J Phys Chem A [JOURNAL]
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200 papers
Donor-Acceptor Strength from the Real-Space-Partitioning of One Particle Transition Density Matrix.
Vargas-Rodríguez I, Martín Pendás Á, Francisco Miguelez E … +7 more , Bazán-Jiménez A, Robles J, Mercado-Sánchez I, Chávez-Rocha R, Landa OA, Rocha-Rinza T, García-Revilla MA
J Phys Chem A · 2026 Jun · PMID 42375026 · Publisher ↗
Orbital analysis is a fundamental tool for studying excited states in organic molecules; however, it is not particularly efficient at describing excitonic states, crucial for designing materials with specific optical and...
Orbital analysis is a fundamental tool for studying excited states in organic molecules; however, it is not particularly efficient at describing excitonic states, crucial for designing materials with specific optical and electronic properties. Recently, a method was proposed to connect the exciton model with the orbital picture by analyzing the one-particle transition density matrix (1TDM). Following this idea, we present a new approach to partition the 1TDM based on the Quantum Theory of Atoms in Molecules (QTAIM), which provides a real-space description of the electronic structure. This QTAIM-based partitioning is applied to eight donor-π-acceptor (D-π-A) systems. The results reveal a clear relationship between the chemical nature of molecular fragments and their associated charge-transfer numbers. To visualize this relationship, we introduce a charge-transfer-number matrix representation that explicitly shows how each fragment contributes to the excitation. This analysis directly reveals the push-pull character of the electronic transitions in these compounds. Furthermore, a consistent relationship is observed between the strength of the donor group and the spatial distribution of the hole density, and the strength of the acceptor group with the spatial distribution of the electron density. This relationship is quantitatively confirmed using a set of ten -substituted benzoic acids, where the topological hole and electron densities show clear correlations with Hammett constants. Overall, this work establishes meaningful connections between donor/acceptor strength, hole/electron densities, and the information encoded in the 1TDM, offering a topologically grounded perspective for the analysis of excitons.
A Deterministic Computational Framework for Exact Orientational Averaging and Complete Irreducible SO(3) Decomposition of Dynamic Hyperpolarizability Tensors.
Ziadi K
J Phys Chem A · 2026 Jun · PMID 42374637 · Publisher ↗
We present a deterministic computational framework for the exact orientational averaging and complete SO(3) decomposition of ab initio dynamic first- and second-hyperpolarizability tensors in isotropic media. The method...
We present a deterministic computational framework for the exact orientational averaging and complete SO(3) decomposition of ab initio dynamic first- and second-hyperpolarizability tensors in isotropic media. The method combines analytical rotational averaging with irreducible tensor decomposition to transform molecular-frame Cartesian β and γ tensors into closed laboratory-frame expressions for nonlinear optical observables, eliminating the need for stochastic orientational sampling. For the dynamic first hyperpolarizability, the response is resolved into the = 1a, = 1b, = 1ab, = 2, and = 3 sectors, while the dynamic second hyperpolarizability is decomposed into the = 0, = 1, = 2a, = 2b, = 3, and = 4 sectors, with the = 2ab cross-invariant retained for the duplicated (L = 2) block. A key formal result is that the dynamic = 2 contribution of must be treated as a matrix-valued channel operator because this irreducible representation occurs with multiplicity two; accordingly, it cannot, in general, be reduced to a single scalar invariant. The orientational averages are evaluated analytically through rank-6 and rank-8 rotational tensors, yielding a general Cartesian-to-channel workflow free of Monte Carlo noise. Benchmarking against Monte Carlo rotational sampling confirms the correctness of the analytical treatment. Application to six benzothiadiazole-based donor-acceptor chromophores illustrates how molecular asymmetry, acceptor strength, and excitation wavelength redistribute the nonlinear response across symmetry channels. The methodology is general and applicable to any molecular system for which dynamic hyperpolarizability tensors are available from electronic-structure calculations.
Exploration of the van der Waals Region of the NO Σ + N Σ Collision Complex.
De Matos Loja A, Costen ML, Paterson MJ
J Phys Chem A · 2026 Jun · PMID 42373598 · Publisher ↗
The van der Waals (VdW) region of the potential energy surface (PES) of the collision complex of NO(Σ) and N(Σ) was explored using explicitly correlated coupled-cluster methods. The Rydberg character of the NO(Σ) state n...
