Detailed Density Functional Theory Study Research Articles

Molecular design and characterization of the PANI/yttrium oxide multifunctional nanocomposite material

A detailed density functional theory study was conducted on the nanocomposites formed by polyaniline and yttrium oxide clusters, employing the mixed 6-311G(d,p)/LANL2DZ basis set. The investigation identified the formation of the nanocomposites through strong covalent bonding and moderate electrostatic interactions, resulting in significant binding energies. These interactions contributed to a reduction in the band gap, increased electron activity, and higher chemical reactivity compared to pure polyaniline. The formation of the nanocomposites induced a redshift in the UV-vis absorption spectra, moving the maximum absorption wavelength from the ultraviolet to the visible region, indicating n-type doping. Natural bond orbital analysis confirmed the role of yttrium oxide clusters as electron acceptors, with polyaniline serving as an electron donor.

Exciplex, Not Heavy-Atom Effect, Controls the Triplet Dynamics of a Series of Sulfur-Containing Thermally Activated Delayed Fluorescence Molecules.

The efficiency of thermally activated delayed fluorescence (TADF) in organic materials relies on rapid intersystem crossing rates and fast conversion of triplet (T) excitons into a singlet (S) state. Heavy atoms such as sulfur or selenium are now frequently incorporated into TADF molecular structures to enhance these properties by increased spin-orbit coupling [spin orbit coupling (SOC)] between the T and S states. Here a series of donor-acceptor (D-A) molecules based on 12H-benzo[4,5]thieno[2,3-a]carbazole and dicyanopyridine is compared with their nonsulfur control molecules designed to probe such SOC effects. We reveal that unexpected intermolecular interactions of the D-A molecules with carbazole-containing host materials instead serve as the dominant pathway for triplet decay kinetics in these materials. In-depth photophysical and computational studies combined with organic light emitting diode measurements demonstrate that the anticipated heavy-atom effect from sulfur is overshadowed by exciplex formation. Indeed, even the unsubstituted acceptor fragments exhibit pronounced TADF exciplex emission in appropriate carbazole hosts. The intermolecular charge transfer and TADF in these systems are further confirmed by detailed time-dependent density functional theory studies. This work demonstrates that anticipated heavy-atom effects in TADF emitters do not always control or even impact the photophysical and electroluminescence properties.

Blue-Emissive Antioxidant Carbon Dots Enhance Drought Resistance of Pea (Pisum sativum L.).

Prolonged drought conditions are a critical challenge for agricultural advancement, threatening food security and environmental equilibrium. To overcome these issues, enhancing plant resilience to drought is essential for plant growth and sustainable agriculture. In this study, blue-emitting antioxidant carbon dots (B-CDs), synthesized from citric acid and ascorbic acid, emerged as a promising solution to enhance the drought resistance of peas (Pisum sativum L.). B-CDs can efficiently scavenge reactive oxygen species (ROS), which are harmful in excess to plants under stress conditions. Through detailed experimental analyses and density functional theory (DFT) studies, it is found that these B-CDs possess structures featuring eight-membered aromatic rings with abundant oxygen-containing functional groups, providing active sites for reactions with ROS. The practical benefits of the B-CDs are evident in tests with pea plants exposed to drought conditions. These plants show a remarkable reduction in ROS accumulation, an increase in photosynthetic efficiency due to improved electron transfer rates, and significant growth enhancement. Compared to untreated controls under drought stress, the application of B-CDs results in an impressive increase in the fresh and dry weights of both the shoots and roots of pea seedlings by 39.5 and 43.2% for fresh weights and 121.0 and 73.7% for dry weights, respectively. This suggests that B-CDs can significantly mitigate the negative effects of drought on plants. Thus, leveraging B-CDs opens a novel avenue for enhancing plant resilience to abiotic stressors through nanotechnology, thereby offering a sustainable pathway to counter the challenges of drought in agriculture.

