Artykuły w czasopismach: „Highest Occupied Molecular orbitals (HOMO) Offsets”

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Murata, Ryo, Zhe Wang i Manabu Abe. "Singly Occupied Molecular Orbital−Highest Occupied Molecular Orbital (SOMO−HOMO) Conversion". Australian Journal of Chemistry 74, nr 12 (2021): 827. http://dx.doi.org/10.1071/ch21186.

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Singly occupied molecular orbital−highest occupied molecular orbital (SOMO−HOMO) conversion (inversion), SHC, is a phenomenon in which the SOMO is lower in energy than the doubly occupied molecular orbitals (DOMO, HOMO). A non-Aufbau electronic structure leads to unique properties such as a switch in bond dissociation energy and the generation of high-spin species on one-electron oxidation. In addition, the pronounced photostability of these species has been reported recently for application in organic light-emitting devices. In this review article, we summarise the chemistry of SOMO−HOMO converted (inverted) species reported to date.

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Tanaka, Jiro. "QUANTUM CHEMICAL STUDY ON THE DOPING MECHANISM OF CUPRATE SUPERCONDUCTORS". International Journal of Modern Physics B 14, nr 29n31 (20.12.2000): 3691–96. http://dx.doi.org/10.1142/s0217979200004234.

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Molecular orbital calculations on the model clusters of cuprate superconductor are presented to show the mechanism of insulator to metal transition. Highest occupied molecular orbitals (HOMO) of the model clusters of one-dimensional chain showed that the metallic carrier will appear above 6% doping level, which is consistent with experimental results.

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AUGSTEIN, B. B., i C. FIGUEIRA DE MORISSON FARIA. "HIGH-ORDER HARMONIC GENERATION IN DIATOMIC MOLECULES: QUANTUM INTERFERENCE, NODAL STRUCTURES AND MULTIPLE ORBITALS". Modern Physics Letters B 26, nr 02 (20.01.2012): 1130002. http://dx.doi.org/10.1142/s021798491130002x.

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We present a summarizing account of a series of investigations of high-order harmonic generation (HHG) in diatomic molecules beyond the single-active electron and single-active orbital approximation. In these investigations, we include not only the highest occupied molecular orbital (HOMO), but also the lower lying orbitals and the lowest unoccupied molecular orbital (LUMO) in modified versions of the strong-field approximation. We employ perturbation theory around the HOMO, multielectron wavefunctions and initial coherent superpositions of the HOMO and LUMO. The imprints of multiple orbitals, nodal structures and two-center interference on the HHG spectra are investigated in detail, for homonuclear and heteronuclear molecules. We find that, in many situations, different molecular orbitals can be traced back to different energy regions in the spectra. Furthermore, imprints of nodal structures in heteronuclear molecules can be understood by analyzing nodal planes in isoelectronic homonuclear molecules. This opens up a wide range of possibilities for molecular imaging applications.

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Wolfe, Saul, Zheng Shi, C. E. Brion, James Rolke, Yenyou Zheng, Glyn Cooper, Delano P. Chong i C. Y. Hu. "Electron momentum spectroscopy of the frontier electrons of DABCO does not support an sp3 hybrid lone-pair description". Canadian Journal of Chemistry 80, nr 3 (1.03.2002): 222–27. http://dx.doi.org/10.1139/v01-201.

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The highest occupied molecular orbital (HOMO) and next-highest occupied molecular orbital (NHOMO) valence orbital electron density distributions of 1,4-diazabicyclo[2.2.2]octane (DABCO) have been investigated by electron momentum spectroscopy, a technique that probes the orbital-like nature of valence (frontier) electron transfer out of a molecule. The experimental results are compared to a range of 6-311++G** calculations to assess the relative merits of three different orbital models that have commonly been used in chemistry. The delocalized (correlated) canonical KohnSham orbitals calculated using the B3LYP or B3PW91 functionals and density functional theory provide near quantitative agreement with the observed valence electron momentum density distributions, and the delocalized canonical molecular orbitals of HartreeFock (independent particle) theory are in semiquantitative agreement. In contrast, Pauling's widely used and taught valence bond (hybridization) model, which is equivalent to a localized molecular orbital description, does not correspond at all to the experimental measurements. It follows that, for considerations of electron transfer, the "lone pairs" of DABCO are not localized or hybridized, but rather exist as nondegenerate orbitals that are delocalized differently over the molecular framework. The existence of two different experimental valence orbital electron densities of DABCO provides direct confirmation of the frontier orbital HOMONHOMO energy splitting and reordering predicted many years ago by Hoffmann et al. using extended Hückel theory, and interpreted in terms of "through bond" and "through space" interactions.Key words: orbitals, lone pairs, orbital interaction, hybridization.

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Ren, Zhongxue, Yan Yang, Yalei Zhu, Xiaolei Zan, Jing Zhao i Zengxiu Zhao. "Three-dimensional tomographic imaging of CO molecular orbitals reveals multi-electron effects". Journal of Physics B: Atomic, Molecular and Optical Physics 54, nr 18 (22.09.2021): 185601. http://dx.doi.org/10.1088/1361-6455/ac2e4b.

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Abstract According to the asymmetric molecular orbital reconstruction algorithm, which divides orbital into gerade and ungerade components and which does not depend on the unidirectional recollisional condition, we obtain the two-dimensional highest occupied molecular orbital (HOMO) of CO based on the directly calculated transition dipole moment and the harmonic spectra calculated by the Lewenstein model, respectively, which is the three-dimensional (3D) HOMO projected onto the plane perpendicular to the laser propagation direction. In order to retrieve the full orbital function, a 3D molecular orbital tomography (MOT) method is developed and is successfully applied to the reconstructions of the HOMO of CO, which simplifies the 3D imaging process of orbitals of linear molecules, and is expected to be extended to reconstruct the 3D orbitals of nonlinear molecules. In addition, the time-dependent density functional theory is employed to acquire the harmonic spectra of CO in a 800 nm and 1500 nm wavelength laser, respectively. The comparison of these two reconstruction results helps identify the multi-electron effects for asymmetric MOT, which requires further study. This work advances the development of MOT and is expected to reveal multi-electron effects in orbital imaging of complex polyatomic molecules.

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STARIKOV, E. B. "IMPORTANCE OF CHARGE TRANSFER EXCITATIONS IN DNA ELECTRON SPECTRUM: A ZINDO SEMIEMPIRICAL QUANTUM-CHEMICAL STUDY". Modern Physics Letters B 18, nr 16 (10.07.2004): 825–31. http://dx.doi.org/10.1142/s0217984904007360.

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Electron spectra of DNA model compounds, adenosine-thymidine and guanosine-cytidine nucleoside base pairs, as well as the relevant homogeneous stacked base pair steps in A-DNA and B-DNA conformations, were investigated using ZINDO semiempirical quantum-chemical method. This work confirms that, in DNA with intact Watson–Crick hydrogen bonding and base stacking, the highest occupied molecular orbitals (HOMO) are residing on purine base residues, whereas the lowest unoccupied molecular orbitals (LUMO) — on pyrimidine base residues. In general, the present results are satisfactorily comparable with the available experimental data. The role of charge transfer excitations in the polymer DNA 260 nm spectral band is discussed.

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Braga, Letícia S., Daniel H. S. Leal, Kamil Kuca i Teodorico C. Ramalho. "Perspectives on the Role of the Frontier Effective-for-Reaction Molecular Orbital (FERMO) in the Study of Chemical Reactivity: An Updated Review". Current Organic Chemistry 24, nr 3 (4.05.2020): 314–31. http://dx.doi.org/10.2174/1385272824666200204121044.

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Molecular orbitals are critical in the rationalization of several chemical reactions. Thus, the frontier molecular orbital theory, proposed by Fukui's group, postulated the importance of the Highest Occupied Molecular Orbital (HOMO) and the Lowest Unoccupied Molecular Orbital (LUMO) for chemical reactions. It should be kept in mind, however, that there are limitations of this theory and new perspectives about the chemical reactivity have recently been arisen based on composition and location of other frontier molecular orbitals. In this review, we have reported the development and the most recent applications of the Frontier Effective-for-Reaction Molecular Orbital (FERMO) concept, which describes the breaking and formation of new chemical bonds and can in turn, provide important clues that modulate chemical reactivity of atoms and molecules.

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Tang, Zengguang, Liujiang Zhang, Zhenhuang Su, Zhen Wang, Li Chen, Chenyue Wang, Guoping Xiao i Xingyu Gao. "A Study of Interfacial Electronic Structure at the CuPc/CsPbI2Br Interface". Crystals 11, nr 5 (14.05.2021): 547. http://dx.doi.org/10.3390/cryst11050547.

