Chen Q, Lian L, Xing L
… +3 more, Miao L, Shi J, Wang Z
J Phys Chem A
· 2026 Jun · PMID 42340936
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Exhaust gas recirculation (EGR) technology creates opportunities for chemical interactions between transportation fuels and NO. In this study, 2-ethylfuran (2EF), a representative component of furan-based biofuels, was s...Exhaust gas recirculation (EGR) technology creates opportunities for chemical interactions between transportation fuels and NO. In this study, 2-ethylfuran (2EF), a representative component of furan-based biofuels, was selected to systematically investigate its reaction kinetic characteristics with those of NO. Rate constants over a wide temperature range of 298-2400 K were calculated using multistructural canonical variational transition-state theory (MS-VTST) combined with a multidimensional tunneling correction method. The results show that the reaction rate exhibits a strong temperature dependence across the entire temperature range. This dependence is determined not only by the structure of fuel molecules but also by whether O-atom or N-atom attack occurs. In the low-temperature range (298-800 K), the combined effects of multistructural torsional anharmonicity, variational effects, and tunneling effects do not outweigh the influence of energy barrier height on reaction rates, causing the order of the rate constants to still follow the energy barrier height trend. In both NO-addition and H-abstraction mechanisms, the reactions involving N-atom attack on 2EF are kinetically dominant. Notably, the tunneling effect plays a significant role in H-abstraction reactions in the low temperature range (T ⩽ 500K). This study identifies key kinetic factors governing the reaction of furan-based biofuels with NO, thereby providing crucial theoretical support for refining the interaction mechanism between oxygenated furan biofuels and NO under EGR conditions.
J Phys Chem A
· 2026 Jun · PMID 42339611
·
Publisher ↗
The rational design of fluorescent organic molecules is central to the development of advanced linear and nonlinear photonic materials. Purine-based compounds have emerged as promise candidates for several photonics appl...The rational design of fluorescent organic molecules is central to the development of advanced linear and nonlinear photonic materials. Purine-based compounds have emerged as promise candidates for several photonics applications due to their structural similarity to biological nucleobases synthetic versatility and favorable photophysical properties. However, their optical characterization typically generates large and complex data sets that are difficult to interpret, particularly when multiple compounds are analyzed simultaneously. Here, we apply principal component analysis (PCA) to a series of purine derivatives to systematically investigate the relationships between molecular descriptors and photophysical performance. The PCA model applied in the optical properties of the set captures 76.8% of the total variance within the first two principal components, enabling clear clustering of molecules according to their electronic structure. Importantly, by applying PCA directly to one- and two-photon absorption spectra, we achieve effective spectral deconvolution with 91.87% and 94.51%, respectively, isolating contributions associated with intensity, spectral shifts, and bandwidth. The robustness of this approach is validated through accurate spectral reconstruction. To extend the analysis toward predictive modeling, multiple linear regression (MLR) was employed to correlate PCA-derived features from one-photon absorption data with the transition dipole moment (). The proposed PCA-MLR framework effectively captures the intrinsic relationships within the spectra of the studied group, minimizing the need for extensive experimental trials. The resulting model exhibits excellent predictive performance ( = 0.9728) and accurately estimating the = 7.07D of an external validation molecule with a deviation of approximately 2.5%. Overall, this PCA-MLR framework provides a powerful and efficient strategy for interpreting complex photophysical data sets and accelerating the design and optimization of organic molecules for linear and nonlinear photonic applications.
Electrochemical water oxidation (WO) plays a central role in hydrogen production strategies for the energy transition, as it constitutes the main kinetic bottleneck of the overall process. Herein, a computational study w...Electrochemical water oxidation (WO) plays a central role in hydrogen production strategies for the energy transition, as it constitutes the main kinetic bottleneck of the overall process. Herein, a computational study was carried out to investigate the mechanism and activity of [Cu(MePyclen)] as an electrocatalyst toward WO, involving the pyridine-embedded macrocylic ligand MePyclen (MePyclen = 4,7,10-trimethyl-1,4,7,10-tetraaza-2,6-pyridinophane). Several pyridine-embedded Cu complexes at different electronic states have been computationally determined for the electrooxidation steps, revealing an intricate mechanism for the catalyst activation. Subsequently, the TOF-determining step of the catalytic cycle was estimated to be the O-O coupling via two viable reaction pathways: through single- or double-water coordination modes. In the first pathway, a buffer-mediated water nucleophilic attack coupled with single-electron transfer (SET-WNA) is involved, whereas the second proceeds through an intramolecular oxygen coupling (IOC) mechanism. Additionally, outer-sphere electron transfer steps might play an important role in generating reactive species that promote the O-O coupling. Overall, through a detailed theoretical screening of electrocatalytic reaction steps, we were able to compare the distinct mechanistic features of these electrocatalysts based on their electronic and steric features, possibly opening new possibilities for the rational design of ligands for WO catalyzed by Cu complexes.
