Functional B3LYP Research Articles

Fast and Accurate Determination of the Singlet–Triplet Gap in Donor–Acceptor and Multiresonance TADF Molecules by Using Hole–Hole Tamm–Dancoff Approximated Density Functional Theory

AbstractOne of the requirements to design efficient emitters based on the multiresonance (MR)‐ or donor–acceptor (D‐A) thermally activated delayed fluorescence (TADF) materials is a relatively small energy gap between the lowest singlet and triplet excited states (ΔEST). High‐level ab initio calculations of their ΔEST provide benchmark results, but they are very time consuming and little practical for large‐size systems. Here, the performances of hole–hole Tamm–Dancoff approximated density functional theory (hh‐TDA‐DFT) and the functional dependent accuracy of hh‐TDA are examined on ΔEST of a large number of MR‐ and D‐A TADF molecules. The results indicate that hh‐TDA combined with the hybrid functional B3LYP can predict ΔEST values for a wide number of MR‐TADF molecules with mean absolute error (MAE) within 0.04 eV with correlation as high as 0.75. For D‐A TADF molecules, ΔEST is less sensitive to the nature of the functionals, with MAE as low as 0.07 eV. The larger discrepancy between ΔEST obtained from hh‐TDA‐DFT and experimental data in several oxygen‐containing MR‐TADF molecules is assumed to stem from the aggregation tendency of these compounds in solution. These findings provide important insights on the role of aggregation in reducing the ΔEST of MR‐TADF compounds.

Propylthiouracil drug adsorption on pristine, Cu, Ag, and Au decorated AlP nanosheets

B3LYP, M06-2X, and B97D density functionals are utilized for probing the effect of decorating Cu, Ag, and Au on the sensing performance of an aluminum phosphide nanosheet (AlPNS) in detecting the propylthiouracil (PTU) drug. We predict that the interaction of pure AlPNS with PTU is physisorption, and the sensing response (SR) of AlPNS is approximately 3.1. The adsorption energy of PTU changes from −5.1 to −18.7, −18.9, and −19.3 kcal/mol by decorating the Cu, Ag, and Au metals into the AlPNS, respectively. Also, the corresponding sensing response (SR) meaningfully rises to 53.4, 65.1, and 84.2. It indicates that by increasing the atomic number of metals, the sensitivity of metal decorated AlPNS (metal@AlPNS) is increased. Therefore, we found that Au-decorating much more increases the sensitivity of AlPNS toward PTU drug. The SR of metal@AlPNS slightly decreases in the water solvent.

A novel copper (II) complex containing pyrimidine-4-carboxylic acid: Synthesis, crystal structure, DFT studies, and molecular docking

A new Cu(II) complex of pyrimidine-4-carboxylic acid was synthesized and characterized through a combination of single-crystal XRD, Ultraviolet-Visible (UV-Vis), and Fourier Transform Infrared Spectroscopy (FT-IR). The Cu(II) complex adopts six-coordinate, distorted octahedral geometry around the Cu (II) center. The ground state geometry of the copper compound was optimized using the Density Functional Theory (DFT) method with unrestricted hybrid density functional B3LYP. The vibrational spectra of the Cu(II) complex and similar molecules were described and compared with calculated data obtained by the DFT/UB3LYP/6–31G(d,p) method. The experimental UV-Vis absorption spectrum was compared to the simulated data using time-dependent (TD)-DFT. The effect of the solvent was carried out using the integral equation formalism-polarized continuum model (IEF-PCM). Global reactivity descriptors (ionization potential, chemical hardness, electron affinity, etc.) were surveyed by using the DFT/UB3LYP and DFT/UCAM-B3LYP methods. The non-linear optical (NLO) parameters of the complex were calculated by using the UB3LYP method with 6–31G(d,p) basis set. Furthermore, the molecular docking study was also performed to display interactions between the B-DNA and the Cu(II) complex.

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.