The van der Waals (VdW) region of the potential energy surface (PES) of the collision complex of NO(Σ) and N(Σ) was explored using explicitly correlated coupled-cluster methods. The Rydberg character of the NO(Σ) state necessitated a sufficiently large and diffuse basis set. Basis set superposition error endemic to such systems was mitigated by the use of an explicitly correlated method in addition to a counterpoise correction, subsequent benchmarking was performed via both energetics and molecular properties such as the dipole and quadrupole moment. The method ultimately used was CCSD(T)-F12a/t-aug-cc-pVTZ, with the full VdW PES constructed through a series of three-dimensional cuts exploring the space between key orientations. A broad main minimum well was observed surrounding the linear nitrogen-to-nitrogen ("LN") orientation with a maximum depth of -239.51 cm at an intermolecular separation of . This new PES is useful for interpretation of recent molecular beam scattering experiments.
The Molecular and Electronic Structure of NdF.
Tufekci BA, Ariyarathna IR, Foreman K … +1 more , Bowen KH
J Phys Chem A · 2026 Jun · PMID 42373585 · Publisher ↗
The molecular and electronic structures of NdF and NdF were elucidated through a combined anion photoelectron spectroscopy and quantum chemistry investigation. The anion photoelectron spectrum of NdF yielded an experimen...
The molecular and electronic structures of NdF and NdF were elucidated through a combined anion photoelectron spectroscopy and quantum chemistry investigation. The anion photoelectron spectrum of NdF yielded an experimental vertical detachment energy (VDE) of 1.11 eV, in excellent agreement with the theoretical estimate of 1.106 eV. The calculated adiabatic electron affinity (AEA) of 1.055 eV lies close to the VDE, consistent with the similar optimized structures of the anion and neutral. Geometry optimizations confirm that both NdF and NdF adopt bent C structures with the anion possessing a A (4f6s) ground state and the neutral possessing a A (4f6s) ground state. Extensive multireference calculations reveal a dense manifold of low-lying neutral excited states. Moreover, we juxtapose NdF with its periodic analogue UF, showing similar metal-centered s-electron photodetachment, bent anion/neutral structures, and largely nonbonding 4f/5f electrons. Together, these results demonstrate the collaborative utilization of aPES with relativistic multireference calculations for the electronic structure of f-element molecules.
The Two-Photon Polarization Ratio Explains Unusual Shape of the Two-Photon Absorption Spectra of Dyes and Detects Weak Excitonic Coupling in Fluorescent Protein Dimers.
Cusick A, Thuen A, Schultz S … +5 more , Puhl Iii HL, Hines K, Kim Y, Vogel SS, Drobizhev M
J Phys Chem A · 2026 Jun · PMID 42372028 · Publisher ↗
Two-photon absorption is a nonlinear optical process in which a molecule simultaneously absorbs two photons. It finds use in two-photon fluorescence microscopy, providing high spatial resolution and deep imaging of biolo...
Two-photon absorption is a nonlinear optical process in which a molecule simultaneously absorbs two photons. It finds use in two-photon fluorescence microscopy, providing high spatial resolution and deep imaging of biological tissues. Understanding the physical mechanisms of two-photon absorption will help optimize excitation conditions and design brighter probes for two-photon microscopy. The two-photon polarization ratio (Ω), defined as the ratio of the two-photon absorption strength of circularly and linearly polarized light─carries indispensable information on the symmetry of electronic, vibronic, and excitonic transitions. Here, we present a physical model based on few-state approximations to derive analytical expressions for Ω as a function of molecular dipole moment matrix elements. The model accounts for an unusual, Herzberg-Teller vibronic coupling of the permanent dipole moments to the bond-length alternating vibrational coordinate(s). Using this framework, we analyze both monomeric systems (Rhodamine 6G, TM-BODIPY, and the chromophore in fluorescent protein Venus) and a dimeric Venus protein. For the monomers, Ω measurements allow us to resolve the two-photon absorption spectra into components corresponding to the Franck-Condon vibronic progressions similar to those observed in one-photon absorption, as well as new vibronic progressions built upon Herzberg-Teller replicas of the bond-length alternating vibration(s), only pertinent to two-photon absorption. Our model explains previously reported broadening and blue shift of the two-photon absorption spectra of dyes relative to their one-photon absorption counterparts. For the Venus dimer protein, spectral dependence of Ω helps to resolve strongly overlapping excitonic J- and H-transitions and specify mutual geometrical arrangement of the two chromophores.
