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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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

First-order derivatives of energies with respect to atomic coordinates are widely computed and used in quantum chemistry simulations. The rapidly emerging technology of quantum computing offers a new paradigm for solving relevant quantum chemistry equations. In this work, we have achieved analytical calculations of atomic forces based on the Hellmann–Feynman theorem within the framework of the variational quantum eigensolver. The accuracy of the approach is demonstrated by calculating the atomic forces of H2, LiH, H2O, and NH3 molecules, which are in excellent agreement with values obtained from full configuration interaction calculations. In particular, for systems with degenerate molecular orbitals, the analytical approach has a significant accuracy advantage over finite-difference-based methods and will not involve additional computational effort on a quantum computer. The calculated forces are further used to optimize the geometries of NH3 and CH4 molecules and to perform ab initio molecular dynamics simulations for the umbrella inversion of NH3, demonstrating the feasibility of the approach in practical quantum chemistry simulations. [ABSTRACT FROM AUTHOR]

Theoretical discussions are given on issues in relativistic molecular orbital theory to which the quantum electrodynamics (QED) Hamiltonian is applied. First, several QED Hamiltonians previously proposed are sifted by the orbital rotation invariance, the charge conjugation and time reversal invariance, and the nonrelativistic limit. The discussion on orbital rotation invariance shows that orbitals giving a stationary point of total energy should be adopted for QED Hamiltonians that are not orbital rotation invariant. A new total energy expression is then proposed, in which a counter term corresponding to the energy of the polarized vacuum is subtracted from the total energy. This expression prevents the possibility of total energy divergence due to electron correlations, stemming from the fact that the QED Hamiltonian does not conserve the number of particles. Finally, based on the Hamiltonian and energy expression, the Dirac–Hartree–Fock (DHF) and electron correlation methods are reintroduced. The QED-based DHF equation is shown to give information on positrons from negative-energy orbitals while having the same form as the conventional DHF equation. Three electron correlation methods are derived: the QED-based configuration interactions and single- and multireference perturbation methods. Numerical calculations show that the total energy of the QED Hamiltonian indeed diverged and that the counter term is effective in avoiding the divergence. The relativistic molecular orbital theory presented in this article also provides a methodology for dealing with systems containing positrons based on the QED Hamiltonian. [ABSTRACT FROM AUTHOR]

The UV photochemistry of small heteroaromatic molecules serves as a testbed for understanding fundamental photo-induced chemical transformations in moderately complex compounds, including isomerization, ring-opening, and molecular dissociation. Here, a combined experimental-theoretical study of 268 nm UV light-induced dynamics in 2-iodothiophene (C4H3IS) is performed. The dynamics are experimentally monitored with a femtosecond extreme ultraviolet (XUV) probe that measures iodine N-edge 4d core-to-valence transitions. Experiments are complemented by density functional theory calculations of both the pump-pulse induced valence excitations and the XUV probe-induced core-to-valence transitions. Possible intramolecular relaxation dynamics are investigated by ab initio molecular dynamics simulations. Gradual absorption changes up to ∼0.5 to 1 ps after excitation are observed for both the parent molecular species and emerging iodine fragments, with the latter appearing with a characteristic rise time of 160 ± 30 fs. Comparison of spectral intensities and energies with the calculations identifies an iodine dissociation pathway initiated by a predominant π → π* excitation. In contrast, initial excitation to a nearby n⟂ → σ* state appears unlikely based on a significantly smaller oscillator strength and the absence of any corresponding XUV absorption signatures. Excitation to the π → π* state is followed by contraction of the C–I bond, enabling a nonadiabatic transition to a dissociative π → σ C − I * state. For the subsequent fragmentation, a relatively narrow bond-length region along the C–I stretch coordinate between 230 and 280 pm is identified, where the transition between the parent molecule and the thienyl radical + iodine atom products becomes prominent in the XUV spectrum due to rapid localization of two singly occupied molecular orbitals on the two fragments. [ABSTRACT FROM AUTHOR]

The feature vector mapping used to represent chemical systems is a key factor governing the superior data efficiency of kernel based quantum machine learning (QML) models applicable throughout chemical compound space. Unfortunately, the most accurate representations require a high dimensional feature mapping, thereby imposing a considerable computational burden on model training and use. We introduce compact yet accurate, linear scaling QML representations based on atomic Gaussian many-body distribution functionals (MBDF) and their derivatives. Weighted density functions of MBDF values are used as global representations that are constant in size, i.e., invariant with respect to the number of atoms. We report predictive performance and training data efficiency that is competitive with state-of-the-art for two diverse datasets of organic molecules, QM9 and QMugs. Generalization capability has been investigated for atomization energies, highest occupied molecular orbital–lowest unoccupied molecular orbital eigenvalues and gap, internal energies at 0 K, zero point vibrational energies, dipole moment norm, static isotropic polarizability, and heat capacity as encoded in QM9. MBDF based QM9 performance lowers the optimal Pareto front spanned between sampling and training cost to compute node minutes, effectively sampling chemical compound space with chemical accuracy at a sampling rate of ∼ 48 molecules per core second. [ABSTRACT FROM AUTHOR]

