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The linear scaling divide–expand–consolidate (DEC) framework is expanded to include unrestricted Hartree–Fock references. By partitioning the orbital space and employing local molecular orbitals, the full molecular calculation can be performed as independent calculations on individual fragments, making the method well-suited for massively parallel implementations. This approach also incorporates error control through the fragment optimization threshold (FOT), which maintains precision and consistency throughout the calculations. A benchmark was conducted for correlation energies of open-shell systems and the relative energies of both open- and closed-shell molecules at the MP2 level of theory. The full calculation result is achieved as the FOT approaches zero. For correlation energies, an FOT of 10−3 is sufficient to recover over 98% of the full result in all cases. However, for relative energies and the electronic energy component of oxidation potentials, a tighter FOT of 10−4 is required to keep the DEC error within 10% for both open- and closed-shell molecules. This is likely due to a lack of systematic error cancellation for the molecules with vastly different chemical natures. Therefore, for accurate relative energies, the FOT should be an order of magnitude lower, and additional caution is needed, particularly for large systems. The DEC method extension to unrestricted references maintains favorable features of linear scaling and can be implemented in a massively parallel algorithm to calculate correlation energies for large open-shell systems. [ABSTRACT FROM AUTHOR]

Reliable computational methodologies and basis sets for modeling x-ray spectra are essential for extracting and interpreting electronic and structural information from experimental x-ray spectra. In particular, the trade-off between numerical accuracy and computational cost due to the size of the basis set is a major challenge, since molecular orbitals undergo extreme relaxation in the core-hole state. To gain clarity on the changes in electronic structure induced by the formation of a core-hole, the use of sufficiently flexible basis for expanding the orbitals, particularly for the core region, has been shown to be essential. This work focuses on the refinement of core-hole ionized state calculations using the equation-of-motion coupled cluster family of methods through an extensive analysis on the effectiveness of "hybrid" and mixed basis sets. In this investigation, we utilize the CVS-EOMIP-CCSD method in combination and construct hybrid basis sets piecewise from readily available Dunning's correlation consistent basis sets in order to calculate x-ray ionization energies (IEs) for a set of small gas phase molecules. Our results provide insights into the impact of basis sets on the CVS-EOMIP-CCSD calculations of K-edge IEs of first-row p-block elements. These insights enable us to understand more about the basis set dependence of the core IEs computed and allow us to establish a protocol for deriving reliable and cost-effective theoretical estimates for computing IEs of small molecules containing such elements. [ABSTRACT FROM AUTHOR]

The self-consistent field (SCF) procedure is the standard technique for solving the Hartree–Fock and Kohn–Sham density functional theory calculations, while convergence is not theoretically guaranteed. Direct minimization methods, such as the augmented Lagrangian method (ALM) and second-order SCF (SOSCF), obtain the SCF solution by minimizing the Lagrangian with the gradient. In SOSCF, molecular orbitals are optimized by truncating the Taylor expansion of a unitary matrix represented in exponential form to ensure the orthonormality condition. This study proposes an alternative algorithm for direct-energy minimization to obtain an SCF solution using ALM Lagrangian by adopting sequential Givens rotations between occupied and virtual orbitals. The Givens rotation corresponds to unitary transformations that guarantee orthogonality and avoid variational collapse. Complex gradients for sequential Givens rotation were obtained by the error back-propagation method, which is based on the chain rule. Illustrative applications clarified the features of the present DGR methods by comparing with other SCF algorithms such as direct inversion in iterative subspace, SOSCF, and ALM. [ABSTRACT FROM AUTHOR]

The intersection of quantum chemistry and quantum computing has led to significant advancements in understanding the potential of using quantum devices for the efficient calculation of molecular energies. Simultaneously, this intersection enhances the comprehension of quantum chemical properties through the use of quantum computing and quantum information tools. This paper tackles a key question in this relationship: Is the nature of the orbital-wise electron correlations in wavefunctions of realistic prototypical cases classical or quantum? We address this question with a detailed investigation of molecular wavefunctions in terms of Shannon and von Neumann entropies, common tools of classical and quantum information theory. Our analysis reveals a notable distinction between classical and quantum mutual information in molecular systems when analyzed with Hartree–Fock canonical orbitals. However, this difference decreases dramatically, by ∼100-fold, when natural orbitals are used as reference. This finding suggests that orbital correlations, when viewed through the appropriate basis, are predominantly classical. Consequently, our study underscores the importance of using natural orbitals to accurately assess molecular orbital correlations and to avoid their overestimation. [ABSTRACT FROM AUTHOR]

This research elucidates the intricate nature of electronic coupling in the redox-active (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO), commonly utilized in organic radical batteries. This study employs a combination of classical molecular dynamics and various electronic coupling calculation schemes. Within the context of the generalized Mulliken–Hush method, the electronic couplings are investigated via the complete active space self-consistent field approach, in combination with n-electron valence state perturbation theory, to provide an accurate description of both static and dynamic electron correlation as well as using (time-dependent) density functional theory simulations. Furthermore, the electronic communication between redox-active sites is studied using the cost-efficient density functional theory (DFT)-based frontier molecular orbital (FMO) approach. Our study reveals the dependence of the electronic coupling on the distance and the relative orientation of the redox pairs (TEMPO and TEMPO+). Apart from the expected exponential distance dependence, we found pronounced orientation dependence, with coupling values varying up to 0.2 eV, which is reflected by a substantial basis set dependency of the couplings, in particular at short distances. In addition, our study highlights the limitations of the DFT-based FMO method, in particular at short intermolecular distances between the redox-active sites, which may lead to a mixing of the involved molecular orbitals. This comparison will provide us with the most cost–accuracy-effective method for calculating electronic couplings in TEMPO–TEMPO+ systems. [ABSTRACT FROM AUTHOR]

Encapsulation of coordination complexes within the confined spaces of self-assembled hosts is an effective method for creating supramolecular assemblies with distinct chemical and physical properties. Recent studies with calix-resorcin[4]arene hydrogen-bonded hexameric capsules revealed that encapsulated metal complexes exhibit enhanced and blue-shifted photoluminescence compared to their unencapsulated forms. The photophysical change has been hypothetically attributed to encapsulation-induced confinement, which isolates the metal complex from the solvent, suppressing stabilization of the excited state of the guest by solvent reorganization and structural relaxation, and altering the local environment, such as solvent polarity and viscosity, around the guest. In this study, density-functional theory calculations were conducted to explore how encapsulation affects the photophysical properties of a cationic iridium complex within a hydrogen-bonded hexameric capsule. The encapsulation-induced emission shift was analyzed by separating it into three factors: suppression of solvent reorganization, suppression of structural relaxation of the complex, and electronic interactions between the complex and the capsule. The findings indicate that the photoluminescence modulation is driven by the electronic interaction between the host and guest, which affects the energy levels of the molecular orbitals involved in the T1 excited state and the suppression of excited-state structural relaxation of the Ir complex due to the presence of the host. This study advances our understanding of the photophysical dynamics of coordination complexes within the confined spaces of hexameric capsules, providing a valuable approach for tuning the excited state properties of guest molecules. [ABSTRACT FROM AUTHOR]

