Highest Occupied Molecular Orbital And Lowest Unoccupied Molecular Orbital Research Articles

Therapeutic Delivery Potential of Covalent Organic Framework (COF): Intuition from Theoretical Calculations

AbstractRegardless of the benefits, pharmaceutical companies are reticent to engage further in covalent organic framework‐based drug development and drug delivery systems, preferring rather to explore preexisting chemical compound libraries for drug delivery. As such, this study aims to account for the efficacy of covalent organic frameworks (COFs) in the delivery of seven conventional drugs: Acetaminophen, Clodronic Acid, Hydroxyurea, Mercaptoporine, Thiotepa, Tioguanine, and Arsenic trioxide. Herein, Gaussian 16 software package is employed for the purpose of optimizing the systems at the DFT/ωB97XD/def2svp level of theory. Substantially, the nature of the inter‐ and intra‐ molecular interactions between the COF and each of the drugs utilized resulted in the re‐adjustment of the molecular orbitals and yielded a distinct set of results for the most reactive and least stable and vice versa as deducible from the magnitudes of the highest occupied molecular orbital and lowest unoccupied molecular orbital (HOMO‐LUMO) gaps. Furthermore, the natural bond orbital (NBO) study indicates that the interacting molecules exhibit similar stability and reactivity, as evidenced by the proximity of their mean stabilization energies. Additionally, the topological analysis revealed that the most positive interaction occurred in Acetaminophen_COF, Clodronic acid_COF, Hydroxyurea_COF, and Tioguanine_COF. Also, the adsorption studies demonstrate that the above‐mentioned drugs have weak interaction kinetics when they interact with the investigated COF. Strong adsorbing contacts were detected in the interactions of Arsenic trioxide, Hydroxyurea, and Tioguanine with the COF in the order Arsenic trioxide_COF < Hydroxyurea_COF < Tiog_COF, with corresponding values of −9.413 kcal/mol, −12.550 kcal/mol, and −17.570 kcal/mol, respectively. Overall, the study hypothesizes that when delivering the various drugs studied through the COF to biological systems, Acetaminophen, Hydroxyurea, Tioguanine, and Mercaptopurine have high reactivity with the COF and would be better adsorbed on it, as well as a longer recovery time of desorption due to their high adsorption on the COF surface.

Intermolecular Interactions between Nitrosourea and Polyoxometalate compounds

AbstractHerein, the aim of this work was to investigate the intermolecular interactions between polyoxometalate (POMs) as a drug‐delivery system with nitrosourea at different sites: CH3, COOH, NH2, NO2 and OCH3 using density functional theory (DFT) at the M062X/LanL2DZ level of theory. The result showed that, the lowest bond lengths recorded for the adsorbate and the nanocage were 1.40Å, 1.64Å, 1.40Å and 1.57Å for NU/POM(CH3), NU/POM(NH2), NU/POM(NO2) and NU/POM(OCH3) respectively. The NU/POM(NO2) system had the highest adsorption energy in the three phases: −32.039, −26.95, and −29.38 kcal/mol for gas, solvent, and benzene respectively and the lowest was shown in NU/POM(OCH3) with −14.10, −10.33, −12.29 kcal/mol. The energy gap was found to be the highest in NU/POM(NO2) with 5.061eV followed by NU/POM and NU/POM(COOH) 4.020eV and 4.003eV respectively. It has been clearly shown that NU/POM(NO2) density peak in the Highest occupied molecular orbital and Lowest unoccupied molecular orbital (HOMO/LUMO) plot was above 5 and this go in line with the electronic properties possessing a stable nature. In the NBO analysis, after adsorption of the nitrosourea (NU), the NU/POM(NO2) system recorded the highest energy with 1309.42 kcal/mol and the lowest in NU/POM(OCH3) with 921.75 kcal/mol. The system with NO2 possess more stability, chemical hardness, electrophilicity index and strong interactions. It has a better surface interaction than other compounds found in Nitrosourea.