Unveiling the molecular insights of 2-(carboxymethyl) benzoic acid: A density functional theory approach towards structural and biological attributes

Nowadays density functional theory (DFT) is one of the best methods to explore the vibrational modes and structure of the biological system. Quantum mechanical calculations are performed using gas phase and different solvents (DMSO, methanol and water). The derived global reactive parameters, structural and topological study provides the clear insight of the 2-(Carboxymethyl) benzoic acid. Depth studies of DFT proves the existence of hydrogen bonds between donor and acceptor in the compound, which is supportive for the biological applications. In this paper, different experimental and computational simulated FT-IR, FT-Raman, UV–Vis spectral studies are used to explicate vibration assignments of the 2-(Carboxymethyl) benzoic acid. Experimentally observed vibrational frequency is compared with theoretically simulated spectrum. B3LYP method with 6–311++G (d, p) basis set is used in DFT to optimize the 2-(Carboxymethyl)benzoic acid structure. The most stable lower energy conformer is identified using potential energy surface (PES) analysis using Gaussian 16 W software. ESP, HOMO-LUMO, NBO, and QTAIM calculations have evinced an adequate electronic characterization of 2-(Carboxymethyl) benzoic acid. Further, van der Waals and steric interactions among 2-(Carboxymethyl) benzoic acid have been discussed with the help of RDG study. Hirshfeld surface studies establish the existing various interaction among molecules and total packing arrangement of the crystal structure. Due to the high biological activity score, 2-(Carboxymethyl) benzoic acid is a good therapeutic candidate. Lipophilicity analysis of 2-(Carboxymethyl)benzoic acid clearly explicates the bioactivity properties and its effective drug applications. Further, molecular docking investigates that the compound can be used as anticancer medication. The detailed DFT study of the 2-(Carboxymethyl) benzoic acid justified its biological applications of the present communication. The calculated NLO parameters of 2-(Carboxymethyl)benzoic acid evidenced for good efficacy in diverse filed application has been discussed.

Hydrogen bonding in glassy trehalose-water system: Insights from density functional theory and molecular dynamics simulations.

We report a detailed density functional theory and molecular dynamics study of hydrogen bonding between trehalose and water, with a special emphasis on interactions in the amorphous solid state. For comparison, water-water interactions in water dimers and tetramers are evaluated using quantum calculations. The results show that the hydrogen bonding energy is dependent not only on the geometry (bond length and angle) but also on the local environment of the hydrogen bond. This is seen in quantum calculations of complexes in vacuum as well as in amorphous solid states with periodic boundary conditions. The temperature-induced glass transition in the trehalose-water system was studied using molecular dynamics simulations with varying cooling and heating rates. The obtained parameters of the glass transition are in good agreement with the experiments. Moreover, the dehydration of trehalose in the glassy state was investigated through a gradual dehydration with multiple small steps under isothermal conditions. From these simulations, the values of water sorption energy at different temperatures were obtained. The partial molar enthalpy of mixing of water value of -18 kJ/mol found in calorimetric experiments was accurately reproduced in these simulations. These findings are discussed in light of the hydrogen bonding data in the system. We conclude that the observed exothermic effect is due to different responses of liquid and glassy matrices to perturbations associated with the addition or removal of water molecules.

Stereoselectivity control in Rh-catalyzed β-OH elimination for chiral allene formation

Stereoselectivity control and understanding in the metal-catalyzed reactions are fundamental issues in catalysis. Here we report sterically controlled rhodium-catalyzed SN2’-type substitution reactions of optically active tertiary propargylic alcohols with arylmetallic species affording the non-readily available enantioenriched tetrasubstituted allenes via either exclusive syn- or anti-β-OH elimination, respectively, under two sets of different reaction parameters. Detailed mechanistic experiments and density functional theory (DFT) studies reveal that the exclusive anti-Rh(I)-OH elimination is dictated by the simultaneous aid of in situ generated boric acid and ambient water, which act as the shuttle in the hydroxy relay to facilitate the Rh(I)-OH elimination process via a unique ten-membered cyclic transition state (anti-TS2_u). By contrast, the syn-Rh(III)-OH elimination in C–H bond activation-based allenylation reaction is controlled by a four-membered cyclic transition state (syn-TS3) due to the steric surroundings around the Rh(III) center preventing the approach of the other assisting molecules. Under the guidance of these mechanistic understandings, a stereodivergent protocol to construct the enantiomer of optically active tetrasubstituted allenes from the same starting materials is successfully developed.

