Quantum Chemical Approach Research Articles

Graphene/MWCNT/copper-nanoparticle fabricated printed electrode for diclofenac detection in milk and drinking water: Electrochemical and in-silico analysis

This study investigates the electrochemical sensing of Diclofenac sodium. A single carbon printed electrode was modified with the combination of graphene (GRP), multi-walled carbon nanotube (MWCNT), and copper-nanoparticle (CuNP) blended with oleic acid (OA) (i.e. CuNP@OA) as working electrode material of the three-electrode system (i.e. GRP-MWCNT-CuNP@OA). Here, copper nanoparticles, being responsible for catalysis, are embedded on the matrix comprising of GRP and MWCNT which serves as the conductive matrix material for electrode. The OA acts as a stabilising agent for the active CuNPs. The chemical sensitivity feature (in terms of binding interaction) of the GRP-MWCNT-CuNP@OA composite model interacting with the Diclofenac has been examined by implementing quantum chemical calculation approaches like molecular modelling, semi-empirical, QTAIM, and NCI-plot based tools. Some useful and important properties have also been examined using electronic parameters such as HOMO, LUMO, HOMO-LUMO gap, charge transfer (CT), QTAIM-based topological parameters, etc. which could indeed be helpful for the experimentalists in understanding the structural, stability/energetics, and electronic features of the probed composite models at nano-level. Further, the characterization of the composite was carried out through some sophisticated characterization techniques like scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX), and powder XRD. Cyclic voltammetry (CV) is used for studying stability of the composite and chemical kinetics of the oxidation of Diclofenac sodium. Differential pulse voltammetry (DPV) was used to evaluate the sensing performance of the above-mentioned material by determining the lower range detection limit of Diclofenac (57.7 nM) and linear range (17.41 μM – 206.45 μM) of the electrochemical sensor. Further to validate the results obtained, real sample analysis was performed using the developed electrode in drinking water and milk spiked with Diclofenac.

Theoretical Analysis of Superior Photodegradation of Methylene Blue by Cerium Oxide/Reduced Graphene Oxide vs. Graphene.

Density functional theory and a semi-empirical quantum chemical approach were used to evaluate the photocatalytic efficiency of ceria (CeO2) combined with reduced graphene oxide (rGO) and graphene (GP) for degrading methylene blue (MB). Two main aspects were examined: the adsorption ability of rGO and GP for MB, and the separation of photogenerated electrons and holes in CeO2/rGO and CeO2/GP. Our results, based on calculations of the adsorption energy, population analysis, bond strength index, and reduced density gradient, show favorable energetics for MB adsorption on both rGO and GP surfaces. The process is driven by weak, non-covalent interactions, with rGO showing better MB adsorption. A detailed analysis involving parameters like fractional occupation density, the centroid distance between molecular orbitals, and the Lewis acid index of the catalysts highlights the effective charge separation in CeO2/rGO compared to CeO2/GP. These findings are crucial for understanding photocatalytic degradation mechanisms of organic dyes and developing efficient photocatalysts.

Exploration of sensing behavior B3O3 quantum dot toward methyl halides; a quantum chemical approach

In this study, B3O3 quantum dot has been used for sensing of various methyl halides for the first time. The suitable cavity of B3O3 makes it more suitable for the sensing of variety of analytes. The three, very simple and most important methyl halides (CH3F, CH3Cl and CH3Br) are selected to adsorb on B3O3 surface. Density functional theory (DFT) method with appropriate basis set was implemented. Among the considered complexes, methyl bromide complex CH3Br@B3O3) showed higher interaction energy of −16.90 kcal mol−1. The noncovalent interaction (NCI) analysis identified the existence of van der Waals interactions among all analytes and adsorbent. The density of state (DOS) and natural bond orbital (NBO) charges analyses identified the charge transfer and conductive properties of B3O3 nanosheet after interaction with alkyl halides. Frontier molecular orbital study revealed the electronic attributes of considered complexes. It is revealed that B3O3 quantum dot can be a very good choice for sensing of methyl halides and could be helpful for monitoring and reducing the environmental pollution.