We calculated the one- (OPA) and two-photon absorption (TPA) spectra of two large water-soluble stilbene derivatives presenting TPA cross sections of about 400 GM. However, the reported experimental TPA spectra present a spectral gap region, and a theoretical study of these promising molecules seems now timely and relevant. These molecules are composed of 200 or more atoms, becoming a challenge to obtain the TPA spectra even using density functional theory at the time-dependent quadratic response formalism. Thus, both OPA and TPA were also calculated using the INDO-S semi-empirical method. We used explicit solvent molecules using the sequential-quantum mechanics/molecular mechanics to include the solvent effects. Our results show that different transitions are participating in the OPA and TPA processes and that exchange–correlation functionals, including larger Hartree–Fock contributions, provide a better description of the OPA spectra; however, the opposite trend is observed on the TPA spectra. Alternatively, INDO-S/CISD, including contributions from single and double excitations, systematically describes both OPA and TPA bands with similar shifts and better reproduces the relative intensities of the two TPA bands compared to the experimental ones. The OPA spectra are characterized by a Highest Occupied Molecular Orbital-Lowest Unoccupied Molecular Orbital (HOMO–LUMO) excitation, while the low-energy TPA band is ascribed to a single transition encompassing the (HOMO-1)–LUMO and HOMO–(LUMO+1) excitations and the high-energy one is a combination of several transitions. Thus, although more studies are required to better assess the capability of the INDO-S/CISD method in describing the TPA spectra of large molecules, our results corroborate that it is a promising alternative. [ABSTRACT FROM AUTHOR]

By considering only one electronic state per molecule, charge transport models of molecular solids neglect intramolecular charge transfer. This approximation excludes materials with quasi-degenerate spatially separated frontier orbitals, such as non-fullerene acceptors (NFAs) and symmetric thermally activated delayed fluorescence emitters. By analyzing the electronic structure of room-temperature molecular conformers of a prototypical NFA, ITIC-4F, we conclude that the electron is localized on one of the two acceptor blocks with the mean intramolecular transfer integral of 120 meV, which is comparable with intermolecular couplings. Therefore, the minimal basis for acceptor–donor–acceptor (A–D–A) molecules consists of two molecular orbitals localized on the acceptor blocks. This basis is robust even with respect to geometry distortions in an amorphous solid, in contrast to the basis of two lowest unoccupied canonical molecular orbitals withstanding only thermal fluctuations in a crystal. The charge carrier mobility can be underestimated by a factor of two when using single site approximation for A–D–A molecules in their typical crystalline packings. [ABSTRACT FROM AUTHOR]

High pressure has been recognized as an important tool in molecule and materials research, and thus, it is expected to be used to understand the evolution of electronic states and geometric structures in superatoms. In this work, by studying three characteristic axial compressions on a typical endohedral metallofullerene superatom U@C28 with Td symmetry, we find that the triplet ground electronic state is preserved when the compression moves along the direction that reduces the symmetry to D2d, but the electronic state of the structure compressed along the direction of symmetry reduction to C2v or Cs is transformed into a singlet. The transition is attributed to the distinction in the response of electron spin to different axial compressions, which results in a change in the electron occupation mode of the system. Furthermore, we also confirm the gradual evolution from stereo to near-plane superatoms and the connection between their electron structures. This is reflected in the fact that the electron density distributions of the superatomic molecular orbitals (SAMOs) with extension along the restricted degrees of freedom ( D z 2 , F z 3 SAMOs) gradually contract, and the delocalization destruction of special orbitals is associated with this freedom. In addition, Raman and ultraviolet–visible spectra show a hyperchromic effect and redshift of characteristic peaks during axial compression, which are expected to be used for fingerprinting the superatomic planarization. Therefore, our work provides new insights based on high pressure for future research toward the discovery of physical properties and applications of superatoms. [ABSTRACT FROM AUTHOR]

Proton transfer is crucial in various chemical and biological processes. Because of significant nuclear quantum effects, accurate and efficient description of proton transfer remains a great challenge. In this Communication, we apply constrained nuclear–electronic orbital density functional theory (CNEO-DFT) and constrained nuclear–electronic orbital molecular dynamics (CNEO-MD) to three prototypical shared proton systems and investigate their proton transfer modes. We find that with a good description of nuclear quantum effects, CNEO-DFT and CNEO-MD can well describe the geometries and vibrational spectra of the shared proton systems. Such a good performance is in significant contrast to DFT and DFT-based ab initio molecular dynamics, which often fail for shared proton systems. As an efficient method based on classical simulations, CNEO-MD is promising for future investigations of larger and more complex proton transfer systems. [ABSTRACT FROM AUTHOR]

We studied the stability of a system consisting of a positron (e+) and two lithium anions, [Li−; e+; Li−], using first-principles quantum Monte Carlo calculations combined with the multi-component molecular orbital method. While diatomic lithium molecular dianions Li 2 2 − are unstable, we found that its positronic complex can form a bound state with respect to the lowest energy decay into the dissociation channel Li 2 − and a positronium (Ps). The [Li−; e+; Li−] system has the minimum energy at the internuclear distance of ∼3 Å, which is close to the equilibrium internuclear distance of Li 2 − . At the minimum energy structure both an excess electron and a positron are delocalized as orbiting around the Li 2 − molecular anion core. A dominant feature of such a positron bonding structure is described as the Ps fraction bound to Li 2 − , unlike the covalent positron bonding scheme for the electronically isovalent [H−; e+; H−] complex. [ABSTRACT FROM AUTHOR]

Complete active space second-order perturbation theory (CASPT2) is useful for accurately predicting properties of complex electronic structures, but it is well known that it systematically underestimates excitation energies. The underestimation can be corrected using the ionization potential–electron affinity (IPEA) shift. In this study, analytic first-order derivatives of CASPT2 with the IPEA shift are developed. CASPT2-IPEA is not invariant with respect to rotations among active molecular orbitals, and two additional constraint conditions are necessary in the CASPT2 Lagrangian to formulate analytic derivatives. The method developed here is applied to methylpyrimidine derivatives and cytosine, and minimum energy structures and conical intersections are located. By comparing energies relative to the closed-shell ground state, we find that the agreement with experiments and high-level calculations is indeed improved by the inclusion of the IPEA shift. The agreement of geometrical parameters with high-level calculations may also be improved in some cases. [ABSTRACT FROM AUTHOR]