Stabilizing the 8π-Conjugated Bicyclic Species via Two-Dimensional Superatomic-Molecule Theory.
Ling M, Yuan Q, Pan Y … +2 more , Li D, Cheng L
J Phys Chem A · 2026 Jun · PMID 42371802 · Publisher ↗
The electronic structure of various 8π-conjugated bicyclic species has been extensively studied for decades. Herein, we proposed an intrinsic regulatory mechanism for stabilizing 8π bicyclic species via heteroatom doping...
The electronic structure of various 8π-conjugated bicyclic species has been extensively studied for decades. Herein, we proposed an intrinsic regulatory mechanism for stabilizing 8π bicyclic species via heteroatom doping in a CH molecule. Based on the recently developed two-dimensional (2D) superatomic-molecule theory, CH can be treated as a 2D superatomic O molecule with superatomic double bonds. Nevertheless, the O is unstable due to its large superatomic radius, which hinders the formation of side-by-side superatomic π-bonds. Subsequently, a series of 8π bicyclic species are constructed by atom doping to stabilize the superatomic π-bond. It is found that the electronegativity of the doping atom effectively shifts the positions of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), thereby increasing the energy gap and stabilizing the superatomic π-bond. Particularly, the aromaticity of 8π-BNH and 8π-BNOH molecules is comparable to that of benzene and naphthalene, surpassing their inorganic analogues. This regulatory mechanism is further validated in the tricyclic 12π-CH (O) and 14π-CH (O) conjugated species. This work expands 2D superatomic bonding and provides several promising structural units for graphene-based 2D materials to achieve band gap regulation.
Data-Derived Conceptual DFT Nucleophilicity Index.
Fliszkiewicz B, Suska H, Popiel S
J Phys Chem A · 2026 Jun · PMID 42366754 · Publisher ↗
The accurate characterization of nucleophilicity has attracted the attention of research groups worldwide for many years. So far, no universally applicable descriptor that correlates closely with experimental observation...
The accurate characterization of nucleophilicity has attracted the attention of research groups worldwide for many years. So far, no universally applicable descriptor that correlates closely with experimental observations has been established. In this study, the behavior of the two conceptual DFT nucleophilicity indices is examined for a broad set of chemical compounds using semiempirical methods. The presented analysis reveals that the tested indices do not reliably capture experimental nucleophilicity trends when applied outside of small reference sets, leading to weak correlations with Mayr's reactivity scale. To address these shortcomings, an empirical nucleophilicity index, , is constructed through symbolic regression, incorporating frontier orbital energies, CDFT-based reactivity descriptors, atom-specific Fukui functions, local charge information, and solvent characteristics. Although the derived global model outperforms conventional descriptors ( = 0.737), substantially higher accuracy ( = 0.811) is obtained only when the models are further refined according to molecular scaffold. Collectively, these findings expose the inherent limitations of existing global CDFT nucleophilicity indices and demonstrate the potential of data-driven strategies to build context-aware reactivity descriptors.
Interconversion Mechanisms in HN-O-NH: Rotamerism, Pyramidal Inversion, or Akamptisomerism?
Freitas MP
J Phys Chem A · 2026 Jun · PMID 42363906 · Publisher ↗
Conformational isomerism is a fundamental aspect of molecular behavior, yet bond-angle inversion (akamptisomerism) remains a rare and poorly understood mechanism, with evidence largely limited to B-O-B-bridged macrocycle...
Conformational isomerism is a fundamental aspect of molecular behavior, yet bond-angle inversion (akamptisomerism) remains a rare and poorly understood mechanism, with evidence largely limited to B-O-B-bridged macrocycles. In this study, the conformational landscapes of X-O-X systems (X = B, C, N, and O) were investigated to assess the generality of this process. Conformational searches and energy profiles were computed at the GFN2-xTB and B3LYP/def2-TZVP levels. The results indicate that akamptisomerism is not a viable pathway in these systems. A linear geometry was located but corresponds to higher-order saddle points rather than a true transition state and is associated with prohibitive energy costs (>70 kcal mol). In contrast, HN-O-NH undergoes interconversion via rotamerism and, more favorably, trigonal pyramidal inversion, with barriers of ∼15 and ∼8 kcal mol, respectively. These findings indicate that akamptisomerism is not a general feature of X-O-X motifs and likely requires specific geometric constraints, such as those found in macrocyclic environments.