Metrological aspects of a gas-phase DFT/B3LYP quantum-chemical approach to prioritize radical scavenging activity among a group of olive oil phenols

Metrological aspects of a gas-phase DFT/B3LYP quantum-chemical approach to prioritize radical scavenging activity among a group of olive oil phenols

Pentaphosphorylation via the Anhydride of Dihydrogen Pentametaphosphate: Access to Nucleoside Hexa- and Heptaphosphates and Study of Their Interaction with RibonucleaseA.

Pentametaphosphate is the little studied cyclic pentamer of the metaphosphate ion, [PO3]5 5-. We show that the doubly protonated form of this pentamer can be selectively dehydrated to provide the anhydride [P5O14]3- (1). This trianion is the well-defined condensed phosphate component of a novel reagent for attachment of a pentaphosphate chain to biomolecules all in one go. Here, we demonstrate by extending adenosine monophosphate (AMP) and uridine monophosphate (UMP) to their corresponding nucleoside hexaphosphates, while adenosine diphosphate (ADP) and uridine diphosphate (UDP) are phosphate chain-extended to the corresponding nucleoside heptaphosphates. Such constructs are of interest for their potential biological function with respect to RNA-processing enzymes. Thus, we go on to investigate in detail the interaction of the polyanionic constructs with ribonuclease A, a model protein containing a polycationic active site and for which X-ray crystal structures are relatively straightforward to obtain. This work presents a combined experimental and quantum chemical approach to understanding the interactions of RNase A with the new nucleoside hexa- and heptaphosphate constructs.

Using Adiabatic Energy Splitting To Compute Dexter Energy Transfer Couplings.

Dexter energy transfer and transport (DET) are of broad interest in energy science, and DET rates depend on electronic couplings between donor and acceptor species. DET couplings are challenging to compute since they originate from both one- and two-particle interactions, and the strength of this interaction drops approximately exponentially with donor-acceptor distances. Using adiabatic energy splitting to compute DET couplings has advantages because adiabatic states can be calculated directly using conventional quantum chemical methods. We describe a minimum energy splitting method to compute the DET coupling by altering molecular geometries to drive the systems into a T1/T2 energy quasi-degenerate-activated DA complex. We explore the accuracy of various quantum chemical approaches to calculate the Dexter couplings.

Quantum chemical modeling of alkane 2D monolayer formation on graphene

The paper presents a quantum chemical approach for assessment of the thermodynamic parameters of association for alkanes CnH2n+2 (n = 6–14) and polyaromatic hydrocarbons (PAH) of the coronene series as model structures of the graphene surface within the framework of semiempirical methods. The enthalpy, entropy and Gibbs energy of formation and binding for alkanes with PAH were calculated using the PM3 and PM6-DH2 methods. It is shown that an adequate description of the interactions in the regarded complexes requires the use of PM6-DH2 method, since it contains corrections for dispersion interactions and hydrogen bonds. The parallel orientation of the alkane molecule relative to the coronene plane is proved to be more energetically preferable than perpendicular one, which is consistent with experimental data.Intermolecular C–H/π interactions are revealed to be crucial in the 2D film formation of alkanes on graphene/graphite. While interactions between alkane molecules make a destabilizing contribution due to the implementation of energetically unfavorable types of intermolecular CH/HC interactions. This stipulates a threshold chain length of alkanes capable of film formation on the graphene/graphite surface at standard temperature: 14 and 19 carbon atoms for parallel and perpendicular oriented alkanes, respectively. The obtained threshold values of the alkane chain length, as well as the geometric parameters of their orientation in 2D monolayers on the graphene/graphite surface are consistent with available experimental data.