-propyl nitrate (NPN, CHCHCHONO), a prevalent atmospheric alkyl nitrate (RONO), is a key component of secondary organic aerosol (SOA) and a critical NO reservoir. To support atmospheric pollution control, its OH-initiate...-propyl nitrate (NPN, CHCHCHONO), a prevalent atmospheric alkyl nitrate (RONO), is a key component of secondary organic aerosol (SOA) and a critical NO reservoir. To support atmospheric pollution control, its OH-initiated degradation mechanism, kinetics, atmospheric lifetime, and subsequent reactions were systematically investigated using density functional theory (DFT) and multistructural canonical variational transition state theory with small curvature tunneling (MS-CVT/SCT). Conformational searches identified the most stable conformers of NPN and the transition states for α-, β-, and γ-C-H H-abstraction, with α- and β-C-H abstractions as dominant pathways. Rate constants and branching ratios were calculated with multistructural torsional (MS-T) anharmonicity correction. The total rate constants show minimal variation (±2%) at 200-263 K, with an average value of ∼7.03 × 10 cm molecule s; at 263-1000 K, they agree well with experimental values and display weak positive temperature dependence, with a calculated value of 7.59 × 10 cm molecule s at 298 K. The atmospheric lifetime of NPN is 1.02-18.56 days at 217-298 K. Given the scarcity of experimental data on OH-initiated oxidation of NPN, the comprehensive kinetic and mechanistic results presented herein provide valuable supplementary data for atmospheric chemistry databases and offer guidance for future experimental investigations.
Electronic and infrared spectra of HCO ( = 3-7) chains contained in a cryogenically cooled ion trap are measured using resonance-enhanced photodissociation spectroscopy. The HCO chains, which possess X̃Σ ground electroni...Electronic and infrared spectra of HCO ( = 3-7) chains contained in a cryogenically cooled ion trap are measured using resonance-enhanced photodissociation spectroscopy. The HCO chains, which possess X̃Σ ground electronic states, are prepared through spin-forbidden association reactions between HC chains and CO molecules, both of which have X̃Σ ground states. Infrared spectra of N-tagged HCO ( = 4-7) chains measured over the 550-1820 cm range exhibit weak bands associated with chain stretch and bend vibrational modes, with more intense C≡C and CO stretch bands predicted to occur in the 2200-2300 cm region. Electronic spectra of bare HCO ( = 3-6) chains measured over the 400-900 nm range are dominated by the C̃Σ ← X̃Σ band systems, with the origin band's wavelength shifting by ≈+80 nm for each added C subunit, consistent with theoretical predictions. The origin bands of HCO, HCO, and HCO chains coincide in wavelength with λ4762.2, λ5828.6, and λ6862.6 diffuse interstellar bands (DIBs) observed along the sightline toward HD 183143, although bands in the laboratory spectra are broader than the DIBs.
We present a numerical analysis on the nature of the interactions that determine the philicity of a molecule based on molecular dynamics simulations. Specifically, the focus is on a binary mixture of alkanes and perfluor...We present a numerical analysis on the nature of the interactions that determine the philicity of a molecule based on molecular dynamics simulations. Specifically, the focus is on a binary mixture of alkanes and perfluoroalkanes representing lipophilic and fluorophilic molecules. The enthalpic factors that lead to the mixing/demixing phase behavior are subject to study, as this phase behavior constitutes the basis of the concept of philicity. A particular feature of the present study is the application of an energy decomposition scheme, which enables the elucidation of the sensitivity of effective interaction strengths between atoms of a given species to variations in the elementary parameters of the pairwise interatomic interaction potentials (in our case, Lennard-Jones potentials).
