DFT Methodology Research Articles

Exploring rotational isomerism of fluorescent diarylethenes comprising 2-naphthyl and regioisomeric oxazoyl groups. A combined experimental and computational study

In the paper a phenomenon of rotational (conformational) isomerism within 1,2-diarylethenic compounds (DAE) comprising heteroarene ring of oxazole is explored on the example of the fluorescent naphthyl-vinyl-oxazole framework. In this regard three regioisomers of a n-(2-(naphthalen-2-yl)vinyl)oxazole molecule (nNVOx), differing in the oxazole substitution pattern (n = 2, 4, 5), are synthesized and methodically investigated by means of electronic UV–Vis spectroscopy combined with chemometric methods for spectral data analysis. Design of the experiments and interpretation of their output is additionally supported by quantum-chemical simulations based on the (TD) DFT methodology. As the result, all the studied nNVOx compounds are unveiled to simultaneously occur in form of at least two non-equivalent rotational isomers, varying in the conformation taken by the arene moieties with respect to the central vinyl fragment. The individual rotamers are then demonstrated to exhibit non-identical spectroscopic properties expressed by differences in corresponding absorption and fluorescence profiles, thereby ultimately confirming the impact of rotamerism onto the investigated molecular systems.

Alkali Metal‐Doped Fullerenes as Hydrogen Storage—A Quantum Chemical Investigation

AbstractThe quest for alternative energy sources has been spurred by the drawbacks and environmental risks of fossil fuels, with hydrogen emerging as a viable contender. But finding materials that can effectively store hydrogen with the best adsorption energy is a major obstacle to building a hydrogen‐based economy. As a result, a significant amount of research has been conducted worldwide to examine fullerene's (C60) potential for hydrogen adsorption. The results of extensive DFT calculations are presented here, pertaining to the adsorption of hydrogen molecules onto fullerenes doped with alkali metals, namely Rubidium (Rb), Ceasium (Cs), and Fransium (Fr). The study analyzes a number of parameters, such as global properties, electronic, optical, and surface annihilation energy. These analyses are performed using the Gaussian 09 simulation package with the 6–31G/B3LYP level of theory DFT methodology. The findings show that an exothermic process is involved in the adsorption of hydrogen onto fullerene doped alkali elements, as evidenced by the negative adsorption energy. The attractive interactions between the polarized dipole of hydrogen molecules and the surface dipole of doped fullerenes can be the cause of this exothermicity. These results imply that fullerenes decorated with alkali metals are promising as likely hydrogen storage media.

Structural activity of synthesized pyrimidine-thiophene and pyrimidine-thiadiazole conjugates as anticancer agents

New pyrimidine linked thiophene conjugates 5a-d and thiadiazole conjugates 7a-d through a carboxamide bridge were synthesized and characterized by the spectral data (IR, NMR and mass). Exploration of the isolated conjugates’ characteristics using DFT methodology revealed that they had angular configurations with distinctive outline of the FMO’s belonging to the thienyl- and thiadiazolyl-pyrimidine classes. In accordance, the FMO’s energy values of these analogues disclosed reduced energy gap (ΔEH-L=3.66–3.86 eV) than the parent 4 (4.49 eV) and may be arranged as: 7c < 7d < 5c < 5d < 5a < 5b < 7b < 7a < 4. Meanwhile, the cytotoxic effectiveness of the synthesized conjugates was assessed against different cancer cell lines using IC50 values in comparison to 5-Fu, drug reference. The data showed that the acrylamide derivative 4 exhibited the most potent cytotoxicity against MCF-7 and PC3 (IC50 6.11 ± 0.10 and 7.19 ± 0.04 μM, respectively). Moreover, the carbonic anhydrases inhibitory effect on hCA IX and hCA IIX have been evaluated, using acetazolamide (as standard), showing greater impact on hCA IX compared to hCA IIX. Molecular docking has been applied to investigate the nature of the binding interactions with the target amino acid residues, and it disclosed that the pyrimidine-thiophene conjugates 5d and 5c had the highest binding scores. Finally, the SwissADME pharmacokinetic properties of synthesized conjugates indicated that the acrylamide compound 4 exhibited acceptable pharmacokinetic manners, such GI absorption, solubility, no BBB permeation, and slight CYP450 inhibition, implying a promising therapeutic candidate.