Proton Solvation Free Energy in Liquid Ammonia at Room Temperature

AbstractThe investigation of experimental pKa values in liquid ammonia at room temperature for a series of 30 organic compounds containing eight distinct chemical groups enabled an accurate assessment of the proton ammoniation free energy. The deprotonation free energies, as well as the solvation free energies of acids and conjugate bases, were computed using a combination of quantum chemical and electrostatic approaches. Two thermodynamic schemes were employed to reproduce experimental pKa values while scanning a large interval of probable values of proton ammoniation free energy. The desired quantity corresponded to the lowest mean absolute deviation of the overall reproduced pKa values of the series. As a result, the proton ammoniation free energy was evaluated to be −275.0 Kcal/mol. Test results show that this proposed value is well suited for pKa calculation in liquid ammonia at room temperature.

Advancing optoelectronic characteristics of Diketopyrrolopyrrole-Based molecules as donors for organic and as hole transporting materials for perovskite solar cells

A stable and efficient hole-transport material (HTM) is crucial for high-performance perovskite solar cells (PSCs). A 2,2′,7,7′-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9′-spirobifluorene (Spiro-MeOTAD) being used widely to prepare highly efficient PSCs. However, Spiro-MeOTAD has some limitations due to its complex synthesis, which increases its cost, and it also requires dopants to improve its performance. Therefore, we designed thirteen unique small-molecule-based HTMs (MK1-MK13), which are easy to synthesize, highly cost-effective, and don’t require dopants to prepare efficient PSCs. Their electrical and optical properties are then investigated theoretically using advanced quantum chemical approaches. The designed molecules showed lower energy gaps and improved optical and optoelectronic characteristics because of the improved phase inversion geometry. The detailed photo-physical and optoelectronic characteristics have been studied using density functional theory (DFT) and time-dependent (TD-DFT) calculations. Moreover, we investigated the impact of holes and electrons and the density of states, open-circuit voltage, frontier molecular orbital, transition density matrix, and other structural and photovoltaic characteristics of these materials. Among these, the MK3 molecule possesses the much narrower optical band gap of 1.04 eV and absorbance (λ max) of 684 nm, respectively. In addition, a profound investigation of the MK3/PC61BM blend shows excellent charge transfer at the acceptor–donor interface. Therefore, our proposed technique is necessary for generating appropriate photovoltaic materials for efficient optoelectronic devices and is helpful in further advancing the field.

Investigating the Potential Pharmacological Applications of 5-Hydroxy-2 (hydroxymethyl)-4H pyran-4 one through Electronic Characterization and MM-GBSA Studies for Oxidative Stress and Tyrosinase Inhibition: A Quantum Chemical Approach

The study thoroughly examines the possible applications of 5 Hydroxy – 2 (hydroxymethyl) – 4 H pyran – 4 one. Through Quantum chemical analysis, the research rigorously evaluates the compound's properties, including its optoelectronics, geometrical structure, and intermolecular interactions. The geometrical structure parameters were optimized using a 6–311++G(d,p) basis set in the DFT/B3LYP method, and the resulting geometrical factors were then scaled to calculate probable vibrational wavenumbers. The Mulliken charges and MEP map were used to locate electrophilic, nucleophilic regions, and chemical reactivity was described using FMOs and Fukui function assessments. The multiwfn was employed to investigate topological analysis (surface distance projection and Hirshfeld maps). The UV-visible spectrum was used to estimate the absorption of maximum wavelengths, which was then correlated with the TD-DFT, DOS, and band structure investigations. The study also calculated parameters, including Total Energies, ZPE, Entropy, Dipole moment, and Heat Capacity for monomeric and dimeric units. Pharmacokinetics were used to determine the biological characteristics of the compound. The MM-GBSA simulation was performed, and the results suggest that this compound has the potential to be an enhancing anti-oxidant protection agent due to its high binding affinity and intermolecular interactions. These findings are crucial in developing therapeutic agents with pharmacological effects and potential toxicities.