A major bottleneck in organic light-emitting diode (OLED) devices is that up to 75% of electrically generated excitons are nonemissive, arising from the 1:3 formation ratio of singlet (S) to triplet (T) excitons, with tr...A major bottleneck in organic light-emitting diode (OLED) devices is that up to 75% of electrically generated excitons are nonemissive, arising from the 1:3 formation ratio of singlet (S) to triplet (T) excitons, with triplets typically being dark in organic dyes. Molecules exhibiting an inverted singlet-triplet gap, where the first excited singlet state lies energetically below the first excited triplet state, have recently emerged as promising OLED emitters. These inverted singlet-triplet (IST) systems enable efficient triplet harvesting via exothermic reverse intersystem crossing due to the negative S-T gap. However, a disadvantage of IST chromophores is their intrinsically low emission intensity. Heptazine (Hz) and its derivatives are among the most extensively studied IST molecules, but the 5AP (1,3,4,6,9b-pentaazaphenalene) chromophore is gaining attention due to its inherent, albeit weak, emissive character arising from its lower symmetry in comparison with Hz. A synthetically viable strategy to enhance emission in IST systems is the introduction of substituent groups. In this work, we investigated the S-T energy gap and the S-S oscillator strength of 5AP derivatives by evaluating the effects of a family of electron-donating groups as well as of a family of electron-accepting groups. Our results provide design guidelines for the development of efficient 5AP-based OLED emitters.
Utilizing redox mediators (RMs) in aprotic Li-O batteries as catalysts provides promising solutions to several challenges, including high overpotential, cathode passivation, and electrolyte instability, while enabling th...Utilizing redox mediators (RMs) in aprotic Li-O batteries as catalysts provides promising solutions to several challenges, including high overpotential, cathode passivation, and electrolyte instability, while enabling the solution-phase catalysis. Despite these advantages, the fundamental origin of their electrochemical activity and how it governs the solution-phase pathway remain poorly understood. To bridge this gap, we systematically explored the stability of reactive intermediates and their influence on solution-phase LiO formation using a series of anthraquinone-based RMs: anthraquinone (AQ), 1-nitroanthraquinone (MNAQ), 1,5-dinitroanthraquinone (1,5-DNAQ), and 1,8-dinitroanthraquinone (1,8-DNAQ). All the studied RMs facilitate the formation of stable intermediate complexes with Li, O, and LiO, thereby promoting the solution-phase LiO formation pathway. Among them, 1,8-DNAQ exhibits the enhanced coordination with Li through cooperative participation of carbonyl and nitro oxygens, highlighting the role of the NO functional group in dual-site binding. The introduction of electron-withdrawing NO groups systematically raises the reduction potential (AQ < MNAQ < 1,5-DNAQ < 1,8-DNAQ), approaching the ideal value of 2.96 V, which is consistent with experimental observations. A correlation is observed between the NO substitution, reduction potential, and the LUMO energy, unveiling the underlying origin of the potential shift. Interestingly, the rise in reduction potential is not solely dictated by LUMO energy tuning through functional group modification but also by the thermodynamic stabilization of the reduced species. The involvement of the NO group enables electron delocalization, which stabilizes the reduced species and results in an enhanced redox performance compared to the unsubstituted AQ. The following study establishes a structure-property relationship linking the electronic structure, stability of reduced species, and redox activity. It demonstrates how NO functionalization correlates with the tuning of reduction potential. These insights provide design principles for developing redox mediators to enhance the catalytic activity and reversibility in next-generation Li-O batteries.
This study investigates the photoabsorption cross-section spectra of the atmospheric volatile organic compound acrolein in both gas and aqueous phases by incorporating nuclear quantum effects (NQEs) at the cost of classi...This study investigates the photoabsorption cross-section spectra of the atmospheric volatile organic compound acrolein in both gas and aqueous phases by incorporating nuclear quantum effects (NQEs) at the cost of classical molecular dynamics. Using adaptive quantum thermal bath (adQTB) method the zero point energy leakage (ZPEL) is treated, which has plagued standard quantum thermal bath (QTB) dynamics. The spectroscopic results obtained are in excellent agreement with quantum molecular dynamics (path-integral MD) method, experimental observation and previous works on photoabsorption spectrum of acrolein molecule. The adQTB approach was able to capture weak n → π* transitions and broadening in the gas phase, as well as the blue shift and reduced peak intensity due to solvent effects in the aqueous phase. The adQTB method is shown to perform─if not better─at par with PIMD in gas and solvent phase while being much superior to classical MD and standard QTB method particularly for solvated systems. This work shows that using adQTB method, it is possible to overcome the ZPEL and use the QTB-based method to study spectroscopic properties.