The structures and chemical bond evolution of ditantalum doped carbon clusters Ta2Cn−/0 (n = 1–7) were studied via size-selected anion photoelectron spectroscopy and theoretical calculations. It is found that Ta2C−/0 has a triangular structure and Ta2C2−/0 has a quasi-rhombus structure with C2v symmetry. Ta2C3− has a quasi-planar structure with a carbon atom and a C2 unit interacting with two tantalum atoms, and the lowest-energy isomer of neutral Ta2C3 has a triangular bipyramid structure with three carbon atoms around the Ta2 unit. Ta2C4−/0 has two C2 units connected with the Ta2 unit in parallel. Two isomers of Ta2C5− are observed, where both isomers have one carbon atom and two C2 units bound to the Ta2 unit in different ways. The most stable structure of neutral Ta2C5 has one carbon atom added on top of the Ta2C4 cluster. The most stable structures of Ta2C6-7−/0 can be viewed as a C2 unit and a C3 unit capping a butterfly like Ta2C4 structure, respectively. Molecular orbital analysis shows that neutral Ta2C3 has a large gap between its highest occupied molecular orbital and lowest unoccupied molecular orbital. Chemical bonding analysis reveals that the Ta–Ta interactions in Ta2Cn−/0 (n = 1–7) clusters are slightly weaker than the Ta–Ta interaction in bare Ta2 due to the participation in forming multicenter bonds. [ABSTRACT FROM AUTHOR]

In this study, the effects of chlorine substitution on the valence orbitals and electronic states of 3-chloropyridine (3-CP) were investigated utilizing high-resolution vacuum ultraviolet mass-analyzed threshold ionization (VUV-MATI) spectroscopy and computational methods. High-quality vibrational spectra were obtained from the VUV-MATI spectra of 3-CP isotopomers (35Cl and 37Cl), revealing high-quality vibrational spectra for the lowest cationic states. The adiabatic ionization energies (AIEs) of these isotopomers were accurately determined, providing detailed information about the electronic structure and ionization dynamics. Intense spectra peaks were linked with the D1 excited state of the 3-CP cation, with vibronic transitions in this state closely matching those predicted by Franck–Condon simulations. This provided insights into the cationic structure and the roles of the highest occupied molecular orbital (HOMO) and the HOMO-1. The HOMO was primarily a π orbital of the pyridine ring, while the HOMO-1 consisted of nonbonding orbitals. The AIEs suggested that meta-chlorine substitution stabilizes nonbonding orbitals less effectively than ortho substitution, indicating closely spaced electronic states in the 3-CP cation. Minor discrepancies in vibrational frequencies and intensities, particularly above 800 cm−1, suggested the presence of vibronic coupling, warranting further investigation. Overall, this study provided a comprehensive understanding of the vibronic and ionization properties of 3-CP, emphasizing the influence of the position of the chlorine substitution on molecular orbitals and the value of advanced theoretical and experimental approaches for analyzing the vibrational spectra of complex molecules. [ABSTRACT FROM AUTHOR]

The features and the electronic character of the states for the Ni 2p x-ray photoelectron spectroscopy (XPS) of Ni(OH)2 were analyzed. This detailed analysis is based on ab initio molecular orbital wavefunctions for a cluster model of Ni(OH)2. The theory is validated by comparison with experiment. Then, advanced methods are used to explain and contrast the properties of different groups of ionic states. An important conclusion is that in most cases, the ionic states cannot be described with a single configuration or determinant. Despite this essential many-body character of the XPS, we demonstrate that it is possible to understand the origin of the main and satellite XPS features in terms of their orbital character. [ABSTRACT FROM AUTHOR]

The features and the electronic character of the states for the Ni 2p x-ray photoelectron spectroscopy (XPS) of Ni(OH)2 were analyzed. This detailed analysis is based on ab initio molecular orbital wavefunctions for a cluster model of Ni(OH)2. The theory is validated by comparison with experiment. Then, advanced methods are used to explain and contrast the properties of different groups of ionic states. An important conclusion is that in most cases, the ionic states cannot be described with a single configuration or determinant. Despite this essential many-body character of the XPS, we demonstrate that it is possible to understand the origin of the main and satellite XPS features in terms of their orbital character. [ABSTRACT FROM AUTHOR]

We present a new methodology to calculate the strong light-matter coupling between photonic modes in microcavities and large molecular aggregates that consist of hundreds of molecular fragments. To this end, we combine our fragment molecular orbital long-range corrected time-dependent density functional tight-binding methodology with a generalized Tavis–Cummings Hamiltonian. We employ an excitonic Hamiltonian, which is built from a quasi-diabatic basis that is constructed from locally excited and charge-transfer states of all molecular fragments. To calculate polaritonic states, we extend our quasi-diabatic basis to include photonic states of a microcavity and derive and implement the couplings between the locally excited states and the cavity states and built a Tavis–Cummings Hamiltonian that incorporates the intermolecular excitonic couplings. Subsequently, we demonstrate the capability of our methodology by simulating the influence of the electric field polarization on the polaritonic spectra for a tetracene aggregate of 125 monomers. Furthermore, we investigate the dependence of the splitting of the upper and lower polaritonic branches on the system size by comparing the spectra of five different tetracene clusters. In addition, we investigate the polariton dispersion of a large tetracene aggregate for electric field polarizations in the x, y, and z directions. Our new methodology can facilitate the future study of exciton dynamics in complex molecular systems, which consist of up to hundreds of molecules that are influenced by strong light–matter coupling to microcavities. [ABSTRACT FROM AUTHOR]

Most chemical processes happen at a local scale where only a subset of molecular orbitals is directly involved and only a subset of covalent bonds may be rearranged. To model such reactions, Density Functional Theory (DFT) is often inadequate, and the use of computationally more expensive correlated wavefunction (WF) methods is required for accurate results. Mixed-resolution approaches backed by quantum embedding theory have been used extensively to approach this imbalance. Based on the frozen density embedding freeze-and-thaw algorithm, we describe an approach to embed complete active space self-consistent field simulations run in the OpenMolcas code in a DFT environment calculated in CP2K without requiring any external tools. This makes it possible to study a local, active part of a chemical system in a larger and relatively static environment with a computational cost balanced between the accuracy of a WF method and the efficiency of DFT, which we test on environment–subsystem pairs. Finally, we apply the implementation to an oxygen molecule leaving an aluminum (111) surface and a ruthenium(IV) oxide (110) surface. [ABSTRACT FROM AUTHOR]