Determination of Graphene Migration Single Defect Site and Its Electronic Structure with Various Sizes

The planar hexagon graphene nanoflakes can deform their shape to be distorted after the single vacancy site creation. In this work, density functional theory (DFT) calculations are performed massively on a series sizes of graphene flake with all possible single vacancy site to determine its energetic, structural and electronic properties. It is found that the planar original graphene nanoflakes deform after a single vacancy is generated, and the deformation of graphene nanoflakes decreases with the increase of flake diameter. The formation energy of graphene nanoflakes with single vacancy indicates the stability increases with the size graphene nanoflakes increases. The HOMO-LUMO (Highest Occupied Molecular Orbital and Lowest Unoccupied Molecular Orbital) gap values are only highly related to the size of the system and much less related to different migration locations. The calculate the root mean squared deviation (RMSD) is also calculated to quantify the geometric distortion between original atomic structure and the structures after the creation of single vacancy. The results provide insights into better understanding of the relationship between the formation energy and the size, as well as the distortion change as a function of the graphene flake size, and sufficiently perspective into quantifying the uncertainties in these measurements.

Vibrational (FT-IR, FT Raman), electronic and docking studies and wave function analysis with quantum chemical computation on 3-Bromophenyl acetic acid: A potential amidase inhibitor

The structure of 3-Bromo Phenyl Acetic acid (3BPAA) is optimized and its special features are probed by the FTIR, FT-Raman, UV-Visible and NMR with density functional theory calculations by B3LYP level with 6-311++G(d,p) basis set. The electronic properties were discussed with help of UV-Vis spectrum, MEP (Molecular electrostatic potential) and HOMO-LUMO (Highest occupied molecular orbital and Lowest unoccupied molecular orbital) plots. The energy band gap is found as 4.4437eV. The chemical shift is determined from proton and carbon NMR (Nuclear magnetic resonance) plot by Gauge Independent Atomic Orbital (GIAO) method. The surface analysis such as ELF (Electron localization function), LOL (Localized orbital locator) and ESP (Electrostatic potential) maps are plotted by wave function analyzer. Thermodynamic functions are studied and correlated with the graph. FMO and Fukui functions were calculated and found that the title compound is a chemically soft material. The NLO behavior of the compound is also examined and reported to have higher hyperpolarizability value greater than urea, the reference material ensuring good non-linear optical (NLO) activity. The molecular docking is performed by AUTODOCK tool, its study reveals that the title compound binds well with the protein L- glucorante reductose inhibition. Thus the present work study reports the structural, chemical, electronic, thermodynamic and biological activities of 3BPAA.

Spectroscopic theoretical studies and wave function analysis on 1-Phenyl sulfonyl Pyrrole with quantum chemical computation techniques

The present work investigates on structural and chemical studies on 1-Phenyl Sulfonyl Pyrrole(1PSP) using quantum computational methods. The revamped geometric structure and its parameters were obtained through density functional theory (DFT). The electronic absorption transitions were discussed with different solvents were carried out by TD-DFT (Time Dependent Density Functional Theory) method. The IR intensities and Raman activites are tabulated for vibrational wavenunbers and its corresponding PED (Potential Energy Distribution) assignments in percentage were obtained from VEDA4 software. The inter and intra molecular interactions, electrophilic, nucleophilic and chemical reactivity sites are identified by Molecular electrostatic Potential (MEP), HOMO-LUMO (Highest Occupied Molecular Orbital and Lowest Unoccupied Molecular Orbital) and GCRD (Global chemical reactivity descriptors). Mulliken atomic charges were discussed with Natural Bond Orbital (NBO) analysis. Thermodynamic property and Non-linear optical deportment of the title compound is also talked about. Besides the electron localization function map, the density of states are also mapped with Multiwfn software, a wavefunction analyzer.

A Preliminary First Principle Study on Photochromism of Diarylethene Molecules

Photochromism in some diarylethene molecules have been studied by using hybrid density functional theory using the ground state energy consideration. In particular, B3LYP functional and all electron basis set 6-311G (2d,2p) as implemented in Gaussian09 suites of program has been used to investigate the energy difference of two stable isomers of stilbene, azobenzene, cyclooctane, and 1,2, dimethylcyclohexane molecules. The energy difference is corroborated to calculate the frequencies of photons that are required to induce photochromism in these molecules in vacuum and in solvation state. The study found that the molecules exhibit photochromism at various frequency range from infra-red to ultraviolet. The binding energy per atom, charge distribution, HOMO-LUMO (Highest Occupied Molecular Orbital and Lowest Unoccupied Molecular Orbital) gap are also calculated for all the molecules in vacuum, water and ethanol solvent. The results obtained are in accordance with the experimental observations.