One dimensional water chain as a zipper in a new polymorph of trans [Cu(vanilin)2(H2O)2].2(H2O) crystal–A case of water induced polymorphism

A new polymorph [Cu(II)(vanillin)2(H2O)2].2(H2O) has been synthesized and characterized by single crystal X-ray structural studies. Two other crystals having same formula and coordination unit but differing supramolecular arrangement due to slightly different role played by water molecules have already been reported in the literature [B. Kozlevˇcar et al. Z. Naturforsch., B: Chem. Sci. 2005, 60, 1273][Kozlevčar et al. Acta Chim. Slov. 2005, 52, 40–43]. The current compound is another polymorph in this system which has arisen again due to a different supramolecular arrangement which is water induced. Hirshfeld surface and energy framework analysis have been employed to compare these three polymorphs by assessing the nature of intermolecular interactions. In the current compound strong OH···O hydrogen bonding interactions between coordinated water molecules and –OH group attached to vanillin ligand leads to parallel alignment of successive coordination units leading to a supramolecular ribbon topology that runs along the crystallographic a-axis. A zigzag chain of single file water chain is positioned in between successive ribbons which acts as a zipper giving rise to a 2D supramolecular arrangement of the molecular complexes. In two other reported polymorphs instead of a single file water chain a cyclic water motif has been observed. The electronic structure of the complex explored using DFT methodology. This set of three polymorphs is an interesting example of water induced polymorphism.

Complete degradation of propranolol by a water falling film non-thermal plasma reactor: The effects of input power and plasma gases on transformation pathway

Propranolol, a beta-blocker, is a widely used drug for cardiovascular diseases. A synthetic sample containing propranolol (PRO) solution at native pH was recirculated up to ten times through an original coaxial non-thermal plasma reactor with a water falling film. Different discharge conditions, feed gasses, and power greatly influenced the extent of PRO degradation and the abundance of degradation products. The highest degradation rates were achieved in Ar plasma, either pure or in a mixture with O2, with over 70% of PRO degraded after only two passes through the DBD reactor. The full non-thermal plasma treatment was followed by a minimal change of pH value and conductivity. On the other hand, ambient air as the feed gas resulted in 60% of PRO degradation rate after the full treatment and contributed to a major drop in pH value and an increase in the conductivity of the treated solution. The structures of 47 degradation products in all three gases were identified and the degradation pathway is proposed, supported by DFT methodology. Scavenging experiments demonstrated that hydroxyl radical was predominant when plasma was generated using ambient air and Ar, while it had a minimal effect on the degradation in the mixture of Ar and O2. The desired level of propranolol decomposition was achieved only by the adjustment of the nonchemical parameters of the treatment, such as plasma gas composition and power. These results imply that a non-thermal plasma reactor is a highly effective method for pharmaceutical wastewater treatment, with no catalysts added.

Vibrational spectroscopy of interstellar PAHs: 1-cyanonaphthalene and 2-cyanonaphthalene

In this work, we present a comprehensive experimental and theoretical study of the vibrational spectra of PAH molecules recently detected in the interstellar medium: 1-cyanonaphthalene and 2-cyanonaphthalene. The room temperature IR spectra of 1- and 2-cyanonaphthalene in the region 100–3100 cm−1 and their vibrational Raman spectra in the region 35–3100 cm−1 are reported here for the first time. A detailed spectral analysis is carried out using quantum chemical calculations employing the DFT methodology. Anharmonic corrections using the VPT2 method yield excellent agreement with the experimental spectra. A re-investigation of the vibrational spectrum of the parent molecule: naphthalene validates the experimental and theoretical methods used. A consistent set of assignments is reported for the fundamental bands of 1- and 2-cyanonapththalene. The experimental and theoretical data presented here would be useful inputs for modelling the role of cyanonaphthalene in astrophysical processes.

A Theoretical Investigation for Exploring the Potential Performance of Non-Fullerene Organic Solar Cells Through Side-Chain Engineering Having Diphenylamino Groups to Enhance Photovoltaic Properties.