Mechanism and Origins of Regio- and Stereoselective Alkylboration of Endocyclic Olefins Enabled by Nickel Catalysis.

The Ni-catalyzed alkylboration of endocyclic olefins is a stereo- and regioselective approach for the synthesis of boron-containing compounds. We report a detailed density functional theory (DFT) study to elucidate the mechanism and origins of the stereo-, chemo-, and regioselectivity of alkylboration of endocyclic olefins enabled by nickel catalysis. The alkylboration proceeds via the migratory insertion of alkenes, β-H elimination of the Ni(II) complex, subsequent migratory insertion leading to a new Ni(II) complex, combined with an alkyl radical, and reductive eliminations. The electronic effects of the endocyclic olefins synergistically control the regioselectivity toward the C1- and C2-position boration. In C1-position boration, a more electron-deficient carbon atom tends to combine with an electron-rich -Bpin group and leads to C1-position boration products. The stereoselectivity is influenced by the solvent effect, and the interaction between the substrate and Ni-catalyzed groups, the low-polarity solvent 1,4-dioxane, and a favorable steric hindrance effect result in the cis-alkylboration product. Chemoselectivity toward 1,3-alkylboration results from the steric hindrance effects of the -Bpin group.

Novel Fluorinated Biphenyl Compounds Synthesized via Pd(0)-Catalyzed Reactions: Experimental and Computational Studies.

Five new difluorinated biphenyl compounds, 4'-(tert-butyl)-3,4-difluoro-1,1'-biphenyl (TBDFBP), 1-(3',4'-difluoro-[1,1'-biphenyl]-4-yl)ethanone (DFBPE), 3',4'-difluoro-2,5-dimethoxy-1,1'-biphenyl (DFDMBP), 3,4-difluoro-3'-nitro-1,1'-biphenyl (DFNBP), and (3',4'-difluoro-[1,1'-biphenyl]-3-yl)(methyl)sulfane (DFBPMS), have been successfully synthesized by the well-known Suzuki-Miyaura coupling with excellent yields averaging 78%. UV-visible, Fourier transform infrared ,and 13C NMR and 1H NMR spectroscopies along with single-crystal X-ray diffraction (SC-XRD) analysis (for TBDFBP and DFBPE) were used for the structure elucidation of the synthesized compounds. The SC-XRD results demonstrated the crystal systems of the studied compounds, TBDFBP and DFBPE, to be monoclinic, and their space groups were found to be P21/c. Also, a detailed density functional theory study was performed. The calculated structures for TBDFBP and DFBPE were found to agree quite well with the experimental results. The natural bonding orbital charge analysis suggested that molecules of these compounds should interact quite noticeably with each other in the solid phase and with polar solvent molecules. Molecular electrostatic potential analysis suggests that accumulation of positive and negative potential implies possibility of quite significant dipole-dipole intermolecular interactions in crystals of these compounds, as well as quite strong interactions with polar solvent molecules. The global reactivity parameters analysis suggests all compounds to be quite stable in redox reactions, with the compound DFNBP being relatively more reactive and the compounds TBDFBP and DFDMBP being relatively more stable.

Curious Behavior of Fe3+-As3+ Chemical Interactions and Nucleation of Clusters in Aqueous Medium.

The simultaneous presence of Fe3+ and As3+ ions in groundwater (higher ppb or lower ppm level concentrations at circumneutral pH) as well as in acid mine drainages (AMDs)/industrial wastewater (up to few thousand ppm concentration at strongly acidic pH) are quite common. Therefore, understanding the chemical interactions prevalent between Fe3+ and As3+ ions in aqueous medium leading to nucleation of ionic clusters/solids, followed by aggregation and growth, is of great environmental significance. In the present work, we attempt to probe the nucleation process of Fe3+-As3+ clusters in solutions of various concentrations and pHs (from AMD to groundwater-like) using a combination of experimental and theoretical techniques. Interestingly, our study reveals nucleation of primary FeAs clusters in nearly all of them independent of concentration or pH. Theoretical studies employed density functional theory (DFT) to predict the primary clusters as stable Fe4As4 units. The surprising resemblance of these clusters with known Fe3+-As3+ minerals at the local level was observed experimentally, which provides an important clue about solid-phase growth from a range of Fe3+-As3+ solutions. Our experimental findings are further supported by a stepwise reaction mechanism established from detailed DFT studies.

