HOMO Energy Gap Research Articles

Comprehensive spectroscopic (FT-IR, FT-Raman, 1H and 13C NMR) identification and computational studies on 1-acetyl-1H-indole-2,3-dione

AbstractFourier transform infrared (FT-IR) and FT-Raman spectra of 1-acetyl-1H-indole-2,3-dione (N-acetylisatin) were recorded in the solid phase and analyzed. The molecular geometry, vibrational frequencies, infrared intensities, Raman activities and atomic charges were calculated using density functional theory (DFT/B3LYP) calculations with a standard 6-311++G(d,p) basis set. The fundamental vibrational modes of N-acetylisatin were analyzed and fully assigned with the aid of the recorded FT-IR and FT-Raman spectra. The simulated FT-IR and FT-Raman spectra showed good agreement with the experimental spectra. The stability of the molecule, arising from hyper-conjugative interactions and charge delocalization, was analyzed using natural bond orbital (NBO) analysis. The dipole moment (µ), polarization (α) and hyperpolarization (β) values of N-acetylisatin were also computed. The potential energy distribution (PED) was computed for the assignment of unambiguous vibrational fundamental modes. The HOMO and LUMO energy gap illustrated the chemical activity of N-acetylisatin. The energy and oscillator strength were calculated by DFT. Gauge–including atomic orbital NMR (1H and 13C) chemical shift calculations were performed and compared with the experimental values. Thermodynamic properties (heat capacity, entropy and enthalpy) of the compound at different temperatures were also calculated.

Dyeing properties of the disperse dyes containing cyano group based on benzisothiazole for polyester fabrics under alkali condition

One step dyeing of polyethylene terephthalate (PET) fabrics combining pretreatment and dyeing under the alkali condition was developed for cleaner production. One step dyeing of PET fabrics required that the dye used has good acid and alkali stability. In this paper, dyeing properties of three azo disperse dyes containing cyano group based on benzisothiazole, 3- (4-N-ethoxyl-N-cyanoethyl -phenyldiazenyl)-5-nitro-2,1-benzisothiazole (D1), 3-(4-N-ethyl-N-cyanoethyl- phenyldiazenyl)- 5-nitro-2,1-benzisothiazole (D2), and 3-(N-benzyl-N-cyanoethyl- phenyldiazenyl)-5-nitro-2,1-benzisothiazole (D3), were investigated under alkali condition. The results showed that polyester fabrics could be well dyed with D1, D2 and D3 under the acid condition. However, D1 was decomposed while dyeing at the alkali solution. D2 and D3 had excellent color yields under the alkali condition. The acid-alkali stability and the structure change were analyzed by UV-vis spectrum and high pressure liquid chromatography (HPLC). Gaussian 09 program package was used to optimize geometry by B3LYP method and 6-31G (d) basis set. The solvation energy of D1 in water was higher than those of D2 and D3. The electron withdrawn effect of the hydroxyl affected the energy gap of HOMO and LUMO orbits. D2 and D3 showed excellent stability in the strong alkali medium. And the dyed polyester fabrics with D2 and D3 at the alkali condition also had good fastness properties.

Correlating cluster size and NLO response of complexes aggregated with bifurcated metal bonds: a DFT study

In the present work, the cooperativity effect on the NLO response of clusters aggregated with bifurcated metal bonds is reported by DFT calculations at the CAM-B3LYP/6-311++G(d,p) level. Linear clusters of (LiN(CHO)2)1-5 and (NaN(CHO)2)1-5 which are connected with bifurcated metal bonds have been selected as model systems. Stabilization energies, polarizability, first hyperpolarizability, energy gap of HOMO and LUMO, and charge transfer (CT) were obtained at the same level of optimization. In the studied clusters, first hyperpolarizability is increased by cluster size and its values were obtained in ranges of 606.1–1327.4 and 1239.4–2071.1 a.u. for (LiN(CHO)2)1-5 and (NaN(CHO)2)1-5 clusters, respectively. The many-body analysis was carried out to determine two-body and many-body contributions in total interaction-induced properties. TD-DFT calculations were performed to compute the crucial electronic transitions of the related clusters. UV–vis spectra exhibit red shift due to cooperativity effects.