Multiple-Valence Aluminum and the Electronic and Geometric Structure of AlnOm Clusters

Electronic stability in aluminum clusters is typically associated with either closed electronic shells of delocalized electrons or a +3 oxidation state of aluminum. To investigate whether there are alternative routes toward electronic stability in aluminum oxide clusters, we used theoretical methods to examine the geometric and electronic structure of Al nO m (2 ≤ n ≤ 7; 1 ≤ m ≤ 10) clusters. Electronically stable clusters with large HOMO-LUMO (highest occupied molecular orbital and lowest unoccupied molecular orbital) gaps were identified and could be grouped into two categories. (1) Al2 nO3 n clusters with a +3 oxidation state on the aluminum and (2) planar clusters including Al4O4, Al5O3, Al6O5, and Al6O6. The structures of the planar clusters have external Al atoms bound to a single O atom. Their electronic stability is explained by the multiple-valence Al sites, with the internal Al atoms having an oxidation state of +3, whereas the external Al atoms have an oxidation state of +1.

Capturing Volatile Organic Compounds Employing Superalkali Species.

In this study, the interactions between the superalkali species Li3 F2 and four volatile organic compounds (VOCs), methanol, ethanol, formaldehyde, and acetaldehyde, are assessed using the CBS-QB3 composite model. Adiabatic ionization energy (AIE), adiabatic electron affinity (AEA), binding energy (BE), charge transfer (▵q), and highest occupied molecular orbital and lowest unoccupied molecular orbital (HOMO-LUMO) gaps have been computed. Stronger interactions are observed between Li3 F2 and the aldehydes than alcohols. The smaller aldehydes show a larger BE with Li3 F2 than the bigger aldehydes. However, alcohol clusters do not show this trend due to their weak interactions (low BEs). Both alcohol clusters increase their binding energies as they become cations. This unexpected behavior is explained based on molecular orbital arguments.

Experimental and computational studies of L-tartaric acid single crystal grown at optimized pH

The good quality l-tartaric acid (LTA) single crystal of size 12 × 09 × 02 mm3 has been grown by slow solvent evaporation technique by optimizing the pH of aqueous solution. The crystallographic data and crystalline phase of grown LTA crystal has been determined using the powder X-ray diffraction study. The ground state molecular geometry of LTA molecule was optimized by means of CAM-B3LYP/6-31G* level of theory using density functional theory (DFT) approach. The qualitative and quantitative analysis of LTA crystal has been undertaken by means of energy dispersive spectroscopic technique. The UV–visible spectral analysis has been performed to determine the optical transparency of LTA crystal in the range of 190–1100 nm and the optical band gap has been evaluated using the transmittance data. The time dependent-DFT (TDDFT) was employed for calculating the absorption spectrum of the title molecule at B3LYP/6-31G*, CAM-B3LYP/6-31G*, LC-BLYP/6-31G*, M06/6-31G*, PBE1/6-31G* levels of theory. The highest occupied molecular orbital and lowest unoccupied molecular orbital (HOMO-LUMO) energy gap was found to be around 6.02 eV at B3LYP/6-31G* level of theory. The Kurtz-Perry powder test has been undertaken to determine the frequency doubling conversion efficiency of LTA crystal. The laser induced third order nonlinear optical (TONLO) effects occurring in LTA crystal have been evaluated by employing the Z-scan analysis at 640 nm. The phase change in refraction nonlinearity, nature of nonlinear absorption and cubic susceptibility of LTA crystal has been evaluated and their respective magnitudes have been determined. The laser damage threshold of LTA crystal has been investigated using the Nd:YAG laser operative at 1064 nm. The frequency response of dielectric constant and dielectric loss of LTA crystal has been investigated at different temperatures ranging from room temperature to 90 °C. The static dipole moment, polarizability and first hyperpolarizability has been evaluated and compared with standard urea molecule.