Preparation, Crystal Structure, Supramolecular Assembly, and DFT Studies of Two Organic Salts Bearing Pyridine and Pyrimidine.

The effective preparation of two new pyrimidine- and pyridine-based organic crystalline salts with substituted acidic moieties (i.e., (Z)-4-(naphthalen-2-ylamino)-4-oxobut-2-enoic acid (DCNO) and 2-hydroxy-3,5-dinitrobenzoic acid (PCNP)) using methanol as a solvent has been reported. These molecular salts have ionic interactions that are responsible for their structural stabilization in their solid-state assemblies. The crystal structures of DCNO and PCNP were determined by the single-crystal X-ray diffraction (SCXRD) technique. The SCXRD study inferred that cations and anions are strongly packed due to N-H···O, N-H···N, and C-H···O noncovalent interactions in DCNO, whereas in PCNP, N-H···N noncovalent interactions are absent. The noncovalent interactions in both organic crystalline salts were comprehensively investigated by Hirshfeld surface analysis. Further, a detailed density functional theory (DFT) study of both compounds was performed. The optimized structures of both compounds supported the existence of the H-bonding and weak dispersion interactions in the synthesized organic crystalline salt structures. Both compounds were shown to have large and noticeably different HOMO/LUMO energy gaps. The atomic charge analysis results supported the SCXRD and HSA results, showing the formation of intermolecular noncovalent interactions in both organic crystalline salts. The results of the natural bond orbital (NBO) analysis confirmed the existence of (relatively weak) noncovalent interactions between the cation and anion moieties of their organic crystalline salts. The global reactivity parameters (GRPs) analysis showed that both organic crystalline salts' compounds should be quite thermodynamically stable and that DCNO should be less reactive than PCNP. For both compounds, the molecular electrostatic potential (MEP) analysis results support the existence of intermolecular electrostatic interactions in their organic crystalline salts.

Solidification/stabilisation behaviours of Zn2+ in magnesium potassium phosphate cement: Experiments and density functional theory study

The solidification/stabilisation behaviours of Zn2+ in magnesium potassium phosphate cement (MKPC) have not been thoroughly investigated. Herein, a series of experiments and a detailed density functional theory (DFT) study were conducted to investigate the solidification/stabilisation behaviours of Zn2+ in MKPC. The results showed that the compressive strength of MKPC reduced with the addition of Zn2+ because the formation of MgKPO4·6H2O (the main hydration product in MKPC) was delayed with the addition of Zn2+, as discovered by the crystal characteristics, and because Zn2+ exhibited a lower binding energy in MgKPO4·6H2O compared to Mg2+, as revealed by DFT results. Additonally, Zn2+ had little influence on the structure of MgKPO4·6H2O, and Zn2+ existed in MKPC as the formation of Zn2(OH)PO4, which was decomposed in the range of around 190–350 °C. Moreover, there were a lot of well-crystallised tabular hydration products before the addition of Zn2+, but the matrix was comprised of irregular prism crystals after adding Zn2+. Furthermore, the leaching toxicity of Zn2+ of MKPC was much smaller than the requirements of Chinese and European standards.

Reactivity and Selectivity of the Diels-Alder Reaction of Anthracene in [Pd6L4]12+ Supramolecular Cages: A Computational Study.

