An improved chain of spheres for exchange algorithm

Carbocation charge as an interpretable descriptor for the catalytic activity of hydrolytic nanozymes

A universal theory for predicting the catalytic activity of hydrolytic nanozymes has yet to be developed. Herein, by investigating the polarization and hydrolysis mechanisms of nanomaterials towards amide bonds, carbocation charge was identified as a key electronic descriptor for predicting catalytic activity in amide hydrolysis. Through machine learning correlation analysis and the Sure Independence Screening and Sparsifying Operator (SISSO) algorithm, this descriptor was interpreted to associate with the d-band center and Lewis acidity on the nanomaterial surface. On this basis, copper nanoparticles (Cu NPs) were discovered to exhibit significant hydrolytic activity. Further, peptidomic analysis and molecular dynamics simulations showed that Cu NPs demonstrated substrate selectivity. In the presence of water molecules, hydrophobic amino acid residues were driven towards the nanomaterial surface by hydrophobic groups of proteins, leading to the preferential hydrolysis of peptide bonds linked to these residues. This study provided a theoretic framework for predicting highly efficient hydrolytic nanozymes with broad potential applications.

Structural Changes in Metal Chalcogenide Nanoclusters Associated with Single Heteroatom Incorporation

Atomically precise nanoclusters (NCs) are promising building blocks for designing materials and interfaces with unique properties. By incorporating heteroatoms into the core, the electronic and magnetic properties of NCs can be precisely tuned. To accurately predict these properties, density functional theory (DFT) is often employed, making the rigorous benchmarking of DFT results particularly important. In this study, we present a benchmarking approach based on metal chalcogenide NCs as a model system. We synthesized a series of bimetallic, iron-cobalt chalcogenide NCs [Co6-xFexS8(PEt3)6]+ (x = 0-6) (PEt = triethyl phosphine) and investigated the effect of heteroatoms in the octahedral metal chalcogenide core on their size and electronic properties. Using ion mobility-mass spectrometry (IM-MS), we observed a gradual increase in the collision cross section (CCS) with an increase in the number of Fe atoms in the core. DFT calculations combined with trajectory method CCS simulations successfully reproduced this trend, revealing that the increase in cluster size is primarily due to changes in metal-ligand bond lengths, while the electronic properties of the core remain largely unchanged. Moreover, this method allowed us to exclude certain multiplicity states of the NCs, as their CCS values were significantly different from those predicted for the lowest-energy structures. This study demonstrates that gas-phase IM-MS is a powerful technique for detecting subtle size differences in atomically precise NCs, which are often challenging to observe using conventional NC characterization methods. Accurate CCS measurements are established as a benchmark for comparison with theoretical calculations. The excellent correspondence between experimental data and theoretical predictions establishes a robust foundation for investigating structural changes of transition metal NCs of interest to a broad range of applications.

Accelerating Fock Build via Hybrid Analytical-Numerical Integration

A hybrid analytical-numerical integration scheme is introduced to accelerate the Fock build in self-consistent field (SCF) and time-dependent density functional theory (TDDFT) calculations. To evaluate the Coulomb matrix J[D], the density matrix D is first decomposed into two parts, the superposition of atomic density matrices D⊕A and the rest DR = D-D⊕A. While J[D⊕A] is evaluated analytically, J[DR] is evaluated fully numerically [with the multipole expansion of the Coulomb potential (MECP)] during the SCF iterations. Upon convergence, DR is further split into those of near (DRC) and distant (DRL) atomic orbital (AO) pairs, such that J[DRC] and J[DRL] are evaluated seminumerically and fully numerically (with MECP). Such a hybrid J-build is dubbed "analytic-MECP" (aMECP). Likewise, the analytic evaluation of K[D⊕A] and seminumerical evaluation of K[DR] are also invoked for the construction of the exchange matrix K[D] during the SCF iterations. The chain-of-spheres (COSX) algorithm [Chem. Phys. 356, 98 (2009]) is employed for K[DR] but with a revised construction of the S-junctions for overlap AO pairs. To distinguish from the original COSX algorithm (which does not involve the partition of the density matrix D), we denote the presently revised variant as COSx. Upon convergence, DR is further split into those of near (DRC) and distant (DRL) AO pairs followed by a rescaling, leading to D ~ R C and D ~ R L , respectively. K [ D ~ R C ] and K [ D ~ R L ] are then evaluated analytically and seminumerically (with COSx), respectively. Such a hybrid K-build is dubbed "analytic-COSx" (aCOSx). Extensive numerical experimentations reveal that the combination of aMECP and aCOSx is highly accurate for ground state SCF calculations (< μ E h / atom error in energy) and is particularly efficient for calculations of large molecules with extended basis sets. As for TDDFT excitation energies, a medium grid for MECP and a coarse grid for COSx are already sufficient.

Two-fold proton coupled electron transfer of a Ta(V) aniline complex mediated by a redox active NNN pincer ligand

We report the proton-coupled electron transfer (PCET) reactivity of an octahedral Ta(V) aniline complex supported by an acridane-derived redox active NNN pincer ligand. The reversible binding of aniline to a Ta(V) dichloride induces significant coordination-induced bond weakening (CIBW) of the aniline N-H bonds. This enables a rare two-fold hydrogen atom abstraction, resulting in a terminal imido complex and a two-electron oxidation of the NNN pincer ligand, all while maintaining the metal's oxidation state. The bond dissociation free energies (BDFEs) of the aniline and a transient radical amido complex are estimated through stoichiometric reactions with different hydrogen atom abstractors and donors, further supported by density functional theory calculations.

Arene Ring Expansion by Ruthenium η6-Arene Complexes

Transition metal π-arene complexes enable the dearomatization of benzene rings to access diversified unsaturated carbocycles through multistep synthetic procedures involving sequential addition of nucleophiles and electrophiles. This work details a single-step dearomatization process by reaction of Ru(η6-arene) complexes with enolates derived from α-halo or α-(tosyloxy)esters to directly transform π-coordinated arenes to ring-expanded cycloheptatrienes.

The Best of Both Worlds: ΔDFT Describes Multiresonance TADF Emitters with Wave-Function Accuracy at Density-Functional Cost

With their narrow-band emission, high quantum yield, and good chemical stability, multiresonance thermally activated delayed fluorescence (MR-TADF) emitters are promising materials for OLED technology. However, accurately modeling key properties, such as the singlet-triplet (ST) energy gap and fluorescence energy, remains challenging. While time-dependent density functional theory (TD-DFT), the workhorse of computational materials science, suffers from fundamental issues, wave function-based coupled-cluster (CC) approaches, like approximate CC of second-order (CC2), are accurate but suffer from high computational cost and unfavorable scaling with system size. This work demonstrates that a state-specific ΔDFT approach based on unrestricted Kohn-Sham (ΔUKS) combines the best of both worlds: on a diverse benchmark set of 35 MR-TADF emitters, ΔUKS performs as good as or better than CC2, recovering experimental ST gaps with a mean absolute deviation (MAD) of 0.03 eV at a small fraction of the computational cost of CC2. When combined with a tuned range-separated LC-ωPBE functional, the excellent performance extends to fluorescence energies and ST gaps of MR- and donor-acceptor TADF emitters and even molecules with an inverted ST gap (INVEST), rendering this approach a jack of all trades for organic electronics.