Recognition of switching on or off fluorescence emission spectrum on the Schiff-bases as a Mg2+ chemosensor: A first principle DFT and TD-DFT study

Today, due to convenience, rapid diagnosis and etc., chemosensors are widely used to detect metal ions. In the current research, through DFT and TD-DFT methods, 8-hydroxyquinoline-5-carbaldehyde-(benzotriazol-1′-acetyl) (QCH) ligand was used to identify Mg2+ cation and investigate its fluorescence emission spectrum mechanism. In order to investigate electronic properties, natural bond orbital (NBO) analysis, reduced density gradient (RDG) plots and electron localization function (ELF) as well as, changes in energy gap of HOMO and LUMO orbitals in the ground state, in water solution were used. Energy gap underwent change about ΔE = 0.17 eV in the presence of Mg2+ cation. Using TD-DFT calculations the optical absorption and emission of QCH ligand was investigated in the presence and absence of Mg2+cation. QCH ligand lacks emission spectrum but in the presence of Mg2+cation shows an emission spectrum in the wavelength of λEmi = 611 nm. Using electron-hole theory, photoinduced electron transfer (PET) process and fluorescence emission spectrum mechanism were investigated. Turning on emission spectrum in the presence of Mg2+ cation is due to stopping charge transfer from chelator to fluorophore.

Synthesis, X-ray single crystal structure, likelihood of occurrence of intermolecular contacts, spectroscopic investigation and DFT quantum chemical calculations of zwitterionic complex: 1-Ethylpiperaziniumtrichlorozincate (II)

The synthesis and the X-ray structure of the Zn(II) zwitterionic complex:1-ethylpiperaziniumtrichlorozincate (II) are described. In the atomic arrangement, the ZnCl3N entities, grouped in pairs, are deployed along the b-axis to form layers. The organic entities are inserted between these layers through NH⋯Cl and CH⋯Cl hydrogen bonds to form infinite three-dimensional network. The 3D Hirshfeld surfaces were investigated for intermolecular interactions. The optimized geometry, Mulliken charge distribution, molecular electrostatic potential (MEP) maps and thermodynamic properties have been calculated using the Lee-Yang-Parr correlation functional B3LYP with the LanL2DZ basis set. The HOMO and LUMO energy gap and chemical reactivity parameters were made. The 13C and 15N CP-MAS NMR spectra are in agreement with the X-ray crystal structure. The vibrational absorption bands were identified by infrared spectroscopy. DFT calculations allowed the attribution of the NMR peaks and of the IR bands.

Theoretical thermochemical studies of phenylacetylene scaffolds

Phenylacetylene scaffolds are known to be an important component in electronic devices, but their thermochemistry has not been studied so far. In this paper, we systematically calculate the strain energies (SE) and the standard enthalpies of formation (ΔfH298°) of sixteen linear polyynes-substituted benzene (PSB) and seven cyclic[n]orthophenyleneacetylenes ([n]COPAs) (n=2–8). The geometries and vibrational frequencies of PSB were calculated at B3LYP/6–31+G(d,p), mPW1PW91/6–31+G(d,p), and M06-2X/6–31+G(d,p) levels of theory and for [n]COPAs, mPW1PW91/6-31G(d) was used. Isodesmic and homodesmotic reactions approach were used to calculate SE and ΔfH298°. The results show that ΔfH298°of PSB increases steadily with the increasing the numbers of CC linkage, and endothermicΔfH298°of these molecules are indicative of an acetylene substituent strain. The SE per-unit monomer (SE/n), and ΔfH298°per-unit monomer (ΔfH298°/n) of [n]COPAs were calculated and results were compared with its meta and para counterpart. In addition, electronic properties such as HOMO, LUMO and HOMO-LUMO energy gap were calculated.

Electrochemical oxygen reduction mechanism on FeN2-graphene.