Low-energy (0–14 eV) resonance electron interaction and fragment species produced by dissociative electron attachment (DEA) for enantiomeric forms of glutamic acid (Glu) are studied under gas-phase conditions by means of DEA spectroscopy and density functional theory calculations. Contrary to a series of amino acids studied earlier employing the DEA technique, the most abundant species are not associated with the elimination of a hydrogen atom from the parent molecular negative ion. Besides this less intense closed-shell [Glu – H]– fragment, only two mass-selected negative ions, [Glu – 19]– and [Glu – 76]–, are detected within the same electron energy region, with the yield maximum observed at around 0.9 eV. This value matches well the energy of vertical electron attachment into the lowest normally empty π* COOH molecular orbital of Glu located at 0.88 eV according to the present B3LYP/6-31G(d) calculations. Although the detection of asymmetric DEA properties a priori is not accessible under the present experimental conditions, "chirality non-conservation" can be associated with some decay channels. Evidently, the measured spectra for the L- and D-forms are found to be identical, the results, nevertheless, being of interest for the forthcoming experiments utilizing spin-polarized electron beam as a chiral factor in the framework of conventional DEA technique. [ABSTRACT FROM AUTHOR]

A low-cost approach for stochastically sampling static exchange during time-dependent Hartree–Fock-type propagation is presented. This enables the use of an excellent hybrid density functional theory (DFT) starting point for stochastic GW quasiparticle energy calculations. Generalized Kohn–Sham molecular orbitals and energies, rather than those of a local-DFT calculation, are used for building the Green function and effective Coulomb interaction. The use of an optimally tuned hybrid diminishes the starting point dependency in one-shot stochastic GW, effectively avoiding the need for self-consistent GW iterations. [ABSTRACT FROM AUTHOR]

We introduce the concept of Kohn–Sham fragment localized molecular orbitals (KS-FLMOs), which are Kohn–Sham molecular orbitals (MOs) localized in specific fragments constituting a generic molecular system. In detail, we minimize the local electronic energies of various fragments, while maximizing the repulsion between them, resulting in the effective localization of the MOs. We use the developed KS-FLMOs to propose a novel energy decomposition analysis, which we name Kohn–Sham fragment energy decomposition analysis, which allows for rationalizing the main non-covalent interactions occurring in interacting systems both in vacuo and in solution, providing physical insights into non-covalent interactions. The method is validated against state-of-the-art energy decomposition analysis techniques and with high-level calculations. [ABSTRACT FROM AUTHOR]

The results of relativistic calculations of nuclear magnetic resonance shielding tensors (σ) for the thallium monocation (Tl+), thallium hydride (TlH), and thallium halides (TlF, TlCl, TlBr, TlI, and TlAt) are presented as obtained within a four-component polarization propagator formalism and a two-component linear response approach within the zeroth-order regular approximation. In addition to a detailed analysis of relativistic effects performed in this work, some quantum electrodynamical (QED) effects on those nuclear magnetic resonance shieldings and other small contributions are estimated. A strong dependence of σ(Tl) on the bonding partner is found, together with a very weak dependence of QED effects with them. In order to explain the trends observed, the excitation patterns associated with relativistic ee (or paramagnetic-like) and pp (or diamagnetic-like) contributions to σ are analyzed. For this purpose, the electronic spin-free and spin-dependent contributions are separated within the two-component zeroth-order regular approximation, and the influence of spin–orbit coupling on involved molecular orbitals is studied, which allows for a thorough understanding of the underlying mechanisms. [ABSTRACT FROM AUTHOR]

We report the x-ray absorption spectrum (XAS) of the tert-butyl radical, C4H9. The radical was generated pyrolytically from azo-tert-butane, and the XAS of the pure radical was obtained by subtraction of spectra recorded at different temperatures. The bands in the XAS were assigned by ab initio calculations that are in very good agreement with the experimental data. The lowest energy signal in the XAS is assigned to the C1s electron transition from the central carbon atom to the singly occupied molecular orbital (SOMO), while higher transitions correspond to C1s excitations from terminal carbon atoms. Furthermore, we investigated the fragmentation of the radical following resonant C1s excitation by electron–ion-coincidence spectroscopy. Several fragmentation channels were identified. The C1s excitation of the terminal carbons is associated with a stronger fragmentation tendency compared to the lowest C1s excitation of the central carbon into the SOMO. For this core excited state, we still observe an intact parent ion, C 4 H 9 + , and a comparatively higher tendency to dissociate into CH 3 + + C 3 H 6 + . [ABSTRACT FROM AUTHOR]

An ab initio molecular orbital study has been performed to explore the structural rearrangement and dissociation of SiH 4 + radical cation at the X ̃ 2 T 2 ground electronic state. All stationary points located on the lowest adiabatic sheet of Jahn–Teller (JT) split X ̃ 2 T 2 state are fully optimized and characterized by performing harmonic vibrational frequency calculations. The structural rearrangement is predicted to start with JT distortions involving the doubly-degenerate (e) and triply-degenerate (t2) modes. The e mode reduces the initial Td symmetry of the SiH 4 + ground state to a D2d saddle point, which eventually dissociates into the SiH 3 + ( 2 A 1 ) + H products via C3v local minimum. In turn, an e-type bending of αH-Si-H yields the SiH 2 + ( 2 A 1 ) + H2 products through the first C3v local minimum and then the Cs(2A′) global minimum. In the alternative pathway, the t2 mode distorts the initial Td symmetry into a loosely bound C3v local minimum, which further dissociates into the SiH 3 + ( 2 A 1 ) + H asymptote via totally symmetric Si–H stretching mode, and SiH 2 + ( 2 A 1 ) + H2 products via H–Si–H bending (e) mode through the Cs(2A′) global minimum. It is further predicted that the Cs global minimum interconverts equivalent structures via a C2v transition structure. In addition, the two dissociation products are found to be connected by a second C2v transition structure. [ABSTRACT FROM AUTHOR]