The spin‐orbit coupling corrected absorption spectra of osmium complexes, [Os(bpy) 3] 2+ and [Os(phen) 3] 2+, were calculated by using ab initio multireference perturbation method (NEVPT2) with relativistic effects taken into account throughout ZORA approximation and corresponding all‐electron basis sets. For the same purpose, the time‐dependent DFT techniques were used. A very good agreement between NEVPT2 and experimental spectra should be highlighted, especially for the MLCT transitions that occur in visible and near‐UV regions (16,000−33,000 cm −1). Moreover, the present study offers description of excited states of titled osmium complexes and their spectra interpretation using molecular orbitals. [ABSTRACT FROM AUTHOR]

Protein–ligand binding prediction typically relies on docking methodologies and associated scoring functions to propose the binding mode of a ligand in a biological target. Significant challenges are associated with this approach, including the flexibility of the protein–ligand system, solvent‐mediated interactions, and associated entropy changes. In addition, scoring functions are only weakly accurate due to the short time required for calculating enthalpic and entropic binding interactions. The workflow described here attempts to address these limitations by combining supervised molecular dynamics with dynamical averaging quantum mechanics fragment molecular orbital. This combination significantly increased the ability to predict the experimental binding structure of protein–ligand complexes independent from the starting position of the ligands or the binding site conformation. We found that the predictive power could be enhanced by combining the residence time and interaction energies as descriptors in a novel scoring function named the P‐score. This is illustrated using six different protein–ligand targets as case studies. [ABSTRACT FROM AUTHOR]

An auxiliary polarization formulation of the fragment molecular orbital (FMO) method is developed, combining a basis set correction computed for capped isolated fragments with a polarization obtained from uncapped fragments. For a set of organic and inorganic test systems, it is shown that the total energy and atomic charges are accurately reproduced with respect to full unfragmented calculations. It is demonstrated that the method is accurate for computing electronic excited states. The developed approach is applied to rank the isomers of chignolin from experimental NMR data (PDB: 1UAO) according to their relative energy. Contributions of polarization and basis set effects to pair interactions between fragments are elucidated. [ABSTRACT FROM AUTHOR]

A fruitful debate took place recently in literature, discussing the enhanced Diels–Alder reactivity of tropone derivatives for which the carbonyl polarity was reversed by means of umpolung. Karas et al. sustained that the umpolung increases the antiaromatic character of the ring, affecting the highest occupied molecular orbital (HOMO)/least unoccupied molecular orbital (LUMO) energies, speeding up the reaction. Tiekink et al. challenged this interpretation by sustaining that the asynchronicity of the reaction mechanisms, rather than orbital energy perturbation, was the main responsible for the smaller reaction barriers. We shed light on this dispute by computing full interaction quantum atom (IQA) and quantum theory of atoms in molecules (QTAIM) analyses over complete intrinsic reaction coordinate (IRC) paths for the Diels–Alder reaction of tropone and its umpolung derivatives, using the same systems studied by Karas et al. and Tiekink et al. Our results confirm that the asynchronicity is indeed very high for those reactions with smaller reaction barriers and offer an atom‐by‐atom and bond‐by‐bond analysis of the entire IRC pathways. Even though asynchronicity and lower reactions barriers seem to be related, antiaromaticity and lower barriers are related as well, but discussing both these interpretations does not necessarily require arguments on HOMO/LUMO energies to be invoked. [ABSTRACT FROM AUTHOR]

Contact‐electrification at solid–liquid interfaces (SL‐CE) and contact‐electro‐catalysis (CEC) are two blooming research areas with promising applications in sustainable energy, sensing, and chemical processes. However, prior research has neglected the impact of electronic defects on the ability of high‐performance tribo‐materials, like fluorinated polymers, to perform SL‐CE/CEC. Here, through first‐principle calculations, the addition of surface functional groups to fluorinated ethylene propylene (FEP) enables the tuning of its molecular orbitals' positions, and displacing deep‐level defect states from the HOMO‐LUMO gap is shown. Thereafter, FEP films are modified accordingly by plasma etching; resulting in a significant performance improvement of up to 202% (charge) in SL‐CE experiments, and up to 398% (kinetic rate) in CEC dye degradation. This study provides a theoretical and experimental framework to design high‐performance materials for SL‐CE and CEC, and insights into their physical mechanisms and defect passivation, which are all fundamental for the advancement of these fields. [ABSTRACT FROM AUTHOR]

A new class of benzisoxazole‐Chromene (BC) analogues containing acyl hydrazones BCA (5a‐5m) were obtained by the condensation of different benzo hydrazides with BCs in good yield. All the synthesized BCA analogues were evaluated for their in‐silico activity against Acetylcholine Esterase (AChE). According to docking experiments, the co‐crystallized ligand was outperformed by derivatives 5e (4‐benzisoxazole‐chromene‐3‐(4hydroxyphenyl) acrylohydrazide), 5m (7‐chloro,4‐hydroxy) and 5l (8‐methyl, m‐nitro) showed superior binding modes and binding free energies whereas compound 5j (8‐methyl, 4‐hydroxy) showed appropriate binding energy. These moieties containing acyl hydrazone has shown 4‐fold increase in the binding interactions and orientation. According to ADMET and toxicity studies, derivatives 5e, 5m, 5j, and 5l had the potential to be drugs and have proven to be safe when evaluated using seven toxicity models. Further on checking selectivity with the other cholinesterase enzyme, 5l came out to be selective towards AChE whereas 5e & 5j were acting on another target as well. Finally, DFT analysis validated the binding of the derivatives towards AChE and moreover Molecular Dynamic investigation revealed that 5l is the most capable candidate to interact with the target receptor by comparing its molecular orbital energies, molecular electrostatic potential maps, and ligand movement against the co‐crystallized Ligand. [ABSTRACT FROM AUTHOR]