The field of supramolecular metal-organic cage catalysis has grown rapidly in recent years. However, theoretical studies regarding the reaction mechanism and reactivity and selectivity controlling factors for supramolecular catalysis are still underdeveloped. Herein, we demonstrate a detailed density functional theory study on the mechanism, catalytic efficiency, and regioselectivity of the Diels-Alder reaction in bulk solution and within two [Pd6L4]12+ supramolecular cages. Our calculations are consistent with experiments. The origins of the catalytic efficiency of the bowl-shaped cage 1 have been elucidated to be the host-guest stabilization of the transition states and the favorable entropy effect. The reasons for the switch of the regioselectivity from 9,10-addition to 1,4-addition within the octahedral cage 2 were attributed to the confinement effect and the noncovalent interactions. This work would shed light on the understanding of [Pd6L4]12+ metallocage-catalyzed reactions and provide a detailed mechanistic profile otherwise difficult to obtain from experiments. The findings of this study could also aid to the improvement and development of more efficient and selective supramolecular catalysis.

B(3,4,5-F3H2C6)3 Lewis acid-catalysed C3-allylation of indoles.

Herein we report the B(3,4,5-F3H2C6)3-catalysed C3-allylation of indoles using allylic esters. 25 examples of C3-allylated products are presented in up to 97% yield. The mechanism for the reaction was explored using detailed Density Functional Theory (DFT) studies.

First-principles study of elastic and thermodynamic properties of UO2, γ-UO3 and α-U3O8

A detailed solid-state density functional theory study of uranium dioxide (UO2), gamma uranium trioxide (γ-UO3), and alpha triuranium octoxide (α-U3O8), which are very common materials throughout the nuclear fuel cycle, was carried out. DFT simulations of these three oxides were presented using both PBE+U and LDA+U functionals to examine their mechanical and thermodynamic properties. The computed lattice parameters were found to be in very good agreement with previous experimental results. The values of elastic properties like bulk, shear, and Young's modulus, as well as Poisson's ratio, were predicted, and the calculated Debye temperature was reported. The elastic anisotropy of UO2, γ-UO3, and α-U3O8 was calculated for the first time, from which the anisotropic degrees of these oxides were revealed by the values of anisotropic parameters and three-dimensional surface constructions of elastic properties. In addition, thermodynamic properties of UO2, γ-UO3, and α-U3O8, including heat capacity, entropy, enthalpy, phonon free energy, and Gibbs free energy, were determined as a function of temperature in the range of 0 - 2000 K. The computed thermodynamic values show an overall good agreement with available experiments, especially at low temperatures. The obtained physical parameters can provide meaningful data for further experimental investigations and promote the development of nuclear fuel cycles.

Detailed Density Functional Theory Study of the Cationic Zirconocene Compound [Cp(C5H4CMe2C6H4F)ZrMe

Detailed density functional theory studies at the B3LYP and PBE-D3 levels of theory were performed on the cationic compound [Cp(C5H4CMe2C6H4F)ZrMe]+, with the F atom occupying either the ortho, meta, or para positions of the arene ring. In all cases, the arene ring coordinates with the cationic zirconium metal. The nature of this coordination is such that for the meta- or para-substituted arene ring, it is predominantly the ortho carbon atom of the C–H bond which interacts with the metal, as evident from noncovalent interaction studies. This is further corroborated by the natural bond orbital and quantum theory of atoms in molecular studies. In the case of the F atom being in the ortho position, we obtained clear-cut evidence for a Zr–F coordination.

Stereoselective Olefination with Sterically Demanding Julia-Kocienski Reagents: Total Synthesis of Oxo-prothracarcin, Oxo-tomaymycin, and Boseongazepine B.

Total syntheses of three pyrrolo[1,4]benzodiazepine anticancer antibiotic family members oxo-prothracarcin, oxo-tomaymycin, and boseongazepine B are described. The total syntheses feature late-stage stereoselective olefination employing modified Julia–Kocienski reagents that can be conveniently prepared in only two steps and allows for a significant reduction in the number of linear steps. Detailed density functional theory (DFT) studies explain the stereochemical outcome of the key step.