Basis sets consisting of functions that form linearly independent products (LIPs) have remarkable applications in quantum chemistry but are scarce because of mathematical limitations. We show how to linearly transform a given set of basis functions to maximize the linear independence of their products by maximizing the determinant of the appropriate Gram matrix. The proposed method enhances the utility of the LIP basis set technology and clarifies why canonical molecular orbitals form LIPs more readily than atomic orbitals. The same approach can also be used to orthogonalize basis functions themselves, which means that various orthogonalization techniques may be viewed as special cases of a certain nonlinear optimization problem. [ABSTRACT FROM AUTHOR]

Localization procedures are an important tool for analysis of complex systems in quantum chemistry, since canonical molecular orbitals are delocalized and can, therefore, be difficult to align with chemical intuition and obscure information at the local level of the system. This especially applies to calculations obeying periodic boundary conditions. The most commonly used approach to localization is Foster–Boys Wannier functions, which use a unitary transformation to jointly minimize the second moment of the orbitals. This procedure has proven to be robust and fast but has a side effect of often mixing σ - and π -type orbitals. σ / π -separation is achieved by the Pipek–Mezey Wannier function (PMWF) approach [Lehtola and Jónsson, J. Chem. Theory Comput. 10, 642 (2014) and Jónsson et al., J. Chem. Theory Comput. 13, 460 (2017)], which defines the spread functional in terms of partial charges instead. We have implemented a PMWF algorithm in the CP2K software package using the Cardoso–Souloumiac algorithm to enable their application to real-time time-dependent density functional theory. The method is demonstrated on stacked CO 2 molecules, linear acetylenic carbon, boron and nitrogen co-doped graphene, and nitrogen-vacancy doped diamond. Finally, we discuss its computational scaling and recent efforts to improve it with fragment approaches. [ABSTRACT FROM AUTHOR]

Understanding core level shifts in aromatic compounds is crucial for the correct interpretation of x-ray photoelectron spectroscopy (XPS) of polycyclic aromatic hydrocarbons (PAHs), including acenes, as well as of styrenic polymers, which are increasingly relevant for the microelectronic industry, among other applications. The effect of delocalization through π aromatic systems on the stabilization of valence molecular orbitals has been widely investigated in the past. However, little has been reported on the impact on the deeper C1s core energy levels. In this work, we use first-principles calculations at the level of many body perturbation theory to compute the C1s binding energies of several aromatic systems. We report a C1s red shift in PAHs and acenes of increasing size, both in the gas phase and in the molecular crystal. C1s red shifts are also calculated for stacked benzene and naphthalene pairs at decreasing intermolecular distances. A C1s red shift is in addition found between oligomers of poly(p-hydroxystyrene) and polystyrene of increasing length, which we attribute to ring–ring interactions between the side-chains. The predicted shifts are larger than common instrumental errors and could, therefore, be detected in XPS experiments. [ABSTRACT FROM AUTHOR]

Uniquely, large-bipolarons' self-trapped holes occupy superoxygens, each comprising four oxygens circumscribed by four coppers in a CuO2 plane, formed as oxygens relax inward and coppers relax outward. Critically, concomitant oxygen-to-copper electron transfer eliminates copper spins. The d-symmetry of superoxygens' ground state molecular orbital tracks the superoxygens' predominant zero-point radial vibrations. These large bipolarons' distinctive charge transport, absorption, magnetism, local atomic vibrations, condensation into a liquid, and subsequent superconductivity are consistent with cuprate superconductors' long-established unusual properties. [ABSTRACT FROM AUTHOR]

Chemical phenomena involving near-degenerate electronic states, such as conical intersections or avoided crossing, can be properly described using quasi-degenerate perturbation theory. This study proposed a highly scalable quasi-degenerate second-order N-electron valence state perturbation theory (QD-NEVPT2) using the local pair-natural orbital (PNO) method. Our recent study showed an efficient implementation of the PNO-based state-specific NEVPT2 method using orthonormal localized virtual molecular orbitals (LVMOs) as an intermediate local basis. This study derived the state-coupling (or off-diagonal) terms to implement QD-NEVPT2 in an alternative manner to enhance efficiency based on the internally contracted basis and PNO overlap matrices between different references. To facilitate further acceleration, a local resolution-of-the-identity (RI) three-index integral generation algorithm was developed using LMOs and LVMOs. Although the NEVPT2 theory is considered to be less susceptible to the intruder-state problem (ISP), this study revealed that it can easily suffer from ISP when calculating high-lying excited states. We ameliorated this instability using the imaginary level shift technique. The PNO-QD-NEVPT2 calculations were performed on small organic molecules for the 30 lowest-lying states, as well as photoisomerization involving the conical intersection of 1,1-dimethyldibenzo[b,f] silepin with a cis-stilbene skeleton. These calculations revealed that the PNO-QD-NEVPT2 method yielded negligible errors compared to the canonical QD-NEVPT2 results. Furthermore, we tested its applicability to a large photoisomerization system using the green fluorescent protein model and the ten-state calculation of the large transition metal complex, showcasing that off-diagonal elements can be evaluated at a relatively low cost. [ABSTRACT FROM AUTHOR]

Hückel molecular orbital (HMO) theory provides a semi-empirical treatment of the electronic structure in conjugated π-electronic systems. A scalable system-agnostic execution of HMO theory on a quantum computer is reported here based on a variational quantum deflation (VQD) algorithm for excited state quantum simulation. A compact encoding scheme is proposed here that provides an exponential advantage over the direct mapping and allows for quantum simulation of the HMO model for systems with up to 2n conjugated centers with n qubits. The transformation of the Hückel Hamiltonian to qubit space is achieved by two different strategies: an iterative refinement transformation and the Frobenius-inner-product-based transformation. These methods are tested on a series of linear, cyclic, and hetero-nuclear conjugated π-electronic systems. The molecular orbital energy levels and wavefunctions from the quantum simulation are in excellent agreement with the exact classical results. However, the higher excited states of large systems are found to suffer from error accumulation in the VQD simulation. This is mitigated by formulating a variant of VQD that exploits the symmetry of the Hamiltonian. This strategy has been successfully demonstrated for the quantum simulation of C60 fullerene containing 680 Pauli strings encoded on six qubits. The methods developed in this work are easily adaptable to similar problems of different complexity in other fields of research. [ABSTRACT FROM AUTHOR]

The article discusses various aspects of quantum electrodynamics (QED) Hamiltonians and their formulations. It examines different schemes and equations used in QED calculations, highlighting inconsistencies and incorrect manipulations in some approaches. The text also discusses the nonrelativistic limit of the QED Hamiltonian, the accuracy of different Hamiltonians, and the transformation of equations and variables. It concludes by providing recommendations for the use of certain Hamiltonians and discussing the charge conjugation and time reversal transformations in QED. The work was supported by funding from the National Natural Science Foundation of China and the Mount Tai Scholar Climbing Project of Shandong Province. [Extracted from the article]