Interpretable Machine Learning of Nanoparticle Stability through Topological Layer Embeddings.
Hawthorne F, Seixas L, Almeida JM … +2 more , Woellner CF, Tromer RM
J Phys Chem A · 2026 Jun · PMID 42363905 · Publisher ↗
The stability of chemically complex nanoparticles is governed by an immense configurational space arising from heterogeneous local atomic environments across surface and interior regions. Efficiently identifying low-ener...
The stability of chemically complex nanoparticles is governed by an immense configurational space arising from heterogeneous local atomic environments across surface and interior regions. Efficiently identifying low-energy configurations within this space remains a central challenge for first-principles-based materials discovery, particularly when the available reference data are limited. Here, we introduce a data-efficient and physically interpretable machine-learning framework based on a fragmented, layer-resolved descriptor that explicitly decomposes nanoparticles into surface, intermediate, and core environments using a topology-driven definition. This representation preserves a compact and fixed feature dimensionality while retaining spatial resolution, enabling controlled emphasis on different regions of the nanoparticle through physically motivated weighting schemes. Coupled with gradient-boosted decision-tree models and a ranking-based learning strategy, the proposed framework enables accurate identification of the most stable nanoparticle configurations using only a few hundred density functional theory reference calculations. Ranking performance metrics demonstrate near-saturation of correlation, high top- recall, and rapidly vanishing regret at moderate training set sizes, highlighting the strong data efficiency of the approach. Beyond predictive performance, layer-weighting and SHAP-based interpretability analyses reveal how surface segregation, coordination topology, and local chemical disorder contribute differently to stability across spatial regions of the nanoparticle. The framework is system and code-agnostic, requiring only atomic coordinates, chemical species, and a scalar target energy, and is therefore directly transferable to other multicomponent nanostructures and to alternative first-principles or machine-learning energy methods.
Magic Cluster Anion LaCu: From Superatomic Electronic Structure to Spherical Aromaticity.
Chen XF, Li HF, Zhang JM … +2 more , Wu WH, Wang HQ
J Phys Chem A · 2026 Jun · PMID 42363897 · Publisher ↗
In this work, we systematically investigate the structural evolution and stability of lanthanum-doped copper cluster anions LaCu ( = 1-16) via unbiased global structure search and density functional theory (DFT) calculat...
In this work, we systematically investigate the structural evolution and stability of lanthanum-doped copper cluster anions LaCu ( = 1-16) via unbiased global structure search and density functional theory (DFT) calculations. Among these clusters, species at multiple sizes exhibit enhanced energetic stability, whereas LaCu is structurally distinguished by its compact half-cage geometry. Complementary Mulliken population analysis and energy decomposition analysis (EDA) reveal that the central La atom donates its valence electrons to the surrounding Cu cage, giving rise to the 16-electron superatomic closed-shell configuration that underpins the cluster stability. Adaptive natural density partitioning (AdNDP) analysis confirms that this exceptional stability originates from multicenter delocalized bonds spanning the entire Cu cage; meanwhile, isochronous chemical shielding surface (ICSS) analysis uncovers strong spherical aromaticity, as evidenced by a pronounced shielding peak at 193 ppm. These findings elucidate the synergistic effect between electrostatic attraction and superatomic electronic shell closure and provide theoretical guidance for the rational design of rare-earth-doped superatomic clusters toward functional material applications.
High-Accuracy Extrapolated Ab Initio Thermochemistry of CO, HCO, CS, and HCS.
Kolter M, Vázquez Quesada J, Thorwirth S … +1 more , Harding ME
J Phys Chem A · 2026 Jun · PMID 42361344 · Publisher ↗
Enthalpies of formation for CO, HCO, CS, and HCS have been determined using an extended HEAT (High-accuracy Extrapolated Ab initio Thermochemistry) protocol. Special attention has been paid to estimating conservative 95%...
