Calculations Of Complexes Research Articles

EXAMPLE OF DESIGNING A TAIL SYSTEM OF A DRILLING RIG BU 5000 DGU WITH EQUIPMENT MODERNIZATION

The materials of the article consider examples of the calculation of a technological complex for drilling a well with a depth of 4870 m, analyze the complex of mechanisms of the tackle system of the BU 5000 DGU drilling rig when drilling wells, establish the advantages and disadvantages of the used tackle systems. The feasibility and economic efficiency of introducing the proposed technical solutions for the modernization of the tackle system by introducing a device for laying the spent tackle rope is substantiated, its design is proposed, the technical feasibility is substantiated, the economic effect of implementing the modernized design of the tackle system is calculated. Methods for studying the main parameters and types of equipment for testing are selected. The issue of drawing up research documentation is considered. Based on the results of the studies of the operation of the modernized crown block, which were obtained in the process of performing experimental and laboratory work, three-dimensional models of the components were built in SolidWorks.

Essential Considerations for Free Energy Calculations of RNA-Small Molecule Complexes: Lessons from the Theophylline-Binding RNA Aptamer.

Alchemical free energy calculations are widely used to predict the binding affinity of small molecule ligands to protein targets; however, the application of these methods to RNA targets has not been deeply explored. We systematically investigated how modeling decisions affect the performance of absolute binding free energy calculations for a relatively simple RNA model system: theophylline-binding RNA aptamer with theophylline and five analogs. The goal of this investigation was 2-fold: (1) understanding the performance levels we can expect from absolute free energy calculations for a simple RNA complex and (2) learning about practical modeling considerations that impact the success of RNA-binding predictions, which may be different from the best practices established for protein targets. We learned that magnesium ion (Mg2+) placement is a critical decision that impacts affinity predictions. When information regarding Mg2+ positions is lacking, implementing RNA backbone restraints is an alternative way of stabilizing the RNA structure that recapitulates prediction accuracy. Since mistakes in Mg2+ placement can be detrimental, omitting magnesium ions entirely and using RNA backbone restraints are attractive as a risk-mitigating approach. We found that predictions are sensitive to modeling experimental buffer conditions correctly, including salt type and ionic strength. We explored the effects of sampling in the alchemical protocol, choice of the ligand force field (GAFF2/OpenFF Sage), and water model (TIP3P/OPC) on predictions, which allowed us to give practical advice for the application of free energy methods to RNA targets. By capturing experimental buffer conditions and implementing RNA backbone restraints, we were able to compute binding affinities accurately (mean absolute error (MAE) = 2.2 kcal/mol, Pearson's correlation coefficient = 0.9, Kendall's τ = 0.7). We believe there is much to learn about how to apply free energy calculations for RNA targets and how to enhance their performance in prospective predictions. This study is an important first step for learning best practices and special considerations for RNA-ligand free energy calculations. Future studies will consider increasingly complicated ligands and diverse RNA systems and help the development of general protocols for therapeutically relevant RNA targets.

Equilibrium and Nonequilibrium Ensemble Methods for Accurate, Precise and Reproducible Absolute Binding Free Energy Calculations.

Free energy calculations for protein-ligand complexes have become widespread in recent years owing to several conceptual, methodological and technological advances. Central among these is the use of ensemble methods which permits accurate, precise and reproducible predictions and is necessary for uncertainty quantification. Absolute binding free energies (ABFEs) are challenging to predict using alchemical methods and their routine application in drug discovery has remained out of reach until now. Here, we apply ensemble alchemical ABFE methods to a large data set comprising 219 ligand-protein complexes and obtain statistically robust results with high accuracy (<1 kcal/mol). We compare equilibrium and nonequilibrium methods for ABFE predictions at large scale and provide a systematic critical assessment of each method. The equilibrium method is more accurate, precise, faster, computationally more cost-effective and requires a much simpler protocol, making it preferable for large scale and blind applications. We find that the calculated free energy distributions are non-normal and discuss the consequences. We recommend a definitive protocol to perform ABFE calculations optimally. Using this protocol, it is possible to perform thousands of ABFE calculations within a few hours on modern exascale machines.