Developing efficient long‐wavelength thermally activated delayed fluorescence (TADF) emitters is a challenging issue due to inherent limitations of the energy‐gap law. In this contribution, a new molecular design of cyanobenzene‐decorated quinoxaline acceptor, combining two or four cyanobenzene acceptors and a rigid carbazole donor, is successfully utilized to construct long‐wavelength TADF emitters (tCzQx2CN and tCzQx4CN). The two additional cyanobenzene units at the 5‐ and 8‐positions of the quinoxaline acceptor are presumed to interlock the molecular rotations and improve the acceptor strength. Compared with tCzQx2CN, tCzQx4CN exhibits orange‐red emission with a considerable bathochromic shift (>35 nm), as expected. Owing to its enhanced charge transfer and well‐separated highest‐occupied and lowest‐unoccupied molecular orbitals, tCzQx4CN exhibits reduced singlet‐triplet energy splitting and improves reverse intersystem crossing. An organic light–emitting diode (OLED) of tCzQx4CN manifestes bright orange‐red emission (λEL ≈581 nm), a superior external quantum efficiency (EQE) of ≈23.7% (compared with that of tCzQx2CN), and a satisfactory operational lifetime. Furthermore, a tCzQx4CN‐sensitized red‐hyperfluorescent OLED device exhibits excellent performance with an EQE of 16.0% and a CIE(x,y) of (0.62, 0.37). This design would potentially pave the way for constructing red/deep‐red TADF emitters by using a diverse combination of donor/acceptor units. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) calculations were carried out to investigate the absorption spectra and photoelectric properties of new metal-free dyes integrating an acene group positioned proximal to the donor moiety, exemplified by the 2-amino pyrrole. A linear carbon chain (LCC) with varying lengths serves as the link between the donor group and two distinct electron-attracting groups: cyanoacrylate and a derivative of pyridinium salt. Molecular orbital analysis reveals strategically positioned energy levels for efficient electron recovery, ensuring favorable thermodynamics for injection. UV-VIS absorption properties underscore superior outcomes for dyes with longer π–spacers, particularly those with pentacene showcase a panchromatic effect extending beyond 920 nm. Furthermore, the study explores the electron transfer process at the dye–semiconductor interface, emphasizing stable adsorption modes and favorable interactions. Photovoltaic property estimations, considering electron injection and recombination rates, indicate that dyes with pyridinium salt as the withdrawing group, specifically, P-Pen-4-A2 and P-Ant-4-A2, exhibit excellent values for both open-circuit voltage (Voc) and short-circuit photocurrent density (Jsc), thus demonstrating superior photovoltaic outcomes. The investigation of J–V curves predicts outstanding photoelectric conversion efficiency values of 29.72% and 27.90% for these dyes. Moreover, derivatives incorporating cyanoacrylate yields commendable PCE values of 20.30% and 25.01% for P-Ant-4-A2 and P-Pen-4-A2. Classical molecular dynamics simulations (MD) demonstrate that, over the course of 200 ns simulation time, the dyes maintain a vertical adsorption configuration. These results underscore the potential of the designed dyes for both standalone and co-sensitizing applications, presenting a promising avenue for the development of efficient and panchromatic DSSCs. [ABSTRACT FROM AUTHOR]

The detection of volatile organic compounds (VOCs) in exhaled gas is crucial for noninvasive diagnostic applications in lung cancer. Herein, we systematically employed first-principle calculations to investigate the utilization of nanoclay as a sensing material for the development of sensitive biosensors for VOCs. In this study, the effect of VOCs adsorption on the structural and electronic properties of pristine kaolinite (Kaol) and transition metal [TM(II/III)] doped kaolinite [TM(II/III)-Kaol, TM = Fe, Co, and Ni] was investigated. The calculation results show that TM doping induces a slight structural perturbation, and VOCs lead to a decrease in the bandgap of pristine TM(II/III)-Kaol. Additionally, we have comprehensively discussed that the adsorption of VOCs causes significant changes in the electronic behavior of TM(II/III)-Kaol, including density of states, charge transfer, molecular front orbitals, and work functions. In particular, we also have calculated the recovery time to determine the reusability of the designed sensor material. Our results specifically support the fact that TM(II/III)-Kaol can be an attractive sensing material for VOCs biosensors. [ABSTRACT FROM AUTHOR]

The reaction mechanism for the formation of the pseudo‐silaazatriene 1 (LN(SiMe3)2−Si−N−Si(L)NSiMe3; L=PhC−(NtBu)2) by the reaction of 1 equivalent of bis‐silylene (LSi−SiL; L=PhC(NtBu)2) with 3 equivalents of azide Me3SiN3 has been explored at M06/def2‐TZVPP//BP86‐D3(BJ)/def2‐TZVPP level of theory. The reaction mechanism is guided by the high Lewis basicity of the silicon lone pair and the high Lewis acidic character of Si−N bonds, as well as by the high tendency to eliminate N2 from Me3SiN3. The first step of the reaction is the formation of [3+1] cycloaddition product (I1) by the synergetic interactions of the lone pair on the silylene silicon with the π* molecular orbital of Me3SiN3 which is majorly localized on the terminal nitrogen atom, and the donation of the σ‐type lone pair on the nitrogen atom connected to the SiMe3 group with the Si−N σ* orbital on silylene. The elimination of N2 from I1 results in the formation of pseudo‐silaimine intermediate I2 having a dicoordinated, monovalent nitrogen atom. The most favourable pathway involves the second addition of Me3SiN3 followed by N2 elimination resulting bis‐silaimine intermediate I4‐P2. The highly reactive lone pair on the dicoordinated, monovalent nitrogen atom can be coordinated to the Si−N σ* MO of the second silylene moiety resulting in Si−N bond formation and Si−Si bond cleavage. This step is similar to the SN2′ reaction where the incoming nucleophile and the leaving group are on the same side resulting in the formation of silaimine I5. Further, the [3+1] cycloaddition of one more molecule of Me3SiN3 followed by N2 elimination results in the formation of silaimine intermediate I7. I7 undergoes 1,3‐silyl migration leading to the final product 1. The lone pairs on di‐ and tricoordinated nitrogen centres of all the intermediates are stabilized by hyperconjugative interactions. The delocalized hyperconjugative interaction stabilizes the lone pairs in 1. [ABSTRACT FROM AUTHOR]