Spectroscopic Investigations, Computational Studies and Molecular Properties of Naphthalene Derivatives

Theoretical studies have been carried out on bio active molecules such as Naphthalene (npa) and its derivatives naphthalene-2-sulfonic acid (nsa) and 1-nitroso-2-naphthol (nnol) using both Ab initio HF and DFT-B3LYP methods with 6-311++G(d,2p) basis sets. The geometrical parameters, molecular properties and vibrational spectra of nsa, nnol and npa were calculated and analyzed. Geometrical optimizations of the nsa, nnol and npa molecules were done by Density Functional Theory (DFT) using the B3LYP function and Hartree-Fock (HF) level with 6-311++G(d,2p) basis set. The optimized molecular geometry and computed vibrational spectra are compared with experimental results which show significant agreement. DFT and HF global chemical reactivity descriptors (chemical hardness, total energy, electronic chemical otential and electrophilicity) are calculated for the title molecules and used to predict their relative stability and reactivity.

Theoretical design, synthesis and third-order non-linear optical properties of thiophene and tetrafluorobenzene based low band gap conducting polymers

Low band gap donor-acceptor type π-conjugated conducting polymers P(BT-4FPH), P(3METH-4FPH) and P(TH-4FPH) were theoretically designed using Gaussian 09 with two hybrid functionals B3LYP, HSE06/6–31 G (d,p) basis set. Oscillator strength and excitation energy of the monomers were determined by TD-DFT/B3LYP/6–31 G (d,p) method. Copolymers were synthesized by the direct arylation polymerization method. Structural characterization was done by FTIR and 1H NMR spectra. Thermal stabilities of the copolymers were evaluated by TG. The molecular weights of the copolymers were obtained by Gel permeation chromatography. Cyclic voltammetry (CV) was used to observe the electrochemical band gaps of the copolymers. Theoretical observations from HSE06/6–31 G (d,p) method supported the experimental results. Third-order non-linear optical properties and optical limiting effect of the copolymers were studied at different laser intensities using the open-aperture Z-scan technique at 532 nm in DMSO. P(BT-4FPH) exhibited strong optical non-linearity with reverse saturable absorption when compared with P(3METH-4FPH) and P(TH-4FPH) with non-linear absorption coefficient β = 1.20 × 10−8 m/W at 20 µJ. Optical threshold values obtained for the copolymers were low which indicated that the polymers could be used for optical power limiting devices. Among the three synthesized copolymers, P(BT-4FPH) exhibited higher molecular weight, lowest electrochemical band gap and showed strong non-linear absorption with lowest optical threshold value of 0.009 GW/cm2 at 10 µJ due to the increased delocalization of π- electrons over the conjugated backbone of donor-acceptor units.

Decomposition of 2,4,6-trinitrotoluene (TNT) and 5-nitro-2,4-dihydro-3H-1,2,4-triazol-3-one (NTO) by Fe13O13 nanoparticle: density functional theory study.

To obtain more insight into the mechanisms of the decomposition of energetic compounds, we performed a computational study of the interaction of Fe13O13 nanoparticles with two energetic molecules such as 2,4,6-trinitrotoluene (TNT) and 5-nitro-2,4-dihydro-3H-1,2,4-triazol-3-one (NTO). The density functional theory using M06-2X, B3LYP, and BLYP density functionals was applied. We found that the reactivity of these molecules strongly depends on the place of adsorption (so-called top and bottom planes of Fe13O13). Namely, only the interaction with the bottom plane results in the thermodynamic characteristics of the decomposition that provide a medium reaction rate for the studied processes. Several pathways for such decomposition were found. One of them is the inter-complex oxygen transfer of nitro-group oxygen to Fe13O13. This pathway results in the formation of adsorbed nitroso compounds. The second pathway describes a more complex decomposition that includes the transfer of the nitro-group oxygen accompanied by the hydrogen transfer. In all cases, the interaction of energetic molecules with Fe13O13 nanoparticles takes place along with a barrier-less electron transfer from Fe13O13 to TNT or NTO species.

First-principle studies of electronic, elastic and vibrational properties of barytocalcite and paralstonite