Importance of Charge Balance for the Embedding of Zwitterionic Solutes in the Fragment Molecular Orbital Method.

Three new schemes of induced solvent charges for the auxiliary polarization formulation of the fragment molecular orbital method are proposed and compared to the original approach. It is found that the charge balance of the solute and solvent embeddings is crucial for maintaining a proper gap between occupied and virtual orbitals of fragments for zwitterionic systems in solution. The original instability is eliminated with the new scheme of fragment-specific solvent charges. The developed stable embedding method is applied to perform MP2/aug-cc-pVTZ calculations of a protein-ligand complex containing 1102 amino acid residues.

Synthesis, characterization, X-ray structure, and DFT calculations of Zn complex encompassing HLN2O ligand: Relevance in cytotoxicity and antifungal photodynamic therapy.

This article presents the synthesis, characterization, and X-ray crystallographic features of one new Zn complex derived from a Salen-type tridentate ligand (HLN2O). A single-crystal diffraction study determined the complex crystal structure, which confirms that it crystallizes in the orthorhombic space group P212121. The single-crystal structure is constructed using the unique mononuclear component [ZnLN2°] and supramolecular CH∙∙∙π type interaction, resulting in a 1D structure. The IR, HRMS, and NMR study also support the complex structure. The Zn metal centre has a distorted square pyramidal geometry with τ value of 0.49. The Hirshfeld surfaces and 2D fingerprint confirm predominant H…H (77.9 %) interactions, with minor H…O, H…C, and H…N (5.0 %, 4.9 %, and 0.2 %). DFT calculations employed the B3LYP-D3/Lanl2DZ class of theory. FMO/MEP explains the complex reactivity perspective, while IP (4.71 eV) and low EA (1.11 eV) suit biological applications. The bonding gateway was analysed using NBO/QTAIM-NCI and ELF-LOL plots. Cytotoxicity was assessed using the Trypan blue exclusion method and tested against the DLA cell line, showing effectiveness against the DLA cell and suggesting complex potential as an anticancer agent. Antifungal photodynamic therapy (APDT) explored that ligand and Zn complex have significant activity against C. albicans. Finally, molecular docking simulations substantiate the experimental findings.

Elucidation of Electronic Structures of Mixed-Valence States Induced by dσ-π Charge Delocalization in Linear-Chain and Discrete Rhodium-Dioxolene Tetrameric Complexes.

We have successfully synthesized unique linear-chain and discrete mixed-valence tetrameric complexes, {[Rh(3,6-DBDiox-4,5-S2CO)(CO)2]4·hexane}∞ (4) and [Rh(3,6-DBDiox-4,5-S2CO)(CO)2]4 (5), by carefully choosing the solvent. X-ray photoelectron spectra (XPS) confirm that 4 and 5 are in the Rh(I,II) mixed-valence state. Analyses of the metrical oxidation state (MOS) of dioxolene ligands reveal that in 4 and 5, the electron density corresponding to one electron per tetramer is transferred from Rh(I) ions to semiquinonato ligands, and the transferred charge is delocalized throughout the four dioxolene ligands. Due to their mixed-valence state, 4 and 5 are semiconductors with relatively high electrical conductivity at room temperature. Density functional theory (DFT) calculations of tetrameric complex demonstrated for the first time that the dσ* orbitals of the Rh atoms and the π* orbitals of the semiquinonato ligands, which are originally highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), respectively, strongly hybridize with each other, leading to the Rh(I,II)-semiquinonato/catecholato mixed-valence state. Furthermore, time-dependent (TD)-DFT calculations have also revealed that the low energy absorption band observed centered at 5700 cm-1 is attributed to a charge transfer from [dσ*(Rh)] (HOMO) or [π*(SQ)-dσ*(Rh)] (HOMO-1) to [π*(SQ)-dσ*(Rh)] (LUMO/LUMO+1). Although 4 and 5 are tetramers with nearly identical structures, their magnetic interactions are found to differ significantly depending on their crystal structures.