In women who die from cancer, breast cancer is the most common cause of death. The development of small molecular scaffolds as specific Cyclin-dependent kinase (CDK) inhibitors is a promising strategy in the discovery of anti-breast cancer drugs. Isoindolin-1-ones are heterocyclic compounds with useful therapeutic properties. In this study, a library of 48 isoindolinones has been virtually screened by molecular docking that showed high binding affinity up to − 10.1 kcal/mol and conventional hydrogen bonding interactions with active amino acid residues of CDK7. The molecular dynamics simulation (MDS), fragment molecular orbital (FMO), density functional theory (DFT), and pharmacokinetics studies of the best two docked scored ligands 7 and 14 have been studied. Examining the ligand root mean square deviation and hydrogen bonding occupancy of the 100 ns MDS trajectory, both ligands 7 and 14 showed docked pose stability. FMO calculations displayed that LYS139 and LYS41 are majorly contributing to the binding interactions with ligands 7 and 14 in the docked poses. DFT studies of ligands 7 and 14 showed high values of global softness and low values of global hardness and chemical potential thus displaying chemically reactive soft molecules and this influences their anti-cancer activity. Our hits exhibited superior qualities to known CDK7 inhibitors, according to the comprehensive pharmacokinetic parameters that were predicted. The results indicate that isoindolin-1-one moieties are good candidates for anti-cancer action and could serve as effective CDK7 inhibitors. [ABSTRACT FROM AUTHOR]

We present herein the synthesis of novel pseudo‐metalla‐carbaporphyrinoid species (1M: M=Pd and Pt) achieved through the inner coordination of palladium(II) and platinum(II) with an acyclic N‐confused tetrapyrrin analogue. Despite their tetrapyrrole frameworks being small, akin to well‐known porphyrins, these species exhibit an unusually narrow HOMO–LUMO gap, resulting in an unprecedentedly low‐energy absorption in the second near‐infrared (NIR‐II) region. Density functional theory (DFT) calculations revealed unique dπ‐pπ‐conjugated electronic structures involving the metal dπ‐ligand pπ hybridized molecular orbitals of 1M. Magnetic circular dichroism (MCD) spectroscopy confirmed distinct electronic structures. Remarkably, the complexes feature an open‐metal coordination site in the peripheral NN dipyrrin site, forming hetero‐metal complexes (1Pd‐BF2 and 1Pt‐BF2) through boron difluoride complexation. The resulting hetero metalla‐carbaporphyrinoid species displayed further redshifted NIR‐II absorption, highly efficient photothermal conversion efficiencies (η; 62–65 %), and exceptional photostability. Despite the challenges associated with the theoretical and experimental assessment of dπ‐pπ‐conjugated metalla‐aromaticity in relatively larger (more than 18π electrons) polycyclic ring systems, these organometallic planar tetrapyrrole systems could serve as potential molecular platforms for aromaticity‐relevant NIR‐II dyes. [ABSTRACT FROM AUTHOR]

The field of organic solar cells has witnessed notable advancements in the past few years, mostly due to the development of novel materials for the active layer. The current investigations reveal the potential of nine previously unexplored molecules (TP1–TP9) designed by end group modification of TPT4F molecule. These molecules were investigated at MPW1PW91/6‐31G (d, p) with DFT and TD‐DFT approach to study the various photovoltaic and geometrical parameters. The results obtained through computations indicated improvement in the investigated parameters. The terminal group modification shifted the absorption maximum towards longer wavelength in the UV‐visible region. Highly conjugated modified acceptors reduced the band gap. The lower excitation energies increased the rate of charge transfer. The designed molecules showed improved excited state lifetime in comparison to the reference. The open circuit voltage was determined using the PTB7 polymer, which exhibited a noticeable improvement, especially in TP1 (1.70 eV), TP3 (1.75 eV), TP4 (1.68 eV), TP6 (1.85 eV), and TP7 (1.75 eV) when compared with reference (1.59 eV). Moreover, charge transfer investigations of designed molecules with PTB7 complex were performed by analyzing the concentration of charge transfer over molecular orbitals, that is, HOMO to LUMO. All of the preceding investigations targeted to achieve high‐efficiency organic cells reveal that the altered molecules can be considered effective candidates to tackle future energy problems. [ABSTRACT FROM AUTHOR]

