative electron transfer.

Theoretical studies on photo-induced electron transfer process on [Thioridazine].C60 nano-complex; a first principle DFT and TD-DFT

In this study, using the density functional theory (DFT) and time dependent density functional theory (TD-DFT) methods, the physical and chemical properties of the Thioridazineand fullerene C60 nano complex were studied. The most important goal was increasing C60 dipolar moment as a novel drug delivery system to carry Thioridazineand. Several descriptors were used in the ground state, including electrochemical properties based on the HOMO and LUMO orbital energy, hardness, softness, chemical potential, and Mulliken charge. The dipole moment of this nano-complex is about 2.61D, which indicates its moderate solubility in polar solvents. The UV-Vis spectrum obtained with the CAM-B3LYP method shows that the absorption spectrum has blue-shifted by about λ = 24 nm after formation of the complex. Based on the calculations in the excited state and the hole-electron theory in the first three modes, a photo-induced electron transfer (PET) phenomenon was observed at different absorption wavelengths for the complex. Using the Marcus theory of electron transfer, the free energy of activation for electron transfer and the free energy of electron transfer for all PETs were calculated.

Electron Transfer in Films of Atomically Precise Gold Nanoclusters

In applications of monolayer-protected gold clusters, assessing the dynamic behavior of the capping monolayer is crucial, as this determines the cluster’s effective size and electron-transfer (ET) properties. Here, we describe a systematic study on the effect of the monolayer thickness on the ET between molecular Au25(SR)180 nanoclusters in films. The length of the ligands protecting the Au core was varied by using a series of linear-chain thiolate (SCnH2n+1) protected Au25 clusters, where n = 3, 4, 5, 6, 7, 8, and 10. The effect of branching was assessed by using the 2-methyl-1-butanethiolate-protected Au25 cluster. Conductivity measurements were carried out on dry films obtained by drop-casting Au25(SR)180 solutions onto interdigitated gold electrodes. Changing the alkyl chain from C3 to C10 induces a smooth decrease in the film conductivity by 3.5 orders of magnitude. By using electrochemically determined Stokes radii, the conductivity results were transformed into the corresponding ET rate constants (kETs) between neighboring clusters. kET exponentially depends on the distance, and the data show that the average Au center-to-center distance in the film is not larger than the sum of two Stokes radii. This indicates that linear alkyl chains hold a detectable degree of fluidity in films, although not as much as in solution, as shown by the trend of the corresponding heterogeneous standard rate-constant values. For both physical states, these conclusions are precisely confirmed by the much slower ET rate determined for the Au25 cluster protected by the hindered thiolate. ET in films was also studied as a function of temperature, and the results were analyzed in the framework of the ET theory. We found that the outer and inner reorganization energies increase with n. For these ETs, the electronic coupling resonance between the reactant and product states, HRP, ranges from 12 (n = 3) to 0.7 cm–1 (n = 10) and therefore ETs are nonadiabatic. The data also show that 3/4 of the effect of distance on kET is related to HRP, while the rest is associated with the intrinsic barrier and thus the distance dependence of the outer and inner reorganization energies.

Visible-light-driven photocatalytic inactivation of S. aureus in aqueous environment by hydrophilic zinc oxide (ZnO) nanoparticles based on the interfacial electron transfer in S. aureus/ZnO composites

Waterborne diseases caused by pathogenic microorganisms pose severe threats to human health. ZnO nanoparticles (NPs) hold great potentials as an effective, economical and eco-friendly method for water disinfection, but the exact antimicrobial mechanism of ZnO NPs under visible-light illumination is still not clear. Herein, we investigate the visible-light-driven photocatalytic inactivation mechanism of amino-functionalized hydrophilic ZnO (AH-ZnO) NPs against Staphylococcus aureus (S. aureus) in aqueous environment from the perspective of electron transfer theory. The results show that the antibacterial effects of AH-ZnO NPs are dependent on the AH-ZnO NPs concentration and treatment time. The bulk ORP value and released Zn2+ concentration in AH-ZnO NPs solutions increase with AH-ZnO NPs concentration. The SEM and intracellular protein leakage results indicate that AH-ZnO NPs can adhere to S. aureus surface without causing obvious cell membrane disruption. The photoluminescence (PL) intensity and fluorescence lifetime of AH-ZnO NPs are remarkedly decreased after adding S. aureus, which confirms the electron transfer from S. aureus to AH-ZnO NPs. Moreover, the ΔPL intensity is closely correlated with the inactivation efficiency, demonstrating that the interfacial electron transfer in S. aureus/AH-ZnO NPs composites contributes to the antibacterial activity, which is speculated to disrupt the normal respiratory electron transfer chain of S. aureus, thereby causing intracellular ROS generation, cell membrane depolarization and eventually apoptosis-like death.