The crystal structure, electronic, elastic and vibrational properties of two natural BaCa(CO3)2 polymorphs (barytocalcite and paralstonitis) were studied by the density functional theory methods using the hybrid B3LYP and gradient PBE functionals, taking into account the dispersion correction D3 to the total energy in the basis of localized orbitals of the CRYSTAL package, under the pressure about 3 GPa. It is shown that the cell volume of hexagonal paralstonite obtained by the PBE-D3 method per formula unit is 0.065 Å3 larger, and the total energy is 0.011 eV lower than that of a monoclinic barytocalcite. The parameters of the equation of state in the Birch-Murnaghan form are determined. The elastic constants of single crystals and, in the Voigt-Royce-Hill approximation, the elastic moduli and elastic wave velocities of polycrystals are calculated. In the electron energy spectrum, the width of the upper valence band is 0.85 eV in barytocalcite, and 0.94 eV in paralstonite, while the band gap is 4.85 eV and 4.36 eV, respectively, and it decreases with increasing pressure at rates of − 0.01 and − 0.02 eV/GPa. The frequencies and intensities of normal long-wave oscillations are calculated with the B3LYP functional. It is shown that qualitative differences in the spectra of infrared absorption and Raman scattering of light for two phases should be sought in the range of 1300÷1580 cm−1 in the region of intramolecular vibrations, and for the spectra of infrared absorption in the region of 260÷310 cm−1, and for light scattering in the range of 130÷180 cm−1 in the region of lattice vibrations.

Spectroscopic, conformational analysis, structural benchmarking, excited state dynamics, and the photovoltaic properties of Enalapril and Lisinopril

There have been numerous attempts to theoretically design a better photovoltaic property with much interest on how to improved absorption and emission parameters of most reactive compounds in respect to dye – sensitized solar cells (DSSCs). This is regardless of the promising futures of the photovoltaic properties. However, for such effective design, it is necessary to understand the electronic and photophysical properties of the dye systems. Herein detailed density functional theory (DFT) and time – dependent DFT (TD-DFT) investigation of the excited state characteristics and the influence of various solvents: water, acetone, ethanol and chloroform on the photophysical properties of enalapril and lisinopril were investigated along with the experimental spectral (UV–vis and FT-IR) analysis. The electronic structure calculations were conducted using the 6–311++G(d,p) basis set in combination with B3LYP, M06-2X, and ꞷB97XD DFT functionals for the structural benchmarking investigations of the studied compounds. Results of the excitation electronic analysis of enalapril was observed to have wavelength absorption in the order gas > chloroform > ethanol > water which correspond to 229.19, 228.81, 228.85, 229.03 nm respectively while Lisinopril have the order of chloroform > gas > water > ethanol which present ethanol have the highest transition energy. In all the studied structured, the transition assignment corresponds to π → π* all corresponding to the Frank -Condon local excitation. It can be inferred from the photovoltaic properties that among the studied compounds in four different phases enalapril have the highest oscillator strength, but the values of light-harvesting efficiency (LHE) varies and show greater stability in Lisinopril. Lisinopril was observed to have the highest value of VOC compared to Enalapril this further confirmed the result obtained from the frontier molecular orbitals.

Spectroscopic, quantum chemical and molecular docking studies on friedelin, the major triterpenoid isolated from Garcinia imberti

Friedelin, a Garcinia imberti isolate, was subjected to a detailed theoretical study using the density functional theory. Theoretical calculations, such as optimized geometry, electronic, vibrational spectroscopic, intermolecular interactions, and insilico screening were performed. DFT at hybrid functional B3LYP was chosen, and the 6–311++G(d, p) level of theory was used for all simulations. The first three rings of the compound are in chair conformation (trans arrangement), while the remaining two rings are in boat conformation (cis arrangement). Transannular, flagpole, and stereo electronic hyperconjugative interactions are observable throughout the optimal geometry because of the conformation therein. Non-covalent H...H interactions is also confirmed by Hrishfeld surface analysis. NBO and NPA analyses have confirmed stereo electronic hyperconjugative interactions and C-H...O intramolecular hydrogen bonding interactions. The estimated vibrational wavenumbers and the experimentally determined values have an excellent correlation. The TD-DFT computations were performed both in solvent (chloroform) and gaseous phase, and agree with the experimental values. The molecule was tested insilico against tuberculosis protein 4FDO using the Schrodinger suite's Glide docking software. After the docking studies, the compound's drug-likeness and ADMET predictions were calculated, and the results indicated that it could be exploited as a tuberculosis treatment option.

Titanium doping effect on the sensing performance of ZnO nanosheets toward phosgene gas

The density functional B3LYP was utilized for scrutinizing the effect of Ti-doping on the sensing performance of a ZnO nano-sheet (ZnONS) in detecting phosgene. Pure ZnONS had a weak interaction with phosgene, and the sensing response (SR) was approximately 9.4. There was an increase in the energy of adsorption (Ead) for phosgene from −5.5 to −22.8 kcal mol−1 after the doping of a Ti atom onto the surface of ZnONS. Following the doping of Ti, there was also a dramatic increase in the SR to 84.2. The recovery time (RT) for the desorption of phosgene from the ZnONS that was doped with Ti was 16.4 s. This suggested that Ti-doped ZnONS might be used as a phosgene sensor with a high sensitivity and a shorter RT.