Objective: A sequence of biologically active vanillin acetamides bearing heterocyclic moiety (VHAs) specifically vanillin isoniazid acetamide (VISO), vanillin-2-pyridine acetamide (V2PR), vanillin-4-pyridine acetamide (V4PR), and vanillin-2-pyrimidine acetamide (V2PM) are synthesized and methodically characterized by spectroscopic techniques such as Nuclear Magnetic Resonance (1H and 13C NMR), Electrospray Ionization Mass, Fourier Transform Infrared and Ultraviolet-Visible spectroscopy. Further, the VHAs are inspected for in vitro biological activities such as anti-inflammatory by protein anti-denaturation, antidiabetic by enzyme inhibition method and the in vitro results are linked with the reference drug. Methods: To the acetonitrile solution of intermediate TBTU and trimethylamine is added at room temperature. The reaction mixture is stirred for 30 min and then the corresponding amine is added. The reaction mixture is stirred for 4 h and the reaction mixture is extracted with ethyl acetate. The evaporation of the solvent yielded the VHAs. The anti-inflammatory activity of VHAs is tested disbursing the Bovine serum albumin denaturation technique. The antidiabetic activity of VHAs is tested using the α-amylase inhibition method. Results and Discussion: The designed VHAs were successfully synthesized, well characterized by necessary spectroscopic techniques (1H and 13C NMR), Electrospray Ionization Mass and the structure of the VHAs was very clearly interpreted and discussed. The chemical structure and electronic topographies of VHAs agree with the biological activity distinctions. Hence, thorough analysis has been achieved in the computational methods such as Frontier molecular orbitals, molecular electrostatic potential and Mulliken charge distribution studies using the density functional theory method. The correlation between in vitro studies and docking results revealed that structural and electronic properties production an important role in biological activity. Conclusions: The VHAs obtainable very well α-amylase inhibitory activity and comparable results were obtained in the molecular docking studies. [ABSTRACT FROM AUTHOR]

In order to investigate the effect of terminal donors on the structures and photophysical properties, four donor (D1)-acceptor (A)-π bridge-donor (D2) prototype fluorophores were synthesized and characterized. Single crystal analysis indicated that changing the types of terminal donors (D2) would give rise to different frontier molecular orbitals and molecular packing modes, leading to their different emission behaviors in solid states. In dilute solution, the four D–A–π-D compounds displayed different absorption and emission behaviors in dilute solution with solvatochromism properties. Assisted by the quantum chemical calculations and wave function analysis, the essence of optical properties of four compounds were explored. The results indicated that changing the types of terminal donors (D2) can affect the structures and photophysical properties of such donor (D1)-acceptor (A)-π bridge-donor (D2) prototype fluorophores, which provided guidance to design new fluorophores. [ABSTRACT FROM AUTHOR]

The bottom-up fabrication of supramolecular and self-assembly on various substrates has become an extremely relevant goal to achieve prospects in the development of nanodevices for electronic circuitry or sensors. One of the branches of this field is the self-assembly of functional molecular components driven through non-covalent interactions on the surfaces, such as van der Waals (vdW) interactions, hydrogen bonding (HB), electrostatic interactions, etc., allowing the controlled design of nanostructures that can satisfy the requirements of nanoengineering concepts. In this context, non-covalent interactions present opportunities that have been previously explored in several molecular systems adsorbed on surfaces, primarily due to their highly directional nature which facilitates the formation of well-ordered structures. Herein, we review a series of research works by combining STM (scanning tunneling microscopy) with theoretical calculations, to reveal the processes used in the area of self-assembly driven by molecule Landers equipped with functional groups on the metallic surfaces. Combining these processes is necessary for researchers to advance the self-assembly of supramolecular architectures driven by multiple non-covalent interactions on solid surfaces. [ABSTRACT FROM AUTHOR]

The present work reports the antitumor activity and a comprehensive study of the Cu(II) complex with 1,10-phenanthroline and l-tyrosine, synthesized by slow solvent evaporation method. X-ray powder diffraction (XRPD) showed that the complex crystallizes in a monoclinic structure with P21/c-space group. All IR- and Raman-active bands were assigned and vibrational properties were evaluated under solvation effects from quantum chemical calculations using density functional theory (DFT). Additionally, optimized geometry, electrostatic potential surface, spatial distribution, and energies of molecular orbitals HOMO and LUMO, as well as chemical reactivity indexes, were obtained using PBE1PBE theoretical level. Antitumor activity of the complex was evaluated through cytotoxic tests in vitro in tumor cell lines PC3 and SNB-19, presenting IC50 equal to 1.5 μM and 2.9 μM, respectively. Additionally, ADME parameters were evaluated to study the drug-like properties of the synthesized complex. Therefore, our findings suggest that the complex presents a promising antitumor activity, with the potential to be used in cancer chemotherapy treatment. [ABSTRACT FROM AUTHOR]

The ternary complexes of the zinc(II), [Zn(met)(gly)(Cl)2] (1), and [Zn(met)(hist)(Cl)2] (2) are synthesized and illustrated utilizing spectroscopic and analytical measurements, and the geometry of the complexes has been identified to be octahedral. The Coats Red fern approach was employed to enumerate the thermodynamic and kinetic variables for both the Zn(II) complexes' decomposition. The quantum chemical variables were estimated utilizing the molecular orbital conformations' energy distribution, which was derived from optimal geometric shapes to test the stabilization of both complexes. DNA‐binding investigations by UV–Vis absorption, fluorescence, and viscosity were all exploited to examine the bonding properties between Zn(II) complexes and ct‐DNA, and a groove mode of bonding was established. The interactions between complexes and BSA/HSA were investigated by employing absorption and emission spectroscopic methods. The results demonstrate that complexes have a powerful ability to diminish BSA and HSA luminescence intensity, and overall associating mode is predominantly a static quenching process. The cytotoxic effect of the two Zn(II) complexes was additionally examined in human breast adenocarcinoma (MCF‐7 and MDA‐MB‐231) cell lines by employing the MTT technique. The IC50 values for every cell line were derived. Each of the two complexes was functional in both cell lines. [ABSTRACT FROM AUTHOR]