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In this article, CsPbI2Br perovskite thin films were spin-coated on FTO, on which CuPc was deposited by thermal evaporation. The electronic structure at the CsPbI2Br/CuPc interface was examined during the CuPc deposition by in situ X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS) measurements. No downward band bending was resolved at the CsPbI2Br side, whereas there is ~0.23 eV upward band bending as well as a dipole of ~0.08 eV identified at the molecular side. Although the hole injection barrier as indicated by the energy gap from CsPbI2Br valance band maximum (VBM) to CuPc highest occupied molecular orbital (HOMO) was estimated to be ~0.26 eV, favoring hole extraction from CsPbI2Br to CuPc, the electron blocking barrier of ~0.04 eV as indicated by the offset between CsPbI2Br conduction band minimum (CBM) and CuPc lowest unoccupied molecular orbital (LUMO) is too small to efficiently block electron transfer. Therefore, the present experimental study implies that CuPc may not be a promising hole transport material for high-performance solar cells using CsPbI2Br as active layer.

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Harvey, Pierre D., Peter Johnston i Neil J. Coville. "Electron inductive perturbation(s) of heteronuclear metal–metal bonds. Isocyanide and indenyl derivatives of the mixed metal dimers [(η5–C5H5)Fe(CO)2Re(CO)5] and [MnRe(CO)10]". Canadian Journal of Chemistry 72, nr 10 (1.10.1994): 2176–82. http://dx.doi.org/10.1139/v94-276.

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The properties of the heteronuclear metal–metal bonds in the unbridged [η5–C5H5)Fe(CO)2Re(CO)5−n(CNR)n] and [(η5–C9H7)Fe(CO)2Re(CO)5−n(CNR)n complexes (n = 0, 1, 2; R = tert-butyl (tBu) and 2,6-dimethylphenyl (Xy)) and the two equatorially substituted isomers of [MnRe(CO)8(CN-tBu)2] have been investigated theoretically by Extended Hückel Molecular Orbital calculations (EHMO) and experimentally by UV–visible spectroscopy, electrochemistry, and by microRaman or FT-Raman spectroscopy. The expected dσ* orbital is the lowest unoccupied molecular orbital (LUMO), mainly fabricated by interactions of the metal [Formula: see text] orbital, but the dπ* and dσ orbitals are the highest occupied molecular orbital (HOMO) and HOMO-1, respectively, as demonstrated experimentally from the UV–visible spectra. The EHMO computations demonstrate the mixing between these two dπ* (and dδ) and dσ MO orbitals. The influence of substituent effects on the spectroscopic and electrochemical properties is complicated and is interpreted in terms of inductive effects and relative destabilisation of the dσ, dπ*, and dσ* molecular orbitals. Finally, the metal–metal stretching frequencies for four mixed metal dimers (MnRe and FeRe) are reported.

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LU, JING, XINWEI ZHANG i XIANGENG ZHAO. "ELECTRONIC PROPERTIES OF HETEROFULLERENES C59X (X=Si, O AND Be)". Modern Physics Letters B 14, nr 01 (10.01.2000): 23–29. http://dx.doi.org/10.1142/s0217984900000057.

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It has been found in earlier calculations that by replacing one C atom with one N atom, one electron is doped in the lowest unoccupied molecular orbital (LUMO) of C60 while by replacing with one B atom, one hole is doped in the highest occupied molecular orbital (HOMO) of C60. In this paper, we have performed discrete-variational local density functional calculations on single silicon, oxygen and beryllium-substituted heterofullerenes. No carrier is doped in the C60-derived orbitals upon Si substitution except for the reduced LUMO–HOMO gap. Two electrons are doped in the LUMO of C60 upon O substitution and instead, two holes are doped in the HOMO of C60 upon Be substitution. Ionization potentials and electron affinities can be altered dramatically by substitution and in general, C60 becomes more reactive upon substitution.

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Fowe, Emmanuel Penka, i André Dieter Bandrauk. "Nonlinear time-dependent density functional theory investigation and visualization of ionizations in CO2 — Effects of laser intensities and molecular orientations". Canadian Journal of Chemistry 88, nr 11 (listopad 2010): 1186–94. http://dx.doi.org/10.1139/v10-108.

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Time-dependent density functional theory (TDDFT) studies of the ionization of CO2 by intense laser pulses Io ≥ 1 × 1014 W/cm2, at 800 nm are presented using the LB94 and the LDA potentials. Results reveal that for lower laser peak intensity, Io = 3.5 × 1014 W/cm2, the highest occupied molecular orbital (HOMO) contributes significantly to ionization owing to its lower ionization potential (IP), whereas the inner orbitals play the important role for higher laser peak intensities. Even though such lower orbitals have higher IP, the ionization process occurs when orbital densities are maximum along the direction of the laser field polarization. These findings are confirmed through the analysis of the images from the time-dependent electron localization function (TDELF) and the spectra of higher order harmonic generation (HOHG). Additionally, in spite of the IP difference between Kohn–Sham orbitals from LDA and LB94 potentials, our results show almost the same trend for both.

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Zheng, Yu Jie, Qi Zhang, Omololu Odunmbaku, Zeping Ou, Meng Li i Kuan Sun. "Tuning the carrier type and density of monolayer tin selenide via organic molecular doping". Journal of Physics: Condensed Matter 34, nr 8 (1.12.2021): 085001. http://dx.doi.org/10.1088/1361-648x/ac3691.

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Abstract Utilizing first-principles calculations, charge transfer doping process of single layer tin selenide (SL-SnSe) via the surface adsorption of various organic molecules was investigated. Effective p-type SnSe, with carrier concentration exceeding 3.59 × 1013 cm−2, was obtained upon adsorption of tetracyanoquinodimethane or 2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-quinodimethane on SL-SnSe due to their lowest unoccupied molecular orbitals acting as shallow acceptor states. While we could not obtain effective n-type SnSe through adsorption of tetrathiafulvalene (TTF) or 1,4,5,8-tetrathianaphthalene on pristine SnSe due to their highest occupied molecular orbitals (HOMO) being far from the conduction band edge of SnSe, this disadvantageous situation can be amended by the introduction of an external electric field perpendicular to the monolayer surface. It is found that Snvac will facilitate charge transfer from TTF to SnSe through introducing an unoccupied gap state just above the HOMO of TTF, thereby partially compensating for the p-type doping effect of Snvac. Our results show that both effective p-type and n-type SnSe can be obtained and tuned by charge transfer doping, which is necessary to promote its applications in nanoelectronics, thermoelectrics and optoelectronics.

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Masan, Samuel E. P. P., Fitri N. Febriana, Andi H. Zaidan, Ira Puspitasari i Febdian Rusydi. "Evaluation of the Electronic Structure Resulting from ab-initio Calculations on Simple Molecules Using the Molecular Orbital Theory". Jurnal Penelitian Pendidikan IPA 7, nr 1 (28.01.2021): 107. http://dx.doi.org/10.29303/jppipa.v7i1.545.

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Hartree Fock (HF) and Density Functional Theory (DFT) have been commonly used to model chemical problems. This study uses the Molecular Orbital Theory (MOT) to evaluate the electronic structure of five diatomic molecules generated by HF and DFT calculations. The evaluation provides an explanation of how the orbitals of a molecule come to be and how this affects the calculation of the physical quantities of the molecule. The evaluation is obtained after comparing the orbital wave functions calculated by MOT, HF, and DFT. This study found that the nature of the Highest Occupied Molecular Orbital (HOMO) of a molecule is determined by the valence orbital properties of the constituent atoms. This HOMO property greatly influences the precision of calculating the molecular electric dipole moment. This shows the importance of understanding the orbital properties of a molecule formed from the HF and DFT calculations

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Majid, Abdul, Sidra Arif, Tariq M. Younes, Mohammad Alkhedher i Sayed M. ElDin. "DFT Study of Heteronuclear (TMFeO3)x Molecular Clusters (Where TM = Sc, Ti, Fe and x = 2, 4, 8) for Photocatalytic and Photovoltaic Applications". Energies 15, nr 19 (2.10.2022): 7253. http://dx.doi.org/10.3390/en15197253.