In silico exploration of phytocompounds from AYUSH-64 medicinal plants against SARS CoV-2 RNA-dependent RNA polymerase

BackgroundThe AYUSH 64 formulation helps to treat mild to moderate cases of COVID-19. Although several drugs have been proposed to combat COVID-19, no medication is available for SARS-CoV-2 infection. The RNA-dependent RNA polymerase (RdRp) is the pivotal enzyme of SARS-CoV-2 replication, so it could be considered a better drug target for experimental studies. ObjectiveThe AYUSH-64 formulation plants exhibited multiple therapeutic properties; thus, the present study aims to screen the phytocompounds of these plants against SARS CoV2 RdRp to identify specific compounds that could potentially affect COVID-19 infection. Materials and methodsPatchDock and AutoDock tools were used for docking experiments. MD simulations and Density Functional Theory (DFT) calculations of protein-ligand Picroside-I and Remdesivir complexes were carried out in GROMACS v2019.4 and Gaussian 09 software, respectively. ResultsAmong the tested, five phytocompounds (Picroside I, Oleanolic acid, Arvenin I, II, and III) from AYUSH-64 medicinal plants showed possible binding with RdRp catalytic residues (Ser759, Asp760, and Asp761). Of these, Picroside I exhibited hydrogen bond interactions with NTP entry channel residues (Arg553 and Arg555). The MM-PBSA free energy, RMSD, Rg, PCA, and RMSF analysis suggested that the Picroside I complex showed stable binding interactions with RdRp in the 50 ns simulation. In addition to this, Picroside I revealed its robust and attractive nature toward the target protein, as confirmed by DFT. ConclusionThe results of this study have proposed that Picroside I from AYUSH 64 medicinal plant compounds was the selective binder of catalytic and NTP entry channel residues of SARS-CoV2 RdRp thereby; it may considered as a potential inhibitor of SARS-CoV2 RdRp.

Effect of Direct and Water-Mediated Interactions on the Identification of Hotspots in Biomolecular Complexes with Multiple Subsystems.

Identification of important residues in biochemical complexes is often a crucial step for many problems in molecular biology and biochemistry. A method is proposed to identify hotspots in biomolecular complexes based on a new metric, derived from networks representing molecular subunits (residues, bridging solvent molecules, ligands etc.) connected by interactions. A singular value decomposition of the weighted adjacency matrix is used to construct a scalar rank for each subunit that reflects its importance in the residue interaction network. This metric is called the singular value centrality. In addition, a new formalism is proposed to account for water-mediated interactions in the ranking of residues. Interactions for a residue network can be provided by various computational methods. In this work interactions are obtained from full quantum-mechanical calculations of protein-protein complexes using the fragment molecular orbital method. The ranking results are shown to be in good agreement with earlier computational and experimental studies. The developed method can be used to gain a deeper insight into the role of subunits in complex biomolecular systems.

Al–O–Al defect complexes as possible candidates for channel electron mobility reducing trapping centers in 4H-SiC metal–oxide–semiconductor field-effect transistors

The deep-level drain current transient spectroscopy (Id-DLTS) measurements of Al-doped SiC metal–oxide–semiconductor field-effect transistors (MOSFETs) strongly suggest that the reduction in the channel mobility at low temperatures is related to a shallow trap detectable at 70 K. Using the Shockley–Reed–Hall (SRH) theory, the level of this trap has been extracted to be around 0.15 eV below the conduction band minimum of SiC. Density functional theory (DFT) calculations of AlSiNCAlSi and AlSiOCAlSi defect complexes have found one configuration of the AlSiOCAlSi complex, which has a charge transition level within the SRH extracted trap level range. Therefore, we suggest that these AlSiOCAlSi defects are likely candidates for traps responsible for the channel mobility reduction.

Design, synthesis, structural characterization, molecular docking, antibacterial, anticancer activities, and density functional theory calculations of novel MnII, CoII, NiII, and CuII complexes based on pyrazolone-sulfadiazine azo-dye ligand