From Chemical Drawing to Electronic Properties of Semiconducting Polymers in Bulk: A Tool for Chemical Discovery.

A quantum chemistry (QC)/molecular dynamics (MD) scheme is developed to calculate electronic properties of semiconducting polymers in three steps: (i) constructing the polymer force field through a unified workflow, (ii) equilibrating polymer models, and (iii) calculating electronic structure properties (e.g., density of states and localization length) from the equilibrated models by QC approaches. Notably, as the second step of this scheme is generally the most time-consuming one, we introduce an alternative method to compute thermally averaged electronic properties in bulk, based on the simulation of a polymer chain in the solution of its repeat units, which is shown to reproduce the microstructure of polymer chains and their electrostatic effect (successfully tested for five benchmark polymers) 10 times faster than state-of-the-art methods. In fact, this scheme offers a consistent and speedy way of estimating electronic properties of polymers from their chemical drawings, thus ensuring the availability of a homogeneous set of simulations to derive structure-property relationships and material design principles. As an example, we show how the electrostatic effect of the polymer chain environment can disturb the localized electronic states at the band tails and how this effect is more significant in the case of diketopyrrolopyrrole polymers as compared to indacenodithiophene and dithiopheneindenofluorene ones.

In-Electrospray source Hydrogen/Deuterium exchange coupled to multistage fragmentation for the investigation of the protonation and fragmentation pathways of gas phase ions.

Identification of molecules in complex natural matrices relies on matching the fragmentation spectra of ions under investigation and the spectra acquired for the corresponding analytical standards. Currently, there are many databases of experimentally measured tandem mass spectrometry spectra (such as NIST, MzCloud, and Metlin), and considerable progress has been made in the development of software for predicting tandem mass spectrometry fragments in silico using combinatorial, machine learning, and quantum chemistry approaches (such as MetFrag, CFM-ID, and QCxMS). However, the electrospray ionization molecules can be ionized at different sites (protonated or deprotonated), and the fragmentation spectra of such ions are different. Here, we are using the combination of the in-ESI source hydrogen/deuterium exchange reaction and MSn fragmentation for the investigation of the fragmentation pathways for different protomers of organic molecules. It is shown that the distribution of the deuterium in the fragment ions reflects the presence of different protomers. For several molecules, the distribution of deuterium was traced up to the MS5 level of fragmentation revealing many unusual and unexpected effects. For example, we investigated the loss of HF from the ciprofloxacin and norfloxacin ions and observed that for ions protonated at -COOH group, the eliminating hydrogen always comes from -NH group. When ions are protonated at another site, the elimination of hydrogen with a probability of 30% occurs from the -NH group, and with a probability of 70%, it originates from other sites on the molecule. Such effects were not described previously. Quantum chemical simulation was used for the verification of the protonated structures and simulation of the corresponding fragmentation spectra.

Electrochemical and quantum chemical approaches to the study of dopamine sensing using bentonite and l-cysteine modified carbon paste electrode

This work presents a significant investigation involving both electrochemical experiment and quantum chemical simulation approaches. The objective was to characterize the electrochemical detection of dopamine (DA). The detection was carried out using a modified carbon paste electrode (CPE) incorporating bentonite (Bent) and l-cysteine (CySH) (named as CySH/Bent/CPE). To understand and explain the oxidation mechanism of DA on the CySH/Bent modified electrode surface, the coupling of the two approaches were exploited. The CySH/Bent/CPE showed excellent electroactivity toward DA such as good sensibility, selectivity, stability, and regenerative ability. The developed sensor shows a dynamic linear range from 0.8 to 80 μM with a limit of detection and quantification of 0.5 μM and 1.5 μM, respectively. During the quantitative analysis of DA in presence of ascorbic acid (AA) and uric acid (UA) the electrochemical oxidation signals of AA, DA, and UA distinctly appear as three separate peaks. The potential differences between the peaks are 190 mv, 150 mv, and 340 mV for the AA–DA, DA–UA, and AA–UA oxidation pairs, respectively. These observations stem from square wave voltammetry (SWV) studies, along with the corresponding redox peak potential separations. The developed sensor is simple and accurate to monitor DA in human serum samples. On the other hand, CySH acts as an electrocatalyst on the CySH/Bent/CPE surface by increasing its active electron transfer sites, as suggested by the quantum chemical modeling with analytical results of Fukui. Furthermore, the voltammetric results obtained agree well with the theoretical calculations.