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The computational modeling of metal oxide clusters for photovoltaic application is carried out by using density functional theory. The structural and electronic properties of heteronuclear (TMFeO3)x molecular clusters (where x = 2, 4, 8 and TM = Sc, Ti, Fe) are investigated in detail. The physical parameters such as energy gap, formation energy, binding energy, and stability are determined. The computed values and trends in electronegativity (χ), chemical potential (μ), hardness (η) and softness (S), positions of highest occupied molecular orbitals (HOMO) and lowest unoccupied molecular orbitals (LUMO), and HOMO-LUMO gap with varying cluster sizes are discussed. The iso-surface plots with relaxed structure related to the frontier MOs are described to shed light on the charge transfer mechanism. In the entire series of the studied clusters, the computed gap of (Fe2O3)8 was found minimal and thus suitable for red light absorption, whereas (TiFeO3)2 exhibited a maximum gap which shows potential for blue light absorption. The clusters exhibiting different values of the gap are found suitable to absorb the solar radiation. HOMO and LUMO position with their energy differences in the clusters are found compatible for applications in photocatalytic and photovoltaic applications. The observed trend in the computed parameters points to the potential of the simulated materials for application in a TiO2-based semiconducting photoanode to harvest sunlight.

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Ermolaev, Vadim, Tatiana Gerasimova, Liliya Kadyrgulova, Ruslan Shekurov, Egor Dolengovski, Aleksandr Kononov, Vasily Miluykov i in. "Ferrocene-Containing Sterically Hindered Phosphonium Salts". Molecules 23, nr 11 (25.10.2018): 2773. http://dx.doi.org/10.3390/molecules23112773.

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The synthesis and physical properties of the series of the ferrocenyl-containing sterically hindered phosphonium salts based on di(tert-butyl)ferrocenylphosphine is reported. Analysis of voltamogramms of the obtained compounds revealed some correlations between their structures and electrochemical properties. The elongation of the alkyl chain at the P atom as well as replacement of the Br− anion by [BF4]− shifts the ferrocene/ferrocenium transition of the resulting salts into the positive region. DFT results shows that in the former case, the Br− anion destabilizes the corresponding ion pair, making its oxidation easier due to increased highest occupied molecular orbital (HOMO) energy. Increased HOMO energy for ion pairs with the Br− ion compared to BF4− are caused by contribution of bromide atomic orbitals to the HOMO. The observed correlations can be used for fine-tuning the properties of the salts making them attractive for applications in multicomponent batteries and capacitors.

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Li, Jin, Yufan Wang, Zhaoyu Ran, Hang Yao, Boxue Du i Tatsuo Takada. "Molecular Structure Modulated Trap Distribution and Carrier Migration in Fluorinated Epoxy Resin". Molecules 25, nr 13 (6.07.2020): 3071. http://dx.doi.org/10.3390/molecules25133071.

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Surface charge accumulation on epoxy insulators is one of the most serious problems threatening the operation safety of the direct current gas-insulated transmission line (GIL), and can be efficiently inhibited by the surface modification technology. This paper investigated the mechanisms of fluorination modulated surface charge behaviors of epoxy resin through quantum chemical calculation (QCC) analysis of the molecular structure. The results show that after fluorination, the surface charge dissipation process of the epoxy sample is accelerated by the introduced shallow trap sites, which is further clarified by the carrier mobility model. The electron distribution probability of the highest occupied molecular orbitals (HOMO) under positive charging and the lowest unoccupied molecular orbitals (LUMO) under negative charging shows distinctive patterns. It is illustrated that electrons are likely to aggregate locally around benzenes for the positively charged molecular structure, while electrons tend to distribute all along the epoxy chain under negatively charging. The calculated results verify that fluorination can modulate surface charge behaviors of epoxy resin through redesigning its molecular structure, trap distribution and charging patterns.

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Zeng, Guang, Hanming Li, Fang Tan, Yue Xin i Shengdong Zhang. "A narrow band gap non-fullerene electron acceptor based on a dithieno-3,2-b:2′,3′-dlpyrrole unit for high performance organic solar cells with minimal highest occupied molecular orbital offset". RSC Advances 13, nr 21 (2023): 14703–11. http://dx.doi.org/10.1039/d3ra01021j.

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A new narrow band gap acceptor based on a dithieno-3,2-b:2',3'-dlpyrrole unit was synthesized. By blending a polymer PBTIBDTT with a small HOMO offset of 0.02 eV, the device gave a high PCE of 11.25% with a relatively high Voc of 0.83 V.

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Felegari, Zahra, i Majid Monajjemi. "AIM and NBO analyses on the interaction between SWCNT and cyclophosphamide as an anticancer drug: A density functional theory study". Journal of Theoretical and Computational Chemistry 14, nr 03 (maj 2015): 1550021. http://dx.doi.org/10.1142/s0219633615500212.

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In this work, the molecular structures of single-walled carbon nanotube (SWCNT), cyclophosphamide and cyclophosphamide–SWCNT complex were optimized B3LYP/6–31G* level of theory. The nanotube used in this study was a (5,5) SWCNT including 150 C atoms. The NBO analysis showed that the transfer electron can be occurred from the lone pair of oxygen (donor atom) in the cyclophosphamide to the σ* or π* orbitals of the carbon atoms (acceptor atoms) in the SWCNT. The highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO) and energy gap (HOMO–LUMO) were calculated for the studied structures and the results indicated the stability of the complex. In addition, the calculated chemical shift isotropy (σ) and the chemical shift anisotropy (Δσ) confirmed the interaction between cyclophosphamide and SWCNT. Also, the results of the atoms in molecule (AIM) theory indicated that the H 145– O 164 bond is a partial covalent bond.

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Fowe, Emmanuel Penka, i André Dieter Bandrauk. "Nonlinear time-dependent density functional theory studies of the ionization of CO2 by ultrashort intense laser pulses". Canadian Journal of Chemistry 87, nr 7 (lipiec 2009): 1081–89. http://dx.doi.org/10.1139/v09-074.

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Time-dependent density functional theory (TDDFT) studies of the ionization of CO2 by intense laser pulses (3.50 × 1014, 1.40 × 1015, 2.99 × 1015, and 1.25 × 1016 W/cm2) at 800 nm (ω = 0.0584 au) are presented in the nonlinear nonpertubative regime. Special emphasis is placed on elucidating molecular orbital orientation and various peak-intensities effects on the ionization processes. The results reveal that molecular orbital ionizations are strongly sensitive to their symmetry and the laser intensities. Most notably, we found that with a proper choice of the laser intensity (3.5 × 1014 W/cm2), the sensitivity is strong enough such that the nature and symmetry of the highest occupied molecular orbital (HOMO) can be directly probed and visualized from the angular dependence of laser-induced ionization. At higher intensities, ionization is found to occur also from inner orbitals, thus complicating the imaging of simple orbitals. A time-dependent electron-localization function (TDELF) is used to get a visual insight on the time evolution process of the electron density.

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Gorai, Deepak K., i T. K. Kundu. "First Principle Study of Na and P Co-Doped Heptazine Based Monolayer g-C₃N₄". Materials Science Forum 978 (luty 2020): 369–76. http://dx.doi.org/10.4028/www.scientific.net/msf.978.369.

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Elements doping is a powerful way to alter the electronic structure and enhancing the photo catalytic activity of materials by relaxing the surrounding chemical bonds and forming new chemical bond. In this work, we have performed, the first principle density functional theory calculations to investigate the geometric, electronic and optical properties of pristine, Na-doped and P-doped as well as Na and P (Na/P) co-doped heptazine based monolayer graphitic carbon nitride (g-C3N4). The co-doping process results in significantly narrow band gap of g-C3N4. The optical absorption shows better visible-light response compare to pristine g-C3N4. After doping the highest occupied molecular orbitals (HOMO) and lowest unoccupied molecular orbitals (LUMO) show strong delocalization and indicates photo generated electron/hole (e-/h+) pair disunion abilities of doped systems are superior than pristine heptazine based monolayer g-C3N4. Thus the co-doping with Na and P elements is an effective technique to boost the photocatalytic performance of heptazine based monolayer g-C3N4.

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Tsai, Huai-Wen, Kan-Lin Hsueh, Mei-Hsin Chen i Che-Wun Hong. "Electronic and Optical Properties of Polythiophene Molecules and Derivatives". Crystals 11, nr 11 (25.10.2021): 1292. http://dx.doi.org/10.3390/cryst11111292.

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The electronic and optical properties of polythiophene (PT) for polymer light-emitting diodes (PLEDs) were calculated using density functional theory (DFT) and time-dependent DFT. We calculated the electronic and optical properties of thiophene and PT polymers with degrees of polymerization (DP) from 2 to 30 monomers (T1–T30) and their derivatives. The associated highest occupied molecular orbital (HOMO) energy, lowest unoccupied molecular orbital (LUMO) energy, band gaps, electron orbitals, and molecular structures were determined. As the DP increased, the LUMO energy gradually decreased, and the HOMO energy gradually increased. The band gap of PT approached 2 eV as the DP of the PT polymer increased from 1 to 30. The calculations and exchange–correlation functional were verified against values in the literature and experimental data from cyclic voltammetry (redox potential) and ultraviolet-visible, photoluminescence, and ultraviolet photoelectron spectra. The color of PT PLEDs can be adjusted by controlling the DP of the polymer and the substituents.