Hydrothermal Stability of Active Sites in Cu-Exchanged Small-Pore Zeolites for the Selective Catalytic Reduction of NOx

Combining operando X-ray absorption spectroscopy (XAS) and computational modelling shows unequivocally the distribution of active species in fresh and hydrothermally aged Cu-CHA and Cu-AEI zeolites during NH3-assisted selective catalytic reduction of NOx. Four principal species co-exist: (i) CuI cations coordinated to NH3, (ii) CuI cations coordinated to the zeolite framework, (iii) solvated CuII cations, and (iv) framework-coordinated CuII species (CuII st) formed upon hydrothermal ageing of the zeolite sample. The CuII st species were only observed in the hydrothermally aged zeolite samples and are formed upon the interaction of hydrated CuII cations with extra-framework Al (EFAl) generated during the hydrothermal treatment. These sites are inactive for NOx reduction, leading to a decrease in the catalytic performance of the hydrothermally aged zeolites. CuII st formation was higher in Cu-CHA (~46 %) than in Cu-AEI (~28 %). The better hydrothermal stability of Cu in the AEI framework is attributed to the tortuous channel structure of AEI that hinders the migration of hydrated CuII cations during hydrothermal ageing.

Regulating Interface Dipole Interaction between Ethers and Active Species Toward Highly Stable Li-SPAN Batteries

Sulfurized polyacrylonitrile (SPAN) is recognized as a promising organic cathode for long-lifespan lithium metal batteries. Nevertheless, the irreversible cleavage/formation of multiple sulfur-sulfur (S-S) bonds of SPAN within conventional ether-based electrolytes results in loss of active S species, severe capacity fading and shuttle effects. Herein, we propose a new electrolyte based on dipropyl ether (PE) solvent for Li-SPAN batteries. Benefiting from the particular chain-coordination structure and weak dipole interactions with Li+ and active species, the resulting electrolyte not only achieves low desolvation energy barrier and high Li+ transference number, but also displays stable electrolyte-electrode interface (EEI). Consequently, the full cells utilizing this electrolyte exhibit good cyclability, outstanding capacity retention and superior extreme-temperature (-50 °C to 50 °C) performance. Furthermore, the Ah-scale pouch cell with lean electrolyte (2.5 g Ah-1) achieves record cycle stability with 96.5 % capacity retention after 75 cycles, which deliver an initial specific energy density of 150 Wh kg-1 (based on the weight of the entire cell). Impressively, this strategy demonstrates universality in a series of organic electrodes employing with PE-based electrolytes. This work highlights the strategy for modulating the dipole interaction at EEI for long-lifespan Li-organic batteries at extreme conditions.

Revealing the Role of Electronic Effect to Modulate the Photophysics and Z-Scan Responses of o-Locked GFP Chromophores

Three novel core green fluorescent protein (GFP) chromophore analogues, based on a doubly locked conformation and variable electronic effects by replacing one hydrogen with bromine, iodine, and methyl, respectively, have been synthesized to modulate the push-pull effect. These chromophores exhibited intramolecular H-bonding, as evidenced by single-crystal X-ray and 1H NMR studies. The fluorescence quantum yields (ϕf) of all of the chromophores were found to be more than an order of magnitude higher (∼0.2) than the unlocked chromophores (∼0.01). It was found that the electronic effect did affect the nonradiative rates, as the quantum yields were found to vary with respect to different analogues in the same solvents. The effect of the push-pull effect was also evident by a higher Stokes-shifted emission in the case of the methyl derivative with respect to the bromo- and iodo-analogues. Furthermore, the emission spectra of these GFP chromophores were found to show positive solvatochromism, which was supported by a quantum chemical calculation. A detailed study, correlating the observed spectral changes with various solvent functions and supported by computational results, established a facile proton transfer, followed by twisted intramolecular charge transfer (TICT) to be the major nonradiative channels of these chromophores. Besides, a completely novel usage of these chromophores was explored for the first time by studying their third-order nonlinear optical characteristics in DMSO using a single-beam Z-scan technique. All of the chromophores exhibited tunable nonlinear refraction (NLR) and nonlinear absorption (NLA) properties that depend upon different substituent groups present in the chromophores. Here, the NLR was due to the effect of self-defocusing, whereas the NLA was triggered by reverse saturable absorption, which is attributed to the two-photon absorption (TPA) process. Surprisingly, the efficiency of the TPA ability of the chromophores was found to be a function of the induced electronic effect. Hence, this work opens a new route for the utility of the ortho-locked GFP chromophores in the field of nonlinear optical applications.

A General and Transferable Local Hybrid Functional for Electronic Structure Theory and Many-Fermion Approaches

Density functional theory has become the workhorse of quantum physics, chemistry, and materials science. Within these fields, a broad range of applications needs to be covered. These applications range from solids to molecular systems, from organic to inorganic chemistry, or even from electrons to other Fermions, such as protons or muons. This is emphasized by the plethora of density functional approximations that have been developed for various cases. In this work, two new local hybrid exchange-correlation density functionals are constructed from first-principles, promoting generality and transferability. We show that constraint satisfaction can be achieved even for admixtures with full exact exchange, without sacrificing accuracy. The performance of the new functionals CHYF-PBE and CHYF-B95 is assessed for thermochemical properties, excitation energies, Mössbauer isomer shifts, NMR spin-spin coupling constants, NMR shieldings and shifts, magnetizabilities, and EPR hyperfine coupling constants. Here, the new density functional shows excellent performance throughout all tests and is numerically robust only requiring small grids for converged results. Additionally, both functionals can easily be generalized to arbitrary Fermions as shown for electron-proton correlation energies. Therefore, we outline that density functionals generated in this way are general purpose tools for quantum mechanical studies.

DFT investigation of green stabilizer reactions: curcumin in nitrocellulose-based propellants

CONTEXT

Nitrocellulose, widely used in energetic materials, is prone to thermal and chemical degradation, compromising safety and performance. Stabilizers are molecules used in the composition of nitrocellulose-based propellants to inhibit the autocatalytic degradation process that produces nitrous gases and free nitric acids. Curcumin, (1E,6E)-1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione, known for its antioxidant properties and a potential green stabilizer, was investigated using Density Functional Theory (DFT) focusing on its interaction with nitrogen dioxide. Two mechanisms were analyzed: aromatic ring nitration and free radical formation. The results indicate that nitration of the aromatic ring of curcumin and the formation of a curcumin-based free radical are viable. The computed Gibbs free activation energy (∆‡G°) and the activation enthalpy (∆‡H°) for two different temperatures, 298.15 K (room temperature) and 363.15 K (typical temperature in aging tests), are respectively 43.64 kcal/mol and 44.78 kcal/mol for the first reaction, and 31.54 kcal/mol and 35.31 kcal/mol for the second. The radical-based mechanism favors improved kinetics. These findings demonstrate curcumin's potential as an effective stabilizer, providing comparable performance to traditional compounds with lower environmental impact.

METHODS

DFT calculations were carried out using Gaussian 09 and Orca 5.0.1 packages. The ωB97M-V, B3LYP, and M062X functionals were employed with the 6-311 + G(d) and 6-311G(d) basis sets. Solvent effects were modeled using the Conductor-like Polarizable Continuum Model (CPCM) and Solvation Model based on Density (SMD) continuum solvent models. Thermochemical data were computed using the same levels of calculation.

Acceleration without Disruption: DFT Software as a Service

Density functional theory (DFT) has been a cornerstone in computational chemistry, physics, and materials science for decades, benefiting from advancements in computational power and theoretical methods. This paper introduces a novel, cloud-native application, Accelerated DFT, which offers an order of magnitude acceleration in DFT simulations. By integrating state-of-the-art cloud infrastructure and redesigning algorithms for graphic processing units (GPUs), Accelerated DFT achieves high-speed calculations without sacrificing accuracy. It provides a user-friendly and scalable solution for the increasing demands of DFT calculations in scientific communities. The implementation details, examples, and benchmark results illustrate how Accelerated DFT can significantly expedite scientific discovery across various domains.