Preparation of copper ferrite by sol–gel method and the synergistic catalytic for the thermal decomposition of ammonium perchlorate

In the present work, copper ferrite was prepared by a simple and mild sol–gel method followed by low-temperature calcination, and characterized by various analytical techniques. The X-ray diffraction (XRD) analysis suggests that the copper ferrite with the spinel-type ferrite crystal forms have been successfully prepared. More crystal defects are observed in copper ferrite crystals than in the pure iron oxide and copper oxide crystals. The scanning electron microscopy (SEM) and nitrogen adsorption–desorption analyses reveal that the prepared copper ferrites are mesoporous structures with large specific surface areas and the specific surface area increases with the increase of Fe content. The effects of the structure of copper ferrite on its catalytic activity for the thermal decomposition of ammonium perchlorate (AP) and the catalytic mechanism were investigated and explored based on the thermogravimetric analysis of the decomposition process. It is found that the copper ferrites prepared at the molar ratios of Cu/Fe of 1/2 and 1/4 exhibit the best catalytic activities for the thermal decomposition of AP. The synergistic catalytic mechanism of Cu–Fe–O is proposed based on the electron transfer and proton transfer theories for the thermal decomposition of AP.

How the Donor/Acceptor Spin States Affect the Electronic Couplings in Molecular Charge-Transfer Processes?

The electronic coupling matrix element HAB is an essential ingredient of most electron-transfer theories. HAB depends on the overlap between donor and acceptor wave functions and is affected by the involved states’ spin. We classify the spin-state effects into three categories: orbital occupation, spin-dependent electron density, and density delocalization. The orbital occupancy reflects the diverse chemical nature and reactivity of the spin states of interest. The effect of spin-dependent density is related to a more compact electron density cloud at lower spin states due to decreased exchange interactions between electrons. Density delocalization is strongly connected with the covalency concept that increases the spatial extent of the diabatic state’s electron density in specific directions. We illustrate these effects with high-level ab initio calculations on model direct donor–acceptor systems relevant to metal oxide materials and biological electron transfer. Obtained results can be used to benchmark existing methods for HAB calculations in complicated cases such as spin-crossover materials or antiferromagnetically coupled systems.

Interrogation of O-ATRP Activation Conducted by Singlet and Triplet Excited States of Phenoxazine Photocatalysts.