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Liu, Yan-Ling, Xue-Qin Ran, Ji-Kang Feng, Ai-Min Ren i Lu-Yi Zou. "Optical and Electronic Properties of Doubly Ortho-linked cis-4,4'-Bis(diarylamino)stilbene/Fluorene Hybrids". Australian Journal of Chemistry 63, nr 1 (2010): 125. http://dx.doi.org/10.1071/ch08257.

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Doubly ortho-linked cis-4,4′-bis(diarylamino)stilbene/fluorene hybrids have potential application in organic light emitting diodes. These organic molecules can function as efficient hole transport materials, with sky-blue emission and high efficiency and stability. To reveal the relationship between the properties and structures of these functional materials, we apply quantum-chemical techniques to investigate their optical properties and electronic structures. It is found that 8- and 8′-substituents give an antibonding contribution to the highest occupied molecular orbitals (HOMO), thus increasing the HOMO energy, implying an enhancement of hole-creating ability. Changes in ionization potentials confirm this presumption. The absorption and emission spectra exhibit red shifts to some extent with the various 8- and 8′-substituents, which are in good agreement with the experimental values. The Stoke shifts range moderately from 40 to 86 nm, due to the rigid spiral structure that hinders geometrical relaxation.

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Shen, Wanting, Lihong Han, Dan Liang, Chunfang Zhang, Quhe Ruge, Shumin Wang i Pengfei Lu. "Structural, stability, and vibrational properties of BinPm clusters". International Journal of Modern Physics B 32, nr 10 (13.04.2018): 1850117. http://dx.doi.org/10.1142/s0217979218501175.

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An in-depth investigation is performed on stability mechanisms, electronic and optical properties of III–V semiconductor vapor phases clusters. First principles electronic structure calculations of CAM-B3LYP are performed on neutral Bi[Formula: see text]P[Formula: see text] (n + m [Formula: see text] 14) clusters. The geometrical evolution of all stable structures remains amorphous as the clusters size increases. Binding energies (BEs), energy gains and highest occupied molecular orbital and lowest unoccupied molecular orbital (HOMO–LUMO) gaps confirm that all four-atom structures of Bi[Formula: see text]P[Formula: see text] clusters have more stable optical properties. Orbitals composition and vibrational spectra of stable clusters are analyzed. Our calculations will contribute to the study of diluted bismuth alloys and compounds.

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Mamand, D. M., i H. M. Qadr. "Quantum computations and density functional theory on corrosion inhibition efficiency of BIA, HBT, MBI and PIZ compounds". Himia, Fizika ta Tehnologia Poverhni 14, nr 2 (30.06.2023): 159–72. http://dx.doi.org/10.15407/hftp14.02.159.

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This study determined the corrosion inhibition levels of benzimidazole (BIA), 1-hydroxybenzotriazole (HBT), methylbenzimidazole (MBI) and 4-phenylimidazole (PIZ). By using simulation, it was possible to have a complete relationship with the experimental work because the results were completely consistent. Density functional theory (DFT) and Monte Carlo simulations were used to calculate several quantum chemical parameters. The molecules are simulated using quantum chemical calculations with Gaussian09 software. Fundamental factors determining the corrosion order of molecules are the highest-energy occupied and lowest-energy unoccupied molecular orbitals (HOMO and LUMO), frontier molecular orbital energy, back donating energy, electrophilicity, nucleophilicity, energy gap ∆E, absolute electronegativity (χ), softness, the number of electrons (∆N) transferred from inhibitors to iron, the dipole moment (μ), the global hardness (η) and the total energy.

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Abdulhasan, Haithem, Ahmed Al-Yasari i Rahman Alasadi. "Theoretical Study on Molecular Structure and Electronic Properties of New 1,3-Diaza-adamantan-6-ones Derivatives". Indonesian Journal of Chemistry 20, nr 3 (9.05.2020): 638. http://dx.doi.org/10.22146/ijc.44403.

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In this study, the structural geometry and vibrational frequencies (IR) of 1,3-Diaza-adamantane-6-ones derivatives including Adamantane (A), 1,3-Diaza-adamantan (D), 1,3-Diaza-adamantan-6-one (DO), 5-Benzyl-1,3-diaza-adamantan-6-one (BD), 5-(4-Hydroxybenzyl)-1,3-diaza-adamantan-6-one (HBD), 5-(4-Methoxybenzyl)-1,3-diaza-adamantan-6-one (MBD), and 5-(4-Hydroxy-3-methoxybenzyl)-1,3-diaza-adamantan-6-one (HMBD) were theoretically studied. In addition, molecular orbital energies, including the highest occupied molecular orbitals (HOMOs), and lowest unoccupied molecular orbitals (LUMOs), and electronic properties of the titled molecules were theoretically studied using the computational method. Optimized molecular structures were obtained by DFT method with the hybrid B3LYP functional at a relatively small basis set of 6-31G. The calculated vibrational wavenumbers were obtained using the same level of the theory mentioned above. The contributions to the molecular orbitals of adamantane and substituted-phenyl groups in the title compounds were determined. Moving from A to HMBD, a decrease in the value of LUMO and total energy are noticed, while an increase in the value of HOMO is noted. These findings are supported by the decreasing in the EHOMO-LUMO gap values. Furthermore, a decrease in the value of ionization potential (IP) is obtained, while an increase in the electronegativity (EA) is observed.

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OKAJIMA, TOSHIHIRO, HITOSHI FUJIMOTO, MICHINORI SUMITOMO, TOHRO ARAKI, EISUKE ITO, HISAO ISHII, YUKIO OUCHI i KAZUHIKO SEKI. "SOFT X-RAY ABSORPTION SPECTRA OF THE LITHIUM PHTHALOCYANINE RADICAL". Surface Review and Letters 09, nr 01 (luty 2002): 441–46. http://dx.doi.org/10.1142/s0218625x0200252x.

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In near edge X-ray absorption fine structure (NEXAFS) spectra of carbon (C) and nitrogen (N) K-edge regions were measured for the stable radical compound lithium phthalocyanine (LiPc). The observed spectra were compared with those of metal free Pc ( H 2 Pc ), copper Pc (CuPc), and zinc Pc (ZnPc). The spectral features in the C K-edge region of LiPc were different from those of other Pcs in the low photon energy region. An additional peak around 283.5 eV was observed only in the spectrum of LiPc. On the other hand, the spectral features of these MPcs in the N K-edge region were similar and did not show a corresponding extra peak. These results were explained by the patterns of molecular orbitals of these Pcs and the selection rules of X-ray absorption in the localized core-hole picture. The extra peak observed in the C K-edge region is assigned to the excitation from C1s to the highest occupied molecular orbital (HOMO), which is only singly occupied due to the radical nature of the phthalocyanine ring. Group-theoretical consideration indicated that the transition from N1s to the HOMO is not allowed, and this explains the lack of an extra peak at the N K-edge.

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27

Jin, Feng, Jianyu Yuan, Wenping Guo, Yalong Xu, Yannan Zhang, Chuanxiang Sheng, Wanli Ma i Haibin Zhao. "Improved Charge Generation via Ultrafast Effective Hole-Transfer in All-Polymer Photovoltaic Blends with Large Highest Occupied Molecular Orbital (HOMO) Energy Offset and Proper Crystal Orientation". Advanced Functional Materials 28, nr 31 (12.06.2018): 1801611. http://dx.doi.org/10.1002/adfm.201801611.

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Rajendrachari, Shashanka, Gururaj Kudur Jayaprakash, Anup Pandith, Abdullah Cahit Karaoglanli i Orhan Uzun. "Electrocatalytic Investigation by Improving the Charge Kinetics between Carbon Electrodes and Dopamine Using Bio-Synthesized CuO Nanoparticles". Catalysts 12, nr 9 (2.09.2022): 994. http://dx.doi.org/10.3390/catal12090994.

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We have successfully studied the charge transfer kinetics between carbon paste electrodes and dopamine using green synthesized rectangular monoclinic CuO nanoparticles (NPs) prepared by Alchemilla vulgaris leaves with the one-pot green synthesis method. The scanning electron microscopy (SEM) results confirmed the monoclinic structure with a particle size of around 85 nm. The investigation of thermal properties was carried out by thermogravimetric (TG) and differential thermal analysis (DTA). We also studied the electrochemical response of green synthesized CuO nanoparticles to detect Dopamine (DA) using cyclic voltammetry, which was proven to be an excellent electrocatalyst for the electro-oxidation of DA. The fabricated CuO nanoparticle modified carbon paste electrode (CMCPE) depicts fantastic selectivity, robustness, and sensitivity in analyzing DA in clinical and pharmaceutical preparations. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) orbitals of the DA were studied using positive and negative charges at the CuO modified carbon paste electrode interface. Frontier molecular orbitals of DA are plotted to understand electron transfer reactivity at the electrode interface.