Experimental Spin State Determination of Iron(II) Complexes by Hirshfeld Atom Refinement

In this study, we present the first experimental determination of the spin state of transition metal complexes by using Hirshfeld Atom Refinement. For the demonstration, the two iron(II) complexes, (NH4)2Fe(SO4)2 ⋅ 6 H2O and lFe(pic)3jCl2 ⋅ EtOH were investigated. The method involves the refinement using wavefunctions of different spin multiplicity and comparison against experimental diffraction data by means of refinement indicators and residual electron density. Our results show a clear distinction between high-spin and low-spin configurations, even for compounds with spin-crossover behavior. The presented work demonstrates the potential of Hirshfeld Atom Refinement for the experimental determination of spin states in transition metal complexes.

Single-Component Coordination Polymers with Excitation Wavelength- and Temperature-Dependent Long Persistent Luminescence toward Multilevel Information Security

Metal-organic hybrid materials with long persistent luminescence (LPL) properties have attracted a lot of attention due to their enormous potential for applications in information encryption, anticounterfeiting, and other correlation fields. However, achieving multimodal luminescence in a single component remains a significant challenge. Herein, we report two two-dimensional LPL coordination polymers: {[Zn2(BA)2(BIMB)2]·2H2O}n (1) and {[Cd(BA)(BIMB)]·3H2O}n (2) (BIMB = 1,3-bis(imidazol-1-yl)benzene; BA = butanedioic acid). Their LPL colors can be adjusted by the excitation wavelength or temperature variation in a single-component coordination polymer, achieving multimode color adjustment from green to orange or blue to yellow. X-ray single-crystal diffraction analysis and theoretical calculations demonstrate that abundant intermolecular interactions, ligand-to-ligand charge transfer (LLCT) transitions, and heavy atom effects of the central metal can realize multicolor afterglow. This work provides a convenient strategy for new pattern multicolor LPL materials and may also inspire new ideas for advanced information encryption technologies.

Advanced Charge Extended Hückel (CEH) Model and a Consistent Adaptive Minimal Basis Set for the Elements Z = 1-103

The Charge Extended Hückel (CEH) model, initially introduced for adaptive atomic orbital (AO) basis set construction (J. Chem. Phys. 2023, 159, 164108), has been significantly revised to enhance accuracy and robustness, particularly in challenging electronic situations. This revision includes an extension toward f-elements, covering actinoids with their f-electrons in the valence space. We present a novel noniterative approximation for the electrostatic contribution to the effective Fock matrix, which substantially improves performance in polar or charged systems. Additionally, the training data set for elements Z = 1-103 has been expanded to encompass even more chemically diverse reference molecules as well as dipole moments and shell populations in addition to atomic charges. It includes a greater variety of "mindless" molecules (MLMs) as well as more complex electronic structures through open-shell and highly charged species. The revised method achieves mean absolute errors for atomic charges q of approximately 0.02 e- for randomly selected (mostly organic) molecules and 0.09 e- for MLMs, outperforming both classical charge models and established tight-binding methods. Furthermore, the revised CEH model has been validated through density functional theory calculations with the updated adaptive q-vSZP AO basis set on common thermochemical databases. Consistent with the extension of the CEH model, q-vSZP has also been variationally optimized and tested for elements Z = 58-71 and 87-103. The original versions of both CEH and q-vSZP are now considered deprecated.

Calculated ionization energies, orbital eigenvalues (HOMO), and related QSAR descriptors of organic molecules: a set of 61 experimental values enables elimination of systematic errors and provides realistic error estimates

Ionization energies (IEs) of organic compounds come in different forms-adiabatic, vertical, as electrode potentials, or as orbital eigenvalues via Koopmans' theorem. They have been linked to the reactivity towards electrophiles and have been used to quantitatively describe electron transfer processes. The de novo prediction of IEs is only meaningful when an estimate of the prediction's uncertainty is included. Pulsed-field ionization (PFI) experiments have quantified adiabatic IEs with unprecedented precision. In this work, a new set of PFI-derived IEs is compiled from the literature as a benchmark for prediction methods. This set includes many common functional groups, a size range from diatomics to two aromatic rings, and IEs between 7 and 14 eV. The first-principles CCSD(T)/CBS protocol presently used reproduces these values within 0.05 eV. For adiabatic IEs and vertical IEs/orbital eigenvalues predicted using approximate density functional theory (DFT), linear regression models are proposed, so that IEs calculated using different methods can be directly compared on a physical scale. This elimination of systematic errors improves the error statistics and allows the performance of predicted IEs to be evaluated if used in quantitative structure-property or -activity relationships, as the latter implicitly correct a descriptor's bias. Owing to the structural scope of the test set, the minimum and maximum deviations from experiment should correspond to those expected for common organic molecules. Deviations from reference values found for orbital eigenvalues but also for IEs calculated explicitly with HF or semi-empirical MO methods were as large as 0.5 eV to 2.0 eV. Such large errors could also propagate into quantitative structure-property models, as shown in illustrative examples of oxidation rate constants in solution.

Spectroscopic and Quantum Chemical Evidence of Amine-CO2 and Alcohol-CO2 Interactions: Confirming an Intriguing Affinity of CO2 to Monoethanolamine (MEA)

A recent broadband rotational spectroscopic investigation of the cross-association mechanisms of CO2 with monoethanolamine (MEA) in molecular beams [F. Xie et al., Angew. Chem. Int. Ed., 2023, 62, e202218539] revealed an intriguing affinity of CO2 to the hydroxy group. These findings have triggered the present systematic vibrational spectroscopic exploration of weakly bound amine··CO2 and alcohol··CO2 van der Waals cluster molecules embedded in inert "quantum" matrices of neon at 4.2 K complemented by high-level quantum chemical conformational analyses. The non-covalent interactions formed between the amino and hydroxy groups and the electron-deficient carbon atom of CO2 are demonstrated to lift the degeneracy of the doubly degenerate intramolecular CO2-bending fundamental significantly with characteristic observed spectral splittings for the amine··CO2 (≈35-45 cm-1) and alcohol··CO2 (≈20-25 cm-1) interactions, respectively, despite the almost identically predicted total association energies (≈12-14 kJ·mol-1) for these van der Waals contacts, as revealed by benchmark Domain-based Local Pair Natural Orbital Coupled Cluster DLPNO-CCSD(T) theory. These high-level theoretical predictions reveal significantly higher "geometry preparation energies" for the amine··CO2 systems leading to a more severe distortion of the CO2 linearity upon complexation in agreement with the infrared spectroscopic findings. The systematic combined spectroscopic and quantum chemical evidences for cross-association between CO2 and amines/alcohols in the present work unambiguously confirm an intriguing binding preference of CO2 to the hydroxy group of the important carbon capture agent MEA, with an accurate vibrational zero-point energy corrected association energy (D0) of 13.5 kJ·mol-1 at the benchmark DLPNO-CCSD(T)/aug-cc-pV5Z level of theory.

Deciphering Pyramidanes: A Quantum Chemical Topology Approach

C[C4H4], the simplest compound of the [4]-pyramidane family, has so far eluded experimental characterization, although several of its analogs, E[C4(SiMe3)4] in which the E apex atom is a tetrel group element, have been successfully prepared. The non-classical bonding mode of E, similar to that found in propellanes, has prompted a considerable number of theoretical studies to unravel the nature of the apex-base interaction. Here, we contribute to this knowledge by analyzing the electron localization function (ELF) and classical QTAIM descriptors; as well the statistical distribution of electrons in atomic regions by means of the so-called electron distribution functions (EDFs), calculation of multicenter indices (MCI) as aromaticity descriptors and by performing orbital invariant energy decompositions with the interacting quantum atoms (IQA) approach on a series of E[C4(SiMe3)4] compounds. We find that the bonding evolves from covalent to electrostatic as E changes from C to Pb, with an anomaly when E=Si, which is shown to be the most charged moiety, compatible with an aromatic [C4(SiMe3)4]2- scaffold in the pyramidane base.