Small-Basis Set Density-Functional Theory Methods Corrected with Atom-Centered Potentials.

Density functional theory (DFT) is currently the most popular method for modeling noncovalent interactions and thermochemistry. The accurate calculation of noncovalent interaction energies, reaction energies, and barrier heights requires choosing an appropriate functional and, typically, a relatively large basis set. Deficiencies of the density-functional approximation and the use of a limited basis set are the leading sources of error in the calculation of noncovalent and thermochemical properties in molecular systems. In this article, we present three new DFT methods based on the BLYP, M06-2X, and CAM-B3LYP functionals in combination with the 6-31G* basis set and corrected with atom-centered potentials (ACPs). ACPs are one-electron potentials that have the same form as effective-core potentials, except they do not replace any electrons. The ACPs developed in this work are used to generate energy corrections to the underlying DFT/basis-set method such that the errors in predicted chemical properties are minimized while maintaining the low computational cost of the parent methods. ACPs were developed for the elements H, B, C, N, O, F, Si, P, S, and Cl. The ACP parameters were determined using an extensive training set of 118655 data points, mostly of complete basis set coupled-cluster level quality. The target molecular properties for the ACP-corrected methods include noncovalent interaction energies, molecular conformational energies, reaction energies, barrier heights, and bond separation energies. The ACPs were tested first on the training set and then on a validation set of 42567 additional data points. We show that the ACP-corrected methods can predict the target molecular properties with accuracy close to complete basis set wavefunction theory methods, but at a computational cost of double-ζ DFT methods. This makes the new BLYP/6-31G*-ACP, M06-2X/6-31G*-ACP, and CAM-B3LYP/6-31G*-ACP methods uniquely suited to the calculation of noncovalent, thermochemical, and kinetic properties in large molecular systems.

Investigations of The Most Active Compound As Anti-dental Caries between Chemical Constituents of Miswak

The present study deals with quantum calculations to investigate some chemical descriptors of the main components of miswak extract to evaluate the most potent agents that used as anti dental caries between all the chemical components present in this plant. The chemical descriptors such as HOMO, LUMO, Energy gap, softness, hardness and electrophilicity was used as indicators to evaluate the activity of each component. Using hyperchem-8 package, density functional theory (DFT) was used as quantum method at the basis set L631G* with B3LYP function as the exchange–correlation. It can be concluded that benzyl isothiocyanate is considered as the potent agent that prevent dental careis due to the comparison of several chemical descriptors studied by DFT method

Different metal-decorated aluminum phosphide nanotubes as hydrazine sensors for biomedical applications.

B3LYP, B97D, and M06-2X density functionals are utilized for probing the effect of decorating X (X = Co, Ti, Sc, or Ca) metals on the sensing performance of an aluminum phosphide nanotube (AlPNT) in detecting the hydrazine (HZ) gas. We predict that the interaction of pristine AlPNT with HZ is physisorption, and our calculated sensing response (SR) of AlPNT is approximately 2.7. The adsorption energy of HZ changes from - 4.6 to - 21.0, - 21.9, - 22.4, and - 23.8kcal/mol by decorating the Co, Ti, Sc, and Ca metals into the AlPNT surface, respectively. Also, Co, Ti, Sc, and Ca rise the SR to 22.5, 36.8, 50.4, and 89.0, respectively, indicating that by increasing the atomic radius of metals, the sensitivity is more increased. So, we concluded that Ca much more increases the sensitivity of AlPNT toward HZ. Our calculations demonstrate that the electrostatic interaction has the main contribution in the formation of HZ/X decorated AlPNT (X@AlPNT) complexes. The expected recovery time is 22.0s for the HZ desorption from the Ca@AlPNT at 298K. Finally, we found that all of the X@AlPNTs have superior sensing performance toward HZ compared to the X@carbon nanotubes.