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29

Li, Yu-Qiong, Qian He, Jian-Hua Chen i Cui-Hua Zhao. "Electronic and chemical structures of pyrite and arsenopyrite". Mineralogical Magazine 79, nr 7 (grudzień 2015): 1779–89. http://dx.doi.org/10.1180/minmag.2015.079.7.05.

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AbstractThe first-principles plane-wave pseudopotential method is used to study the electronic and chemical structures of pyrite (FeS2) and arsenopyrite (FeAsS). The results indicate that an antibonding interaction occurs between Fe and As atoms in arsenopyrite. This interaction results in the Fe atom being repelled towards the S atom to stabilize antibonding orbitals, causing a larger S–Fe–S angle in arsenopyrite than in pyrite and a distortion in the arsenopyrite structure. In arsenopyrite, Fe–Fe distances are alternately long and short. The low spin density of the Fe d electrons supports this configuration in arsenopyrite. However, electron density calculations indicate that there is negligible electron density present between Fe atoms. This result indicates that cation-anion interactions are dominant in arsenopyrite. The pyrite Fe 3d orbital is split below the Fermi level, whereas the arsenopyrite Fe 3d orbital is not split, which can be attributed to the stronger interatomic bonding effects between Fe and S atoms in pyrite compared to arsenopyrite. It is found that the d-p orbital interactions between Fe and S atoms lead to bonding-antibonding splitting in both pyrite and arsenopyrite. However, the bonding effects between pyrite Fe and S atoms are stronger than in arsenopyrite. In arsenopyrite, the bonding interaction between the As 4p and Fe 3d orbitals is very weak, while the antibonding effect is very strong. The p-p orbital interaction is the dominant effect in As–S bonding. Frontier orbital calculations indicate that the Fermi levels of pyrite and arsenopyrite are notably close to each other, resulting in similar electrochemical activities. Orbital coefficient results show that the pyrite Fe 3d and S 3p orbitals are the active orbitals in the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), respectively. In the case of arsenopyrite, Fe 3d orbitals are very active in both the HOMO and LUMO. Moreover, the activity of the As 4p in the HOMO is greater than S 3p, whereas the opposite situation occurs in the LUMO. Based on these results, As atoms could be one of the active sites for the oxidation of arsenopyrite. In addition, separation of arsenopyrite and pyrite could be achieved by utilizing the difference in chemical reactivities of iron in the two minerals.

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Wang, Songsong, Changliang Han, Liuqi Ye, Guiling Zhang, Yangyang Hu, Weiqi Li i Yongyuan Jiang. "Electronic Properties of Triangle Molybdenum Disulfide (MoS2) Clusters with Different Sizes and Edges". Molecules 26, nr 4 (22.02.2021): 1157. http://dx.doi.org/10.3390/molecules26041157.

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The electronic structures and transition properties of three types of triangle MoS2 clusters, A (Mo edge passivated with two S atoms), B (Mo edge passivated with one S atom), and C (S edge) have been explored using quantum chemistry methods. The highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) gap of B and C is larger than that of A, due to the absence of the dangling of edge S atoms. The frontier orbitals (FMOs) of A can be divided into two categories, edge states from S3p at the edge and hybrid states of Mo4d and S3p covering the whole cluster. Due to edge/corner states appearing in the FMOs of triangle MoS2 clusters, their absorption spectra show unique characteristics along with the edge structure and size.

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31

Merve Şenğül ALPATER, Zaid H. AL-SAWAFF i Fatma KANDEMİRLİ. "Theoretical study of gallium nitride nanocage as a carrier for Cisplatin anticancer drug". Global Journal of Engineering and Technology Advances 9, nr 3 (30.12.2021): 077–85. http://dx.doi.org/10.30574/gjeta.2021.9.3.0166.

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In this paper, the possible interactions between cisplatin Cl2H6N2Pt as an anticancer drug and gallium nitride (Ga12N12) nanocage have been investigated using the DFT/b3lyp/lanl2dz(d,p) level of theory. Three different orientations were used to mimic the cisplatin adsorbed on Ga12N12. To investigate the interaction mechanism between the two components, the adsorption energies and thermodynamic parameters, the electronic properties such as the energies and orbitals distribution of the highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO), the HOMO-LUMO energy gaps (Eg), thermodynamic properties were also investigated. Additionally, some quantum molecular descriptors were calculated to understand molecular reactivity. The main results revealed that the adsorption process of the drug compound on the surface of the nanocage varies with the adsorption site. The process showed that different energies could be obtained, where the highest energy value was when the drug compound was adsorbed with the nanocage at the chlorine atom, with a value of (41.85) kcal/mol. On the other hand, the distance between the drug compound atoms was affected before and after adsorption, which proves the existence of an interaction between the drug compound and the nanocage and considers it as a drug delivery vehicle.

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32

Lee, JaMin, Sae Won Lee i Young Sik Kim. "Theoretical Study of Phenoxaphosphine-Based Blue Organic Light-Emitting Diode Exhibiting Thermally Activated Delayed Fluorescence". Journal of Nanoscience and Nanotechnology 20, nr 11 (1.11.2020): 7187–90. http://dx.doi.org/10.1166/jnn.2020.18855.

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We designed novel thermally activated delayed fluorescence (TADF) materials by combining the electron donors spiro[acridine-9,9′-fluorene] (D1) and 9,9-diphenyl acridan (PAC) with the electron acceptor phenoxaphosphine (OPO) unit (2D1-OPO and 2PAC-OPO) and used those property to compare it with that of the reference material using dimethylacridan (Ac) as an electron donor (Ac-OPO) for blue organic light-emitting diodes (OLEDs). To calculate electron distribution of highest occupied molecular orbitals (HOMO), lowest occupied molecular orbital (LUMO), lowest singlet (S1) energy and lowest triplet (T1) excitation states, density functional theory (DFT) and time-dependent DFT calculation have been used. The calculated energy difference (ΔEST) between the S1 and T1 states of 2D1-OPO (0.125 eV) and 2PAC-OPO (0.153 eV) were as small as that of Ac-OPO (0.127 eV). The results showed that 2D1-OPO is a good candidate for blue OLED emitter because it has an emission wavelength of 441.0 nm as well as a sufficiently small ΔEST value and large oscillator intensity value.

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Jotani, Mukesh M. "Crystal Structure Optimization and Semi-Empirical Quantum Chemical Calculations of Fused Bicyclic Heterocycles". Advanced Materials Research 1087 (luty 2015): 59–63. http://dx.doi.org/10.4028/www.scientific.net/amr.1087.59.

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The crystal structures of two fused pyridine derivatives viz Ethyl 3-amino-6-phenyl-4-tolylfuro[2,3-b]pyridine-2-carboxylate (I) and Ethyl 3-amino-6-phenyl-4-tolylthieno[2,3-b] pyridine-2-carboxylate (II) were optimized by semi-empirical methods using MOPAC2009 program. The geometries optimized for both the structures from Austin Model 1 (AM1) and Parametrization Model 6 (PM6) describe the conformational discrepancy and crystal packing effects. The parametric molecular electrostatic potential (PMEP) calculated by AM1 semi-empirical method describe the involvement of nitrogen and oxygen atoms in the crystal packing interactions in both the structures. The frontier molecular orbitals highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) indicate the intramolecular charge transfer interactions. The HOMED indices computed for the phenyl rings in the structures describe the p-electron delocalization. The linear regression analysis shows good correlation between experimental and theoretical structures.

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BAI, FU-QUAN, TAO LIU, XIN ZHOU, JIAN-PO ZHANG i HONG-XING ZHANG. "THEORETICAL COMPUTATIONAL STUDIES ON ELECTRONIC STRUCTURES, SPECTROSCOPIC PROPERTIES AND NITROGEN HETEROATOM EFFECT OF A SPECIES OF ASYMMETRICAL DIIMINE LIGAND PLATINUM(II) COMPLEXES". Journal of Theoretical and Computational Chemistry 08, nr 04 (sierpień 2009): 603–13. http://dx.doi.org/10.1142/s0219633609004952.