Metal-coordinated nitrogen-doped carbons are highly active in promoting electrochemical oxygen reduction reactions (ORR). The detailed kinetic and thermodynamic ORR behavior on three different FeN2-graphene [FeN2-G (A), (B) and (C)] structures was investigated in this work. The results show that formation of these FeN2-G configurations is energetically favorable; however, not all of them are effective for ORR. The higher HOMO energy and smaller HOMO-LUMO gap of FeN2-G (A) and (C) make them have strong adsorption strengths to ORR intermediates, which leads to occupation the active sites on the catalysts during ORR, and thus loss of catalytic activity. Examination of the results of ∆G of each reduction step also drew the same conclusion. The ∆G of the elementary steps of the ORR at zero electrode potential vs. standard hydrogen electrode are downhill only on FeN2-G (B). Throughout the entire four-electron ORR, the reduction of O to OH displays the highest reaction barrier. When the potential is >0.19V, the reduction of OH species into water is uphill. Therefore, ORR activity is limited by two rate-determining steps on FeN2-G (B) at high potential: O and OH reduction steps.

The solvent (water) and metal effects on HOMO-LUMO gaps of guanine base pair: A computational study

The most stable structures of guanine dimer and metal-mediated guanine base pair complexes were determined both in vacuum and solvent (water). Density functional theory (DFT) method is generally used in the calculations. The calculations of systems containing C, H, N, O is described by 6-311++G(d,p) basis set and LANL2DZ basis set is used for transition metals. Some geometrical parameters, the LUMO, HOMO energy levels and energy gaps of compounds are calculated. Hydrogen bond stabilization energies in dimer and charge transfer in metal complexes are also determined using NBO analysis. The solvent and metal effects on energy gaps of molecules are found. Cu-mediated guanine complex can be preferred for nanotechnological applications due to its good electronic properties.

DFT and TD-DFT investigations of organic dye with different π-spacer used for solar cell

The ground-state geometries and electronic properties of two D–π–A dyes (LEG4 and LEG4F) have been studied by using density functional theory (DFT) and time-dependent density functional theory. LEG4 and LEG4F have the same donor (triphenylamine) and acceptor (carboxylic acid) bridged by different π-spacer. We estimated the light harvesting efficiency, energy levels and electron density, electron accepting power, molar extinction coefficient, electron injection free energy, chemical hardness and reorganization energy. The results demonstrate that LEG4F has higher HOMO energy and lower energy gap, which is benefit to electron transfer. For configuration of LEG4F, it was found that it has a widen absorption spectra and larger maximum absorption strength, bigger light harvesting efficiency and improved electron injection ability in comparison with LEG4. The difference of photoelectric parameters for solar cell has been interpreted from the viewpoint of calculation, which is an important clue for understanding the relationship between structure and performance.

Quantum mechanical analysis, spectroscopic (FT-IR, FT-Raman, UV-Visible) study, and HOMO-LUMO analysis of (1 S ,2 R )-2-amino-1-phenylpropan-1-ol using Density Functional Theory

In this study, the Fourier Transform Infrared (FT-IR) and FT-Raman of (1S,2R)-2-amino-1-phenylpropan-1-ol (abbreviated as 2APPO) have been recorded in the regions 4000-100 cm− 1 and 4000–400 cm− 1, respectively. A complete assignment and analysis of the fundamental vibrational modes of the molecule were carried out. The observed fundamental modes have been compared with the harmonic vibrational frequencies computed using DFT (B3LYP) method by employing 6-31 ++G(d,p) basis set. The vibrational studies were interpreted in terms of potential energy distribution. This study is extended to the HOMO - LUMO analysis to calculate the HOMO and LUMO energy gap (Δ), Ionization potential (I), Electron Affinity (A), Global Hardness (η), Chemical Potential (μ), Global Electrophilicity (ω) and the calculated HOMO, LUMO energy reveals shows that the charge transfers occurring within the molecule. In the thermodynamic properties of the 2APPO compound have been calculated at different temperatures and the results reveal that the standard heat capacities (Cp,m), standard entropies (Sm) and standard enthalpy changes (Hm) increase with rise in temperature.