Identification of a 3-(5-methyl-2-thiazolylamino)phthalide as a new minor groove agent

A new 3-(5-methyl-2-thiazolylamino)phthalide molecule, 3-((5-methylthiazol-2-yl)amino)isobenzofuran-1(3H)-one, was synthesized and characterized experimentally by FT-IR, NMR, UV-Vis, and single-crystal X-ray analysis and theoretically by quantum chemical calculations. The single-crystal X-ray studies revealed that the compound crystallizes in the monoclinic space group P-21/c with unit-cell parameters a = 8.0550(6) Å, b = 6.1386(3) Å, c = 23.3228(18) Å, β = 97.724(6)° and Z = 4. Optimized geometries and the vibrational frequencies were studied at the density functional theory (DFT) level by using the hybrid functional B3LYP with a 6-311 G (d,p) basis set. The title compound was evaluated for its anti-quorum sensing (anti-QS) activity on Chromobacterium violaceum 12472 and additionally for its antibacterial activity against Staphylococcus aureus 29213, Staphylococcus epidermidis 12228, Pseudomonas aeruginosa 27853, Escherichia coli 25922, and Proteus mirabilis 14153. The lowest MIC value was 0.24 μg/mL for S. aureus 29213 and the highest MIC value was 30.75 μg/mL for E. coli 25922. While anti-bacterial activity was observed in those other than the S. epidermidis and P. Mirabilis, anti-QS activity wasn’t detected. Investigations on dsDNA binding affinity indicate that the title compound binds to dsDNA via the groove binding mode. Molecular docking calculations and molecular dynamics simulations results showed also that the title compound prefers binding to the minor groove of dsDNA and remains stable in the minor groove throughout the molecular dynamics simulation. Communicated by Ramaswamy H. Sarma

Study of the Interaction Between Reduced Graphene Oxide and NO2Gas Molecules via Density Functional Theory (DFT)

Electronic properties such as density of state, energy gap, HOMO (the highest occupied molecular orbital) level, LUMO (the lowest unoccupied molecular orbital) level and density of bonds, as well as spectroscopic properties like infrared (IR), Raman scattering, force constant, and reduced masses for coronene C24, reduced graphene oxide (rGO) C24O5and interaction between C24O5and NO2gas molecules were investigated. Density functional theory (DFT) with the exchange hybrid function B3LYP with 6-311G** basis sets through the Gaussian 09 W software program was used to do these calculations. Gaussian view 05 was employed as a supplementary software to investigate the geometrical structure of C24, C24O5and the interaction of C24O5with NO2gas molecule. It shows the energy gap of coronene C243.5 eV because the effect of quantum confinement and the Coulomb interaction geometry greatly influence the quasi-particle band gap and C24Oxwhere x = 1–7 was from 0.89 eV to 1.6862 eV a function of number of oxygen atoms and compared with the experiment value of graphene oxide which was between 1 eV and 2.2 eV. The spectroscopic properties were compared with the experiment value of graphene, graphene oxide and NO2longitudinal optical (LO) modes of 1 585, 1 582 and 1 600 cm−1, respectively. The transition state of the interaction of rGO with nitrogen dioxide and Gibbs energy, enthalpy, activation entropy and reaction at various temperatures between 25°C and 100°C were calculated. The activation energy of C24O5with nitrogen dioxide decreases with increasing temperature.

Effect of Exchange–correlation Functionals on Ground State Geometries, Optoelectronic and Charge Transfer of Triphenylamine-based Dyes

The importance of the Density Functional Theory (DFT) calculation approach lies in their ability to provide a highly accurate prediction of structural and optoelectronic properties. However, the traditional methods of DFT failed to predict optoelectronic properties satisfactorily. Therefore, it will be necessary to examine methods containing different percentages of Hartree-Fock exchange and correlation in order to find the most suitable functionals. DFT and Time-Dependent-DFT (TD-DFT) calculations was carried out using four different functionals approximations incorporating a different amount of Hartree Fock exchange (B3LYP, BHandHLYP, CAM-B3LYP and LCωPBE), in order to evaluate their accuracies to predict the geometrical, optoelectronic and charge transfer properties of four triphenylamine-based dyes for Dye-Sensitized Solar Cells (DSSCs) applications. The functional hybrid B3LYP was the best among adopted functional that reproduced the geometrical, optoelectronic and charge transfer properties. On the other hand, it has been shown that the Hartree-Fock exchange percentage for BHandHLYP, significantly improved TD-DFT results in the case of organic dyes. Moreover, the corrected long-range functionals (CAM-B3LYP and LC-wPBE) present valuable tools for giving results of comparable precision with experimental optical data. In terms of the choice of the most appropriate functional for computational calculation, the obtained results can be useful for future DSSC applications. DOI: http://dx.doi.org/10.17807/orbital.v14i1.1682

Effect of hydrogen bonds and CF3 group on the regioselectivity and mechanism of [3 + 2] cycloaddition reactions between nitrile oxide and 2,4-disubstitutedcyclopentenes. A MEDT study.