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Electronic structures and spectroscopic properties of a series of platinum(II) complexes based on the C-linked asymmetrical diimine ligand (2-pyridyl-pyrazole (1), 2-pyridyl-1,2,4-triazole (2), 2-pyridyl-tetrazole (3), 2-pyrazine-pyrazole (4) have been studied by the time-dependent density functional theory calculations with polarizable continuum model. The ground- and excited-state structures were optimized by the density functional theory and single-excitation configuration interaction methods, respectively. The calculated structures and spectroscopic properties are in agreement with the corresponding experimental data. The results of the spectroscopic investigations revealed that the lowest-energy absorptions have1,3metal-to-ligand charge transfer (MLCT)/1,3single ligand centered charge transfer (ILCT) mixing characters. The highest-occupied molecular orbitals (HOMOs) of 1–4 are composed of Pt ( d yz) and azole, while the lowest-unoccupied molecular orbitals (LUMOs) are mainly localized upon the pyridyl-azolate ligand (70% on the pyridine segment). From 1 to 3, the molecular orbital (MO) energies of HOMO and LUMO are decreased and the HOMO energies are changed more remarkably. This is caused by that the conjugation of the azolate segment of the ligand are enhanced through introducing more N heteroatoms into this segment. As a result of MO energy change, the lowest-energy absorptions are blue-shifted in the order 1 < 2 < 3. With the replacement of pyridyl by pyrazine, the HOMO energy of 4 is comparable to 1, but the LUMO energy is decreased by 0.8 eV, and the lowest-energy absorptions are red-shifted to 2.36 eV. Otherwise, the phosphorescent emissions of these complexes have the 3MLCT/3ILCT characters, and should originate from the lowest-energy absorptions. The emissions of 1–4 are red-shifted in the order 3 < 2 < 1 < 4. The heteroatom effect is suitable for tuning the spectra of this kind of materials.

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Balashova, Tatyana V., Mikhail E. Burin, Vasily A. Ilichev, Alyona A. Starikova, Alexey V. Marugin, Roman V. Rumyantcev, Georgy K. Fukin, Artem N. Yablonskiy, Boris A. Andreev i Mikhail N. Bochkarev. "Features of the Molecular Structure and Luminescence of Rare-Earth Metal Complexes with Perfluorinated (Benzothiazolyl)phenolate Ligands". Molecules 24, nr 13 (27.06.2019): 2376. http://dx.doi.org/10.3390/molecules24132376.

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A set of Sc, Nd, Sm, Eu, Ho, Gd, Er, Yb complexes with perfluorinated 2-(benzothiazol-2-yl)phenolate ligands Ln(SONF)3(DME) were synthesized by the reactions of silylamides Ln[N(SiMe3)2]3 with phenol H(SONF). The structure of the initial phenol, Sc, and Er complexes was established using X-ray analysis, which revealed that the obtained compounds are mononuclear, in contrast to the binuclear non-fluorinated analogues [Ln(SON)3]2 synthesized earlier. All the obtained complexes, both in solid state and in tetrahydrofuran (THF) solutions, upon excitation by light with λex 395 or 405 nm show intense luminance of the ligands at 440–470 nm. The Eu complex also exhibits weak metal-centered emission in the visible region, while the derivatives of Sm luminesces both in the visible and in the infrared region, and Nd, Er, and Yb complexes emit in the near IR (NIR) region of high intensity. DFT (density functional theory) calculation revealed that energy of frontier orbitals of the fluorinated complexes is lower than that of the non-fluorinated counterparts. The level of highest occupied molecular orbital (HOMO) decreases to a greater extent than the lowest occupied molecular orbital (LUMO) level.

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Al-Haideri, Lina Majeed Haider, i Necla Cakmak. "Electronic and structural features of uranium-doped graphene: DFT study". Main Group Chemistry 21, nr 1 (8.04.2022): 295–301. http://dx.doi.org/10.3233/mgc-210143.

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Electronic and structural features of uranium-doped models of graphene (UG) were investigated in this work by employing the density functional theory (DFT) approach. Three sizes of models were investigated based on the numbers of surrounding layers around the central U-doped region including UG1, UG2, and UG3. In this regard, stabilized structures were obtained and their electronic molecular orbital features were evaluated, accordingly. The results indicated that the stabilized structures could be obtained, in which their electronic features are indeed size-dependent. The conductivity feature was expected at a higher level for the UG3 model whereas that of the UG1 model was at a lower level. Energy levels of the highest occupied and the lowest unoccupied molecular orbitals (HOMO and LUMO) were indeed the evidence of such achievement for electronic conductivity features. As a consequence, the model size of UG could determine its electronic feature providing it for specified applications.

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Ramuthai, M., S. Jeyavijayan, R. Premkumar, M. Uma Priya i Naidu Dhanpal Jayram. "Structure, Spectroscopic Investigation, Molecular Docking and In vitro Cytotoxicity Studies on 4,7-dihydroxycoumarin: A Breast Cancer Drug". Journal of Computational Biophysics and Chemistry 21, nr 02 (21.01.2022): 219–36. http://dx.doi.org/10.1142/s2737416522500119.

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Coumarin derivatives are broadly used as anti-inflammatory, antioxidants, anticancer, and antiviral drugs in recent years. In particular, hydroxy coumarins have great importance because of their various biological and pharmacological purposes. The quantum chemical studies of 4,7-dihydroxycoumarin (DHC) have been performed using the cc-pVTZ level of basis set. The DHC molecular structure has been optimized and the computed frequency assignments have been correlated well with the experimental results. The experimental [Formula: see text]C NMR shifts of DHC have been compared with the computed [Formula: see text]C NMR in the dimethyl sulfoxide (DMSO) solution using the Gauge-invariant atomic orbital (GIAO) method. The electron delocalization within the DHC is shown by highest occupied molecular orbitals (HOMO)-lowest unoccupied molecular orbitals (LUMO) energy analysis, and the resulting small energy gap value reveal the molecule’s bioactive characteristics. The natural bond orbital (NBO) analysis approves the bioactive property of the DHC molecule. The DHC compound has a cytotoxic impact on the MCF-7 breast cancer cell line, according to in vitro cytotoxicity studies. The docking study approves that the DHC works as a new inhibitor of breast cancer targeted proteins such as epidermal growth factor receptor (EGFR), estrogen receptor (ER), and progesterone receptor (PR). Thus, this work covers the approach for the evolution of new drugs against breast cancer.

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El-Shamy, I. E., E. Hleli, A. A. Alsheikh, M. A. Yawer, M. A. El-Hashash, J. Dybal i A. M. Abdel-Mohsen. "Synthesis of Some Mono- and Disaccharide-Grafting Phthalazine Derivatives and Some New Se-Nucleoside Analogues: Antibacterial Properties, Quantum Chemical Calculations, and Cytotoxicity". Molecules 28, nr 1 (30.12.2022): 317. http://dx.doi.org/10.3390/molecules28010317.

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A highly efficient and versatile synthetic approach for the synthesis of 4-(pyren-1-ylmethyl)-1-(d-glycosyloxy) phthalazine nucleosides 11a,b, 13, β-S-nucleosides 16, 18, 20, and acyclo C-nucleosides 23a,b, 24, 25 and 27a–f was described and fully characterized. Furthermore, a series of desired new nucleoside analogues containing Se of 4-(pyren-1-ylmethyl) phthalazine-1(2H)-selenone 28–33 were synthesized. The structures of all reported compounds were confirmed by IR, 1H-NMR, 13C-NMR, MS and elemental analysis. All compounds have been screened for their antibacterial and antifungal activities. Maximum activity was shown by 20 and 33a comparable to the standard drugs with lower toxicity. The cytotoxicity of the selected compound was measured and evaluated. The energy gap between the highest occupied molecular orbital and lowest unoccupied molecular orbital was calculated using theoretical computations to reflect the chemical reactivity and kinetic stability of the synthesized compounds. Using density functional theory (DFT), electronic parameters such as the highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO) and the molecular electrostatic potential (MEPS) were calculated. On the basis of different studied structures, these properties were computed in order to elucidate the chemical reactivity and the kinetic stability. Obviously, the band gap energy (Eg) of structures studied reveals that the lowest band gap obtained for the structure 16-a indicates that it has the highest chemical reactivity and lowest kinetic stability.

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Bakhtiari, Atefeh, i Javad Safaei-Ghomi. "Effects of Chiral Ligands on the Asymmetric Carbonyl-Ene Reaction". Synlett 30, nr 15 (23.07.2019): 1738–64. http://dx.doi.org/10.1055/s-0037-1611875.