A Theoretical Study of Positively Curved Circulenes Embedded with Five-Membered Heterocycles: Structures and Inversions

Recently, polycyclic arenes with positive curvature have gained increasing significance in the field of material chemistry. This study specifically explores the inversion barriers of a series of positively curved circulenes by using five-membered heterocycles integrated into the backbone of primitive [5]circulenes and [6]circulenes. For hetero[5]circulenes, where one benzenoid ring is replaced by a heterocycle, the inversion barriers exhibit a strong correlation with the rotary angles of the heterocycles, and larger rotary angles result in lower inversion barriers. Additionally, the aromaticity of the circulene undergoes a significant reduction during the inversion process. As the number n of replaced rings increases, the inversion barriers can be adjusted, demonstrating an almost linear relationship with n. In the case of hetero[6]circulenes, molecules bearing heterocycles with small rotary angles also show positive curvatures. Furthermore, we examine the relationship between the radii of the fitted sphere for the circulenes and the inversion barriers, revealing an intriguing inverse proportionality between the fourth power of the radius and the inversion barrier. We anticipate that this research will offer a fresh perspective on studies related to positively curved polycyclic arenes.

Methoxide-Enabled Zirconium-Catalyzed Migratory Alkene Hydrosilylation

A zirconocene dichloride-catalyzed alkene hydrosilylation is reported that can be applied to non-activated and conjugated terminal and internal alkenes. It involves a catalytic Zr-walk process and leads to a selective conversion to the linear product. Lithium methoxide serves as mild catalyst activating agent, which significantly increases the applicability and operational simplicity in comparison to earlier zirconium(II)-based protocols. Supported by additional experiments and calculations, a mechanism via zirconium(IV) intermediates is proposed. Due to the benign nature and ready-availability of the zirconium catalyst, the reaction is an attractive alternative to established alkene hydrosilylation methods.

Uncovering the Crucial Role of Chelating Structures in Cyano-Alkyl-Phosphate Electrolytes for High-Voltage Lithium Metal Batteries

The inferior oxidative stability of commercial carbonate electrolytes and overgrowth of the electrode-electrolyte interphase (EEI) have largely hindered the development of high-voltage lithium metal batteries. In this study, these challenges are addressed by designing Li+-solvent chelating solvation structures to inhibit solvent decomposition using cyano-alkyl-phosphate as a demonstration. Theoretical and experimental studies confirm that the -P═O and -C≡N groups within diethyl (2-cyanethyl) phosphonate exhibit a comparable ability to coordinate with Li+, facilitating the formation of seven-membered chelating structures. This unique solvation structure contributes to the formation of anion-derived inorganic-rich EEI with high stability and robustness, hindering the further decomposition of the electrolyte. Additionally, the cyano group has a strong complexation with the transition metal (TM) in the cathode to inhibit TM dissolution, thereby ensuring the structural stability of the cathode particle. Utilizing this special chelating structure, the designed electrolyte demonstrates favorable Li plating/stripping reversibility and promising oxidative stability in high-voltage batteries. Consequently, the LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode exhibits a high capacity retention (90%) after operating 300 cycles. Under harsh testing conditions, the 4.6 V Li||NCM811 pouch cell with a capacity of 1.4 Ah (∼295 Wh kg-1 based on the total mass of the cell) retains 70% capacity after 80 cycles. This work provides new insights into the correlation between the solvation structure and oxidative stability of electrolytes, contributing significantly to the advancement of high-voltage lithium metal batteries.

1.3 Å Crystal Structure of E. coli Peptidyl-Prolyl Isomerase B with Uniform Substitution of Valine by (2S,3S)-4-Fluorovaline Reveals Structure Conservation and Multiple Staggered Rotamers of CH2F Groups

(2S,3S)-4-Fluorovaline (FVal) is an analogue of valine, where a single CH3 group is substituted by a CH2F group. In the absence of valine, E. coli valyl-tRNA synthetase uses FVal as a substitute, enabling the production of proteins uniformly labeled with FVal. Here, we describe the production and analysis of E. coli peptidyl-prolyl isomerase B where all 16 valine residues have been replaced by FVal synthesized with a 13C-labeled CH2F group. Although the melting temperature is lower by about 11 °C relative to the wild-type protein, the three-dimensional protein structure is almost completely conserved, as shown by X-ray crystallography. The CH2F groups invariably populate staggered rotamers. Most CH2F groups populate two different rotamers. The increased space requirement of fluorine versus hydrogen does not prohibit rotamers that position fluorine next to a backbone carbonyl carbon. 19F NMR spectra show a signal dispersion over 25 ppm. The most high-field shifted 19F resonances correlate with large 3JHF coupling constants, confirming the impact of the γ-gauche effect on the signal dispersion. The present work is the second experimental verification of the effect and extends its validity to fluorovaline. The abundance of valine in proteins and structural conservation with FVal renders this valine analogue attractive for probing proteins by 19F NMR spectroscopy.

Quantum Chemical Characterization of Rotamerism in Thio-Michael Additions for Targeted Covalent Inhibitors

Myotonic dystrophy type I (DM1) is the most common form of adult muscular dystrophy and is a severe condition with no treatment currently available. Recently, small-molecule ligands have been developed as targeted covalent inhibitors that have some selectivity for and covalently inhibit cyclin-dependent kinase 12 (CDK12). CDK12 is involved in the transcription of elongated RNA sections that results in the DM1 condition. The covalent bond is achieved after nucleophilic addition to a Michael acceptor warhead. Previous studies of the conformational preferences of thio-Michael additions have focused on characterizing the reaction profile based on the distance between the sulfur and β-carbon atoms. Rotamerism, however, has not been investigated extensively. Here, we use high-level quantum chemistry calculations, up to coupled cluster with single, double, and perturbative triple excitations [CCSD(T)], to characterize the nucleophilic addition of an archetypal nucleophile, methanethiolate, to various nitrogen-containing Michael acceptors which are representative of the small-molecule covalent inhibitors. By investigating the structural, energetic, and electronic properties of the resulting enolates, as well as their reaction profiles, we show that synclinal additions are generally energetically favored over other additions due to the greater magnitude of attractive noncovalent interactions permitted by the conformation. The calculated transition states associated with the addition process indicate that synclinal addition proceeds via lower energetic barriers than antiperiplanar addition and is the preferred reaction pathway.

Synthesis of Amorphous and Various Phase-Pure Nanoparticles of Nickel Phosphide with Uniform Sizes via a Trioctylphosphine-Mediated Pathway

Nickel phosphides are of particular interest because they are highly active and stable catalysts for petroleum/biorefinery and hydrogen production. Despite their significant catalytic potential, synthesizing various phase-pure nickel phosphide nanoparticles of uniform size remains a challenge. In this work, we develop a robust trioctylphosphine (TOP)-mediated route to make highly uniform phase-pure Ni12P5, Ni2P, and Ni5P4 nanoparticles. The synthetic route forms amorphous Ni70P30 nanoparticle intermediates. The reactions can be stopped at the amorphous stage when amorphous particles are desired. The amount of P incorporation can be controlled by varying the ratio of TOP to Ni(II). The mechanism for composition control involves the competition of the kinetics of two processes: the addition of the reduced Ni and the incorporation of P into Ni. Uniform Ni70P30 amorphous nanoparticles can be generated at a high TOP-to-Ni(II) ratio, where the P incorporation kinetics is made to dominate. Ni70P30 can later be transformed into phase-pure Ni12P5, Ni2P, and Ni5P4 nanocrystals of uniform size. The transformation can be controlled precisely by modulating the temperature. A UV-vis study coupled with theoretical modeling reveals Ni(0)-TOPx complexes along the synthetic path. This approach may be expanded to create other metal compounds, potentially enabling the synthesis of uniform nanoparticles of a greater variety.