Enthalpies of formation for CO, HCO, CS, and HCS have been determined using an extended HEAT (High-accuracy Extrapolated Ab initio Thermochemistry) protocol. Special attention has been paid to estimating conservative 95% confidence intervals and the uncertainties in HEAT estimates for molecules containing a second-row element. The recommended values (gas phase, 298.15 K, 1 bar) are as follows: Δ(CO) = 337.8 ± 1.6 kJ mol, Δ(HCO) = 1004.0 ± 1.3 kJ mol, Δ(CS) = 583.6 ±3.1 kJ mol, and Δ(HCS) = 1192.2 ± 2.6 kJ mol. The corresponding proton affinities (gas phase, 1 bar) at T = 0 K amount to 857.9 ± 0.6 and 916.0 ± 0.8 kJ mol for CO and CS and at T = 298.15 K to 864.0 ± 0.6 and 921.9 ± 0.8 kJ mol for CO and CS, respectively. The calculated values align with the available data from the ATcT (Active Thermochemical Tables) analysis and some previous experimental and computational results. However, the uncertainties associated with the extended HEAT values presented here are significantly smaller.
Hydrogen Adsorption on Transition-Metal-Decorated Graphene: Thermodynamic and AIMD Insights from DFT and Post-Hartree-Fock Methods.
Vallejo Narváez WE, Vera de la Garza CG, Fomine S
J Phys Chem A · 2026 Jun · PMID 42361292 · Publisher ↗
Hydrogen adsorption on transition-metal-decorated graphene was investigated using a finite graphene nanoflake model combined with revPBE-D4 geometry optimizations and ωB97M-V single-point energies, complemented by PNO-CC...
Hydrogen adsorption on transition-metal-decorated graphene was investigated using a finite graphene nanoflake model combined with revPBE-D4 geometry optimizations and ωB97M-V single-point energies, complemented by PNO-CCSD(T) and DLPNO-CCSD(T) benchmarks for representative systems. Particular attention was paid to the role of spin-state effects and finite-size electronic structure, which are often neglected in periodic models. Electronic-structure analysis reveals size-dependent open-shell character in graphene nanoflakes ─one larger (G) and one smaller (G2)─where G exhibits robust, where G exhibits robust multiconfigurational singlet behavior and G2 a weaker, functional-dependent tendency. CASSCF/NEVPT2 calculations support this picture and corroborate the high-spin assignments of Sc-G and Y-G. Among the metals examined, Y, Nb, and Pd exhibit strong binding to graphene (-0.67 to -1.02 eV), whereas Sc, Zr, and Ni show moderate stabilization. Hydrogen adsorption is strongly system-dependent: the first H adsorption is exergonic for Y, Zr, Nb, Ni, and Pd (-0.56 to -1.63 eV), while Sc becomes favorable only upon adsorption of a second H molecule. In contrast, additional H uptake is generally disfavored for Y, Nb, and Ni, and only moderately favorable for Zr (-0.32 eV) in the second adsorption step. Three representative systems (Pd, Zr, and Sc), spanning distinct bonding regimes─molecular adsorption, dissociative hydride formation, and high-spin configurations─were used to assess the methodology, with ωB97M-V//revPBE-D4 showing close agreement with coupled-cluster interaction energies within these cases. AIMD simulations on Sc-G-2H and Pd-G-H reveal distinct finite-temperature responses: desorption of one H molecule and metal mobility in the Sc system versus persistent H coordination with bond elongation in the Pd case. Overall, the results show that hydrogen adsorption on TM-decorated graphene nanoflakes depends sensitively on the interplay between metal identity, spin state, and finite-size electronic structure.
Rate Constants and Third-Body Collision Efficiencies for Recombination of Na with OH and O: Implications for Flame Inhibition by Alkali Salts.
Jasper AW, Marshall P, Glarborg P
J Phys Chem A · 2026 Jun · PMID 42360859 · Publisher ↗
Flame inhibition by alkali metals has implications for solid fuel combustion, fire safety, and a number of industrial processes. While the mechanism of inhibition is fairly well understood, details related to thermodynam...