A dual responsive colorimetric and fluorescent reversible turn-on chemosensor for iron (Fe3+): Computational and spectroscopic investigations

Herein, we report a highly selective dual responsive chemosensor for detecting iron ion. The structural characterization of synthesized compounds was investigated on the basis of UV–vis, FTIR, 1NMR, 13NMR and Mass spectral data. The sensitivity and selectivity of RDFB toward Fe3+ among different metal ions was examined by absorption, fluorescence, FTIR and mass spectral studies. Complexing with Fe3+ ion leads to spirolactam ring opening of RDFB and consequently causes a color variation from colorless to red. Fe3+-specific binding to RDFB afford a 53-fold enhancement in fluorescence intensity and strong absorption in the visible range. The 1:1 binding mode was proposed on the basis of absorption, FTIR and MS studies. The HOMO and LUMO energy gap for RDFB and RDFB-Fe3+ complex were found to be 3.782eV and 1.875eV suggesting that the interaction of Fe3+ to RDFB reduces the HOMO-LUMO energy gap of the complex and stabilizes the system. The association constant of newly synthesized compound to the receptor is found to be 1.13×105M−1 which further implying the potential of RDFB to acts as a selective chemosensor for Fe3+ ions. Furthermore the reversibility of complexation of RDFB to Fe3+ was also studied by conducting experiments against EDTA.

Interaction of Fluorescent 2-(1-Methoxynaphthalen-4-Yl)-1-(4-Methoxyphenyl)-4, 5-Diphenyl-1H-Imidazole with Pristine Zno, Cu-Doped Zno and Ag-Doped Zno Nanoparticles

A sensitive 2-(1-methoxynaphthalen-4-yl)-1-(4-methoxyphenyl)-4, 5-diphenyl-1H-imidazole (MNMPI) fluorescent sensor for nanoparticulates like ZnO, Cu-doped ZnO and Ag-doped ZnO has been designed and synthesized. Facile preparation of ZnO, Cu-doped ZnO and Ag-doped ZnO nanoparticles by sol-gel method using PVP K-30 as templating agents is reported and characterised by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), UVVisible spectroscopy and photoluminescence spectroscopy (PL). The synthesized sensor release is enhanced by nanocrystalline pristine ZnO but is suppressed by Cu-doped ZnO and Ag-doped ZnO nanoparticles. The suppression of fluorescence is additional by copper than by silver doping. The LUMO and HOMO energy gap of MNMPI associated with Cu-doped ZnO are lowers compared to those of pristine ZnO and thus red shift compared to that with pristine ZnO. The average crystallite sizes of ZnO, Cu-doped ZnO and Ag-doped ZnO have been deduced as 32 nm, 36 nm and 26 nm and calculated surface area for ZnO, Cu-doped ZnO and Ag-doped ZnO are 30.04 m2/g, 40.66 m2/g and 29.37 m2/g respectively. The observed enhanced absorbance with the distributed semiconductor nanoparticle is due to adsorption of MNMPI on semiconductor surface. This is because of the efficient transfer of electron from the excited state of the MNMPI to the conduction band of the semiconductor nanoparticle.

Computational study on the structural and optoelectronic properties of a carbazole-benzothiadiazole based conjugated oligomer with various alkyl side-chain lengths

The effect of the alkyl side-chain length on the structural and optoelectronic properties of poly[N-9′-heptadecanyl-27-carbazole-alt-55-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT) conjugated oligomers have been studied by density functional theory (DFT) and time-dependent density functional theory (TD-DFT). The study was carried out by varying the length of alkyl side-chain attached to the nitrogen atom of the carbazole unit of the PCDTBT oligomers. The structural properties of the optimised oligomers were then studied by determining the bond-length alternation and dihedral angles (Φ) for various side-chain lengths. Total energy calculations for the determination of HOMO energy (EHOMO), LUMO energy (ELUMO), and fundamental energy gap (EGap) were performed using DFT at the B3LYP/6-31G(d), while the first singlet excitation energies (EOpt) were calculated by TD-DFT also at the same level of theory. It was observed that there are no significant structural changes occurring as the alkyl chain lengths are varied. For the electronic properties, very small differences (i.e. ~0.01 eV) were observed for EGap and EOpt while the exciton binding energies (EB) were virtually the same. The results suggest that using shorter alkyl side-chains do not significantly affect the structural and optoelectronic properties of the carbazole-benzothiadiazole based polymer. The observations can aid future computational design studies of analogous systems by reducing large structures thus decreasing computational costs.

