Highest Occupied Molecular Orbital-lowest Unoccupied Molecular Orbital Research Articles

Identification of Potential Carbonic Anhydrase Inhibitors for Glaucoma Treatment Through an In-Silico Approach

Glaucoma is a neurodegenerative disease and second leading cause of blindness in western world. The disease is characterized by an elevated intraocular pressure. Carbonic anhydrase plays a major role by forming aqueous humor and its inhibition can reduce intraocular pressure by partially suppressing the secretion of aqueous humor. Thus in this study, we proposed to identify the potential novel compounds targeting the carbonic anhydrase. The diversity set-II molecules library consisting of 1880 compounds from National Cancer Institute were virtually screened (molecular docking) against human carbonic anhydrase protein. For the obtained best compounds, the nature of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), which determine nucleophilic and electrophilic activity, were calculated by using density functional theory (DFT). The in silico screening suggested 5 best compounds that are effective in comparison to the dorzolamide, a widely used carbonic anhydrase inhibitor for glaucoma treatment. Of the five compounds, 4-nitro-7-[(1-oxidopyridin-1-ium-2-yl) thio] benzofurazan (ZINC01757986) exhibited the better binding affinity (− 9.2 cal/mol) in comparison to dorzolamide (− 7.2 kcal/mol). The DFT studies on novel identified compound, ZINC01757986 exhibited less HOMO–LUMO energy gap, low hardness and more softness (0.2305 eV, 0.1152 eV and 8.6805 eV) when compared to dorzalamide (0.9536 eV, 0.4768 eV and 2.0973 eV). These studies emphasize that ZINC01757986 can be used as potential carbonic anhydrase inhibitor and lead compounds for the development of an effective anti-glaucoma drug. The results emphasize that these compounds could be potential lead molecules for further structure-based discovery of antiglaucoma drugs.

Unraveling the atomic structure, ripening behavior, and electronic structure of supported Au20 clusters.

The free-standing Au20 cluster has a unique tetrahedral shape and a large HOMO-LUMO (highest occupied molecular orbital-lowest unoccupied molecular orbital) gap of around 1.8 electron volts. The "magic" Au20 has been intensively used as a model system for understanding the catalytic and optical properties of gold nanoclusters. However, direct real-space ground-state characterization at the atomic scale is still lacking, and obtaining fundamental information about the corresponding structural, electronic, and dynamical properties, is challenging. Here, using cluster-beam deposition and low-temperature scanning tunneling microscopy, atom-resolved topographic images and electronic spectra of supported Au20 clusters are obtained. We demonstrate that individual size-selected Au20 on ultrathin NaCl films maintains its pyramidal structure and large HOMO-LUMO gap. At higher cluster coverages, we find sintering of the clusters via Smoluchowski ripening to Au20n agglomerates. The evolution of the electron density of states deduced from the spectra reveals gap reduction with increasing agglomerate size.

Synthesis and characterization of porphyrin–pyrene hybrids

Palladium-catalyzed Suzuki–Miyaura coupling of 5-functionalized Ni(II) porphyrins with 1,3,6,8-tetrafunctionalizedpyrenes was carried out to obtain two kinds of porphyrin–pyrene hybrids. These compounds were comprehensively characterized by nuclear magnetic resonance (NMR), high-resolution mass spectrometry and ultraviolet-visible (UV-vis) absorption spectrometry, and their electrochemical properties were studied by both cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Fluorescence spectra for zinc compounds and free-base compounds were performed. In addition, the structure of 4Zn, a porphyrin tetramer, was determined by X-ray diffraction analysis, in which two planes formed by the porphyrin unit and the pyrene moiety adopt nearly perpendicular geometry with two sets of dihedral angles displaying 85.14 (4)[Formula: see text] and 83.90 (4)[Formula: see text], respectively. In the UV-vis absorption spectra, the maximum wavelengths of Soret bands and Q bands for these hybrids were observed at 434 and 648 nm. As the number of porphyrin units increases, the corresponding molar extinction coefficient rises markedly, in which the maximal value is 7.4 × 105 M[Formula: see text] • cm[Formula: see text] belonging to 4Zn. Moreover, the presence of energy transformation from the pyrene moiety to the porphyrin unit has been proved by emission spectra. Finally, the electrochemical properties of these porphyrin–pyrene hybrids were analyzed by using cyclic voltammetry and differential pulse voltammetry, which show that the nickel hybrids possessed the maximal electrochemical highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap and the zinc compounds displayed the minimum electrochemical HOMO–LUMO gap.