Flame inhibition by alkali metals has implications for solid fuel combustion, fire safety, and a number of industrial processes. While the mechanism of inhibition is fairly well understood, details related to thermodynamic properties and rate constants are still in question. In the present work, the recombination of Na with OH (R5) and O (R7), respectively, was characterized theoretically, and the implications for modeling laminar premixed hydrogen flames doped with sodium species were examined. Third-body collision efficiencies and low-pressure-limit rate constants were obtained using newly fitted ab initio-based potential energy surfaces, classical trajectories, and one-dimensional master equation calculations. The results are consistent with available experimental results and aid in the present modeling study by providing rate information for bath gases and conditions that remain unexplored experimentally. Chemical kinetic modeling of relative Na and absolute H and OH profiles in H-fueled laminar, premixed flames doped with a sodium salt shows that the most important radical removal cycle is the sequence Na + OH (+M) → NaOH (+M) (R5), NaOH + H → Na + HO (R12), even under oxidizing conditions. A secondary cycle, Na + O (+M) ⇄ NaO (+M) (R7), NaO + OH → NaOH + O (R14), is less important due to the low thermal stability of NaO. In most flames, reaction R7 is partially equilibrated, and reaction R14 becomes rate-limiting for the second cycle. The flame analysis supports a lower value of than indicated by recent work on KO + OH, but more work is required to confirm this.
Atmospheric Oxidation Kinetics of Monochloramine by Hydroxyl Radical, Carbonyl Oxide, and Sulfur Trioxide Catalyzed by Water.
Xie C, Long B, Truhlar DG
J Phys Chem A · 2026 Jun · PMID 42360060 · Publisher ↗
Monochloramine (NHCl) serves as a reservoir for atmospheric chlorine, contributing to radical chemistry and indirectly affecting ozone formation and the growth of secondary organic aerosols. We investigated the nonphotol...
Monochloramine (NHCl) serves as a reservoir for atmospheric chlorine, contributing to radical chemistry and indirectly affecting ozone formation and the growth of secondary organic aerosols. We investigated the nonphotolytic atmospheric removal of NHCl by the key oxidants OH, CHOO, and SO by using dual-level kinetics calculations based on high-level quantum chemical calculations and density functional theory. The higher level of electronic structure (HL) is coupled cluster theory with single, double, triple, and quadruple excitations and noniterative pentuple excitations with a complete basis [CCSDTQ(P)/CBS] for the OH reaction and CCSDT(Q)/CBS for the CHOO and SO reactions. The kinetics calculations are direct dynamics calculations that combine conventional transition state theory based on coupled cluster electronic structure and variational transition state theory with small-curvature tunneling based on density functional theory. The results reveal that beyond-CCSD(T) contributions can be as large as 0.8 kcal/mol for determining enthalpies of activation. Reaction-specific anharmonicity effects were found to enhance the rate constant at 190 K by a factor of 14 for NHCl + OH and a factor of 8.5 for NHCl···SO + HO; these factors decrease to 6.2 and 4.4, respectively, at 280 K. Anharmonic effects are much smaller (factors ≤1.16) for NHCl + CHOO. Tunneling was found to enhance the rate constant at 190 K by a factor of 4.5 for NHCl + OH and a factor of 20 for NHCl···SO + HO; these factors decrease to 2.0 and 2.3, respectively, at 280 K. The recrossing effects reduce the NHCl + OH rate coefficient by 0.46 at 190 K and 0.67 at 280 K. The contributions of the various sinks for atmospheric NHCl─photolysis, reaction with OH, multiphase processes, and the reaction with SO catalyzed HO─depend on the conditions.
Conformational Preferences Modulated by Heavier Chalcogen Substitution: Study of Complexes between MeChH (Ch = O, S, Se, Te) and Acetophenone.
Banerjee P, Samanta P
J Phys Chem A · 2026 Jun · PMID 42350352 · Publisher ↗
The present work investigates theoretically the conformational preferences for complexes between a series of donor alcohols MeChH, where Ch = O, S, Se, and Te, and a common acceptor molecule acetophenone (APh). The latte...