This study was designed to prepare novel metal chelates obtained from 4-((3-methyl-5-oxo-1-phenyl-pyrazol-4-yl)diazenyl)-N-(pyrimidin-2-yl) benzenesulfon amide (MPSA). They are characterized through CHN-analysis, spectroscopic (1HNMR, FT-IR, UV–Vis), mass, and TG analysis. The FT-IR and UV–visible spectra were related to the computed results and showed good conformity. The mass spectra determined that the ligand's molecular weight and chelates matched well with the found m/z values. The optimization for the studied chelates indicated the formation of distorted octahedral geometry for the prepared chelates. The B3LYP/6–311G** level for the free ligand and the B3LYP/6–311G**-LANL2DZ functional level for the metal ions in chelates were used in density functional theory (DFT) calculations. The results showed that the DFT computations match those of the experimental ones. Using the B3LYP/6–31G(d,p) basis set, TD-DFT/PCM was applied to determine the electronic spectral transitions of the produced compounds. Also, B3LYP/6–31G(d,p) has been utilized to implement the vibrational wavenumbers, and the results are reliable with the innovative ones. The antimicrobial activities of the compounds were experimentally established against a subsection of G+ and G- bacteria. The anticancer activities of the ligand were examined against some cell lines. The MCF7 cell line had the highest activity and was subjected to the anticancer effect of the ligand and its chelates. The cytotoxicity on normal cells was estimated against normal HSF cell lines. The outcomes demonstrated that chelates enhanced their cytotoxic and anticancer properties. Molecular docking mechanisms were done to establish how the obtained substances attach to the breast cancer-targeted protein binding sites,

Replica Exchange of Expanded Ensembles: A Generalized Ensemble Approach with Enhanced Flexibility and Parallelizability.

Generalized ensemble methods such as Hamiltonian replica exchange (HREX) and expanded ensemble (EE) have been shown effective in free energy calculations for various contexts, given their ability to circumvent free energy barriers via nonphysical pathways defined by states with different modified Hamiltonians. However, both HREX and EE methods come with drawbacks, such as limited flexibility in parameter specification or the lack of parallelizability for more complicated applications. To address this challenge, we present the method of replica exchange of expanded ensembles (REXEE), which integrates the principles of HREX and EE methods by periodically exchanging coordinates of EE replicas sampling different yet overlapping sets of alchemical states. With the solvation free energy calculation of anthracene and binding free energy calculation of the CB7-10 binding complex, we show that the REXEE method achieves the same level of accuracy in free energy calculations as the HREX and EE methods, while offering enhanced flexibility and parallelizability. Additionally, we examined REXEE simulations with various setups to understand how different exchange frequencies and replica configurations influence the sampling efficiency in the fixed-weight phase and the weight convergence in the weight-updating phase. The REXEE approach can be further extended to support asynchronous parallelization schemes, allowing looser communications between larger numbers of loosely coupled processors such as cloud computing and therefore promising much more scalable and adaptive executions of alchemical free energy calculations. All algorithms for the REXEE method are available in the Python package ensemble_md, which offers an interface for REXEE simulation management without modifying the source code in GROMACS.

Методология матричного моделирования многокомпонентных многопоточных многоступенчатых энергетических комплексов

Traditionally, heat transfer problems are solved in relation to two-flow systems in which heat exchange is carried out between hot and cold coolants. However, along with two-flow systems, there are often multiflow systems in which the number of coolant flows is three or more. In addition, each energy carrier stream may consist of several components, and the installation may include several stages. Thus, the development of universal approaches and methods for modeling, calculation, and optimization of multi-component multiflow multistage energy complexes within the framework of a unified methodology is an urgent scientific and practical task. A methodology of matrix formalization of modeling heat and mass transfer processes is based on methods and approaches of matrix description of heat and mass transfer systems in energy complexes. The approaches and methods of modeling energy power installations are summarized. Within the framework of the matrix description methodology, the rules and approaches to the development of models of heat and mass transfer processes are formulated in relation to multicomponent multiflow multistage energy complexes. The authors have proposed a solution to the inverse problems with and without considering a phase transition in coolants. Analysis of formulated and solved problems within the framework of the proposed methodology allows us to recommend the use of methods and approaches of matrix modeling of equipment to solve direct and inverse problems for multicomponent multiflow multistage energy complexes for various purposes.