The development of ecofriendly fabrication phenomenon is essential requirement for commercialization of non-fullerene acceptors. Recently, end-capped modeling is employed for computational design of five non-fullerene acceptors to elevate various photovoltaic properties. All new molecules are formulated by altering the peripheral acceptors of CH3-2F and DFT methodology is employed to explore the opto-electronic, morphological and charge transfer analysis. From the computational investigation, all reported molecules manifested red shifted absorption with remarkable reduced band gap. Among investigated molecules, FA1-FA3 evinced effectively decreased value of band gaps and designed molecules have low excitation energy justifying proficient charge transference. The lower values of binding energy of FA1 and FA2 suggest their facile exciton dissociation leading to improved charge mobility. By blending with J61 donor, FA4 have sufficiently enhanced value of VOC (1.72eV) and fill factor (0.9228). Energy loss of the model (R) is 0.57eV and statistical calculation demonstrate that all our modified molecules except FA3 has profoundly reduced energy loss compelling in its pivotal utilization. From accessible supportive outcomes of recent investigation, it is recommended that our modified chromophore exhibit remarkable noteworthy applications in solar cells for forthcoming innovations.

The Identification of Structural Changes in the Lithium Hexamethyldisilazide-Toluene System via Ultrasonic Relaxation Spectroscopy and Theoretical Calculations.

Ultrasonic absorption measurements were carried out over a wide concentration and temperature range by means of a pulse technique to examine the structural mechanisms and the dynamical properties in lithium hexamethyldisilazide (LiHMDS)-toluene solutions. Acoustic spectra revealed two distinct Debye-type relaxational absorptions attributed to the formation of trimers from dimeric and monomer units and to the formation of aggregates between a LiHMDS dimer and one toluene molecule in low and high frequencies, respectively. The formation of aggregates was clarified by means of molecular docking and DFT methodologies. The aggregation number, the rate constants and the thermodynamic properties of these structural changes were determined by analyzing in detail the concentration-dependent relaxation parameters. The low-frequency relaxation mechanism dominates the acoustic spectra in the high LiHMDS mole fractions, while the high-frequency relaxation influences the spectra in the low LiHMDS mole fractions. In the intermediate mole fraction region (0.25 to 0.46), both relaxations prevail in the spectra. The adiabatic compressibility, the excess adiabatic compressibility and the theoretically estimated mean free length revealed a crossover in the 0.25 to 0.46 LiHMDS mole fractions that signified the transition from one structural mechanism related with the hetero-association of LiHMDS dimers with toluene molecules to the other structural mechanism assigned to the formation of LiHMDS trimers. The combined use of acoustic spectroscopy with theoretical calculations permitted us to disentangle the underlying structural mechanisms and evaluate the volume changes associated with each reaction. The results were compared with the corresponding theoretically predicted volume changes and discussed in the context of the concentration effect on intermolecular bonding.

How do quantum chemical descriptors shape hydrogen atom abstraction reactivity in cupric-superoxo species? A combined DFT and machine learning perspective

Employing a fusion of DFT and ML methodologies incorporating fifteen quantum chemical descriptors, we have elucidated the factors governing the reactivity of cupric-superoxo species.

The ternary phase diagram of nitrogen doped lutetium hydrides can not explain its claimed high Tc superconductivity

This paper presents the results of an extensive structural search of ternary solids containing lutetium, nitrogen and hydrogen. Based on thousands of thermodynamically stable structures the convex hull of the formation enthalpies is constructed. To obtain the correct energetic ordering, the highly accurate RSCAN DFT functional is used in high quality all-electron calculations, eliminating possible pseudopotential errors. In this way, a novel lutetium hydride structure (HLu2) is found that is on the convex hull. An electron phonon analysis however shows that it is not a candidate structure for near ambient superconductivity. Besides this structure, which appears to have been missed in previous searches, possibly due to different DFT methodologies, our results agree closely with the results of previously published structure search efforts. This shows, that the field of crystal structure prediction has matured to a state where independent methodologies produce consistent and reproducible results, underlining the trustworthiness of modern crystal structure predictions. Hence it is quite unlikely that a structure, that would give rise within standard BCS theory to the superconducting properties, claimed to have been observed by Dasenbrock-Gammon et al (2023 Nature 615 244), exists. This solidifies the evidence that structures with high Tc conventional superconductivity, that could give rise to the experimental claims, do not exist in this material.

Conformational effects in the vibrational and electronic spectra of propionaldehyde: Experimental and theoretical studies.