Context: In cellular environments, the reduction of disulfide bonds is pivotal for protein folding and synthesis. However, the intricate enzymatic mechanisms governing this process remain poorly understood. This study addresses this gap by investigating a disulfide bridge reduction reaction, serving as a model for comprehending electron and proton transfer in biological systems. Six potential mechanisms for reducing the dimethyl disulfide (DMDS) bridge through electron and proton capture were explored. Thermodynamic and kinetic analyses elucidated the sequence of proton and electron addition. MD-PMM, a method that combines molecular dynamics simulations and quantum-chemical calculations, was employed to compute the redox potential of the mechanism. This research provides valuable insights into the mechanisms and redox potentials involved in disulfide bridge reduction within proteins, offering an understanding of phenomena that are challenging to explore experimentally. Methods: All calculations used the Gaussian 09 software package at the MP2/6–311 + g(d,p) theory level. Visualization of the molecular orbitals and electron densities was conducted using Gaussview6. Molecular dynamics simulations were performed using GROMACS with the CHARMM36 force field. The PyMM program (Python Program for QM/MM Simulations Based on the Perturbed Matrix Method) is used to apply the Perturbed Matrix Method to MD simulations. [ABSTRACT FROM AUTHOR]

Context: Xanthates are organic compounds of great interest in coordination chemistry due to their different basic sites, which allow them to form complexes with different coordination modes and geometries. These compounds are relevant in the environment and act as heavy metal collectors in aqueous environments. In this theoretical–experimental work, electronic spectroscopy studies of n-propyl xanthate complexes with group 12 metals were performed. This study verified structural differences in these systems, depending on the environment in which they are inserted. In addition, structural differences were observed when the solid was changed to an n-hexane solution. Thus, it was observed that the complexes assume a mononuclear structure in solution, while they present a polymeric form in the solid phase. The electronic spectra obtained through TD-DFT calculations were compared to those of the previously synthesized complexes. In the final theoretical analysis, the main orbitals involved in these transitions were assigned using population analysis calculations. The synthesis of the complexes was confirmed through infrared (MID and FAR), UV‒Vis, Raman, and NMR-1H spectroscopic analyses. Methods: The structures of the mononuclear and polymeric complexes were optimized in vacuum and n-hexane. Under vacuum, DFT levels M06L/6–311 + + G** + LANL2TZ and M06L/def2-TZVP were used for the mononuclear complexes, and M06L/LANL2DZ + LANL2 were used for the polymer complexes. For the calculations of the mononuclear complexes in n-hexane, the same level of theory was used for the solid state. TD-DFT calculations for 300 excited states were performed with the same levels of theory and used the optimized structures of the complexes. Furthermore, population analysis was carried out on all the systems studied. Gaussian 09 software was used for the structure optimization, TD-DFT, and population analysis calculations. GaussSum software was used to evaluate the molecular orbitals and electronic spectra. [ABSTRACT FROM AUTHOR]

Novel imidazopyridines hydrazine conjugates were designed and synthesized for their anti‐tubercular (anti‐TB) activity. A cytotoxicity assay was conducted with Vero cells to determine the safety profile of the most effective compounds. It was found that compound (IA3) (MIC=0.78 μM) and (IA8) (MIC=1.12 μM) were nearly 3.7 and 2.5 times more active than pyrazinamide. Based on Density functional theory (DFT), these molecules exhibited better charge transfer between molecular orbital's, which made them suitable for biological applications. Molecular docking on Mycobacterium tuberculosis InhA bound to NITD‐916 (PDB: 4R9S) revealed that compounds possessed greater binding affinity towards proteins. In addition, the most active anti‐TB compounds (IA3) and (IA8) exhibited high levels of interaction with the target protein and exceptional safety profile, suggesting they may prove to be effective leads for new drugs. [ABSTRACT FROM AUTHOR]

In this work, a donor‐acceptor (D‐A) type ligand is prepared to construct Cu(I) and Ag(I) complexes. These complexes possess similar molecular structures, distributions of molecular orbitals, and distributions of electrons and holes in excited states. However, they exhibit distinct photophysical properties, such as luminescent spectra and transient photo‐luminescent decay spectra. Through analysis of deep‐lying molecular orbitals in a tetrahedral field, it is determined that the variation in d‐p π conjugation between the metal cation's d‐orbitals and the π orbitals of the electron‐acceptor part of the D‐A ligand is the reason for the different photophysical properties. This research contributes to an in‐depth understanding of the role of metal ions in luminescent complexes, providing insights from the perspective of coordination chemistry. [ABSTRACT FROM AUTHOR]

Introducing a rigid linear π‐conjugated acetylene linker into a supramolecular building block consisting of a hydrogen‐bond donor side and a hydrogen‐bond acceptor side yields a decrease in cooperativity in the resulting formed quartet. This follows from our Kohn‐Sham molecular orbital and Voronoi deformation density analyses of hydrogen‐bonded macrocycles based on guanine and cytosine nucleobases. The acetylene linker abstracts electron density from the hydrogen‐bond acceptor and donor, making the hydrogen‐bond acceptor more negatively charged and the hydrogen‐bond donor more positively charged and hence suppressing the donor–acceptor charge transfer interaction between the interacting fragments. This, ultimately, hampers the cooperativity in the hydrogen‐bonded macrocycle. We envision that these findings could open the door to new design principles for the development of novel hydrogen‐bond supramolecular macrocycles. [ABSTRACT FROM AUTHOR]