Elaborating the mechanism of a highly selective fluorescent ‘turn-on’ probe to detect the group IIIA ions: a detailed time-dependent density functional theory study

Elaborating the mechanism of a highly selective fluorescent ‘turn-on’ probe to detect the group IIIA ions: a detailed time-dependent density functional theory study

Structure and electronic properties of the HA-CUR conjugate: An insight from the DFT perspective

In this article, we are reporting the results of the first detailed Density Functional Theory (DFT) study of the structure of the hyaluronic acid-curcumin (HA-CUR) compound. The molecular orbitals (MOs), frontier molecular orbitals (FMOs, i.e., energies of the FMOs and HOMO/LUMO gaps), and molecular electrostatic potential (MEP) of the compound have been investigated using the Gaussian 09 package using the hybrid functional B3LYP with the split-valence polarized 6-311G(d,p) basis set (B3LYP/6-311G(d,p) approach). In addition, the NBO (Natural Bond Orbital) charge analysis and NBO bonding analysis for the HA-CUR complex have been performed. The structures of the HA and CUR moieties inside the HA-CUR complex are found noticeably different from their free molecules, and the LUMO of the HA-CUR complex is noticeably stabilized compared to the HA LUMO and to the CUR LUMO, which leads to the noticeable closure of the HA-CUR HOMO/LUMO gap compared to the HA gaps and CUR water-computed gap. The detailed studies carried out on the HA-CUR complex in different aspects will definitely be useful for the researchers working in the area of the novel drug design and pharmaceutical chemistry.

Li- and Na-doped bismuth titanate pyrochlores: From the point of view ab initio calculation and experiment

A detailed combined density functional theory (DFT) and experimental study of the substitution Li and Na in Bi2Ti2O7 pyrochlore (BTO) has been performed. The DFT simulation predicted preference of A-site doping Bi1.5M0.5Ti2O7 rather than B-site doping Bi2Ti1.5M0.5O7 (M – Li, Na) and explained the phase formation process in the Bi-Na-Ti-O system. The computational results are strongly confirmed during the experiment. Na-doped BTO pyrochlores could be obtained only at the low sodium content along with the location of Na atoms at the partially occupied A-sites of pyrochlore, e.g., the Bi1.5Na0.125Ti2O7-δ pyrochlore has been synthesized for the first time. In contrast, Li-doped BTOs could be synthesized at various Li content. The electronic properties of Li-, Na-doped BTOs, which were modeled with range separated hybrid functionals, are found to be in good agreement with the experimental optical properties. These doped pyrochlore compositions were stated to be wide-band indirect semiconductor materials with close band gaps ca. 2.7–2.8 eV. The comprehensive comparative impedance study of the Bi1.6Li0.1Ti2O7-δ and Bi1.5Na0.125Ti2O7-δ pyrochlores have been performed in dry and wet conditions. Below 200 °C, the compounds have high specific resistance (ca. 108–109 Ω·m). With rising temperature from 200 to 750 °C, the bulk conductivity increased up to 10−3 S·cm−1. The conductivity value of Bi1.6Li0.1Ti2O7-δ is lower than that of Bi1.5Na0.125Ti2O7-δ at the same temperatures. The increase in the electrical conductivity of both compounds in a wet atmosphere compared to a dry one was detected. New Li-, Na-doped BTO pyrochlores might be recommended as mixed electronic-ionic conductors.

Adsorption of sorbitan ester surfactant on copper and Cuprous oxide surfaces: A density functional theory study

This work reports a detailed density functional theory study of the adsorption of sorbitan monoacetate (SMA) molecules -as a model of the head group of sorbitan-derived surfactants- on Cu (111) and Cu2O (111) surfaces. Our study includes the most stable adsorption configurations, considering the electron-withdrawing nature of the molecule functional groups and the electron-donating sites on the surface. When SMA adsorbs on Cu (111), van der Waals interactions emerge as the most stabilizing components. In contrast, for Cu2O (111), SMA binds through coordination bonds hydrogen bonds. Charge transfer analysis in the formed Cu-O bonds showed that molecule's oxygen atoms behave as electron withdrawers whereas Cu atoms as electron-donating entities. The non-covalent index analysis revealed that van der Waals interactions in both systems present an attractive component.The results presented help explain how span surfactants head group interacts with Copper and Cuprous oxide (111) surfaces, what type of bonds and interactions are present in the adsorption process, and how strong they are to assess its applicability in area selective deposition techniques as an easily removable Copper passivating agent. Also, the clarified interactions appearing in this metal–organic system may be of great interest for the design of sensing nanodevices.