We report here investigations on conformational effects in the vibrational and electronic spectra of the propionaldehyde (propanal) molecule using FTIR (600-3200cm-1) and vacuum ultraviolet (VUV) synchrotron radiation photoabsorption (52 500-85 000cm-1) spectroscopy respectively. Detailed theoretical calculations (using DFT and TDDFT methodologies) on ground and excited states of the cis and gauche conformers of propanal are performed; a comprehensive spectral analysis of the IR and VUV spectra is presented. A reinvestigation of the IR spectrum reveals several new bands assigned to the gauche conformer based on theoretical calculations. The VUV spectrum exhibits rich Rydberg series structure assigned to ns, np and nd series converging to the first ionization potentials of the two conformers. Earlier assignments of the 3s cis and gauche origins are revised in addition to extending Rydberg series analysis to several higher members. Vibronic bands accompanying the 3s, 4s and 4p Rydberg states are assigned using estimated vibrational frequencies of cis and gauche conformers in the cationic ground state. Simulated potential energy curves of the first few excited states (singlets and triplets) of cis and gauche conformers of propanal help in gaining insights into photodissociation mechanisms and possible conformational effects therein.

Towards Development of High-Performance Perovskite Solar Cells Based on Pyrrole Materials for Hole Transport Layer by Using Computational Approach

Perovskite solar cells (PSCs) have emerged as innovative materials in advanced photovoltaic technology due to their enhanced efficiency and good stability. While considering role of dopant materials in HTMs especially Spiro-OMeTAD through previous studies, a bi-functional dopant named PFPPY has been brought into special attention. Based on framework of experimentally synthesized PFPPY, five dopant molecules (P1–P5) have been designed through structural alterations at peripheral sites. These newly developed molecules, sharing a common core i.e. 1,4-dihydropyrrolo[3,2-b]pyrrole (PPY), were then theoretically studied and related to reference via computational approach. Distribution of frontier molecular orbitals (FMOs) along with density of states, spectral properties, reorganizational energies, binding energy, and transition density matrix analysis was practiced at [Formula: see text]B97XD functional using DFT and TD–DFT methodology. Bathochromic shift of absorption (in dichloromethane) was clearly observed for all designed dopants (P1–P5) than reference PFPPY which sets the ways for reduced optical band gaps ([Formula: see text]. The energy gaps ([Formula: see text] of these five novel designed materials were found to be lesser comparaed to PFPPY which leads to excellent ICT properties. Of all dopant molecules, highest dipole moment (6.511401 D) possessed by P4 is credited to its maximum absorption peak (1008 nm) in infrared region. However, greater hole transfer rate was disclosed by P1 relative to other designed dopants because of its lowest reorganization energy values. According to above computed results, we expect that molecular engineering of pyrrole-based dopant molecules (P1–P5) will allow them to act as promising HTMs. Conclusively, these molecules have potential to substitute PFPPY and are highly recommend in photovoltaic field for future work.

Better performance of Hartree–Fock over DFT: a quantum mechanical investigation on pyridinium benzimidazolate types of zwitterions in the light of localization/delocalization issues

ContextWith the advent of fast computing facilities, combined with rapid emerges of many new and intricate quantum mechanical functionals, computations with pure Hartree–Fock (HF) theory are now-a-days regarded as trivial or obsolete, or even considered as not reliable by many researchers. Consequently, current trends in computational chemistry show extensive use of post-HF theories for smaller molecular systems and various DFT methods for organic and inorganic chemistry related problems (larger molecules/systems). In this contribution, I have tried to show that sometimes, HF might be more suitable over DFT methodologies in addressing structure–property correlations. Molecules studied here were previously synthesized by Boyd in 1966 and important experimental data were produced by Alcalde and co-workers in 1987. Comparison of computed and experimental results clearly shows that HF method was more effective in reproducing the experimental data compared to especially the DFT methodologies. Reliability of HF method was further assured from the very similar results shown by the CCSD, CASSCF, CISD and QCISD methods. Current study also indicates that the localization issue associated with HF proved to be advantageous over delocalization issue of DFT based methodologies, in correctly describing the structure–property correlation for zwitterion systems.MethodsAll computations were performed with Gaussian 09. A wide-range of quantum mechanical methodologies, HF, B3LYP, CAM-B3LYP, BMK, B3PW91, TPSSh, LC-ωPBE, M06-2X, M06-HF, ωB97xD, MP2, CASSCF, CCSD, QCISD, CISD and semi-empirical methods like, Huckel, CNDO, AM1, PM3MM and PM6, were used for investigations.Graphical abstract

Electronic structure of low-lying states of triatomic MoS2 molecule. The building block of 2D MoS2.