Organocatalyzed ATRP (O-ATRP) is a growing field exploiting organic chromophores as photoredox catalysts (PCs) that engage in dissociative electron-transfer (DET) activation of alkyl-halide initiators following absorption of light. Characterizing DET rate coefficients (kact) and photochemical yields across various reaction conditions and PC photophysical properties will inform catalyst design and efficient use during polymerization. The studies described herein consider a class of phenoxazine PCs, where synthetic handles of core substitution and N-aryl substitution enable tunability of the electronic and spin characters of the catalyst excited state as well as DET reaction driving force (ΔGET0). Using Stern-Volmer quenching experiments through variation of the diethyl 2-bromo-2-methylmalonate (DBMM) initiator concentration, collisional quenching is observed. Eight independent measurements of kact are reported as a function of ΔGET0 for four PCs: four triplet reactants and four singlets with kact values ranging from 1.1 × 108 M-1 s-1, where DET itself controls the rate, to 4.8 × 109 M-1 s-1, where diffusion is rate-limiting. This overall data set, as well as a second one inclusive of five literature values from related systems, is readily modeled with only a single parameter of reorganization energy under the frameworks of the adiabatic Marcus electron-transfer theory and Marcus-Savéant theory of DET. The results provide a predictive map where kact can be estimated if ΔGET0 is known and highlight that DET in these systems appears insensitive to PC reactant electronic and spin properties outside of their impact on the driving force. Next, on the basis of measured kact values in selected PC systems and knowledge of their photophysics, we also consider activation yields specific to the reactant spin states as the DBMM initiator concentration is varied. In N-naphthyl-containing PCs characterized by near-unity intersystem crossing, the T1 is certainly an important driver for efficient DET. However, at DBMM concentrations common to polymer synthesis, the S1 is also active and drives 33% of DET reaction events. Even in systems with low yields of ISC, such as in N-phenyl-containing PCs, reaction yields can be driven to useful values by exploiting the S1 under high DBMM concentration conditions. Finally, we have quantified photochemical reaction quantum yields, which take into account potential product loss processes after electron-transfer quenching events. Both S1 and T1 reactant states produce the PC•+ radical cation with a common yield of 71%, thus offering no evidence for spin selectivity in deleterious back electron transfer. The subunity PC•+ yields suggest that some combination of solvent (DMAc) oxidation and energy-wasting back electron transfer is likely at play and these pathways should be factored in subsequent mechanistic considerations.

Confinement Effect on Heterogeneous Electron Transfer in Aqueous Solutions inside Conducting Nanotubes

AbstractAn Fe3+/2+ redox couple in conducting single wall carbon nanotubes filled with water molecules is investigated in the framework of the electron transfer theory and with classical molecular dynamics simulations. The diameter of the nanotubes ranges from 0.8 nm to 3.5 nm. It can be concluded, qualitatively, that the electron transfer rate significantly increases with decreasing nanotube diameter. This effect is explained basically in terms of the solvent reorganization energy. Other factors that can affect the reaction rate are discussed as well.

A Mononuclear Non-Heme Manganese(III)–Aqua Complex in Oxygen Atom Transfer Reactions via Electron Transfer

Metal-oxygen complexes, such as metal-oxo [M(O2-)], -hydroxo [M(OH-)], -peroxo [M(O22-)], -hydroperoxo [M(OOH-)], and -superoxo [M(O2•-)] species, are capable of conducting oxygen atom transfer (OAT) reactions with organic substrates, such as thioanisole (PhSMe) and triphenylphosphine (Ph3P). However, OAT of metal-aqua complexes, [M(OH2)]n+, has yet to be reported. We report herein OAT of a mononuclear non-heme Mn(III)-aqua complex, [(dpaq)MnIII(OH2)]2+ (1, dpaq = 2-[bis(pyridin-2-ylmethyl)]amino-N-quinolin-8-yl-acetamidate), to PhSMe and Ph3P derivatives for the first time; it is noted that no OAT occurs from the corresponding Mn(III)-hydroxo complex, [(dpaq)MnIII(OH)]+ (2), to the substrates. Mechanistic studies reveal that OAT reaction of 1 occurs via electron transfer from 4-methoxythioanisole to 1 to produce the 4-methoxythioanisole radical cation and [(dpaq)MnII(OH2)]+, followed by nucleophilic attack of H2O in [(dpaq)MnII(OH2)]+ to the 4-methoxythioanisole radical cation to produce an OH adduct radical, 2,4-(MeO)2C6H3S•(OH)Me, which disproportionates or undergoes electron transfer to 1 to yield methyl 4-methoxyphenyl sulfoxide. Formation of the thioanisole radical cation derivatives is detected by the stopped-flow transient absorption measurements in OAT from 1 to 2,4-dimethoxythioanisole and 3,4-dimethoxythioanisole, being compared with that in the photoinduced electron transfer oxidation of PhSMe derivatives, which are detected by laser-induced transient absorption measurements. Similarly, OAT from 1 to Ph3P occurs via electron transfer from Ph3P to 1, and the proton effect on the reaction rate has been discussed. The rate constants of electron transfer from electron donors, including PhSMe and Ph3P derivatives, to 1 are fitted well by the electron transfer driving force dependence of the rate constants predicted by the Marcus theory of outer-sphere electron transfer.