This article is a response to a comment made by Professor Liu regarding a previously published paper. The response addresses questions raised by Professor Liu and focuses on three key aspects of the validity of the paper. It explains the use of different contractions in the construction of the QED Hamiltonians and clarifies the commutation relations used in the calculations. The article also highlights that the formulation of the molecular orbital method described in the paper is independent of the ordering of the operators and can derive expressions for various perturbation theories. The response concludes by stating that alternative criteria for the QED Hamiltonians are not ruled out and could be explored in future research. [Extracted from the article]

Using the density functional theory, we conducted a study on the electrification upon contact between hydrophobic liquid molecules and water molecules, revealing localized characteristics of contact-electrification. These "localized features" refer to the specific microscale characteristics where electron transfer predominantly occurs at the contact regions, influenced by factors such as atomic distances and molecular orientations. Although the electrostatic potential and the highest occupied molecular orbital–lowest unoccupied molecular orbital gap offer substantial predictive insights for electron transfer across polymer interfaces, they fall short in capturing the complexities associated with the interaction between hydrophobic liquids and water molecules. The electronegativity of elements at the interface and the localization of molecular orbitals play a decisive role in electron transfer. Simultaneously, for liquid molecules with irregular structures, there is no correlation between the "contact area" and the amount of electron transfer. The "contact area" refers to the surface region where two different liquid molecules come into close proximity. It is defined by the surface area of atoms with interatomic distances smaller than the van der Waals radius. This study challenges traditional assumptions about contact-electrification, particularly in liquid–liquid interfaces, providing new insights into the localized nature of this phenomenon. [ABSTRACT FROM AUTHOR]

Understanding excited-state intramolecular proton transfer (ESIPT) is essential for designing organic molecules to enhance photophysical and luminophore properties in the development of optoelectronic devices. In this context, an attempt has been made to understand the impact of substituents on the ESIPT process of 2-(oxazolinyl)-phenol. Electron donating (EDG: –NH2, –OCH3, and –CH3) and electron withdrawing (EWG: –Cl, –Br, –COOH, –CF3, –CN, and –NO2) substitutions have been computationally designed and screened through density functional theory (DFT) and time-dependent density-functional theory (TDDFT) calculations. Furthermore, the ground state intramolecular proton transfer and ESIPT mechanisms of these designed luminophores are explored using the transition state theory. The results reveal that molecules with EDG show higher absorption and emission peaks than molecules with EWG and also indicate that the mobility of charge carriers in 2-(oxazolinyl)-phenol derivatives is significantly influenced by substituents. We found that the EWGs decrease the reorganization energy and increase the vertical ionization potential and electron affinity values, as well as the highest occupied molecular orbital-lowest unoccupied molecular orbital gap, compared to the EDG substituted molecules. Significantly, the excited state (S1) of the keto emission (K) form shows notably larger values for the EDG substitutions. The intersystem crossing pathway efficiency weakens with reduced spin–orbit coupling matrix element in the enol form with electron-donating substituents and vice versa in the keto form during S1–T3 transitions. Our research links intramolecular proton transfers and triplet generation, making these substituted molecules appealing for optoelectronic devices. Introducing EDGs, such as –NH2, boosts the ESIPT reaction in 2-(oxazolinyl)-phenol. This study guides designing ESIPT emitters with unique photophysical properties. [ABSTRACT FROM AUTHOR]

In order to prepare highly heat-resistant packaging insulation materials, in this paper, bismaleimide/epoxy resin (BMI/EP55) composites with different contents of BMI were prepared by melt blending BMI into amino tetrafunctional and phenolic epoxy resin (at a ratio of 5:5). The microstructures and thermal and electrical properties of the composites were tested. The electrostatic potential distribution, energy level distribution, and molecular orbitals of BMI were calculated using Gaussian. The results showed that the carbonyl group in BMI is highly electronegative, implying that the carbonyl group has a strong electron trapping ability. The thermal decomposition temperature of the composites gradually increased with the increase of BMI content, and the 20% BMI/EP55 composites had the highest heat-resistance index, along with a glass transition temperature (Tg) of >250 °C. At different test temperatures, with increase in the BMI content, the conductivity of epoxy resin composites showed a tendency to first decrease and then increase, the breakdown field strength showed a tendency to first increase and then decrease, and the dielectric constant was gradually decreased. Two trap centers were present simultaneously in the composites, where the shallow trap energy level is the deepest in 20% BMI/EP composites and the deep trap energy level is the deepest in 10% BMI/EP55 composites. Correspondingly, the 10% BMI/EP55 composite had a slower charge decay rate, while the 20% BMI/EP55 had a faster charge decay rate. In summary, the BMI/EP55 composites with high heat resistance and insulating properties were prepared in this study, which provided ideas for preparing high-temperature packaging insulating materials. [ABSTRACT FROM AUTHOR]

We develop and demonstrate how to use the Graphical Unitary Group Approach (GUGA)-based MRCISD with Core–Valence Separation (CVS) approximation to compute the core-excited states. First, perform a normal Self-Consistent-Field (SCF) or valence MCSCF calculation to optimize the molecular orbitals. Second, rotate the optimized target core orbitals and append to the active space, form an extended CVS active space, and perform a CVS-MCSCF calculation for core-excited states. Finally, construct the CVS-MRCISD expansion space and perform a CVS-MRCISD calculation to optimize the CI coefficients based on the variational method. The CVS approximation with GUGA-based methods can be implemented by flexible truncation of the Distinct Row Table. Eliminating the valence-excited configurations from the CVS-MRCISD expansion space can prevent variational collapse in the Davidson iteration diagonalization. The accuracy of the CVS-MRCISD scheme was investigated for excitation energies and compared with that of the CVS-MCSCF and CVS-CASPT2 methods using the same active space. The results show that CVS-MRCISD is capable of reproducing well-matched vertical core excitation energies that are consistent with experiments by combining large basis sets and a rational reference space. The calculation results also highlight the fact that the dynamic correlation between electrons makes an undeniable contribution in core-excited states. [ABSTRACT FROM AUTHOR]