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The carbonyl-ene reaction is one of the most well-known reactions for C–C bond formation. Based on frontier molecular orbitals (FMO), carbonyl-ene reactions occur between the highest occupied molecular orbital (HOMO) of the ene compound bearing an active hydrogen atom at the allylic center and the lowest unoccupied molecular orbital (LUMO) of the electron-deficient enophile, which is a carbonyl compound. A high activation barrier enforces the concerted ene reaction rather than a Diels–Alder reaction at high temperature. Employing a catalytic system can eliminate defects in the ene reaction, and chiral catalysts promote the reaction under mild conditions to produce optically active compounds. In this account, we highlight investigations on the effects of various classes of chiral ligands on intermolecular and intramolecular carbonyl-ene reactions.1 Introduction2 Biaryl-Type Chiral Ligands3 C 1- and C 2-Symmetric Bis(oxazoline) Ligands4 Schiff Base Ligands5 N,N′-Dioxide Ligands6 Conclusions

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40

Penka, Emmanuel Fowe, i André Dieter Bandrauk. "Nonperturbative time-dependent density functional theory (TDDFT) and time-dependent electron localization function (TDELF) study of the ionization of OCS and CS2 with ultrashort intense laser pulses — Orientational effects". Canadian Journal of Chemistry 90, nr 7 (lipiec 2012): 616–24. http://dx.doi.org/10.1139/v2012-039.

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The nonlinear nonperturbative response of OCS and CS2 to ultrashort (few cycles) intense laser pulses was studied numerically by time-dependent density functional theory (TDDFT) methods to understand molecular ionization as a function of laser–molecule orientation. A time-dependent electron localization function(TDELF) was used to visualize the nonlinear nonperturbative electron transfer occurring during the laser pulse. It was found that, for intensities I > 3.5 × 1014 W/cm2, the inner shell Kohn–Sham (KS) molecular orbitals contribute significantly to the ionization, whereas for the intensity I < 3.5 × 1014 W/cm2, the highest occupied molecular orbital (HOMO) shows the dominant response to the field. In general, the ionization rate maxima correspond to the alignment of maximum KS orbital densities with the laser pulse polarization instead of orbital ionization potentials (IP). These findings are corroborated through analysis of the TDELF images, where the ionization occurs from the lone pair or bond regions of the corresponding molecules.

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41

ZHOU, WEIDONG, D. P. SECCOMBE, R. Y. L. CHIM i R. P. TUCKETT. "VUV FRAGMENTATION OF SOME HYDROFLUOROCARBON CATIONS STUDIED USING COINCIDENCE TECHNIQUES". Surface Review and Letters 09, nr 01 (luty 2002): 153–58. http://dx.doi.org/10.1142/s0218625x0200204x.

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Threshold photoelectron–photoion coincidence (TPEPICO) spectroscopy has been used to investigate the decay dynamics of the valence electronic states of the parent cation of several hydrofluorocarbons (HFC), based on fluorine-substituted ethane, in the energy range 11–25 eV. We present data for CF 3– CHF 2, CF 3– CH 2 F , CF 3– CH 3 and CHF 2– CH 3. The threshold photoelectron spectra (TPES) of these molecules show a common feature of a broad, relatively weak ground state, associated with electron removal from the highest-occupied molecular orbital (HOMO) having mainly C–C σ-bonding character. Adiabatic and vertical ionisation energies for the HOMO of the four HFCs are presented, together with corresponding values from ab initio calculations. For those lower-energy molecular orbitals associated with non-bonding fluorine 2pπ lone pair electrons, these electronic states of the HFC cation decay impulsively by C–F bond fission with considerable release of translational kinetic energy. Appearance energies are presented for formation of the daughter cation formed by such a process (e.g. CF 3– CHF +), together with ab initio energies of the corresponding dissociation channel (e.g. CF 3– CHF + + F ). Values for the translational kinetic energy released are compared with the predictions of a pure-impulsive model.

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Chatterjee, Subhojyoti, i Feng Wang. "Electronic structures of hexane isomers studied using quantum mechanics and graph theory". Journal of Theoretical and Computational Chemistry 14, nr 02 (marzec 2015): 1550014. http://dx.doi.org/10.1142/s0219633615500145.

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Electronic and topological properties of hexane ( C 6 H 14) and its five geometric isomers are systematically studied quantum mechanically using several techniques such as positron–electron annihilation gamma-ray spectra, C1s binding energy spectra and carbon nuclear magnetic resonance (NMR) spectra, as well as information derived from graph theory. It is revealed that the Doppler-shift in the gamma-ray spectra of the hexane isomers is in the vicinity of the n-hexane molecule with small structural dependency, in agreement with the fact that the measured Doppler-shifts of other linear alkanes are in the vicinity of hexane. The present study further reveals the electronic structures of hexane isomers, which are deeply rooted into the carbon core electrons, more than mere properties in the valence space. The calculations show that the highest occupied molecular orbitals (HOMOs) of the isomers exhibit less important roles in gamma-ray spectra; whereas the electron–positron annihilation is dominated by the electrons of the lowest occupied valence orbitals (LOVOs) and other valence electrons underneath the HOMO electrons, in agreement with previous findings. The present study further reveals that the C1s binding energies of the isomers exhibit association with the nodes of the isomers using graph theory. That is, more branched carbons likely engage with larger chemical shift, which is indicated by the largest eigenvalues (LEVs) of the adjacency matrix (AM) from graph theory. The chemical shift of the carbon NMR spectra is revealed by the LEVs of the Laplacian matrix (LM) obtained from chemical graph theory.

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Ghiasi, Reza, Morteza Zaman Fashami i Amir Hossein Hakimioun. "A density functional approach toward structural features and properties of C20…N2X2 (X = H, F, Cl, Br, Me) molecules". Journal of Theoretical and Computational Chemistry 13, nr 04 (czerwiec 2014): 1450023. http://dx.doi.org/10.1142/s0219633614500230.

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In this work, the interaction of C 20 with N 2 X 2 ( X = H , F , Cl , Br , Me ) molecules has been explored using the B3LYP, M062x methods and 6-311G(d,p) and 6-311+G(d,p) basis sets. The interaction energies (IEs) obtained with standard method were corrected by basis set superposition error (BSSE) during the geometry optimization for all molecules at the same levels of theory. It was found C 20… N 2 H 2 interaction is stronger than the interaction of other N 2 X 2 ( X = F , Cl , Br , Me ) with C 20. Highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO, respectively) levels are illustrated by density of states spectra (DOS). The nucleus-independent chemical shifts (NICSs) confirm that C 20… N 2 X 2 molecules exhibit aromatic characteristics. Geometries obtained from DFT calculations were used to perform NBO analysis. Also, 14 N NQR parameters of the C 20… N 2 X 2 molecules are predicted.

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Michalík, Martin, Monika Biela, Denisa Cagardová i Vladimír Lukeš. "Influence of catecholic ring torsion on hydroxyflavones". Acta Chimica Slovaca 13, nr 1 (1.04.2020): 49–55. http://dx.doi.org/10.2478/acs-2020-0008.

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AbstractSystematic quantum chemical investigation of quercetin and selected eight mono- and bihydroxyflavonols is presented. Structural analysis based on the Density Functional Theory showed that the energetically preferred conformation of flavonols substituted at the C5 and C3 atoms by a hydroxyl group is stabilised via intramolecular hydrogen bonds occurring between the (C4)O···HO(3 or 5) atomic pairs. Depending on the hydroxyl group positions, energetically preferred torsional orientation of the phenyl ring with respect to the planar benzo-γ-pyrone moiety changed from 0 to 180 degrees. Gas-phase electron transitions were investigated using the time-dependent DFT treatment. The dependence of maximal wavelengths on the torsional deformation of the phenyl ring is of a similar shape, i.e. minima observed for the perpendicular orientation and maxima for the planar one. Shape and energies of the Highest Occupied (HOMO) and Lowest Unoccupied (LUMO) Molecular Orbitals were compared. The obtained theoretical results were compared with available experimental data.

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Stanzel, Jörg, Emad F. Aziz, Matthias Neeb i Wolfgang Eberhardt. "Photoelectron Spectroscopy on Small Anionic Copper-Carbonyl Clusters". Collection of Czechoslovak Chemical Communications 72, nr 1 (2007): 1–14. http://dx.doi.org/10.1135/cccc20070001.

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Anion photoelectron spectroscopy in combination with density functional theory (DFT) calculations has been used to study mono- and dinuclear copper-carbonyl clusters Cun(CO)m- (n = 1, 2; m = 2-5). The adiabatic detachment energies of the anions have been measured which correspond to the electron affinities of the respective neutral species. The corresponding values are 0.95 eV for Cu(CO)2, 1.02 eV for Cu(CO)3, 1.04 eV for Cu(CO)4, 1.43 eV for Cu2(CO)4, and 1.19 eV for Cu2(CO)5. All spectra exhibit a pronounced vibrational fine structure on the adiabatic photodetachment peak. The energy splitting is close to the energy of the C-O stretching vibration of the neutral cluster (final state). The DFT calculations clearly indicate that in all clusters the highest occupied molecular orbital (HOMO) is a CO-derived π* orbital. Furthermore the calculations are used to give insight into geometry, frontier orbitals, vibrational frequencies and spin multiplicity of the neutral and anionic clusters.