In the process of handling and storage of radioactive actinides it is essential to selectively sequester the minor actinides, such as Am and Cm, through a competitive complexation process. Herein we computationally designed two core modified ligands (L21− and L3) through systematic oxygen substitution at the NH sites of dipyriamethyrin (L1_2H), a hexadentate expanded porphyrin, and studied their competitive complexation towards trivalent actinides (An = Am/Cm) from their trichlorides using density functional theory (DFT). We observed shorter An–N bonds and longer An–O bonds in complexes based on core modified ligands (L21− and L3). The An–Cl bond length increases with increasing axial coordination number (i.e., from L12− to L3) to accommodate the ligands. All the bonds were identified to be electrostatic in nature. L12− exhibits shorter bonds and larger bond orders on complexing with Am than with Cm. On moving from complexes of L21− to L3, the An–N bond lengths are shortened, while An–O bond lengths become larger. Between the complexes of Am and Cm, there is marginal difference in their bond distances with L21− and L3. Charge analysis shows ligand to metal charge transfer during coordination, with back-donation from An to N/O and Cl. The calculated spin-density analysis indicates that An remains in its trivalent oxidation state on complexation, while orbital occupation analysis shows that the 5f and 6d orbitals are involved in bonding; this was confirmed by molecular orbital (MO) analysis that shows the complexes of L21− and L3 to exhibit higher degeneracy in their overlapping MOs. Further, the energy decomposition analysis (EDA) confirms that all ionic bonds are primarily due to electrostatic contributions, where the orbital contributions increase from L12− to L3 complexes and maximum covalency was observed in Cm complexes due to the energy matching between the 5f orbitals of Cm and the 2p orbitals of N and Cl, compared to Am. To confirm the competitiveness in the complexation of the ligand towards Am vs. Cm, the thermodynamic parameters were analysed for the ligand and metal substitution reactions. L12− shows more affinity towards Am than Cm, while L21− and L3 prefer Cm. [ABSTRACT FROM AUTHOR]

Pyrazinacenes are linearly fused heteroaromatic rings, with N atoms replacing all apical CH moieties. Component rings may exist in a reduced state, having NH groups instead of N, causing cross-conjugation. These compounds have interesting optical and electronic properties, including strong fluorescence in the near-infrared region and photocatalytic properties, leading to diverse possible applications in bio-imaging and organic synthesis, as well as obvious molecular electronic uses. In this study, we investigated the behavior of seven-ring pyrazinacene 2,3,11,12-tetraphenyl-7,16-dihydro-1,4,5,6,7,8,9,12,13,14,15,16,17,18-tetradecaazaheptacene (Ph4H2N14HEPT), with an emphasis on protic processes, including oxidation, tautomerism, deprotonation, and protonation, and the species resulting from those processes. We used computational methods to optimize the structures of the different species and generate/compare molecular orbital structures. The aromaticity of the species generated by the different processes was assessed using the nucleus-independent chemical shifts, and trends in the values were associated with the different transformations of the pyrazinacene core. The computational data were compared with experimental data obtained from synthetic samples of the molecule tBu8Ph4H2N14HEPT. [ABSTRACT FROM AUTHOR]

The photocatalyst (PC) zinc tetraphenylporphyrin (ZnTPP) is highly efficient for photoinduced electron/energy transfer reversible addition-fragmentation chain transfer (PET-RAFT) polymerization. However, ZnTPP suffers from poor absorbance of orange light by the so-called Q-band of the absorption spectrum (maximum absorption wavelength λ max = 600 nm, at which molar extinction coefficient ε max = 1.0 × 10 4 L/(mol·cm)), hindering photo-curing applications that entail long light penetration paths. Over the past decade, there has not been any competing candidate in terms of efficiency, despite a myriad of efforts in PC design. By theoretical evaluation, here we rationally introduce a peripheral benzo moiety on each of the pyrrole rings of ZnTPP, giving zinc tetraphenyl tetrabenzoporphyrin (ZnTPTBP). This modification not only enlarges the conjugation length of the system, but also alters the a 1 u occupied π molecular orbital energy level and breaks the accidental degeneracy between the a 1 u and a 2 u orbitals, which is responsible for the low absorption intensity of the Q-band. As a consequence, not only is there a pronounced hyperchromic and bathochromic effect ( λ max = 655 nm and ε max = 5.2 × 10 4 L/(mol·cm)) of the Q-band, but the hyperchromic effect is achieved without increasing the intensity of the less useful, low wavelength absorption peaks of the PC. Remarkably, this strong 655 nm absorption takes advantage of deep-red (650–700 nm) light, a major component of solar light exhibiting good atmosphere penetration, exploited by the natural PC chlorophyll a as well. Compared with ZnTPP, ZnTPTBP displayed a 49% increase in PET-RAFT polymerization rate with good control, marking a significant leap in the area of photo-controlled polymerization. [ABSTRACT FROM AUTHOR]

The Hippo pathway controls organ size and homeostasis and is linked to numerous diseases, including cancer. The transcriptional enhanced associate domain (TEAD) family of transcription factors acts as a receptor for downstream effectors, namely yes-associated protein (YAP) and transcriptional co-activator with PDZ-binding motif (TAZ), which binds to various transcription factors and is essential for stimulated gene transcription. YAP/TAZ-TEAD facilitates the upregulation of multiple genes involved in evolutionary cell proliferation and survival. TEAD1–4 overexpression has been observed in different cancers in various tissues, making TEAD an attractive target for drug development. The central drug-accessible pocket of TEAD is crucial because it undergoes a post-translational modification called auto-palmitoylation. Crystal structures of the C-terminal TEAD complex with small molecules are available in the Protein Data Bank, aiding structure-based drug design. In this study, we utilized the fragment molecular orbital (FMO) method, molecular dynamics (MD) simulations, shape-based screening, and molecular mechanics–generalized Born surface area (MM-GBSA) calculations for virtual screening, and we identified a novel non-covalent inhibitor—BC-001—with IC50 = 3.7 μM in a reporter assay. Subsequently, we optimized several analogs of BC-001 and found that the optimized compound BC-011 exhibited an IC50 of 72.43 nM. These findings can be used to design effective TEAD modulators with anticancer therapeutic implications. [ABSTRACT FROM AUTHOR]