Electrocatalytic activity of doped graphene: Quantum-mechanical theory view

Based on the quantum-mechanical theory of electron transfer (ET), the parameter was proposed to describe the electrochemical activity of doped graphenes. The parameter is calculated using the density of states (DOS), local density of state (LDOS) values, which are in turn obtained from the density functional theory (DFT) calculations and reorganization energies of redox system. DOS describes the contribution of the electronic structure of the electrode to the ET process, while the LDOS describes the electron density contribution of the atoms at some distance from the surface electrode. Reorganization energy corresponds to the restriction of solvation shell and bonds in redox system due to ET process. The overall contribution of these parameters enables a comprehensive assessment of the activity that is acceptable for semi-quantitative analysis. Calculations have shown that the proposed activity parameter correlates well with the calculated ET rate constants.Theoretical study of the oxygen reduction reaction (ORR) on graphene doped with p-elements in the framework of quantum-mechanical theory showed that ET activity decreases in series P-Gr > S-Gr > N-Gr > B-Gr > O-Gr > Gr. According to our estimates, the mixed or adiabatic regime of ET is probably observed on doped graphenes for all steps of ORR. Using N- and B-graphenes as an example and activity parameter, the influence of the applied potential and the atomic fraction of the doped element on the ET activity are studied.

Bell-Shaped Electron Transfer Kinetics in Gold Nanoclusters.

Although metal nanoclusters (MNCs) have shown great promise for the further development of photochemical techniques to be applied in diverse areas (e.g., photoelectronic devices, photochemical sensors, photocatalysts, and energy storage and conversion systems), the fundamental problem of their electron transfer behavior still remains unsolved. Herein, a driving force-dependent photoinduced electron transfer process of gold nanoclusters (AuNCs) is clarified for the first time from a rational-designed opposite-charged system. It was found that the electron transfer dynamic of carboxylated chitosan and dithiothreitol-commodified AuNCs (CC/DTT-AuNCs) can be satisfactorily described by the Marcus electron transfer theory. This proved model was applied to estimate the ultrafast charge separation process between CC/DTT-AuNCs and mitoxantrone, which was confirmed by fluorescence quenching and femtosecond transient absorption spectroscopy measurements. We envision that this work will open a new door for understanding the electron transfer behavior of MNCs and facilitate the design of advanced optoelectronic devices.

Structure and chemistry of the solid electrolyte interphase (SEI) on a high capacity conversion-based anode: NiO

Electroanalytical techniques are specialized tools with high-sensitivity that when combined with electron transfer theory can shed light on the mechanisms of highly complex, heterogeneous, multi-step reactions – including SEI formation on LiB anodes.

Interfacial Electron Transfer in Dye-Sensitized TiO2 Devices for Solar Energy Conversion

The development of cost-effective molecular devices that efficiently capture and convert sunlight into other useful forms of energy is a promising approach to meet the world’s increasing energy demands. These devices are designed through a successful combination of materials and molecules that work synergistically to promote light-driven chemical reactions. Light absorption by a surface-bound chromophore triggers a sequence of interfacial electron transfer processes. The efficiencies of the devices are governed by the dynamic balance between the electron transfer reactions that promote energy conversion and undesirable side reactions. Therefore, it is necessary to understand and control these processes to optimize the design of the components of the devices and to achieve higher energy conversion efficiencies. In this context, this review discusses general aspects of interfacial electron transfer reactions in dye-sensitized TiO2 molecular devices for solar energy conversion. A theoretical background on the Marcus-Gerischer theory for interfacial electron transfer and theoretical models for electron transport within TiO2 films are provided. An overview of dye-sensitized solar cells (DSSCs) and dye-sensitized photoelectrosynthesis cells (DSPECs) is presented, and the electron transfer and transport processes that occur in both classes of devices are emphasized and detailed. Finally, the main spectroscopic, electrochemical and photoelectrochemical experimental techniques that are employed to elucidate the kinetics of the electron transfer reactions discussed in this review are presented.

Electron transfer properties of double quantum dot system in a fluctuating environment* *Project supported by the Natural Science Foundation of Shandong Province, China (Grant No. ZR2014AM030).