Möbius carbon nanobelts (MCNBs) have attracted the attention of more and more researchers because of their torsional π conjugated structures and Möbius aromatic characteristics. The Möbius rule showed that 4n π-electron MCNBs were aromatic. Several MCNBs have been successfully synthesized experimentally recently. However, the theoretical studies on the third-order NLO properties and excited state electron transition characteristics of MCNBs have not been reported. We used density functional theory to study the structure, molecular orbitals, aromaticity, absorption spectra and third-order nonlinear optical properties of the MCNB rings. The results show that the aromatic properties of the ring come from the twisted benzene ring on the ring. With the increase of the number of benzene rings and the volume of the rings, the charge transfer region of the MCNBs gradually concentrates on the twisted benzene ring, and the maximum absorption spectrum shows a small red shift. The polarizability αtot values of the MCNBs increased as the number of benzene rings increased from 751.4 a.u. (1) to 3168.0 a.u. (8). And the second-order hyperpolarizability γtot values of the MCNBs increased from 7.4 × 105 a.u. (1) to 2.2 × 107 a.u. (8). The results showed that the larger NLO response depends on the size of MCNBs. This work provided the novel interplay between the size of MCNBs and the third order NLO responses and provided a theoretical basis for the MCNBs as an excellent nonlinear optical material. [ABSTRACT FROM AUTHOR]

The electronic structure of 2(5H)-thiophenone in the gas phase was investigated by ultraviolet photoelectron spectroscopy and x-ray photoemission spectroscopy (XPS) and near edge x-ray absorption fine structure (NEXAFS) spectroscopy at the C 1s, O 1s, and S 2p edges. All assignments of the experimental results are supported by both ab-initio electron propagator outer-valence Green's function (OVGF) calculations for the valence photoemission bands and density functional theory (DFT) and relativistic time dependent DFT calculations for the core levels XPS and NEXAFS spectra. Overall good agreement between experiment and theory is observed; this is especially true for core electron excitations which has permitted an unambiguous assignment of the observed spectral features in terms of single-particle excitations to virtual molecular orbitals. The assignment of the valence band spectra based on OVGF calculations, although satisfactory, points to the importance of electron correlations effects that partially break the single particle picture of ionization. [ABSTRACT FROM AUTHOR]

Applying a strong, constant electric field at single-C60 molecule protrusions formed on a metallic substrate can cause electrons to be emitted from individual single molecules into a vacuum. The shapes of such single molecular electron sources reflect the shapes of the molecular orbitals from which the electrons originate. By illuminating the source with light pulses, photo-excited electrons can be emitted from different molecular orbitals, thereby modulating the electron sources at a subnanometric scale. In this context, we discuss the opportunities presented by this light-induced modulation of electron emission for developing a unique scheme to integrate ultrafast switches into a single molecule and for advancing high-resolution, ultrafast electron microscopy. We also discuss the experimental and theoretical challenges associated with this approach, such as the requirements for picoscale stability and controllability of molecular positions, as well as the need for large-scale ab initio calculations under strong constant fields. [ABSTRACT FROM AUTHOR]

The catalytic performance of gallium-modified FAU (Ga-FAU) zeolite on the ethane-to-aromatics (ETA) process was studied by a two-layer ONIOM (our Own N-layered Integrated molecular Orbital and molecular Mechanics) method implemented in Gaussian software. The whole ETA mechanism includes two pathways: ethane dehydrogenation to ethylene and ethylene aromatization. Four different Ga models ([GaH2]+, [GaH]2+, [GaO]+, and Ga+) have been used over the Ga-FAU zeolite. For the ethane dehydrogenation, the order of reactivity is [GaH]2+ > [GaH2]+ > [GaO]+ > Ga+. We selected the [GaH2]+ site to study the ethylene aromatization. On the [GaH2]+ model, the ethane dehydrogenation could take place through both the stepwise pathway (three steps) and the concerted pathway. The three-step pathway is more favorable than the concerted pathway. The rate-determining step of ethylene aromatization is the dehydrogenation of cyclohexene cation. The ethylene aromatization proceeds more slowly than the ethane dehydrogenation due to the higher energy barrier, and thus, the ethylene molecule should be the major product in the whole ETA process on Ga-FAU. The differential charge density (DCD), reduced density gradient (RDG), and local orbital locator (LOL) were employed to analyze the direction of electron migration and the nature of interactions in different TS fragments. The RDG analysis suggests that except for attractive force, there is strong spatial repulsive interaction between fragments that are close in distance, especially in organic carbon ring. The LOL maps indicate that partial covalent interactions often exist in the region where the chemical bonds are forming or breaking. The DCD plots reveal the variation of electron densities of different TS fragments. The electrons always migrate from the fragments with the negative DCD values to the fragments with the positive DCD values. [ABSTRACT FROM AUTHOR]

Context: High-energy density materials (HEDMs) are integral to modern society and are in high demand. Consequently, the design and synthesis of energetic material molecules have garnered significant research interest. This study focuses on the furazan ring system as a core for developing superior HEDMs. We employed density functional theory (DFT) to assess the properties of 27 novel energetic compounds, including their geometries, densities, enthalpies of formation, detonation velocities, detonation pressures, and molecular orbital energies (HOMO–LUMO). The computation of detonation velocity and detonation pressure was based on theoretical density and enthalpy of formation. The findings revealed that incorporating energetic groups into the furazan framework, linked by sec-ammonia bridge (-NH-), enhances both the detonation performance and oxygen content of the materials. This enhancement guides the future synthetic endeavors aimed at creating advanced HEDMs. Method: DFT has been employed to investigate the detonation performance and stability of energetic materials. Molecular optimization and performance metrics were all calculated using the DFT-B3LYP method with a 6–311 + G* basis set. The optimization and volume calculations were performed using the Gaussian 09 package. The electrostatic potential energy was computed using Multiwfn software. The impact sensitivity of the designed molecules was calculated using the heat of detonation model. [ABSTRACT FROM AUTHOR]

Three polymeric compounds, designated as PA, PB, and PC, were investigated for their nonlinear optical (NLO) characteristics and spectral properties. These compounds, derived from azo and non-azo structures (namely, (E)-butyl 4-((4-bis(2-chloroethyl) amino) phenyl) diazenyl) benzoate, (2E,6E)-4-(4-butoxyphenyl)-2,6-bis(4-hydroxybenzylid) cyclohexanone, and 2-(2,6-bis(4-hydroxystyryl)-4H-pyran-4-ylidene) malononitrile), were evaluated for their linear polarization (α), first (β) and second (γ) hyperpolarizabilities using the finite field method. Spectroscopic characterizations, such as geometrical parameters, and vibrational and electronic absorption spectra, were conducted. The study employed the dispersion-corrected B3LYP-D3 method with a diffused and polarized 6–311 + + G (d, p) basis set, revealing the superior stability of the three polymers compared to other methods. Electronic absorption spectra were computed using time-dependent density functional theory (TD-DFT) at the same level of theory, finding key parameters such as wavelength of electronic transition, oscillator strength, molecular orbital analysis, and electronic properties. The investigation also explored the dependence of NLO properties like α, β, βHRS, and depolarization ratio on global parameters like ionization potential, electron affinity, electronegativity, chemical hardness, and electrophilicity index. PA shows greater sensitivity to the first hyperpolarizability. The obtained results show a high total first hyperpolarizability (βtot) up to 22,894 a.u. and a low energy gap of 0.4 eV. Interestingly, the magnitudes of β obtained from the B3LYP method surpassed those obtained from other methods. These findings suggest that the studied polymeric compounds, especially PA, have significant potential for application in optoelectronic devices due to their superior NLO properties and stability. [ABSTRACT FROM AUTHOR]