Solar Light CO2 Photoreduction Enhancement by Mononuclear Rhenium(I) Complexes: Characterization and Mechanistic Insights

The catalytic efficacy of a novel mononuclear rhenium(I) complex in CO2 reduction is remarkable, with a turnover number (TONCO) of 1517 in 3 h, significantly outperforming previous Re(I) catalysts. This complex, synthesized via a substitution reaction on an aromatic ring to form a bromo-bipyridine derivative, L1 = 2-bromo-6-(1H-pyrazol-1-yl)pyridine, and further reacting with [Re(CO)5Cl], results in the facial-tricarbonyl complex [ReL1(CO)3Cl] (1). The light green solid was obtained with an 80% yield and thoroughly characterized using cyclic voltammetry, nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) spectroscopy, and ultraviolet-visible (UV-vis) spectroscopy. Cyclic voltammetry under CO2 atmosphere revealed three distinct redox processes, suggesting the formation of new electroactive compounds. The studies on photoreduction highlighted the ability of the catalyst to reduce CO2, while NMR, FTIR, and electrospray ionization (ESI) mass spectrometry provided insights into the mechanism, revealing the formation of solvent-coordinated complexes and new species under varying conditions. Additionally, computational studies (DFT) were undertaken to better understand the electronic structure and reactivity patterns of 1, focusing on the role of the ligand, the spectroscopic features, and the redox behavior. This comprehensive approach provides insights into the intricate dynamics of CO2 photoreduction, showcasing the potential of Re(I) complexes in catalysis.

Nature of Charge Transfer Effects in Complexes of Dopamine Derivatives Adsorbed on Graphene-Type Nanostructures

Continuing the investigation started for dopamine (DA) and dopamine-o-quinone (DoQ) (see, the light absorption and charge transfer properties of the dopamine zwitterion (called dopamine-semiquinone or DsQ) adsorbed on the graphene nanoparticle surface is investigated using the ground state and linear-response time-dependent density functional theories, considering the ωB97X-D3BJ/def2-TZVPP level of theory. In terms of the strength of molecular adsorption on the surface, the DsQ form has 50% higher binding energy than that found in our previous work for the DA or DoQ cases (-20.24 kcal/mol vs. -30.41 kcal/mol). The results obtained for electronically excited states and UV-Vis absorption spectra show that the photochemical behavior of DsQ is more similar to DA than that observed for DoQ. Of the three systems analyzed, the DsQ-based complex shows the most active charge transfer (CT) phenomenon, both in terms of the number of CT-like states and the amount of charge transferred. Of the first thirty electronically excited states computed for the DsQ case, eleven are purely of the CT type, and nine are mixed CT and localized (or Frenkel) excitations. By varying the adsorption distance between the molecule and the surface vertically, the amount of charge transfer obtained for DA decreases significantly as the distance increases: for DoQ it remains stable, for DsQ there are states for which little change is observed, and for others, there is a significant change. Furthermore, the mechanistic compilation of the electron orbital diagrams of the individual components cannot describe in detail the nature of the excitations inside the complex.

Molecularly Imprinted Polymers Electrochemical Sensing: The Effect of Inhomogeneous Binding Sites on the Measurements. A Comparison between Imprinted Polyaniline versus nanoMIP-Doped Polyaniline Electrodes for the EIS Detection of 17β-Estradiol

Molecularly imprinted polymers (MIPs) are synthetic receptors made by template-assisted synthesis. MIPs might be ideal receptors for sensing devices, given the possibility to custom-design selectivity and affinity toward a targeted analyte and their robustness and ability to withstand harsh conditions. However, the synthesis of MIP is an inherently random process that produces a statistical distribution of binding sites, characterized by a variety of affinities. This is verified both for bulk MIP materials and for MIP's thin layers. In the present work, we aimed at assessing the effects of inhomogeneous versus homogeneous imprinted binding sites on electrochemical sensing measurements, and the possible implications on the sensor's performance. In the example of an Electrochemical Impedance Spectroscopy (EIS) sensor for the 17β-estradiol (E2) hormone, the scenario of inhomogeneous binding sites was studied by modifying electrodes with an E2-MIP polyaniline (PANI) thin layer, called the "Imprinted PANI layer". In contrast, the condition of discrete and uniform binding sites was epitomized by electrodes modified with a thin PANI layer purposedly doped with E2-MIP nanoparticles (nanoMIPs), which were referred to as "nanoMIP-doped PANI". The behaviors of the two EIS sensors were compared. Interestingly, the sensitivity of the nanoMIP-doped PANI was almost twice with respect to that of the imprinted PANI layer, strongly suggesting that the homogeneity of the binding sites has a fundamental role in the sensor's development. The nanoMIP-doped PANI sensor, which showed a response for E2 in the range 36.7 pM-36.7 nM and had a limit of detection of 2.86 pg/mL, was used to determine E2 in wastewater.

ANI neural network potentials for small molecule pKa prediction

The pKa value of a molecule is of interest to chemists across a broad spectrum of fields including pharmacology, environmental chemistry and theoretical chemistry. Determination of pKa values can be accomplished through several experimental methods such as NMR techniques and titration together with computational techniques such as DFT calculations. However, all of these methods remain time consuming and computationally expensive. In this work we develop a method for the rapid calculation of pKa values of small molecules which utilises a combination of neural network potentials, low energy conformer searches and thermodynamic cycles. We show that neural network potentials trained on different phase and charge states can be employed in tandem to predict the full thermodynamic energy cycle of molecules. Focusing here on imidazolium derived carbene species, the method utilised can easily be extended to other functional groups of interest such as amines with further training.

Reversible Control of Native GluN2B-Containing NMDA Receptors with Visible Light

NMDA receptors (NMDARs) are glutamate-gated ion channels playing a central role in synaptic transmission and plasticity. NMDAR dysregulation is linked to various neuropsychiatric disorders. This is particularly true for GluN2B-containing NMDARs (GluN2B-NMDARs), which have major pro-cognitive, but also pro-excitotoxic roles, although their exact involvement in these processes remains debated. Traditional GluN2B-selective antagonists suffer from slow and irreversible effects, limiting their use in native tissues. We therefore developed OptoNAM-3, a photoswitchable negative allosteric modulator selective for GluN2B-NMDARs. OptoNAM-3 provided light-induced reversible inhibition of GluN2B-NMDAR activity with precise temporal control both in vitro and in vivo on the behavior of freely moving Xenopus tadpoles. When bound to GluN2B-NMDARs, OptoNAM-3 displayed remarkable red-shifting of its photoswitching properties allowing the use of blue light instead of UV light to turn-off its activity, which we attributed to geometric constraints imposed by the binding site onto the azobenzene moiety of the ligand. This study therefore highlights the importance of the binding site in shaping the photochemical properties of azobenzene-based photoswitches. In addition, by enabling selective, fast, and reversible photocontrol of native GluN2B-NMDARs with in vivo compatible photochemical properties (visible light), OptoNAM-3 should be a useful tool for the investigation of the GluN2B-NMDAR physiology in native tissues.

Extensive reference set and refined computational protocol for calculations of 57Fe Mössbauer parameters

Mössbauer spectroscopy is a powerful technique for probing the local electronic structure of iron compounds, because it reports in an element-selective manner on both the oxidation state and coordination environment of the Fe ion. Computational prediction of the two main Mössbauer parameters, isomer shift (δ) and quadrupole splitting (ΔEQ), has long been targeted by quantum chemical studies, and useful protocols based on density functional theory have been proposed. Here we present an extensive curated reference set of Fe compounds that is considerably larger and more diverse than literature precedents. We make a distinction between low-temperature and high-temperature experimental subgroups. This set is employed for optimizing a refined computational protocol utilizing the scalar version of the exact 2-component (X2C) Hamiltonian with the finite nucleus approximation. Attention is devoted to having an accurate and flexible all-electron basis set for Fe. We assess the performance of several DFT methods that cover all representative families and rungs of functionals and find that hybrid functionals with ca. 25-30% exact exchange offer the best accuracy for isomer shifts. The work establishes a refined general protocol of wide applicability that achieves good performance for the prediction of isomer shifts in a wider variety of systems than before, but the limitations of DFT for quadrupole splittings are also highlighted. Finally, comparison of calculated values with high-temperature experimental results shows that the use of an empirical correction factor is required to account for the second-order Doppler shift and to achieve the same quality of correlation as with the low-temperature data.