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46

Alver, Özgür, Mehmet Fatih Kaya, Metin Bilge i Cemal Parlak. "Vibrational Spectroscopic Investigation and Conformational Analysis of Methacrylamidoantipyrine: A Comparative Density Functional Study". Journal of Theoretical Chemistry 2013 (12.09.2013): 1–10. http://dx.doi.org/10.1155/2013/386247.

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FT-IR and Raman spectra of methacrylamidoantipyrine (MAAP) have been reported in the region of 4000–10 cm−1 and 4000–100 cm−1, respectively. The optimized geometric parameters, conformational analysis, normal mode frequencies, and corresponding vibrational assignments of MAAP (C15H17N3O2) have been examined by means of density functional theory (DFT) method using the Becke-3-Lee-Yang-Parr (B3LYP) exchange-correlation functional and the 6-31G++(d,p) basis sets. Vibrational assignments have been made on the basis of potential energy distribution (PED) and the thermodynamics functions, and the highest occupied and the lowest unoccupied molecular orbitals (HOMO and LUMO) of MAAP have been predicted. Calculations are carried out with the possible seven (amide-1–5 and imide-1-2) conformational isomers of MAAP. Comparison between the experimental and theoretical results indicates that the B3LYP method provides satisfactory evidence for the prediction of vibrational wavenumbers, and the amide-1 conformational isomer is supposed to be the most stable form of MAAP.

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Yuan, Haokun, Ran Zhang, Kai Hu i Ruiqin Fang. "Proton-transfer salts of diphenylphosphinic acid with substituted 2-aminopyridine: crystal structure, spectroscopic and DFT studies". Acta Crystallographica Section C Structural Chemistry 79, nr 5 (24.04.2023): 193–203. http://dx.doi.org/10.1107/s2053229623003388.

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Three proton-transfer salts of diphenylphosphinic acid (DPPA) with 2-amino-5-(X)-pyridine (AMPY, X = Cl, CN or CH3), namely, 2-amino-5-chloropyridinium diphenylphosphinate, C5H6ClN2 +·C12H10O2P− (1, X = Cl), 2-amino-5-cyanopyridinium diphenylphosphinate, C6H6N3 +·C12H10O2P− (2, X = CN), and 2-amino-5-methylpyridinium diphenylphosphinate, C6H9N2 +·C12H10O2P− (3, X = CH3), have been synthesized and characterized by FT–IR and 1H NMR spectroscopy, and X-ray crystallography. The crystal structures of compounds 1–3 were determined in the space group P\overline{1} for 1 and 2, and C2/c for 3. All three compounds contain N—H...O hydrogen-bonding interactions due to proton transfer from the O=P—OH group of DPPA as donor to the pyridine N atom of AMPY as acceptor. The proton transfer of compounds 1–3 was also verified by 1H NMR and FT–IR spectroscopy. The stoichiometry of all three proton-transfer salts was determined to be 1:1 and the Benesi–Hildebrand equation was applied to determine the formation constant (K CT) and the molar extinction coefficient (ɛCT) in each case. Theoretical density functional theory (DFT) calculations were performed to investigate the optimized geometries, the molecular electrostatic potentials (MEP) and the highest occupied molecular orbitals (HOMO) and lowest unoccupied molecular orbitals (LUMO) of all three proton-transfer salts. The results showed good agreement between the experimental data and the DFT computational analysis.

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Feng, Simin, Maria Cristina dos Santos, Bruno R. Carvalho, Ruitao Lv, Qing Li, Kazunori Fujisawa, Ana Laura Elías i in. "Ultrasensitive molecular sensor using N-doped graphene through enhanced Raman scattering". Science Advances 2, nr 7 (lipiec 2016): e1600322. http://dx.doi.org/10.1126/sciadv.1600322.

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As a novel and efficient surface analysis technique, graphene-enhanced Raman scattering (GERS) has attracted increasing research attention in recent years. In particular, chemically doped graphene exhibits improved GERS effects when compared with pristine graphene for certain dyes, and it can be used to efficiently detect trace amounts of molecules. However, the GERS mechanism remains an open question. We present a comprehensive study on the GERS effect of pristine graphene and nitrogen-doped graphene. By controlling nitrogen doping, the Fermi level (EF) of graphene shifts, and if this shift aligns with the lowest unoccupied molecular orbital (LUMO) of a molecule, charge transfer is enhanced, thus significantly amplifying the molecule’s vibrational Raman modes. We confirmed these findings using different organic fluorescent molecules: rhodamine B, crystal violet, and methylene blue. The Raman signals from these dye molecules can be detected even for concentrations as low as 10−11M, thus providing outstanding molecular sensing capabilities. To explain our results, these nitrogen-doped graphene-molecule systems were modeled using dispersion-corrected density functional theory. Furthermore, we demonstrated that it is possible to determine the gaps between the highest occupied and the lowest unoccupied molecular orbitals (HOMO-LUMO) of different molecules when different laser excitations are used. Our simulated Raman spectra of the molecules also suggest that the measured Raman shifts come from the dyes that have an extra electron. This work demonstrates that nitrogen-doped graphene has enormous potential as a substrate when detecting low concentrations of molecules and could also allow for an effective identification of their HOMO-LUMO gaps.

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Reyes, Yves Ira A., Li-Yu Ting, Xin Tu, Hsin-Yi Tiffany Chen, Ho-Hsiu Chou i Carmine Coluccini. "Mechanistic Studies of Hydrogen Evolution Reaction on Donor-Acceptor Conjugated Polymer Photocatalysts". Applied Sciences 10, nr 20 (9.10.2020): 7017. http://dx.doi.org/10.3390/app10207017.

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The application of donor-acceptor (D-A) conjugated polymer catalysts for hydrogen evolution reaction (HER) has shown great promise because of the tunability of such catalysts to have desired properties. Herein, we synthesized two polymer catalysts: poly[4,4′-(9-(4-aminophenyl)-9H-carbazole-3,6-diamine-alt-5-oxido-5-phenylbenzo[b]phosphindole-3,7-diyl)dibenzaldehyde] (PCzPO) and poly[N1,N1-bis(4-amino-2-fluorophenyl)-2-fluorobenzene-1,4-diamine-alt-5-oxido-5-phenylbenzo[b]phosphindole-3,7-diyl)dibenzaldehyde] (PNoFPO). The UV-vis absorption spectra showed that the less planar structure and the presence of electronegative fluorine atoms in the donor group of PNoFPO led to a higher optical gap compared to PCzPO, leading to almost five times faster HER rate using PCzPO compared to PNoFPO. However, density functional theory (DFT) calculations show that the frontier orbitals and the highest occupied molecular orbitals – lowest unoccupied molecular orbitals (HOMO-LUMO) gaps of PCzPO and PNoFPO D-A moiety models are very similar, such that, during light absorption, electrons move from donor to acceptor group where proton binding is preferred to happen thereafter. For both PCzPO and PNoFPO D-A moieties, H2 formation through an intramolecular reaction with a barrier of 0.6–0.7 eV, likely occurs at the acceptor group atoms where protons bind through electrostatic interaction. The intermolecular reaction has nearly zero activation energy but is expected to occur only when the repulsion is low between separate polymers chains. Finally, experimental and DFT results reveal the importance of extended configurations of D-A polymers on HER rate.

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Arukalam, I. O., I. O. Madu, N. T. Ijomah, C. M. Ewulonu i G. N. Onyeagoro. "Acid Corrosion Inhibition and Adsorption Behaviour of Ethyl Hydroxyethyl Cellulose on Mild Steel Corrosion". Journal of Materials 2014 (13.03.2014): 1–11. http://dx.doi.org/10.1155/2014/101709.

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The corrosion inhibition of mild steel in 1.0 M H2SO4 solution by ethyl hydroxyethyl cellulose has been studied in relation to the concentration of the additive using weight loss measurement, EIS, polarization, and quantum chemical calculation techniques. The results indicate that EHEC inhibited corrosion reaction in the acid medium and inhibition efficiency increased with EHEC concentration. Further increase in inhibition efficiency is observed in the presence of iodide ions, due to synergistic effect. Impedance results reveal that EHEC is adsorbed on the corroding metal surface. Adsorption followed a modified Langmuir isotherm, with very high negative values of the free energy of adsorption (ΔGads). The polarization data indicate that the inhibitor was of mixed type, with predominant effect on the cathodic partial reaction. The frontier molecular orbitals, HOMO (the highest occupied molecular orbital) and LUMO (the lowest unoccupied molecular orbital) as well as local reactivity of the EHEC molecule, were analyzed theoretically using the density functional theory to explain the adsorption characteristics at a molecular level. The theoretical predictions showed good agreement with experimental results.

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