New benzothiadiazole-based dyes incorporating dithieno[3,2-b:2′,3′-d]pyrrole (DTP) π-linker for dye-sensitized solar cells with different electrolytes

Abstract Benzothiadiazole (BTZ)-based dyes incorporating dithieno[3,2- b :2′,3′- d ]pyrrole (DTP) π-linker has been synthesized for fabricating efficient dye-sensitized solar cells (DSSCs). A reference dye with ethylenedioxythiophene (EDOT) π-linker has also been prepared. The introduction of DTP broadens absorption, provides a more planar skeleton, and reduces HOMO and LUMO energy gap. IMVS and EIS measurements are used to investigate interfacial electron transfer processes of device. Dyes incorporating DTP exhibit more effective inhibition of charge recombination and more conducive to electron injection than the reference dye with EDOT. Therefore, much higher efficiency is obtained in device fabricated by DTP-based dyes, and the best performance achieves a power conversion efficiency of 8.14% by using Co-phen based electrolyte. In contrast, device based on the reference dye reaches 5.22% at most. IPCE characterizations and the effect of Co-bpy and I − /I 3 − redox couple are also discussed. The DTP moiety is a good candidate for the design of BTZ-based sensitizers used in DSSCs.

Spectral investigations, DFT based global reactivity descriptors, Inhibition efficiency and analysis of 5-chloro-2-nitroanisole as π-spacer with donor-acceptor variations effect for DSSCs performance

FTIR, FT-Raman, UV, NMR and quantum chemical calculation studies are performed on 5-chloro-2-nitroanisole, in order to gain the insights of its structural, spectroscopic and electronic properties (Fukui indices, HOMO and LUMO energy gap, MESP and Global reactivity descriptors). A complete vibrational analysis of 5-chloro-2-nitroanisole is performed by HF/B3LYP methods using 6-31G(d,p) basis set. To estimate the electronic transitions, the UV spectra of title compound are predicted in gas phase and ethanol. The obtained absorption maxima at 389.94 nm (in ethanol) is predicted possibly due to HOMO→LUMO transition with 85% contribution and assigned as π-π*. The MESP map shows that the negative potential sites are localized on oxygen atom (O10) as well as the positive potential sites are identified around the hydrogen and ring carbon atoms. The analysis of Fukui indices is also carried out to distinguish the nucleophilic and electrophiic centers. The prediction of reactive sites by MESP is well supported by this Fukui indices analysis. The correlations between the statistical thermodynamics and temperature are also obtained. It is seen that the heat capacities, entropies and enthalpies increase with increasing the intensities of the molecular vibrations. Furthermore, the first hyperpolarizability of 5-chloro-2-nitroanisole is calculated and the results are discussed. This result indicates that 5-chloro-2-nitroanisole is a good candidate of nonlinear optical materials.

Modeling of the electronic, optoelectronics, photonic and thermodynamics properties of 1,4-bis(3-carboxyl-3-oxo-prop-1-enyl) benzene molecule

The modeling of the molecule 1,4-bis(3-carboxyl-3-oxo-prop-1-enyl) benzene has been carried out to study the electronic, optoelectronics, photonic and thermodynamics properties using Hartree–Fock, density functional theory (B3LYP) and MP2 (Moller–Plesset perturbation theory second-order) with the 6-31G and 6-31+G** basis sets. The dipole moment (µ), polarizability (〈α〉), first hyperpolarizability (βmol), dielectric constant (e), electric susceptibility (χ), refractive index (η) and thermodynamics properties of this molecule have been calculated using the same level of theory. The small values of e, and LUMO–HOMO energy gap, and the high values of χ, η, MR, 〈α〉 and (βmol) show that the molecule has very good electronic, optoelectronic and photonic applications. The results of this study show that this molecule is an interesting pi-conjugated molecule whose electronic structure and properties can be regulated over a wide range by variation in backbone structure, by side group substitution, and through intramolecular hydrogen bonding.

Electronic Modulation of the SOMO-HOMO Energy Gap in Iron(III) Complexes towards Unimolecular Current Rectification.