Predicting the stereochemical stability of complex multiple helicenes (MHs) is conventionally hindered by the combinatorial explosion of stereoisomers and the prohibitive () computational scaling of density functional th...Predicting the stereochemical stability of complex multiple helicenes (MHs) is conventionally hindered by the combinatorial explosion of stereoisomers and the prohibitive () computational scaling of density functional theory (DFT). Herein, we introduce the cooperative double helicenyl fragment (CDHF) model, which deconstructs global relative enthalpies into additive local enthalpic contributions to overcome these limitations. Rigorously validated across seven experimentally synthesized MHs, the CDHF model consistently reproduces the energy distribution of expansive stereoisomeric spaces and correctly pinpoints the experimentally isolated global minima. Exploiting its exceptional parameter transferability, the model functions as a modular design toolkit. We demonstrated this utility by rationally engineering a hypothetical pentadecapole helicene encompassing 10,944 stereoisomers. By strategically manipulating local topologies, we shifted its global minimum to a highly symmetric configuration, achieving a computational speedup of approximately 3 × 10 over full-molecule DFT. Photophysically, this symmetry-driven architecture effectively eliminates the internal dichroic cancellation, enhancing the long-wavelength chiroptical purity by 82%. Ultimately, the CDHF model provides a precise thermodynamic blueprint for rationally designing complex chiral architectures, establishing itself as a powerful presynthetic strategy for developing advanced chiroptical materials.
Many-body effects play a governing role in molecular assembly and recognition, yet their physical origins are not fully elucidated. In this work, we extend the recently developed real-space energy decomposition analysis...Many-body effects play a governing role in molecular assembly and recognition, yet their physical origins are not fully elucidated. In this work, we extend the recently developed real-space energy decomposition analysis method, called DM-EDA(RS), to enable the direct visualization and atomic-level quantification of three-body interaction energies. By projection of energy components onto three-dimensional grids, this method uniquely bridges the gap between integrated energy numbers and spatially resolved chemical insight. The results show that three-body cooperativity is driven by highly localized, counterdirectional flows of polarization energy localized on specific atoms. DM-EDA(RS) identifies the real-space energy distribution, directly mapping how interaction terms are transferred across molecular networks. Remarkably, even in systems with nearly zero net cooperativity, intense local energy redistributions are revealed that cancel out globally. This work establishes DM-EDA(RS) as a transformative approach that bridges integrated energy numbers with chemical intuition, providing a spatially resolved tool for probing many-body interactions in complex chemical and biological environments.
We present a combined imaginary-time/real-time time-dependent (TD) approach for evaluating linear absorption spectra of open-shell systems at the electron attachment (EA) and ionization potential (IP) equation-of-motion...We present a combined imaginary-time/real-time time-dependent (TD) approach for evaluating linear absorption spectra of open-shell systems at the electron attachment (EA) and ionization potential (IP) equation-of-motion coupled-cluster (EOMCC) levels of theory and within the exact two-component relativistic framework. The absorption lineshape is given by the Fourier transform of the electric dipole autocorrelation function, which is obtained from a real-time simulation. Approximations of the lowest-energy EA- and IP-EOMCC eigenstates, which are required as initial states for the real-time simulation, are generated by propagating a Koopmans EA/IP state in imaginary time. The TD-EA/IP-EOMCC linear absorption spectra of open-shell atomic (Na, K, Rb, F, Cl, and Br) and diatomic (SiH and ClO) systems closely reproduce those obtained from standard TD-EA/IP procedures carried out in the frequency domain. We find that the existence of low-lying states with non-negligible overlap with the Koopmans determinant impacts the length of the imaginary-time propagation required to obtain an initial state that produces the correct absolute energies and peak height intensities in spectra extracted from the subsequent real-time TD-EA/IP-EOMCC calculations.
Understanding the ligand effects of organic ligand-protected copper clusters toward CO is a prerequisite for improving their rational design for CO capture and conversion. In this work, the regulatory roles of pyridine l...Understanding the ligand effects of organic ligand-protected copper clusters toward CO is a prerequisite for improving their rational design for CO capture and conversion. In this work, the regulatory roles of pyridine ligands on the structure of CuO in CuOPy ( = 0-3) clusters and their reactivity toward CO were investigated through a combination of mass spectrometry and density functional theory (DFT) calculations. Experimental results reveal that pyridine ligands significantly modulate CO adsorption capacity and rate: the CuO cluster adsorbs up to three CO molecules; CuOPy and CuOPy adsorb a maximum of two and one, respectively; and CuOPy shows no adsorption. Notably, the pyridine-ligated CuOPy clusters exhibit reactivity approximately 2 orders of magnitude higher than the bare CuO cation, with CuOPy being the most reactive one among all four CuOPy clusters. DFT calculations indicate that the ligand-induced enhanced reactivity originates from the increased polarity, enlarged effective collision cross section (CCS), and added vibrational degrees of freedom (DOF) rather than CO adsorption energy or charge transfer. These conclusions were further supported by reactions between CuPy clusters and CO. This study revealed the ligand effects on the structures and reactivity of copper-based clusters toward CO at the atomic level, providing useful insights for the design of efficient ligand-protected cluster catalysts for CO capture and conversion.