Density functional theory molecular modeling, chemical synthesis, and antimicrobial behaviour of selected benzimidazole derivatives

Eco-friendly, one-pot, solvent-free synthesis of biologically active 2-substituted benzimidazoles is presented and discussed herein. Novel N-Mannich bases are synthesized from benzimidazoles, secondary amines and formaldehyde, and their structures are confirmed by 1H nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR), and elemental analysis. All benzimidazole derivatives are evaluated by qualitative and quantitative methods against 9 bacterial strains. The largest microbicide and anti-biofilm effect is observed for the 2-(1-hydroxyethyl)-compounds. Density functional theory (DFT) modeling of the molecular structure and frontier molecular orbitals, i.e. highest occupied molecular orbital and lowest unoccupied molecular orbital (HOMO/LUMO), is accomplished by using the GAMESS 2012 software. Antimicrobial activity is correlated with the electronic parameters (chemical hardness, electronic chemical potential, global electrophilicity index), Mullikan atomic charges and geometric parameters of the benzimidazole compounds. The planarity of the compound, symmetry of the molecule, and the presence of a nucleophilic group, are advantages for a high antimicrobial activity. Finally, we briefly show that further accurate processing of such compounds into thin films and hybrid structures, e.g. by laser ablation matrix-assisted pulsed laser evaporation and/or laser-induced forward transfer, may indeed provide simple and environmental friendly, state-of-the-art solutions for antimicrobial coatings.

High efficiency and low driving voltage blue/white electrophosphorescence enabled by the synergistic combination of singlet and triplet energy of bicarbazole derivatives

New host materials (BCz–DBT and BCz–DBF) are synthesized by regrouped 3,3-bicarbazole (BCz) and dibenzothiophene (DBT)/dibenzofuran (DBF). Their thermal, electrochemical, electronic absorption and photoluminescent properties are also carefully investigated. The materials exhibit high glass transition temperatures (Tg) of 134°C and 139°C, respectively. This kind of molecular design can effectively achieve high triplet energies and suitable highest occupied molecular orbital and lowest unoccupied molecular orbital (HOMO/LUMO) energy levels. High external quantum efficiencies (EQE) of sky blue (EQE=25%) and three-color white (EQE=21.4%) phosphorescent OLEDs have been achieved by using BCz–DBF as the host material.

A density-functional study of aluminium, iron, zirconium and cerium microclusters

The geometries and electronic structural properties of AB and ABC (A, B, C = Al, Fe, Zr, Ce) microclusters have been systematically investigated by using a hybrid density-functional method (B3LYP) approach. The spectroscopic constants of ground-state AB and ABC (A, B, C = Al, Fe, Zr, Ce) are obtained, and are found to be in agreement with other available experimental and theoretical results. The calculated gaps between highest occupied molecular orbital and lowest unoccupied molecular orbital (HOMO-LUMO) are clearly changed when X is doped into the AB dimers (X = Al, Fe, Zr, Ce). The calculated results indicate that a triangular form with D3h, C2v or Cs symmetry is the most stable for the corresponding ABC trimers, and, in addition, the possible isomers (linear structure) with D∞h or C∞v symmetry of three-atom clusters were found to be of higher energies. We conclude that AlFe and Al2Fe have the highest chemical stability of all the AB dimers and ABC trimers, respectively, due to the high HOMO-LUMO gap. We also find that the binding energy of Ce3 is the largest in magnitude among all ABC (A, B, C = Al, Fe, Zr, Ce) trimers, as is the case with Ce2 among all AB (A, B, C = Al, Fe, Zr, Ce) dimers. The most stable geometry, charge transfer and possible dissociation channels are also discussed.