Interaction characteristics and mechanism of Cr(VI)/Cr(III) with microplastics: Influence factor experiment and DFT calculation

The coexistence of highly toxic heavy metal chromium and new pollutants microplastics has been widely present, and the interaction behavior and mechanism of the two are crucial for their environmental effects in coexisting environments, which urgently need to be further explored. Firstly, the interaction characteristics of polyamide (PA) and polyethylene (PE) with Cr(VI)/Cr(III) were investigated, where PA exhibited higher adsorption capacity of both Cr(VI) and Cr(III) than PE among various environmental conditions. The higher adsorption energy of PA on Cr(VI)/Cr(III) was also achieved by DFT calculation, and the bending configuration of PA during the adsorption process may be beneficial for its interaction with Cr. Then, the combination of characterization analysis and DFT calculation showed that significant chemical bonding occurred in the interaction between CO bond of PA and Cr(III), weak chemical interactions occurred in the adsorption of PE with Cr(III) and PA with Cr(VI), while the adsorption of PE with Cr(VI) was mainly physical effects. This study provides theoretical support for pollution control of microplastics and chromium in co-existing environment.

Application of the Adiabatic Connection Random Phase Approximation to Electron-Nucleus Hyperfine Coupling Constants

The electron-nucleus hyperfine coupling constant is a challenging property for density functional methods. For accurate results, hybrid functionals with a large amount of exact exchange are often needed and there is no clear "one-for-all" functional which describes the hyperfine coupling interaction for a large set of nuclei. To alleviate this unfavorable situation, we apply the adiabatic connection random phase approximation (RPA) in its post-Kohn-Sham fashion to this property as a first test. For simplicity, only the Fermi-contact and spin-dipole terms are calculated within the nonrelativistic and the scalar-relativistic exact two-component framework. This requires to solve a single coupled-perturbed Kohn-Sham equation to evaluate the relaxed density matrix, which comes with a modest increase in computational demands. RPA performs remarkably well and substantially improves upon its Kohn-Sham (KS) starting point while also reducing the dependence on the KS reference. For main-group systems, RPA outperforms global, range-separated, and local hybrid functionals─at similar computational costs. For transition-metal compounds and lanthanide complexes, a similar performance as for hybrid functionals is observed. In contrast, related post-Hartree-Fock methods such as Møller-Plesset perturbation theory or CC2 perform worse than semilocal density functionals.

Real-space energy decomposition analysis method for qualitative and quantitative interpretations

In the work, a real-space energy decomposition analysis method, called DM-EDA(RS), is introduced based on our recently developed DM-EDA method [Zhang et al., J. Chem. Phys. 160, 174101 (2024)]. The EDA terms in DM-EDA(RS), including electrostatic, exchange, repulsion, polarization, and correlation, are expressed as the summations of grid-based energy density in real-space. This method is able to interpret intermolecular interactions in a unified qualitative and quantitative way. DM-EDA(RS) results provide not only comprehensive explanations for intermolecular interactions but also insights for sub-region interactions involving different functional groups.

Insights into the newly synthesized bi- Mannich base for carbon steel corrosion inhibition in H2S and HCl solution

Adding corrosion inhibitors is considered to be a cost-effective way to inhibit metal corrosion. In this study, we report the synthesis of a bi-mannich base corrosion inhibitor (BMT) with an impressive inhibition efficiency on carbon steel in H2S and HCl co-existing solution. At the BMT concentration of 9 ppm, the inhibition efficiency (η) of 96.9%, 97.6% and 98.0% were determined by weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy, respectively. The adsorption of BMT on the carbon steel surface follows the Langmuir adsorption isotherm, and the calculated free energy indicates that the adsorption is a spontaneous process. This research also delves into understanding the adsorption behavior and corrosion inhibition mechanism of BMT on carbon steel surfaces through quantum chemistry calculations. The results of this study provide guidance for the application of BMT as a corrosion inhibitor in sour and acid environments.

Binary and Halide-free Catalyst Systems Based on Al/Ga/In Aminopyridylbisphenolate Complexes for the Cycloaddition of Epoxides and CO2

Group 13 complexes bearing an aminopyridylbisphenol ligand have been prepared [ML-X; L = ligand, M = Al (X = Cl and Br), Ga (X = Cl, Br, and I), or In (X = Cl)]. The structures of the complexes containing the chloride ligand (ML-Cl; M = Al, Ga, and In) have been directly compared through an X-ray crystallography study, with differences in the monomeric or dimeric nature of their structures observed. All of the complexes obtained have been studied as potential catalysts for the synthesis of cyclic carbonates from epoxides and CO2. It has been found that the indium complex, as part of a traditional binary catalyst system (catalyst + tetra-butylammonium halide cocatalyst), displays the highest catalytic activity and is active under rather mild reaction conditions (balloon pressure of CO2). Meanwhile, it has been found that the GaL-I complex is a competent single-component catalyst (no need for addition of a cocatalyst) at more elevated reaction temperatures and pressures. A full substrate scope has been performed with both developed catalyst systems to demonstrate their applicability. In addition to the experimental results, a density functional theory study was performed on both catalyst systems. These results explain both why the indium catalyst is the most active under binary catalyst system conditions and how the gallium catalyst with an iodide (GaL-I) is able to act as a single-component catalyst in contrast to the indium-based complex.

A solid noncovalent organic double-helix framework catalyzes asymmetric [6 + 4] cycloaddition

Whereas [4 + 2] cycloadditions are among the most powerful tools in the chemist's synthetic arsenal, controlling reactivity and selectivity of [6 + 4] cycloadditions has proven to be extremely challenging. Such transformations, especially if compatible with simple hydrocarbon-based substrates, could ultimately provide a general approach to highly valuable and otherwise difficult to access 10-membered rings. We report here that highly acidic and confined imidodiphosphorimidate catalysts do not catalyze this reaction under homogeneous conditions. Notably, however, they can spontaneously precipitate an insoluble and double helix-shaped noncovalent organic framework, which acts as a distinctively reactive and stereoselective catalyst of [6 + 4] cycloadditions of simple dienes with tropone.

Extension of the D3 and D4 London dispersion corrections to the full actinides series

Efficient dispersion corrections are an indispensable component of modern density functional theory, semi-empirical quantum mechanical, and even force field methods. In this work, we extend the well established D3 and D4 London dispersion corrections to the full actinides series, francium, and radium. To keep consistency with the existing versions, the original parameterization strategy of the D4 model was only slightly modified. This includes improved reference Hirshfeld atomic partial charges at the ωB97M-V/ma-def-TZVP level to fit the required electronegativity equilibration charge (EEQ) model. In this context, we developed a new actinide data set called AcQM, which covers the most common molecular actinide compound space. Furthermore, the efficient calculation of dynamic polarizabilities that are needed to construct CAB6 dispersion coefficients was implemented into the ORCA program package. The extended models are assessed for the computation of dissociation curves of actinide atoms and ions, geometry optimizations of crystal structure cutouts, gas-phase structures of small uranium compounds, and an example extracted from a small actinide complex protein assembly. We found that the novel parameterizations perform on par with the computationally more demanding density-dependent VV10 dispersion correction. With the presented extension, the excellent cost-accuracy ratio of the D3 and D4 models can now be utilized in various fields of computational actinide chemistry and, e.g., in efficient composite DFT methods such as r2SCAN-3c. They are implemented in our freely available standalone codes (dftd4, s-dftd3) and the D4 version will be also available in the upcoming ORCA 6.0 program package.