We generalize and unify Bleaney's theory and related inverse-temperature expansions of magnetic properties of paramagnetic species. Our approach is valid for different properties, including NMR chemical shifts beyond the...We generalize and unify Bleaney's theory and related inverse-temperature expansions of magnetic properties of paramagnetic species. Our approach is valid for different properties, including NMR chemical shifts beyond the point-dipole approximation, and for both transition-metal and lanthanide complexes. We derive an analytical equation for the 1/ term. Furthermore, we implement higher-order terms numerically to investigate the convergence behavior of 1/ expansions. For transition-metal complexes, the second-order and third-order expansions provide quantitatively accurate results for most commonly encountered zero-field splittings. For an isostructural series of lanthanide complexes, the newly derived third-order term substantially improves the accuracy of calculated susceptibility anisotropies compared with Bleaney's second-order theory.
In this work, we investigated the influence of base pairing and π-π stacking interactions on electron attachment-induced shape resonances in the adenine-thymine (AT) base pair. Resonance positions and widths are computed...In this work, we investigated the influence of base pairing and π-π stacking interactions on electron attachment-induced shape resonances in the adenine-thymine (AT) base pair. Resonance positions and widths are computed using a DLPNO-based equation of motion coupled-cluster approach in conjunction with the Padé analytical continuation method. Seven π*-shape resonances are identified for both linear and stacked AT geometries, consistent with the total number of resonances in isolated adenine and thymine. Natural orbital analysis reveals that low-energy resonances exhibit significant electron density delocalization over both nucleobases. This delocalization is enhanced in the stacked geometry, leading to appreciable stabilization and increased lifetimes of the resonance states. These results highlight the important role of intermolecular interactions in modulating electron attachment processes in DNA.
Starting with an all-atom potential energy surface, we apply a recently introduced intramolecular coarse-graining framework to incorporate nuclear quantum effects in molecular cluster simulations without resorting to pat...Starting with an all-atom potential energy surface, we apply a recently introduced intramolecular coarse-graining framework to incorporate nuclear quantum effects in molecular cluster simulations without resorting to path-integral methods. As in previous work [ 2025, 163, 131101], the configuration space is partitioned into slow intermolecular degrees of freedom and fast intramolecular vibrational modes. Here, the latter are treated quantum mechanically within the local harmonic approximation, allowing zero-point energies and finite-temperature vibrational free energy contributions to be included. The resulting temperature-dependent effective free energy surface is sampled using classical Monte Carlo, yielding equilibrium properties that account for nuclear quantum effects while sampling a lower-dimensional configurational space. The approach is applicable to systems in which the slow intermolecular modes are well-described classically. We use the method to assess the nuclear quantum and isotope effects in a benzene cluster and demonstrate that, although very small, they can be quantified.
Phosgene (COCl) is a highly toxic industrial gas, and exploring the photophysical sensing mechanism of fluorescent probes is critical for rational probe optimization. Herein, time-dependent density functional theory (TD-...Phosgene (COCl) is a highly toxic industrial gas, and exploring the photophysical sensing mechanism of fluorescent probes is critical for rational probe optimization. Herein, time-dependent density functional theory (TD-DFT) and thermal vibration correlation function (TVCF) calculations were performed to clarify the excited-state decay mechanism of the 8-EDAB probe. The free 8-EDAB exhibits extremely weak fluorescence (Φ = 0.0045%), while its phosgene cyclized product displays significantly enhanced emission (Φ = 12.44%). The fluorescence turn-on behavior is attributed to cyclization-induced intramolecular charge transfer (ICT) suppression, which greatly reduces the internal conversion rate ( from 10 to 10 s) and switches the dominant excited-state deactivation pathway from nonradiative decay to radiative fluorescence. Both molecules exhibit two-photon absorption capability, revealing potential bioimaging applicability. Furthermore, we rationally designed two hybrid local charge-transfer (HLCT) derivatives, 8-EDAB-S-3NH and 8-EDAB-5CH, whose cyclized products achieve ultrahigh fluorescence quantum yields of 97.28 and 84.39%, respectively. The improved emission originates from dramatically suppressed internal conversion caused by molecular rigidification, rather than reverse intersystem crossing (RISC) triplet harvesting. Unlike the original experimental work, this study provides the first quantitative TVCF-based mode-resolved analysis of internal conversion suppression and demonstrates a predictive HLCT-based design strategy for high-performance phosgene probes.