The present work investigates theoretically the conformational preferences for complexes between a series of donor alcohols MeChH, where Ch = O, S, Se, and Te, and a common acceptor molecule acetophenone (APh). The latter is characterized by two distinct regions of negative electrostatic potential: the directed lone pair electrons on the carbonyl oxygen and the diffuse electronic cloud on its π-ring. It is predicted that when MeOH is the donor, O-H···O hydrogen bonding (H-bonding) to the carbonyl oxygen of APh gives rise to the most preferred APh-MeOH conformer, while H-bonding to its π-cloud is less favored. However, such binding preferences alter remarkably when the heavier alcohols act as the donor. Electronic structure calculations, including those at the CCSD(T)/CBS limit, predict highest stability for conformers bound by a combination of π-hole and σ-hole interactions, both involving the heavy chalcogen atom. The former involves the interaction of its lone pair with the electron-deficient region above the carbonyl group of APh, while the latter involves a chalcogen-bond (Ch-bond) with the π-cloud of APh (Ch···π interaction). Also, the ChH···π H-bonded interactions involving the SH/SeH/TeH donor and the π-cloud on APh become increasingly stable as compared to their carbonyl-bound ChH···O H-bonded counterparts as we move down the group. A chalcogen-chalcogen (Ch···Ch) interaction with the carbonyl oxygen of APh is stabilized only for MeTeH, leading to a Te···O Ch-bond. The important role of heavy atom substitution in biomolecular recognition is thus highlighted. Observed modulations in binding preferences and in the very nature of the nonbonded interactions are attributable to a delicate interplay of electrostatic and dispersion interactions.
Probing the Ultrafast Photodynamics of Dihydroazulene with In Silico Time-Resolved Photoelectron Spectroscopy and Ultrafast Electron Diffraction.
Hillers-Bendtsen AE, Mikkelsen KV, Martinez TJ
J Phys Chem A · 2026 Jun · PMID 42349913 · Publisher ↗
Molecular photoswitches are chemical systems that can undergo reversible chemical transformations following the absorption of light. Such systems find potential application in modern technologies such as molecular electr...
Molecular photoswitches are chemical systems that can undergo reversible chemical transformations following the absorption of light. Such systems find potential application in modern technologies such as molecular electronics, optical data storage, exploitation of solar energy, and much more. In this paper, we present ab initio nonadiabatic molecular dynamics of the dicyano phenyl-substituted dihydroazulene/vinylheptafulvene (DHA/VHF) system using ab initio multiple spawning in combination with state-averaged α-complete active space self-consistent field theory to study the photoinduced electrocyclic ring opening reaction that converts DHA to VHF. Scrutinizing the mechanism of the photoinduced ring opening reaction is crucial to be able to design new derivatives with improved properties and to design experiments that can probe the photoswitching of such systems. Our simulations show that this DHA system photoswitches with a 41% quantum yield on a sub-picosecond time scale. In addition to that, we simulate the time-resolved photoelectron spectrum, which, by comparison to the experimental equivalent, shows that our dynamics reproduce the experiments with high precision. Furthermore, we simulate the (hitherto unmeasured) elastic ultrafast electron diffraction signal and show that it contains significant features directly related to the nuclear dynamics of the photoswitching event. Our atomistic simulations thus identify ultrafast electron diffraction as an excellent technique for studying the photoswitching of DHA/VHF derivatives and that this could aid in the design and development of new related compounds with optimized switching quantum yields.
Experimental and Multiscale Modeling Insights for Radiation-Driven Neptunium Redox Processes at Elevated Temperatures.
Kynman AE, Grimes TS, Mezyk SP … +3 more , Layne B, Cook AR, Horne GP
J Phys Chem A · 2026 Jun · PMID 42347683 · Publisher ↗
Studies of the radiation-driven reactions of actinide elements at elevated temperatures are extremely limited, but important given that radiation heating of used nuclear fuel can affect the radiolytically promoted actini...
Studies of the radiation-driven reactions of actinide elements at elevated temperatures are extremely limited, but important given that radiation heating of used nuclear fuel can affect the radiolytically promoted actinide redox processes occurring in hydroprocessing environments. Under these conditions, the high concentration of nitric acid present makes the reaction of actinides, such as neptunium, with nitric acid radiolysis products significant. Therefore, here we present derivation of the rate coefficients for the reaction of pentavalent neptunium with the nitrate radical at elevated temperature, resulting in Eyring and Arrhenius parameters for this important reaction. We also revisit our previously published multiscale model predictions for radiation-induced neptunium redox chemistry and present an iteration which successfully operates over a wider range of nitric acid concentrations, 0.1-6.0 M.
Excellent Thermal Stability and Environmental Sustainability of Trifluorodimethyl Sulfide as a Potential Alternative Refrigerant.