A modular, composite framework for the utilization of reduced-scaling Coulomb and exchange construction algorithms: Design and implementation

Multiple algorithms exist for calculating Coulomb (J) or exchange (K) contributions to Fock-like matrices, and it is beneficial to develop a framework that allows the seamless integration and combination of different J and K construction algorithms. In Psi4, we have implemented the "CompositeJK" formalism for this purpose. CompositeJK allows for the combination of any J and K construction algorithms for any quantum chemistry method formulated in terms of J-like or K-like matrices (including, but not limited to, Hartree-Fock and density functional theory) in a highly modular and intuitive fashion, which is simple to utilize for both developers and users. Using the CompositeJK framework, Psi4 was interfaced to the sn-LinK implementation in the GauXC library, adding the first instance of noncommercial graphics processing unit (GPU) support for the construction of Fock matrix elements to Psi4. On systems with hundreds of atoms, the interface to the CPU sn-LinK implementation displays a higher performance than all the alternative JK construction methods available in Psi4, with up to x2.8 speedups compared to existing Psi4JK implementations. The GPU sn-LinK implementation, harnessing the power of GPUs, improves the observed performance gains to up to x7.0.

Trapping an Elusive Fe(IV)-Superoxo Intermediate Inside a Self-Assembled Nanocage in Water at Room Temperature

Molecular cavities that mimic natural metalloenzymes have shown the potential to trap elusive reaction intermediates. Here, we demonstrate the formation of a rare yet stable Fe(IV)-superoxo intermediate at room temperature subsequent to dioxygen binding at the Fe(III) site of a (Et4N)2[FeIII(Cl)(bTAML)] complex confined inside the hydrophobic interior of a water-soluble Pd6L412+ nanocage. Using a combination of electron paramagnetic resonance, Mössbauer, Raman/IR vibrational, X-ray absorption, and emission spectroscopies, we demonstrate that the cage-encapsulated complex has a Fe(IV) oxidation state characterized by a stable S = 1/2 spin state and a short Fe-O bond distance of ∼1.70 Å. We find that the O2 reaction in confinement is reversible, while the formed Fe(IV)-superoxo complex readily reacts when presented with substrates having weak C-H bonds, highlighting the lability of the O-O bond. We envision that such optimally trapped high-valent superoxos can show new classes of reactivities catalyzing both oxygen atom transfer and C-H bond activation reactions.

An investigation into transition states of cyclic tetra-atomic silicon and germanium interstellar dust compounds: SixC4-x, GexC4-x, and GexSi4-x (x ∈ {1,2,3})

Presented in this work is a thorough determination of the transition states between the different isomers of cyclic tetra-atomic silicon carbide, germanium carbide, and germanium silicide clusters. Through use of density functional theory (B3LYP-D3BJ, M06-2X, ωB97X-D4, and B2GP-PLYP) in conjunction with the aug-cc-pVTZ basis set, transition state structures and their barrier heights are determined for the interconversions between the various isomers for the family of tetra-atomic SiC, GeC, and GeSi compounds. SiC dust grains are known to be prevalent in interstellar dust, and among this group, so far only diamond-shaped (d-)SiC3 has been detected in the interstellar medium (ISM). Determining which other structures might be detectable not only depends on their intrinsic spectroscopic features, but whether or not they are likely to exist as isomers in interstellar environments. By examining the energy barrier heights for transitions between isomers, we determined that many of these structures are unlikely to exhibit interconversion in the ISM, outside of hotter circumstellar environments. Although Boltzmann population ratios at approximate circumstellar temperatures suggest the presence of higher energy minima, it is likely that once interconversion happens, as molecules travel away from a star and cool, they will get kinetically trapped in the potential energy well they inhabit, making how the ratios freeze out dependent on the time and pathways the molecules take to cool down. As such, many of these higher energy minima may still be good candidates for detection including (rhomboidal) r-SiC3, r-GeC3, r-GeSi3, (trapezoidal) t-Si2C2, r-Ge2C2, and d-Si3C.

Integrated Experimental and Theoretical Investigation of Copper Active Site Properties of a Lytic Polysaccharide Monooxygenase from Serratia marcescens

In this paper, we employed a multidisciplinary approach, combining experimental techniques and density functional theory (DFT) calculations to elucidate key features of the copper coordination environment of the bacterial lytic polysaccharide monooxygenase (LPMO) from Serratia marcescens (SmAA10). The structure of the holo-enzyme was successfully obtained by X-ray crystallography. We then determined the copper(II) binding affinity using competing ligands and observed that the affinity of the histidine brace ligands for copper is significantly higher than previously described. UV-vis, advanced electron paramagnetic resonance (EPR), and X-ray absorption spectroscopy (XAS) techniques, including high-energy resolution fluorescence detected (HERFD) XAS, were further used to gain insight into the copper environment in both the Cu(II) and Cu(I) redox states. The experimental data were successfully rationalized by DFT models, offering valuable information on the electronic structure and coordination geometry of the copper center. Finally, the Cu(II)/Cu(I) redox potential was determined using two different methods at ca. 350 mV vs NHE and rationalized by DFT calculations. This integrated approach not only advances our knowledge of the active site properties of SmAA10 but also establishes a robust framework for future studies of similar enzymatic systems.

Gaseous inhibition of the transsulfuration pathway by cystathionine β-synthase

The transsulfuration pathway plays a key role in mammals for maintaining the balance between cysteine and homocysteine, whose concentrations are critical in several biochemical processes. Human cystathionine β-synthase is a heme-containing, pyridoxal 5'-phosphate (PLP)-dependent enzyme found in this pathway. The heme group does not participate directly in catalysis, but has a regulatory function, whereby CO or NO binding inhibits the PLP-dependent reactions. In this study, we explore the detailed structural changes responsible for inhibition using quantum chemical calculations to validate the experimentally observed bonding patterns associated with heme CO and NO binding and molecular dynamics simulations to explore the medium-range structural changes triggered by gas binding and propagating to the PLP active site, which is more than 20 Å distant from the heme group. Our results support a previously proposed mechanical signaling model, whereby the cysteine decoordination associated with gas ligand binding leads to breaking of a hydrogen bond with an arginine residue on a neighbouring helix. In turn, this leads to a shift in position of the helix, and hence also of the PLP cofactor, ultimately disrupting a key hydrogen bond that stabilizes the PLP in its catalytically active form.

Combining low-cost electronic structure theory and low-cost parallel computing architecture

The computational efficiency of low-cost electronic structure methods can be further improved by leveraging heterogenous computing architectures. The software package TeraChem has been developed since 2008 to make use of graphical processing units (GPUs), particularly their strong single-precision performance, for the acceleration of quantum chemical calculations. Here, we present the implementation of three low-cost methods, namely HF-3c, PBEh-3c, and the recently introduced ωB97X-3c. We show that these can benefit in terms of performance when combined with "consumer grade" GPUs by leveraging the mixed precision integral handling in TeraChem. The current limitation of the latter's GPU integral library is that Gaussian integrals only for functions with angular momentum l < 3 can be computed, which generally restricts the achievable accuracy in terms of the one-particle basis set. Particularly, the implementation of the ωB97X-3c method now enables higher accuracy with this setting which, in turn, provides the most efficient implementation accessible with consumer-grade hardware. We furthermore show that the implemented 3c methods can be combined with the hh-TDA formalism. This gives new and efficient low-cost multi-configurational excited states methods, which are benchmarked for the description of lowest vertical excitation energies in this work. All in all, the combination of these efficient electronic structure theory methods with affordable highly parallelized computing hardware provides an optimal computational and monetary cost to accuracy ratio.