Stabilizing specific intermediates to produce CH4 remains a main challenge in solar‐driven CO2 reduction. Herein, g‐C3N4 is modified with saturated and lacunary phosphotungstates (PWx, x=12, 11, 9) to tailor the CO2 reduction pathway to yield CH4 in high selectivity. Increased lacuna of phosphotungstates leads to higher CH4 yield and selectivity, with a superior CH4 selectivity of 80 % and 40.8 μmol ⋅ g−1 ⋅ h−1 evolution rate for PW9/g‐C3N4. Conversely, g‐C3N4 and PWx alone show negligible CH4 production. The conversion of CO2 to CH4 follows a tandem catalytic process. CO2 is initially activated on g‐C3N4 to form *CO intermediates, meanwhile photogenerated electrons derived from g‐C3N4 transfer to PWx. Then the reduced PWx captures *CO, which is subsquently hydrogenated to CH4. With the injection of two photogenerated electrons, PW9 is capable of adsorbing and activating *CO. However, the reduced PW12 and PW11 are incapable of adsorbing *CO due to the small energy of occupied molecular orbitals, which is the reason for the poorer activity of PWx/g‐C3N4 (x=12, 11) compared with that of PW9/g‐C3N4. This work provides new insights to regulate highly selective CO2 photoreduction to CH4 by utilizing lacuna of polyoxometalates to enhance the interaction of metals in polyoxometalates with key intermediates. [ABSTRACT FROM AUTHOR]

Panchromatic dyes have been highly useful in the realm of optical devices. Here, we report that panchromatic dyes with heterohelicenes have been successfully synthesized using a donor‐acceptor strategy. Our synthesis resulted in the creation of π‐extended aza[5]helicene oligomers with butadiyne linkages, which displayed bathochromically shifted absorption and emission spectra. The solvent‐dependent optical measurements revealed the intramolecular charge transfer characteristic of these molecules, and theoretical calculations described the biased molecular orbitals on the azahelicene units that generated the charge‐transfer characteristic. Encouraged by these results, we also prepared donor‐acceptor‐donor dyads using azahelicenes and dimide derivatives, resulting in panchromatic absorbing characteristics covering the range from 250 nm to 800 nm. Theoretical calculations showed the presence of mixed charge‐transfer transitions and localized transitions on the azahelicene units, which led to a broad light‐absorbing property covering the near IR region. Additionally, we conducted measurements of circular dichroism and circularly polarized luminescence for the obtained products. The g‐values were reduced by oligomerization, indicating that the lowest energy transitions were allowed in nature. [ABSTRACT FROM AUTHOR]

In the present work, five pyrazole-hydrazone biomolecule ligands (L1–L5) were synthesized by condensation between 1H-pyrazole-3-carbohydrazide (2) and aromatic benzaldehydes. Their corresponding structures were elucidated employing NMR and FT-IR spectra and ESI-MS data. Li-Cu(II) complexes (i = 1–5) were evaluated for catecholase activity in situ at standard conditions. The findings disclose that the catecholase oxidation rate varies with the substituted functional groups in ligand and the anion type in the copper (II) salt. Catecholase activity results showed that the L(i = 1–5) -Cu(II)SO4 complexes exhibited efficient catalytic activity, and a maximum activity of 105 ± 42 µM.min−1 is obtained with L5-Cu(II)SO4. DFT and NBO calculations have been carried out to identify the global reactivity and the strength of interaction bonds between the donors and acceptors in L1–L5. The optimized structure of L1–L3 and L5 were found planar, while that of L4 is out of the molecular plan and forms a torsion angle of 18 degrees due to the presence of methoxy and hydroxyl group at meta and para. In L4, the 5-methyl-1H-pyrazole moiety. NBO findings show that the strongest interactions in L1–L5 are those involved in the electronic transition from π-bonding → π*-antibonding and LP → π*- antibonding molecular orbitals. Further, the anti-SARS-CoV-2 of L1–L5 are investigated by estimating their binding affinities into its binding. The docking results reveal that L1–L5 may act as SARS-CoV-2 main protease inhibitors with estimated binding energies in the −6.00 to −8.0 kcal.mol−1 range. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of SBA‐Pr‐Ald‐MA as a modified mesoporous silica material made from SBA‐15 are presented in this work. Meldrum's acid (MA), 2‐chloroquinoline‐3‐carbaldehyde, and 3‐(chloropropyl)‐trimethoxysilane were used to functionalize the SBA‐15. The detection limit of 7.80 × 10−8 M for SBA‐Pr‐Ald‐MA demonstrated its exceptional selectivity toward Fe3+ ions. Density functional theory (DFT) calculations were conducted using B3LYP/6‐311g(d,p)/LANL2DZ to investigate the molecular electrostatic potential (MEP), geometry optimization, molecular orbital analysis, quantum chemical descriptors, and photoinduced electron transfer (PET). Geometry optimization and the MEP diagram verified the mechanism of the interaction obtained from experimental results. PET analysis indicated that the electrons transition to the LUMO of the Pr‐Ald‐MA + Fe3+ complex, leading to maximum fluorescence quenching efficiency. Future research could explore the sensor's application in real‐world environmental monitoring systems and extend its application to detect other hazardous metal ions. [ABSTRACT FROM AUTHOR]