AB-G0W0: A practical G0W0 method without frequency integration based on an auxiliary boson expansion.

Common G0W0 implementations rely on numerical or analytical frequency integration to determine the G0W0 self-energy, which results in a variety of practical complications. Recently, we have demonstrated an exact connection between the G0W0 approximation and equation-of-motion quantum chemistry approaches [J. Tölle and G. Kin-Lic Chan, J. Chem. Phys. 158, 124123 (2023)]. Based on this connection, we propose a new method to determine G0W0 quasiparticle energies, which completely avoids frequency integration and its associated problems. To achieve this, we make use of an auxiliary boson (AB) expansion. We name the new approach AB-G0W0 and demonstrate its practical applicability in a range of molecular problems.

New Pyranone Derivatives and Sesquiterpenoid Isolated from the Endophytic Fungus Xylaria sp. Z184.

The fungus Xylaria sp. Z184, harvested from the leaves of Fallopia convolvulus (L.) Á. Löve, has been isolated for the first time. Chemical investigation on the methanol extract of the culture broth of the titles strain led to the discovery of three new pyranone derivatives, called fallopiaxylaresters A-C (1-3), and a new bisabolane-type sesquiterpenoid, named fallopiaxylarol A (4), along with the first complete set of spectroscopic data for the previously reported pestalotiopyrone M (5). Known pyranone derivatives (6-11), sesquiterpenoids (12-14), isocoumarin derivatives (15-17), and an aromatic allenic ether (18) were also co-isolated in this study. All new structures were elucidated by the interpretation of HRESIMS, 1D, 2D NMR spectroscopy, and quantum chemical computation approach. The in vitro antimicrobial, anti-inflammatory, and α-glucosidase-inhibitory activities of the selected compounds and the crude extract were evaluated. The extract was shown to inhibit nitric oxide (NO) production induced by lipopolysaccharide (LPS) in murine RAW264.7 macrophage cells, with an inhibition rate of 77.28 ± 0.82% at a concentration of 50 μg/mL. The compounds 5, 7, and 8 displayed weak antibacterial activity against Staphylococcus areus subsp. aureus at a concentration of 100 μM.

Growth, experimental and theoretical investigation on the nonlinear optical, vibrational, and electronic properties of L-2-aminobutyric acid D-methionine crystal: a combined experimental and quantum chemical approach

Growth, experimental and theoretical investigation on the nonlinear optical, vibrational, and electronic properties of L-2-aminobutyric acid D-methionine crystal: a combined experimental and quantum chemical approach

Intermolecular interaction of azide, cyano and alkyne-N-phenethylacetamide dimers: Experimental and quantum chemical approach