Theoretical Model for Surface Forces between Cytosine and CNT(6,6-6) Nanotube: Geometry Optimization, Molecular Structure, Intermolecular Hydrogen Bond, Spectroscopic (NMR, UV/Vis, Excited State), FMO, MEP, and HOMO–LUMO Investigations

In the present work, the adsorption of the molecule cytosine on carbon nanotube [CNT] (6,6-6) was investigated for the first time using density functional theory (DFT) calculations in the gas phase. The non-bonded interaction effect of compounds cytosine and CNT(6,6-6) nanotube on the electronic properties, chemical shift tensors and natural charge was investigated. The electronic properties of the obtained complex change after cytosine adsorption. The natural charge analysis showed that the charge transfer occurs between cytosine and CNT(6,6-6) nanotube and it was induced the dipole moment to the CNT(6,6-6) nanotube. Moreover, the formation of an intermolecular hydrogen bond between cytosine and CNT(6,6-6) nanotube has been investigated. The electronic spectra of the isolated molecule cytosine and the complex CNT(6,6-6)/cytosine in the gas phase were calculated by time dependent density functional theory (TD-DFT). The various parameters such as equilibrium geometry, the highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO) of the cytosine and CNT(6,6-6) nanotube were calculated and discussed consequently.

Theoretical insights into sensing of hexavalent chromium on buckled and planar polymeric carbon nitride nanosheets of heptazine and triazine structures

ABSTRACTThe applicability of four surface models of graphitic carbon nitride (planar and corrugated nanosheets of triazine and heptazine structures) to detect hexavalent chromium from contaminated environments was investigated theoretically. The sensing was most favourable on hollow sites but with different coordination numbers and geometrical configurations. A substantial variation in the gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the 2D material (e.g. from 4.12 to 0.36 eV in the case of buckled heptazine structure) delineated the high capability of the sensor toward the detection of the chromium ion. Remarkable charge transfers (4.466–4.558 e) from the sensor to the analyte were evident from the topological analysis. Neglecting the surface corrugation could overestimate the adsorption energy while underestimating the HOMO–LUMO gap of both types of graphitic carbon nitride. The localised orbital locator (LOL) profiles revealed the ionic nature of the interactions.

Palladium (II) Kompleks İyondaki Primer, Sekonder ve Tersiyer Amin Ligandlarının Termo-Fiziksel, Kimyasal Reaktivite ve Biyolojik Özelliklerle Karşılaştırılması: DFT Çalışması

The Palladium is considered as the catalyst for coupling reaction and useful metal in industry. The thermo-physical, chemical reactivity and biological interaction are considered the most expected parameters for use in any area of the chemical industry, the pharmaceutical industry, and academia. The palladium (II) complex ion with different amine ligands are considered under theoretical study by the method of density functional theory (DFT). Some thermo-physical parameters such as free energy, entropy, dipole moment, binding energy, nuclear energy, electronics energy, heat of formation, reactivity properties of molecule like Highest Occupied Molecular Orbital (HOMO), Lowest Unoccupied Molecular Orbital (LUMO), HOMO-LUMO gap, ionization potential, electronegativity, hardness, softness and electron affinity, and biological properties of molecules like charge density, surface area grid, volume, LogP, polarizibility, refractivity, molecular mass, PIC50 were calculated using the computational program of DFT method. The value of HOMO LUMO gap is 10.78, 0.59, 0.50, and 10.73 and PIC50 is -20.41, -8.46, -1.69, and 1.83 for L01, L02, L03, and L04 respectively while the chemical stability is same for L02, and L03, similarly L01 and L04. The QSAR study provides information about their correlation and biological activity as drugs whereas the biological activity was increased with increasing methyl groups. The four palladium (II) complex ions with amine ligands have strong biological activity for L03 and L04, and occur the correlation on thermophysical, chemical reactivity.