Amphiphilic five-coordinate iron(III) complexes with {N2 O2 Cl} and {N2 O3 } coordination spheres are studied to elucidate the roles of electronic structure on the mechanisms for current rectification. The presence of an apical chlorido or phenolato ligand plays a crucial role, and the [Fe(III) {N2 O2 Cl}] species supports an asymmetric mechanism while its [Fe(III) {N2 O3 }] counterpart seems to allow for unimolecular mechanism. The effects of electron-donating and electron-withdrawing substituents in the ligand frameworks are also considered.

Structural and Vibrational Studies (FT-IR, FT-Raman) of Voglibose Using DFT Calculation

In the present study, we report on the Molecular structure and infrared (IR) and FT-Raman studies of Voglibose (VGB) as well as by calculations based on the density functional theory (DFT) approach; utilizing B3LYP/6-31G(d,p) basis set. The targeted interpretation of the vibrational spectra intended to the basis of calculated potential energy distribution matrix (PED) utilizing VEDA4 program. Stability of the molecule arising from hyperconjugative interactions and charge delocalization was studied using natural bond orbital (NBO) analysis. The results show that change in electron density in the σ∗ and π∗ antibonding orbitals and E2 energies confirm the occurrence of intramolecular charge transfer within the molecule. The UV-Visible and NMR spectral analysis were reported by using TD-DFT and gauge GIAO approach respectively and their chemical shifts related to TMS were compared. The lowering of HOMO and LUMO energy gap appears to be the cause for its enhanced charge transfer interactions. Besides, molecular electrostatic potential (MEP) analysis was reported. Due to different potent biological properties, the molecular docking results are also reported.

Structural and Vibrational Studies (FT-IR, FT-Raman) of Voglibose Using DFT Calculation

In the present study, we report on the Molecular structure and infrared (IR) and FT-Raman studies of Voglibose (VGB) as well as by calculations based on the density functional theory (DFT) approach; utilizing B3LYP/6-31G(d,p) basis set. The targeted interpretation of the vibrational spectra intended to the basis of calculated potential energy distribution matrix (PED) utilizing VEDA4 program. Stability of the molecule arising from hyperconjugative interactions and charge delocalization was studied using natural bond orbital (NBO) analysis. The results show that change in electron density in the σ∗and π∗antibonding orbitals and E2energies confirm the occurrence of intramolecular charge transfer within the molecule. The UV-Visible and NMR spectral analysis were reported by using TD-DFT and gauge GIAO approach respectively and their chemical shifts related to TMS were compared. The lowering of HOMO and LUMO energy gap appears to be the cause for its enhanced charge transfer interactions. Besides, molecular electrostatic potential (MEP) analysis was reported. Due to different potent biological properties, the molecular docking results are also reported.

Synthesis, crystal structure analysis, spectral investigations, DFT computations, Biological activities and molecular docking of methyl(2E)-2-{[N-(2-formylphenyl)(4-methylbenzene) sulfonamido]methyl}-3-(4-fluorophenyl)prop-2-enoate, a potential bioactive agent

The title compound methyl(2E)-2-{[N-(2-formylphenyl) (4-methylbenzene)sulfonamido]methyl}-3-(4-fluorophenyl) prop-2-enoate (MFMSF) has been synthesized and single crystals were grown by slow evaporation solution growth technique at room temperature. The grown crystals were characterized by FTIR, 1H NMR, 13C NMR, and single crystal X-ray diffraction. In the crystal, molecules are linked by intermolecular C–H…O hydrogen bonds forming a two-dimensional supramolecular network along [110] direction. The molecular geometry was also optimized using density functional theory (DFT/B3LYP) method with the 6-311G (d,p) basis set in ground state and compared with the experimental data. The entire vibrational assignments of wave numbers were made on the basis of potential energy distribution (PED) by VEDA 4 programme. Stability of the molecule arising from hyper conjugative interactions, charge delocalization has been analyzed using natural bond orbital (NBO) analysis. In addition, NLO, MEP, Mulliken, thermodynamic properties, HOMO and LUMO energy gap were theoretically predicted. The global chemical reactivity descriptors are calculated for MFMSF and used to predict their relative stability and reactivity. The antibacterial activity of the compound was also tested against various pathogens. The molecular docking studies concede that title compound may exhibit PBP-2X inhibitor activity.