A mono‐salamo‐type ligand H2L was prepared to utilize 3‐methoxysalicylaldehyde and a semi‐salamo‐type compound, and its novel trinuclear Ni(II) cluster with two significantly various configurations in the solid state was obtained by reaction of H2L with Ni(II) ions. The trinuclear structure of the Ni(II) cluster was validated by x‐ray technique, and Ni(II) ions exhibited hexa‐coordinated twisted octahedrons. Its structural formula is [Ni3(L)2(μ2‐Cl)2(EtOH)2]. Chloride ions have also successfully double bridged to participate in coordination, and play a critical impact in the trinuclear configuration's stability and charge balance. Two solvent ethanol molecules are also participated in coordination. The coordination ratio of the ligand to the metal ion was verified to be 2:3 by UV–Vis absorption titration spectroscopy. The HOMO and LUMO energies of the frontline molecular orbitals of H2L and the complex were analyzed by DFT calculations, and the energy gap value of the ligand H2L was 4.29 eV, and that of the complex was 0.72 eV. The ligand combined with the metal decreased the energy gap value and produced a more active complex. Furthermore, Hirshfeld surface analysis visualizes the weak interactions of crystalline molecules, and these abundant weak interactions play an especially critical effect in the supramolecular structural self‐assembling. The fluorescent researches proclaimed that the fluorescence intensity of the cluster significantly decreased compared with the ligand, suggesting that this ligand and complex have greater promise for fluorescence sensing. [ABSTRACT FROM AUTHOR]

The vibrations were attributed to 5-chloro-2-mercaptobenzimidazole using FTIR and FT-Raman spectroscopy. The optimized geometrical parameters, IR intensity, and the Raman activity of the vibrational bands were estimated using the Becke three-parameter Lee-Yang-Parr functional and the 6-311++G(d,p) level of theory. These findings are compared with the experimental data. The molecule's HOMO-LUMO energy gap is found to be 4.418 eV. UV-Vis analysis reveals that the π→π* transition, which happens when electron density shifts from nitrogen, sulfur, and chlorine atoms in the molecule, to the electrons of the C-C bonds of the ring. Total density of states was used to assess the molecular orbital contributions. There are 47α and 47β electrons totaling 94 electrons in the DOS spectrum. NBO investigations indicate that a considerable stabilizing energy of 30.37 and 30.90 Kcal/mol was revealed by the lone pair transition of N1 and N3 atoms to π*(C7-C8) and π*(C4-C9). The more electrophilic region, as seen by the red zone in MEP mapping, lies in the vicinity of the nitrogen and sulfur atoms. The molecule's hydrogen atoms are found in the blue nucleophilic area. The theoretical chemical shifts for 1H and 13C NMR ranged from 7.03 to 8.23 ppm and 113.10 to 207.31 ppm, respectively. The docking research showed that the molecule attached to protein 1AQU with a greater binding energy of −6.8 Kcalmol−1. The cytotoxicity of the sample was evaluated against a MCF-7 cell line (IC50 = 16.54 µg/ml) and exhibited a good breast cancer action. In addition, ADMET prediction has been used to estimate the medicinal applicability of the chemical. [ABSTRACT FROM AUTHOR]

Quenching peroxynitrite (a reactive oxidant species) is a vital process in biological systems and environmental chemistry as it maintains redox balance and mitigates damaging effects in living cells and the environment. In this study, we report a systematic analysis of the mechanism of transforming peroxynitrite into nitrate using diaryl selenide in water. Through quantum mechanical calculations, we investigate the dynamic isomerization of peroxynitrite in a homogeneous catalytic environment. The mapped potential energy surfaces (PESs) generated using various methods in conjunction with different basis sets suggest that the isomerization mechanism includes four major steps: the reaction of peroxynitrite with diaryl selenide via oxygen-bound selenium; selenium oxidation in the presence of an appropriate oxidant; oxygen transfer; and ultimately, the generation of nitrate. The molecular orbital analysis suggests a substituent effect on the aromatic ring of diaryl selenide in this reaction. Changes in both molecular orbitals and electrostatic potential highlight the significance of the electron transfer step in ensuring the progression of this reaction. [ABSTRACT FROM AUTHOR]

Carbon materials are commonly integrated with TiO2 to achieve high carrier mobility and excellent photocatalytic performance, and the chemical bond between TiO2 − C is considered as a significant strategy to enhance efficiency. Nevertheless, few analyses have elucidated the formation mechanism of Ti3 + − C bonds and the underlying reasons for the performance enhancement. To address these issues, this study conducts an in‐depth investigation into the electronic structure of TiO2 − C and demonstrates that the charge in the nonbonding molecular orbital t2g of Ti3 + is transferred to the unoccupied 2p energy level of C through the formation of 1π and 2π bonds, i.e., (Ti 3dxz ‐ C 2py) and (Ti 3dxy ‐ C 2px). The hybridization of t2g‐2p orbitals endows the Ti3 + − C bond with higher carrier mobility and a stronger binding force, thereby contributing to stable photocatalytic H2 production. Inspired by this scenario, the NSTiO2/rGO hybrid architecture, featuring the {101}/{001} surface heterojunction and the Ti3 + − C interfacial chemical bond, has been constructed. As a result, the hybrid catalyst exhibited excellent photocatalytic cycling stability of 92.9%$92.9 \,\%$ and an H2 evolution rate of 33.4 mmolh−1g−1. This work proposes a strategy for designing efficient photocatalyst by regulating orbitals to achieve high‐performance photocatalytic methanol splitting. [ABSTRACT FROM AUTHOR]

A series of ten uranium(III) complexes with cyclopentadienyl and monodentate phosphine ligands [UCp3(PR3)] with R=Me, Et, nPr, iPr, tBu, Ph, Cy, F and CF3 was investigated using density functional theory calculations. The ligand dissociation energies were calculated, as well as bonding analysis of the uranium‐phosphorus bond performed, using molecular orbitals, bond orders, quantum theory of atom in molecules (QTAIM) analysis and energy decomposition analysis with natural orbitals for chemical valence (EDA‐NOCV). It was found that the bond orders correlate well with the U−P bond lengths and phosphine cone angles, indicating a large influence of phosphine sterics on the bond properties. All bonding analyses show partial covalent character of the U−P bond, which is most pronounced for PF3 and least for PtBu3. π‐Backbonding was found for the most π‐acidic phosphine ligands. No good correlation was found between the ligand dissociation energies and bond metrics. [ABSTRACT FROM AUTHOR]

AbstractBimetallic catalysis offers a unique approach to diverse bond activation chemistry, complementing the more widely used monometallic catalysis. In this context, bimetallic complexes of 1,8-naphthyridine motifs have been synthesized and studied to mimic the active sites of metalloenzymes and understand their role in C-C bond formation reactions. Specifically, dicopper(I) complexes with naphthyridine ligands are of significant interest due to their distinctive binding mode, which hinges on the interaction of the copper sites with the available molecular orbitals. These naphthyridine-based dicopper(I) complexes have been promising as catalysts for activating terminal alkynes and arenes, enabling several strategic functionalizations, including copper-catalyzed azide-alkyne coupling reactions. This mini-review highlights the reactivity and selectivity of naphthyridine-based dicopper complexes and their importance in metal-metal or metal-ligand cooperativity. [ABSTRACT FROM AUTHOR]