Distance mapping overlap complexity metric for class-imbalance problems

Data complexity for class-imbalance problems is a hot topic in the field of data mining. Classical data complexity measures use techniques such as kNN, which computes the nearest neighbors of each instance. However, the kNN-based method to obtain the nearest neighbors of all instances is an NP-hard problem, which is not conducive to large-scale data complexity calculations. In order to solve this problem, from the global and local perspectives, four distance map complexity metric methods are proposed, and the complexity values is called the distance map overlap index (DMOI). Firstly, we use Mahalanobis distance or standardized Euclidean distance to calculate the distance of the instance to the center point of the data set, and arrange by the distance value of each instance. Then, according to the sequential label vector, iteratively searches the number of map cut-points for each class. Finally, according to the number of map cut-points of different classes, the DMOI of the data set is calculated. Experiments on 50 class-imbalanced datasets show that the DMOI method outperforms state-of-the-art complexity measures for class-imbalanced problems. Although there is still a gap between DMOI and ONB for rule-based or tree-based classifiers, the use of Pearson correlation coefficient shows that DMOI can effectively approximate ONB, and there is a strong positive correlation between them.

Super-Resolution Imaging of Sub-diffraction-Limited Pattern with Superlens Based on Deep Learning

The development of super-resolution imaging techniques has revolutionized our ability to study the nano-scale world, where objects are often smaller than the diffraction limit of traditional optical microscopes. Super-resolution superlenses have been proposed to solve this problem by manipulating the light wave in the near field. A superlens is a kind of metamaterial-based lens that can enhance the evanescent waves generated by nano-scale objects, utilizing the surface plasmon phenomenon. The superlens allows for the imaging of nano-scale objects that would otherwise be impossible to resolve using traditional lenses. Previous research has shown that nanostructures can be imaged using superlenses, but the exact shape of the superlens must be known in advance, and an analytical calculation is needed to reconstruct the image. Localized plasmon structured illumination microscopy is an approach to achieve super-resolution by imaging the superlens-enhanced evanescent wave with illumination shifts. This study proposes a new approach utilizing a conditional generative adversarial network to obtain super-resolution images of arbitrary nano-scale patterns. To test the efficacy of this approach, finite-difference time-domain simulation was utilized to obtain superlens imaging results. The data from the simulation were then used for deep learning to develop the model. With the help of deep learning, the inverse calculation of complex sub-diffraction-limited patterns can be achieved. The super-resolution feature of the superlens based on deep learning is investigated. The findings of this study have significant implications for the field of nano-scale imaging, where the ability to resolve arbitrary nano-scale patterns will be crucial for advances in nanotechnology and materials science.

Quasi-degenerate extension of local N-electron valence state perturbation theory with pair-natural orbital method based on localized virtual molecular orbitals.

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.

Dibutyltin(IV) formulations as potential antitubercular scaffold: DFT assisted emerging advances and mechanism of antitubercular action

Abstract The interplay between N,O-orthometallated, O,O′-chelated, and dibutyltin(IV) groups in biopotent hybrid formulations to combat tuberculosis is deciphered. The present study is concerned with design, generation, spectroscopic, and DFT-assisted structural characterization. It improves understanding of the structure-antitubercular activity relationship and mode of action of some dibutyltin(IV) formulations against Mycobacterium tuberculosis as possible antituberculosis agents. Dibutyltin(IV) formulations of the general formula Bu2SnLL′ (where LH = heterocyclic/non-fluorinated/fluorinated β-diketones and L′H = aminophenol/substituted aminophenols) were generated by the reaction of Bu2SnCl2 with sodium salts of the ligands in 1:1:1 molar ratio. The newly generated dibutyltin(IV) formulations were characterized with the assistance of spectroscopic techniques and mass studies. Computational calculations of some representative complexes (1 and 2) also supported the obtained spectral data. Antituberculosis activity analysis was performed on some representative dibutyltin(IV) complexes (1, 4, and 8). Out of these, complex 4 demonstrated the highest activity against Mycobacterium tuberculosis. The structure-antitubercular activity relationship and mechanism of action of the active complexes against M. tuberculosis were also investigated. An intercluster electron hopping mechanism of mode of action is suggested.

Electronic analysis of n-propyl xanthate complexes with group 12 metals: a theoretical-experimental study.

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. 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.