Using the innovative method of the additional Bloch vector, the electron transfer properties of a double quantum dot (DQD) system measured by a quantum point contact (QPC) in a fluctuating environment are investigated. The results show that the environmental noises in transverse and longitudinal directions play different roles in the dynamical evolution of the open quantum systems. Considering the DQD with symmetric energy level, the Fano factor exhibits a slight peak with the increase of transverse noise amplitude σ T, which provides a basis for distinguishing dynamical phenomena caused by different directional fluctuation noises in symmetric DQD structures by studying the detector output. In the case of asymmetric DQD, the dependence of a detector current involving the level displacement is distinct when increasing the transverse noise damping coefficient τ T and the longitudinal noise damping coefficient τε respectively. Meanwhile, the transverse noise damping coefficient τ T could significantly reduce the Fano factor and enhance the stability of the quantum system compared with the longitudinal one. The Fano factors with stable values as the enhancement of noise amplitudes show different external influences from the detector measurement, and provide a numerical reference for adjusting the noise amplitudes in both transverse and longitudinal directions appropriately in a microscopic experimental process to offset the decoherence effect caused by the measurements. Finally, the research of average waiting time provides unique insights to the development of single electron transfer theory in the short-time limit.

Theory of Electrochemical Proton-Coupled Electron Transfer in Diabatic Vibronic Representation: Application to Proton Discharge on Metal Electrodes in Alkaline Solution

Proton discharge on a metal electrode is an important step in a wide range of electrocatalytic processes. In this proton-coupled electron transfer (PCET) reaction, also denoted the Volmer reaction,...

Molecular design of dibenzo[g,p]chrysene-based hole-transporting materials for perovskite solar cells: A theoretical study

Designed with a steric twisted, π-conjugated dibenzochrysene (DBC) core and arylamine-based electron-donating side arms, four small molecules as hole-transporting materials (HTMs) are simulated with density functional theory and Marcus theory of electron transfer. Our results show that, adding the fluorene moiety in auxiliary side arms and extending the π-conjugated structure can make the highest occupied molecular orbital (HOMO) energy levels down-shifted. By tailoring of electron-donating side arms, the HOMO levels of designed HTMs range from −4.95 to −5.24 eV, which affords a chance for the interfacial energy regulation. Meanwhile, we also find that the suitable extension of π-conjugated side arms and the accessorial sulfur-sulfur interaction may be beneficial for promoting the intermolecular electronic coupling. Coupled with the lower reorganization energy, the DBC-4 (7.08 × 10−1 cm2 v−1 s−1) displays the largest hole mobility. In addition, the better solubility can be expected for the DBC-4 due to the larger solvation free energy, whereas its stability may be somewhat lower. Adding thiophene unit in side arms makes the absorption spectra obviously red-shift. Overall, this work provides some useful clues for designing of high-efficient HTMs, and the DBC-4 is proposed as potential HTM.

Prediction of Internal Reorganization Energy in Photoinduced Electron Transfer Processes of Molecular Dyads.

A novel theoretical methodology is proposed to estimate the magnitude of internal reorganization energy for electron transfer and charge recombination processes in donor-bridge-acceptor (D-B-A) type molecular dyads. The potential energy surface for each process is plotted for the shortest path by assuming a displaced but slightly distorted harmonic oscillator model. Structural changes occurring upon photoexcitation and ionization were exploited to calculate the activation energies needed for electron transfer reactions with the aid of involved vibrational modes. D-B-A dyads consisting of octathiophene (T8) paired with three (di)imide acceptors (naphthalene diimide (NDI), benzene diimide (BDI), and naphthalimide (NI)) were studied as model systems for theoretical calculations. It has been found that T8NDI and T8BDI possess very low activation energies for both forward electron transfer and charge recombination, and hence the rates for relevant processes should be very rapid. In contrast, the activation energies for such processes for T8NI were found to be relatively large, and free energy estimations predict that the charge recombination mechanism in T8NI falls into the inverted regime of Marcus semiclassical electron transfer theory. All of the calculated properties of the dyads are in very good agreement with the available experimental data, suggesting the suitability of the proposed theoretical approach in revealing the photoinduced electron transfer mechanisms of molecular dyads.