Homo- and Heterogeneous Benzyl Alcohol Catalytic Oxidation Promoted by Mononuclear Copper(II) Complexes: The Influence of the Ligand upon Product Conversion

The catalytic properties of three copper complexes, [Cu(en)2](ClO4)2 (1), [Cu(amp)2](ClO4)2, (2) and [Cu(bpy)2](ClO4)2 (3) (where en = ethylenediamine, amp = 2-aminomethylpyridine and bpy = 2,2'-bipyridine), were explored upon the oxidation of benzyl alcohol (BnOH). Maximized conversions of the substrates to their respective products were obtained using a multivariate analysis approach, a powerful tool that allowed multiple variables to be optimized simultaneously, thus creating a more economical, fast and effective technique. Considering the studies in a fluid solution (homogeneous), all complexes strongly depended on the amount of the oxidizing agent (H2O2), followed by the catalyst load. In contrast, time seemed to be statistically less relevant for complexes 1 and 3 and not relevant for 2. All complexes showed high selectivity in their optimized conditions, and only benzaldehyde (BA) was obtained as a viable product. Quantitatively, the catalytic activity observed was 3 > 2 > 1, which is related to the π-acceptor character of the ligands employed in the study. Density functional theory (DFT) studies could corroborate this feature by correlating the geometric index for square pyramid Cu(II)-OOH species, which should be generated in the solution during the catalytic process. Complex 3 was successfully immobilized in silica-coated magnetic nanoparticles (Fe3O4@SiO2), and its oxidative activity was evaluated through heterogenous catalysis assays. Substrate conversion promoted by 3-Fe3O4@SiO2 generated only BA as a viable product, and the supported catalyst's recyclability was proven. Reduced catalytic conversions in the presence of the radical scavenger (2,2,6,6-tetrametil-piperidi-1-nil)oxil (TEMPO) indicate that radical and non-radical mechanisms are involved.

Gold(I)-Catalyzed Intramolecular 7-endo-dig Cyclization of Triene-Yne Systems: New Access towards Azulenothiophenes

We report the direct synthesis of new azulene derivatives through gold-catalyzed cyclization reactions. A five-membered ring as backbone in the applied triene-yne substrates turned out to be crucial to induce the 7-endo-dig cyclization mode necessary to trigger azulene formation. The obtained targets are of high interest due to their potential applications in different fields, like organic materials, medicine or cosmetics. UV/Vis spectra and cyclic voltammetry were measured, based on these the electronic properties were determined. Short two or three step sequences towards the applied starting materials make this approach synthetically highly attractive.

On the brink of self-hydration: the water heptadecamer

For pure, neutral, isolated molecular clusters, (H2O)17 marks the transition from structures with all water molecules on the cluster surface to water self-hydration, i.e., cluster structures around one central water molecule. Getting this right with water model potentials turns out to be challenging. Even the best water potentials currently available, which reproduce collective properties very well, still deliver contradicting results for (H2O)17, when different low-energy isomers from global structure optimizations are examined. Interestingly, ab initio quantum chemistry also struggles with the only seemingly simple question if (H2O)17 is all-surface or water-centered. Hence, although the long history of water potential development may be entering its final phase, it is not quite finished yet.

Comments on "Planar Tetracoordinate Hydrogen: Pushing the Limit of Multicentre Bonding"

In a recent communication (Angew. Chem. Int. Ed. 2024, 63, e202317312), Kalita et al. studied In4H+ system within the frame of single-reference approximation (SRA) and found that the global energy minimum (1 a) adopted the singlet state and a planar tetracoordinate hydrogen (ptH), while the second lowest isomer (1 b) located 3.0 kcal/mol above 1 a and adopted the triplet state as well as non-planar structure with a quasi-ptH. They assessed the reliability of SRA by checking the T1-diagnostic values of coupled cluster calculations. However, according to our multi-configurational second-order perturbation theory calculations at the CASPT2(12,13)/aug-cc-pVQZ (aug-cc-pVQZ-PP for In) level, both 1 a and 1 b exhibit obvious multi-referential characters, as reflected by their largest reference coefficients of 0.928 (86.1 %) and 0.938 (88.0 %), respectively. Moreover, 1 b is 5.05 kcal/mol lower than 1 a at this level, that is, what can be observed in In4H+ system is the quasi-ptH.

Synthesis and Characterization of Isostructural Th(IV) and U(IV) Pyridine Dipyrrolide Complexes

A series of pyridine dipyrrolide actinide(IV) complexes, (MesPDPPh)AnCl2(THF) and An(MesPDPPh)2 (An = U, Th, where (MesPDPPh) is the doubly deprotonated form of 2,6-bis(5-(2,4,6-trimethylphenyl)-3-phenyl-1H-pyrrol-2-yl)pyridine), have been prepared. Characterization of all four complexes has been performed through a combination of solid- and solution-state methods, including elemental analysis, single crystal X-ray diffraction, and electronic absorption and nuclear magnetic resonance spectroscopies. Collectively, these data confirm the formation of the mono- and bis-ligated species. Time-dependent density functional theory has been performed on all four An(IV) complexes, providing insight into the nature of electronic transitions that are observed in the electronic absorption spectra of these compounds. Room temperature, solution-state luminescence of the actinide complexes is presented. Both Th(IV) derivatives exhibit strong photoluminescence; in contrast, the U(IV) species are nonemissive.

A Theoretical Benchmark of the Geometric and Optical Properties for 3d Transition Metal Nanoclusters via Density Functional Theory

Understanding structure-property relationships in atomically precise metal nanoclusters is vital in finding selective and tunable catalysts. In this study, density functional theory (DFT) was used to benchmark seven exchange correlation functionals at different basis sets for 17 atomically precise nanoclusters against experimentally determined geometries, band gaps, and optical gaps. The set contains both monometallic and bimetallic clusters that possess at least two types of 3d transition metals (specifically, Cu, Ni, Fe, or Co). The benchmark highlights that PBE0 is a good functional to use regardless of the basis set, and Minnesota functionals do well with respect to specific metals. Further, while long-range corrected functionals overestimate band and optical gaps, they model absorption features better than the other considered functionals. The study additionally looks at the photoinduced hydrogen evolution reaction (HER) and the CO2 reduction mechanism on nanoclusters reported from the literature.

Photophysical Studies of a Zr(IV) Complex with Two Pyrrolide-Based Tetradentate Schiff Base Ligands

The reaction of two equivalents of N,N'-bis(2-pyrrolylmethylidene)-1,2-phenylenediamine (H2bppda) with tetrabenzylzirconium provided the air- and moisture-stable eight-coordinate complex Zr(bppda)2. Temperature-dependent steady-state and time-resolved emission spectroscopy established weak photoluminescence (ΦPL = 0.4% at 293 K) by a combination of prompt fluorescence and thermally activated delayed fluorescence (TADF) upon visible light excitation at and around room temperature. TADF emission is strongly quenched by 3O2 and shows highly temperature-sensitive emission lifetimes of hundreds of microseconds. The lifetime of the lowest energy singlet excited state, S1, was established by transient absorption spectroscopy and shows rapid deactivation (τ = 142 ps) by prompt fluorescence and intersystem crossing to the triplet state, T1. Time-dependent density functional theory (TD-DFT) calculations predict moderate ligand-to-metal charge transfer (LMCT) contributions of 25-30% for the S1 and T1 states. A comparison of Zr(bppda)2 to related zirconium pyridine dipyrrolide complexes, Zr(PDP)2, revealed important electronic structure changes due to the eight-coordinate ligand environment in Zr(bppda)2, which were correlated to differences in the photophysical properties between the two compound classes.