Hu X, Zhang M, He J … +2 more , Hou H, Wang B
J Phys Chem A · 2026 Jun · PMID 42345445 · Publisher ↗
Trifluorodimethyl sulfide (CHSCF) has been proposed to be a potential alternative refrigerant based on various rigorous quantum chemistry calculations. It is revealed that the half F-substitution is capable of tuning the...
Trifluorodimethyl sulfide (CHSCF) has been proposed to be a potential alternative refrigerant based on various rigorous quantum chemistry calculations. It is revealed that the half F-substitution is capable of tuning the stability and reactivity of dimethyl sulfide (CHSCH) significantly. The strength of both S-C bonds is enhanced. The bond dissociation energies increase by 5-6 kcal/mol with respect to CHSCH, and decomposition temperature of CHSCF is predicted to be 875 K. Meanwhile, the existence of CH group keeps the good reactivity of CHSCF toward OH radicals in the troposphere. Complex-forming H-abstraction to produce HO and CFSCH radicals is the predominant mechanism accompanied by minor S-O association/elimination pathways. The atmospheric lifetime and radiative efficiency of CHSCF is 0.2-1 years and 0.25 Wmppb, respectively, leading to a global warming potential of 9-90 for a 100-year time horizon. The possible degradation products of CHSCF in the atmosphere include both radicals, e.g., CFSCHOO, CFSCHOONO, CFSCHOONO, CFSCHO, CFS, and molecules, e.g., (CFSCHOO), CFSCHOOH, CHO, and CHS(O)CF. The present computational work not only provides interesting insights into the dramatic impact of the partial fluorination on stability and reactivity of sulfides but also demonstrates that CHSCF should be a viable refrigerant replacement for hydrofluorocarbons and even hydrofluoroolefins with excellent thermal stability and environmental sustainability.
Controlling the Delayed Fluorescence-Phosphorescence Balance via Torsional Dynamics and Intramolecular Charge Transfer in Carbazole-Based Aminoboranes.
Dhiman N, Muhammed Munthasir AT, Ghosh S … +2 more , Thilagar P, Umapathy S
J Phys Chem A · 2026 Jun · PMID 42342587 · Publisher ↗
Carbazole-based aminoboranes are promising luminophores exhibiting both delayed fluorescence and room-temperature phosphorescence. However, the structural and electronic factors governing intersystem crossing (ISC) and r...
Carbazole-based aminoboranes are promising luminophores exhibiting both delayed fluorescence and room-temperature phosphorescence. However, the structural and electronic factors governing intersystem crossing (ISC) and reverse ISC (RISC) remain elusive. Using femtosecond transient absorption and stimulated Raman spectroscopy, we reveal that rapid evolution along the B-N stretching/torsional coordinates facilitates the formation of a twisted intramolecular charge-transfer (TICT) state, bringing the singlet and triplet states energetically closer. In a series of -borylated carbazoles, bromine incorporation enhances ISC via heavy-atom effects, while "magic methyl" groups impact the torsional dynamics, which increase the nonradiative relaxation pathway and ISC rate. Solvent-dependent and computational studies found that both ISC and reverse ISC proceed through higher-lying triplet and hybrid charge-transfer states that enable spin flipping. This interplay between torsional control and spin-orbit coupling finely tunes the balance between delayed fluorescence and phosphorescence.
Spin-Resolved Nonlocal Second-Order Fukui Index for Open-Shell Systems from Delocalization Index Response.
Kenouche S
J Phys Chem A · 2026 Jun · PMID 42341147 · Publisher ↗
This work presents the first analytical derivation of the spin-resolved nonlocal Second-Order Fukui Index (SOFI) for open-shell molecular systems. The approach is based on the linear response of interatomic delocalizatio...
This work presents the first analytical derivation of the spin-resolved nonlocal Second-Order Fukui Index (SOFI) for open-shell molecular systems. The approach is based on the linear response of interatomic delocalization indices (δ), providing a direct connection between frontier molecular orbital characteristics and real-space electron-sharing redistribution. The methodology is applied to substituted phenoxyl radicals to quantify how electron-donating (EDG) and electron-withdrawing (EWG) groups modulate α- and β-spin channels. The results provide a detailed map of spin-dependent electronic redistribution upon electron addition or removal. Spin-resolved SOFI indices are shown to be effective nonlocal descriptors for rationalizing radical reactivity. This study establishes a theoretical framework for the quantitative investigation of open-shell systems and the influence of substituents on spin-dependent electronic structure.
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