Molybdenum disulfide (MoS2) is the building component of 1D-monolayer, 2D-layered nanosheets and nanotubes having many applications in industry, and it is detected in molecular systems observed in nature. Here, the electronic structure and the chemical bonding of sixteen low-lying states of the triatomic MoS2 molecule are investigated, while the connection of the chemical bonding of the isolated MoS2 molecule to the relevant 2D-MoS2, is emphasized. The MoS2 molecule is studied via DFT and multireference methodologies, i.e., MRCISD(+Q)/aug-cc-pVQZ(-PP)Mo. The ground state, 3B1, is bent (Mo-S=2.133 Å and φ(SMoS)=115.9°) with a dissociation energy to atomic products of 194.7 kcal/mol at MRCISD+Q. In the ground and in the first excited state a double bond is formed between Mo and each S atom, i.e., . These two states differ in which d electrons of Mo are unpaired. The Mo-S bond distances of the calculated states range from 2.108-2.505 Å, the SMoS angles range from 104.1-180.0°, and the Mo-S bonds are single or double. Potential energy curves and surfaces have been plotted for the 3B1, 5A1 and 5B1 states. Finally, the low-lying septet states of the triatomic molecule are involved in the material as a building block, explaining the variety of its morphologies.

Development of Fluorescent Isocoumarin-Fused Oxacyclononyne - 1,2,3-Triazole Pairs.

Fluorescent isocoumarin-fused cycloalkynes, which are reactive in SPAAC and give fluorescent triazoles regardless of the azide nature, have been developed. The key structural feature that converts the non-fluorescent cycloalkyne/triazole pair to its fluorescent counterpart is the pi-acceptor group (COOMe, CN) at the C6 position of the isocoumarin ring. The design of the fluorescent cycloalkyne/triazole pairs is based on the theoretical study of the S1 state deactivation mechanism of the non-fluorescent isocoumarin-fused cycloalkyne IC9O using multi-configurational ab initio and DFT methodologies. The calculations revealed that deactivation proceeds through the electrocyclic ring opening of the α-pyrone cycle and is accompanied by a redistribution of electron density in the fused benzene ring. We proposed that the S1 excited state deactivation barrier could be increased by introducing a pi-acceptor group into a position that is in direct conjugation with the formed C=O group and has a reduced electron density in the transition state. As a proof of concept, we designed and synthesized two fluorescent isocoumarin-fused cycloalkynes IC9O-COOMe and IC9O-CN bearing pi-acceptors at the C6 position. The importance of the nature of a pi-acceptor group was shown by the example of much less fluorescent CF3 -substituted cycloalkyne IC9O-CF3 .

Titelbild: Guiding Principles for the Rational Design of Hybrid Materials: Use of DFT Methodology for Evaluating Non‐Covalent Interactions in a Uranyl Tetrahalide Model System (Angew. Chem. 33/2023)

Uranyl tetrahalide ions assemble into hybrid material through Non-Covalent Interactions (NCIs) in the presence of organic charge balancing cations. NCIs such as hydrogen bonding serve to stabilize these supramolecular hybrid complexes and act as the fundamental driving force for crystallization. In their Research Article (e202305073), Sara E. Mason, Tori Z. Forbes et al. employed these hybrid complexes as a model system to assess the effect of NCIs on the vibrational properties and formation enthalpies of metal–organic hybrid materials.

Cover Picture: Guiding Principles for the Rational Design of Hybrid Materials: Use of DFT Methodology for Evaluating Non‐Covalent Interactions in a Uranyl Tetrahalide Model System (Angew. Chem. Int. Ed. 33/2023)

Uranyl tetrahalide ions assemble into hybrid material through Non-Covalent Interactions (NCIs) in the presence of organic charge balancing cations. NCIs such as hydrogen bonding serve to stabilize these supramolecular hybrid complexes and act as the fundamental driving force for crystallization. In their Research Article (e202305073), Sara E. Mason, Tori Z. Forbes et al. employed these hybrid complexes as a model system to assess the effect of NCIs on the vibrational properties and formation enthalpies of metal–organic hybrid materials.