Molecular Geometries and Electronic Structures of Methyl Pyropheophorbide-a and (Cationic) Tropolonyl Methyl Pyropheophorbides: DFT Calculation

This study reports on the geometry optimizations and electronic structure calculations for methyl pyropheophorbide (MPPa), tropolonyl methyl pyropheophorbides (TMPPa, ITMPPa), and cationic tropolonyl methyl pyropheophorbides (<TEX>$TMPPa^+{{\cdot}BF_4}^-,\;ITMPPa^+{{\cdot}BF_4}^-,\;TMPPa^+,\;and\;ITMPPa^+$</TEX>) using Local Spin Density Approximation (LSDA/ 6-31G*) and the Restricted Hatree-Fock (RHF/6-31G*) level theory. From the calculated results, we found that substituted cationic tropolonyl groups have larger structural effects than those of substituted neutral tropolonyl groups. The order of structural change effects is <TEX>$ITMPPa^+ > ITMPPa^+{{\cdot}BF_4}^-$</TEX> > ITMPPa, as a result of the isopropyl group. Because it is an electron-releasing group, the substituted isopropyl group electronic effect on a 3-position tropolone increases the Highest Occupied Molecular Orbital and Lowest Unoccupied Molecular Orbital (HOMO-LUMO) energy gap. It was constituted that the larger the cationic characters of these photosensitizers, the smaller the HOMOLUMO band gaps are. The orbital energies of the cationic systems and the ions are stronger than those of a neutral system because of a strong electrostatic interaction. However, this stabilization of orbital energies are counteracted by the distortion of chlorin macrocycle, which results in a large destabilization of chlorin-based compound HOMOs and smaller destabilization of LUMOs as shown in TMPPa (ITMPPa), <TEX>$TMPPa^+{{\cdot}BF_4}^- (ITMPPa^+{{\cdot}BF_4}^-),\;and\;TMPPa^+\;(ITMPPa^+)$</TEX> of Figure 6 and Table 6-7. These results are in reasonable agreement with normal-coordinate structural decomposition (NSD) results. The HOMO-LUMO gap is an important factor to consider in the development of photodynamic therapy (PDT).

Computational investigation of TiSin (n=2–15) clusters by the density-functional theory

The geometries, stabilities, and electronic properties of TiSin (n=2-15) clusters with different spin configurations have been systematically investigated by using density-functional theory approach at B3LYP/LanL2DZ level. According to the optimum TiSin clusters, the equilibrium site of Ti atom gradually moves from convex to surface, and to a concave site as the number of Si atom increases from 2 to 15. When n=12, the Ti atom in TiSi12 completely falls into the center of the Si outer frame, forming metal-encapsulated Si cages, which can be explained by using 16-electron rule. On the basis of the optimized geometries, various energetic properties are calculated for the most stable isomers of TiSin clusters, including the average binding energy, the highest occupied molecular orbital and lowest unoccupied molecular orbital (HOMO-LUMO) gap, fragmentation energy, and the second-order difference of energy. It is found that at size n=6,8,12 the clusters are more stable than neighboring ones. According to the Mulliken charge population analysis, charges always transfer from Si atoms to Ti atom. Furthermore, the HOMO-LUMO gaps of the most stable TiSin clusters are usually smaller than those of Sin clusters.

A computational investigation of copper-doped germanium and germanium clusters by the density-functional theory

The geometries, stabilities, and electronic properties of Ge(n) and CuGe(n) (n = 2-13) clusters have been systematically investigated by using density-functional approach. According to optimized CuGe(n) geometries, growth patterns of Cu-capped Ge(n) or Cu-substituted Ge(n+1) clusters for the small- or middle-sized CuGe(n) clusters as well as growth patterns of Cu-concaved Ge(n) or Ge-capped CuGe(n-1) clusters for the large-sized CuGe(n) clusters are apparently dominant. The average atomic binding energies and fragmentation energies are calculated and discussed; particularly, the relative stabilities of CuGe10 and Ge10 are the strongest among all different sized CuGe(n) and Ge(n) clusters, respectively. These findings are in good agreement with the available experimental results on CoGe10- and Ge10 clusters. Consequently, unlike some transition metal (TM)Si12, the hexagonal prism CuGe12 is only low-lying structure; however, the basket-like structure is located as the lowest-energy structure. Different from some TM-doped silicon clusters, charge always transfers from copper to germanium atoms in all different sized clusters. Furthermore, the calculated highest occupied molecular orbital and lowest unoccupied molecular orbital (HOMO-LUMO) gaps are obviously decreased when Cu is doped into the Ge(n) clusters, together with the decrease of HOMO-LUMO gaps, as the size of clusters increases. Additionally, the contribution of the doped Cu atom to bond properties and polarizabilities of the Ge(n) clusters is also discussed.