Spectroscopic and Time-Dependent DFT Study of the Photophysical Properties of Substituted 1,4-Distyrylbenzenes.

In this contribution, we examine the photophysical properties of 15 totally trans-trans 1,4-distyrylbenzene derivatives (DSBs) functionalized with different electron-donating (ED) and electron-withdrawing (EW) groups by experimental and computational methodologies. We use UV-vis and fluorescence spectroscopies to determine the experimental optical properties such as the maximum absorption (λabsexp) and emission (λemexp) wavelengths, the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) energy gaps (ΔEabsexp), the molar extinction coefficients (ε), the fluorescence quantum yields (Φf), and the fluorescence lifetimes (τ). We also calculate the experimental spontaneous emission decay rate (krexp) and correlate all of these magnitudes to the corresponding calculated properties, maximum absorption (λabscal) and emission (λemcal) wavelengths, vertical transition energies (ΔEabscal), oscillator strength (Fosc), and spontaneous emission decay rate (krcal), obtained by the time-dependent density functional theory method. We analyze the effect of the electronic nature of the substituents on the properties of the DSBs, finding that the ED and EW groups lead to bathochromic shifts. This is consistent with the decrease of ΔE values as the strength of ED and EW substituents increases. We find excellent correlations between calculated and experimental values for λabs, λem, and ΔEabs (r ∼ 0.99-0.95). Additionally, the correlations between the relative ε with Fosc values and the kr values are in good agreement (r ∼ 0.88-0.72) with the experimental properties. Overall, we find that for substituted 1,4-DSBs, computational chemistry is an excellent tool to predict structure-property relationships, which can be useful to forecast the properties of their polymeric analogues, which are usually difficult to determine experimentally.

Quasi-Periodic and Fractal Polymers: Energy Structure and Carrier Transfer.

We study the energy structure and the coherent transfer of an extra electron or hole along aperiodic polymers made of N monomers, with fixed boundaries, using B-DNA as our prototype system. We use a Tight-Binding wire model, where a site is a monomer (e.g., in DNA, a base pair). We consider quasi-periodic (Fibonacci, Thue–Morse, Double-Period, Rudin–Shapiro) and fractal (Cantor Set, Asymmetric Cantor Set) polymers made of the same monomer (I polymers) or made of different monomers (D polymers). For all types of such polymers, we calculate the highest occupied molecular orbital (HOMO) eigenspectrum and the lowest unoccupied molecular orbital (LUMO) eigenspectrum, the HOMO–LUMO gap and the density of states. We examine the mean over time probability to find the carrier at each monomer, the frequency content of carrier transfer (Fourier spectra, weighted mean frequency of each monomer, total weighted mean frequency of the polymer), and the pure mean transfer rate k. Our results reveal that there is a correspondence between the degree of structural complexity and the transfer properties. I polymers are more favorable for charge transfer than D polymers. We compare of quasi-periodic and fractal sequences with that of periodic sequences (including homopolymers) as well as with randomly shuffled sequences. Finally, we discuss aspects of experimental results on charge transfer rates in DNA with respect to our coherent pure mean transfer rates.

Development of software for prediction and virtual screening of antioxidant activity of new synthesized azaheterocyclic compounds

Background: Increasing introduction of innovation technologies into medicine and pharmacology makes it possible to modify and develop further the methods of the development of new medicines. Such methods include virtual screening. In this article approaches to building software for virtual screening of nitric oxide (NO)scavengers in an important class of azaheterocyclic compounds are discussed.Methods: During the study period (from October 2017 to January 2019) the methods for the evaluation of antioxidant activity, as well as quantum-mechanical and statistical calculations were conducted. Quantum-mechanical calculations on HOMO (highest occupied molecular orbital) energy and LUMO (lowest unoccupied molecular orbital) energy descriptors have been conducted using program complex WinMopac 7.2.Results: Evaluation methods of antioxidant activity, quantum-mechanical and statistical calculations have been presented. The algorithm for computer program of virtual screening has been proposed. Prospects and benefits of computer modeling of agent activity are considered.Conclusions: Establishment of computer program for virtual screening will significantly reduce time and resources during researching new synthesized compounds. The algorithm for a computer program of virtual screening has been developed Predictable antioxidant activity data on nitric oxide radical (NO·)inhibition may be calculated in percentage using HOMO and LUMO as the input data for this program.