Rational design by DFT calculations of new metal complexes for photodynamic therapy based on an H2O2-Responsive Ir(III) photosensitizer activatable in physiological environment

A series of complexes based on the structure of an H2O2-responsive Ir(III) phenylpyridine(ppy)-containing complex were designed. The effect of changing the conjugation in the ppy ligands as well as of replacing the Ir(III) metal centre with the isoelectronic Os(II) were evaluated by means of DFT and its time-dependent formulation. The computational exploration of the photophysical properties of all the designed complexes suggest that the character of the low-lying singlet state represent the main factor affecting the region of absorption. In particular, for some of the Ir(III)-based complexes the change of the band character from mixed MLCT/LLCT to almost exclusively LLCT is essential for red-shifting the maximum absorption wavelength together with the destabilization of HOMO thus reducing the HOMO-LUMO energy gap; similarly, the replacement of Ir(III) with Os(II) converts the character of the band to mainly MLCT. The computed spin–orbit coupling constants and the triplet states’ energy confirm that all the designed complexes could, in principle, be able to generate the cytotoxic singlet oxygen under one-photon excitation by energy transfer from the triplet state of the photosensitizer to molecular oxygen, while the production of other types of ROS is precluded, similarly to the reference complex.

Approaching the Complete Basis Set Limit for Spin-State Energetics of Mononuclear First-Row Transition Metal Complexes.

Convergence to the complete basis set (CBS) limit is analyzed for the problem of spin-state energetics in mononuclear first-row transition metal (TM) complexes by taking under scrutiny a benchmark set of 18 energy differences between spin states for 13 chemically diverse TM complexes. The performance of conventional CCSD(T) and explicitly correlated CCSD(T)-F12a/b calculations in approaching the CCSD(T)/CBS limits is systematically studied. An economic computational protocol is developed based on the CCSD-F12a approximation and (here proposed) modified scaling of the perturbative triples term (T#). This computational protocol recovers the relative spin-state energetics of the benchmark set in excellent agreement with the reference CCSD(T)/CBS limits (mean absolute deviation of 0.4, mean signed deviation of 0.2, and maximum deviation of 0.8 kcal/mol) and enables performing canonical CCSD(T) calculations for mononuclear TM complexes sized up to ca. 50 atoms, which is illustrated by application to heme-related metalloporphyrins. Furthermore, a good transferability of the basis set incompleteness error (BSIE) is demonstrated for spin-state energetics computed using CCSD(T) and other wave function methods (MP2, CASPT2, CASPT2/CC, NEVPT2, and MRCI + Q), which justifies efficient focal-point approximations and simplifies the construction of multimethod benchmark studies.

Antioxidant Activity and DFT Calculations of Metal Complexes Derived from a Schiff Base Ligand: Synthesis, Characterization, and Biological Evaluation

AbstractMetal complexes derived from Schiff bases are known to have a wide range of applications, spanning the areas of material and medicinal sciences. Herein, a Schiff base ligand, (Z)‐2‐(((4‐chlorophenyl)imino)methyl)naphthalen‐1‐ol HL, was synthesized via a condensation reaction between 2‐hydroxy‐1‐naphthaldehyde and 4‐chloroaniline using methanol as a solvent in the presence of a catalytic amount of formic acid. The obtained ligand was further reacted with Mn(II), Ni(II), and Cu(II) using their acetate salts in a 1 : 2 stoichiometric ratio of metal to ligand to afford complexes C1–C3, respectively. Physicochemical and analytical techniques consisting of FTIR, UV‐Vis, elemental (CHN and metal content), TGA, HRMS, 1H, and 13 C NMR spectroscopy were deployed to establish the formation of the compounds. Results show that the ligand coordinated with the metal ions through the oxygen and nitrogen atoms of the phenolate and azomethine moieties, respectively, forming ON‐type complexes. Furthermore, the free ligand and its complexes were evaluated for their antioxidant activity compared to the standard (ascorbic acid) using an in vitro DPPH radical scavenging assay. From this investigation, C1 demonstrated higher radical scavenging activity than the free ligand, the complexes, and the standard (ascorbic acid). But the ligand has better scavenging activity than C2 and C3 at higher concentrations. DFT was also used to examine the electronic properties of the compounds, and the data obtained corroborated well with the experimental study.