In this study, we present the synthesis and structure characterization by single-crystal X-ray Diffraction (SC-XRD), Ultraviolet Spectroscopy (UV), Fourier Transform Infrared Spectroscopy (FTIR), Nuclear Magnetic Resonance (NMR) and High-resolution Mass Spectrometry (HRMS) of 2-azido-N-phenethylacetamide (4) and 2-cyano-N-phenethylacetamide (6). Further, Density Functional Theory (DFT) was employed to get a better insight regarding the properties exhibited by the compounds. The computational chemistry has been used to explain and investigate the bimolecular nucleophilic substitution (SN2) and concerted acyl substitution mechanisms for the synthesis of compounds 4 and 6, respectively. Additionally, intrinsic reaction coordinate (IRC) calculations confirm the transition state for these reactions. The X-ray diffraction analysis showed that the compounds 4 and 6 crystallized as monoclinic systems, in space group P21/c and P21/n, respectively. The Hirshfeld Surface Analysis revealed that the main contributions in the crystal packing have H···H, H···N/N···H, H···C/C···H and H···O/O···H interactions. The frontier molecular orbital energies were calculated and the HOMO-LUMO energy gap of 4 and 6 were 10.011 and 10.278 eV, respectively. Theoretical values of electronic transitions, vibrational frequencies and NMR chemical shifts were calculated and compared with experimental results, they all showed good results.

Chromones from the endophytic fungus Bipolaris eleusines

Eight previously undescribed chromones eleusineketones A–H (1–8), as well as eight known compounds (9–16), were isolated from the endophytic fungus Bipolaris eleusines. These planar structures were created using an in-depth analysis of their spectral data, which included 1D, 2D, and HRESIMS data. Furthermore, the absolute configurations of compounds 1, 2, and 6 were determined by spectroscopic analysis and quantum chemical computational approaches, and compound 5 was determined by single-crystal X-ray diffraction analysis. The cytotoxic activity assay revealed that compounds 1 and 5 both inhibited MDA-MB-231 cells with IC50 values of 14.48 μM and 17.99 μM, respectively.

Impact of end‐capped engineering on the optoelectronic characteristics of pyrene‐based non‐fullerene acceptors for organic photovoltaics

AbstractPyrene‐based molecules are being explored as prospective fullerene‐free acceptors for organic solar cells (OSCs), due to their easy accessibility, structural planarity, and excellent electron delocalization. In this work, we successfully designed and analyzed pyrene‐based acceptor materials (QL1–QL8) to investigate their photophysical and electro‐optical parameters. Various geometric parameters were computed at the MPW1PW91/6‐31G(d,p). Advanced quantum chemical approaches were employed to characterize the molecules. All the tailored molecules (QL1–QL8) exhibit a lower bandgap than the reference (R), signifying their superiority. Among these, QL8 was found to have a maximum absorption (λmax) at 791.37 nm and an optical bandgap (ELUMO − EHOMO) minimum of 2.11 eV. Redshifted absorption spectra are observed in both gaseous and solvent phases for all the designed (QL1–QL8) molecules in contrast to R. Among these, QL4 exhibits the highest light harvesting efficiency (0.9826), and open‐circuit voltage. A detailed donor–acceptor investigation of QL8/PBDB‐T revealed the marvelous charge switching at the donor–acceptor interface. The approach used in this study is anticipated to facilitate the manufacturing of highly efficient OSC molecules.

Fault-Tolerant Quantum Algorithm for Symmetry-Adapted Perturbation Theory

The efficient computation of observables beyond the total energy is a key challenge and opportunity for fault-tolerant quantum computing approaches in quantum chemistry. Here, we consider the symmetry-adapted perturbation-theory (SAPT) components of the interaction energy as a prototypical example of such an observable. We provide a guide for calculating this observable on a fault-tolerant quantum computer while optimizing the required computational resources. Specifically, we present a quantum algorithm that estimates interaction energies at the first-order SAPT level with a Heisenberg-limited scaling. To this end, we exploit a high-order tensor-factorization and block-encoding technique that efficiently represents each SAPT observable. To quantify the computational cost of our methodology, we provide resource estimates in terms of the required number of logical qubits and Toffoli gates to execute our algorithm for a range of benchmark molecules, also taking into account the cost of the eigenstate preparation and the cost of block encoding the SAPT observables. Finally, we perform the resource estimation for a heme and artemisinin complex as a representative large-scale system encountered in drug design, highlighting the performance of our algorithm in this new benchmark study and discussing possible bottlenecks that may be improved in future work. Published by the American Physical Society 2024