The mechanism and the regioselectivity of the non-polar [3 + 2] cycloaddition reactions between nitrile oxide and two cyclopentenes were theoretically investigated within the molecular electron density theory (MEDT) using DFT methods, namely the B3LYP, MPWB1K and ωB97XD functionals together with the standard 6-31G(d) basis set. The activation energies of these 32CA reactions are relatively high, due to the low nucleophilic power of both cycloalkenes and the relatively moderate electrophilic nature of the nitrile oxide. The B3LYP and MPWB1K functionals reproduced high relative energies values, while the ωB97XD one yields better values in the kinetic and thermodynamic energies. The completely 4-regioselectivity that observed experimentally has been explained by the analysis of the relative energies, in which the formation of 4-regioismeric cycloadducts is always the more kinetically favored one. The electron localization function (ELF) topological analysis showed that the studied 32CA reactions proceed through two-stage one-step nonconcerted mechanism. The effects of the hydrogen bonds on the regioselectivity determination have been investigated by mean both noncovalent interactions (NCI) and quantum theory of atoms in molecule (QTAIM) analyses, which confirm the presence of high strength N - H···O hydrogen bond and a supplementary weak stabilized H…F hydrogen bonds.

Role of functionalized graphene quantum dots in hydrogen evolution reaction: A density functional theory study

Rapid advances in the field of catalysis require a microscopic understanding of the catalytic mechanisms. However, in recent times, experimental insights in this field have fallen short of expectations. Furthermore, experimental searches of novel catalytic materials are expensive and time-consuming, with no guarantees of success. As a result, density functional theory (DFT) can be quite advantageous in advancing this field because of the microscopic insights it provides and thus can guide experimental searches of novel catalysts. Several recent works have demonstrated that low-dimensional materials can be very efficient catalysts. Graphene quantum dots (GQDs) have gained much attention in past years due to their unique properties like low toxicity, chemical inertness, biocompatibility, crystallinity, etc. These properties of GQDs which are due to quantum confinement and edge effects facilitate their applications in various fields like sensing, photoelectronics, catalysis, and many more. Furthermore, the properties of GQDs can be enhanced by doping and functionalization. In order to understand the effects of functionalization by oxygen and boron based groups on the catalytic properties relevant to the hydrogen-evolution reaction (HER), we perform a systematic study of GQDs functionalized with the oxygen (O), borinic acid (BC2O), and boronic acid (BCO2). All calculations that included geometry optimization, electronic and adsorption mechanism, were carried out using the Gaussian16 package, employing the hybrid functional B3LYP, and the basis set 6-31G(d,p). With the variation in functionalization groups in GQDs, we observe significant changes in their electronic properties. The adsorption energy Eads of hydrogen over O-GQD, BC2O-GQD, and BCO2-GQD is −0.059 eV, −0.031 eV and −0.032 eV respectively. Accordingly, Gibbs free energy (ΔG) of hydrogen adsorption is extraordinarily near the ideal value (0 eV) for all the three types of functionalized GQDs. Thus, the present work suggests pathways for experimental realization of low-cost and multifunctional GQDs based catalysts for clean and renewable hydrogen energy production.

Computational analysis of the formation mechanisms of carbazoles.

Gold-, platinum-, and silver-catalyzed formation mechanisms of carbazole alkaloids were investigated computationally. The structural properties of the reactants were studied in various solvents and with different functionals. The hybrid functionals B3LYP and M06-2X in density functional theory were used to determine and discuss the energetics of the compounds. The electronic properties of groups attached to the terminal alkyne played an essential role in the formation of carbazoles. The stereo- and chemoselectivity of the mechanism were investigated and the natural bond orbitals of the reactants were determined. Furthermore, this theoretical study has suggested a gold-catalyzed alternative mechanism for the synthesis of 1,4-dihydrocyclopenta[b]indole derivative.