Hyperconjugation and Hydrogen Bonding Interactions Effect with the Nonlinear Optical Features of 4-Chlorophenoxy Acetonitrile: An Experimental and DFT Methodology

The compound 4-cholorophenoxy acetonitrile (CPAN) was examined using Nonlinear optical properties in the current study. With the aid of normal coordinate analysis and the SQMFF methodology, vibrational analysis of FT-IR and FT-Raman has been conducted. Natural bond orbital analysis is used to analyze the electronic stability of the compound created by hyper conjugative contacts and charge delocalization, and the Frontier molecular orbital energy gap confirms the molecule’s optical activity. ESP recognizes the nucleophilic and electrophilic areas of molecules, and the chemical implication of molecules was explained using ELF, LOL. Third-order nonlinear optical (NLO) investigations are carried out on a CPAN crystal using the Z-scan technique, and optical properties are established.

Preliminary Evaluation of Lablab purpureus Phytochemicals for Anti-BoHV-1 Activity Using In Vitro and In Silico Approaches.

Lablab purpureus from the Fabaceae family has been reported to have antiviral properties and used in traditional medical systems like ayurveda and Chinese medicine and has been employed to treat a variety of illnesses including cholera, food poisoning, diarrhea, and phlegmatic diseases. The bovine alphaherpesvirus-1 (BoHV-1) is notorious for causing significant harm to the veterinary and agriculture industries. The removal of the contagious BoHV-1 from host organs, particularly in those reservoir creatures, has required the use of antiviral drugs that target infected cells. This study developed LP-CuO NPs from methanolic crude extracts, and FTIR, SEM, and EDX analyses were used to confirm their formation. SEM analysis revealed that the LP-CuO NPs had a spherical shape with particle sizes between 22 and 30 nm. Energy-dispersive X-ray pattern analysis revealed the presence of only copper and oxide ions. By preventing viral cytopathic effects in the Madin-Darby bovine kidney cell line, the methanolic extract of Lablab purpureus and LP-CuO NPs demonstrated a remarkable dose-dependent anti-BoHV-1 action in vitro. Furthermore, molecular docking and molecular dynamics simulation studies of bio-actives from Lablab purpureus against the BoHV-1 viral envelope glycoprotein disclosed effective interactions between all phytochemicals and the protein, although kievitone was found to have the highest binding affinity, with the greatest number of interactions, which was also validated with molecular dynamics simulation studies. Understanding the chemical reactivity qualities of the four ligands was taken into consideration facilitated by the global and local descriptors, which aimed to predict the chemical reactivity descriptors of the studied molecules through the conceptual DFT methodology, which, along with ADMET finding, support the in vitro and in silico results.

Guiding Principles for the Rational Design of Hybrid Materials: Use of DFT Methodology for Evaluating Non-Covalent Interactions in a Uranyl Tetrahalide Model System.

Together with the synthesis and experimental characterization of 14 hybrid materials containing [UO2 X4 ]2- (X=Cl- and Br- ) and organic cations, we report on novel methods for determining correlation trends in their formation enthalpy (ΔHf ) and observed vibrational signatures. ΔHf values were analyzed through isothermal acid calorimetry and a Density Functional Theory+Thermodynamics (DFT+T) approach with results showing good agreement between theory and experiment. Three factors (packing efficiency, cation protonation enthalpy, and hydrogen bonding energy [ ]) were assessed as descriptors for trends in ΔHf . Results demonstrated a strong correlation between and ΔHf , highlighting the importance of hydrogen bonding networks in determining the relative stability of solid-state hybrid materials. Lastly, we investigate how hydrogen bonding networks affect the vibrational characteristics of uranyl solid-state materials using experimental Raman and IR spectroscopy and theoretical bond orders and find that hydrogen bonding can red-shift U≡O stretching modes. Overall, the tightly integrated experimental and theoretical studies presented here bridge the trends in macroscopic thermodynamic energies and spectroscopic features with molecular-level details of the geometry and electronic structure. This modeling framework forms a basis for exploring 3D hydrogen bonding as a tunable design feature in the pursuit of supramolecular materials by rational design.