Interaction patterns in fluidized-bed Fenton process for the degradation of recalcitrant pollutants: theoretical and experimental insights

The interaction of carriers (SiO2) and Fenton’s reagent during the degradation of recalcitrant pollutant by fluidized-bed Fenton process was investigated. Reactive Black 5 (RB5) was selected as a model pollutant since dyes are recalcitrant to conventional treatment technologies. Quantum chemical simulation and experimental approach were employed to predict the potential interactions among the chemical species involved in the process. Quantum chemical parameters such as highest occupied molecular orbital (HOMO) energy, lowest unoccupied molecular orbital (LUMO) energy, HOMO–LUMO energy gaps were computed and analyzed. Response surface methodology was utilized to investigate the effect of operational parameters and optimize the process performance. The analysis of quantum chemical parameters shows that with a comparatively higher EHOMO of − 8.72 eV, SiO2 can interact with Fe3+ (EHOMO = − 18.74 eV), which explains the crystallization of iron oxide on the carriers. The higher EHOMO–LUMO energy gap value of SiO2 (7.92 eV) indicates its potential interaction with Fe2+, Fe3+ and RB5 due to their lower EHOMO–LUMO energy gaps. RB5 exhibited the lowest hardness value (1.23 eV), indicating that it can be degraded by the hydroxyl radical (2.11 eV). For the experimental part, the process can remove up to 80% and 99.94% of the initial COD and color, respectively, under optimum conditions. The most significant parameters affecting the process performance are [Fe2+] and [Dye]. This study has provided insights into the potential interactions occurring in fluidized-bed Fenton process. The results will be useful toward optimization and scale-up of fluidized-bed Fenton process.

Enhanced Open-Circuit Voltage in Perovskite Solar Cells with Open-Cage [60]Fullerene Derivatives as Electron-Transporting Materials.

The synthesis, characterization, and incorporation of open-cage [60]fullerene derivatives as electron-transporting materials (ETMs) in perovskite solar cells (PSCs) with an inverted planar (p-i-n) structure is reported. Following optical and electrochemical characterization of the open-cage fullerenes 2a–c, p-i-n PSCs with a indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOT:PSS)/perovskite/fullerene/Ag structure were prepared. The devices obtained from 2a–b exhibit competitive power conversion efficiencies (PCEs) and improved open-circuit voltage (Voc) values (>1.0 V) in comparison to a reference cell based on phenyl-C61-butyric-acid methyl-ester (PC61BM). These results are rationalized in terms of a) the higher passivation ability of the open-cage fullerenes with respect to the other fullerenes, and b) a good overlap between the highest occupied molecular orbital/lowest unoccupied molecular orbital (HOMO/LUMO) levels of 2a–b and the conduction band of the perovskite.

Electronic transport properties of electrically doped cytosine‐based optical molecular switch with single‐wall carbon nanotube electrodes

This study represents an empirical model of cytosine-based optical molecular switch. This possible biomolecular switch has been designed using the first principle approach which is based on density functional theory and non-equilibrium Green's function. The quantum-ballistic transport property and current-voltage (I-V) characteristics of cytosine-based optomolecular switch have been investigated at 25 THz operating frequency. The influence of highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gaps on the electronic transmission and I-V characteristics has been discussed in detail. The aim of this study is to highlight the minimum conformational change during a single ON-OFF switching cycle. The biomolecule comprises switching behaviour when converts from straightened to twisted form during photo-excitement. The straightened and twisted forms of the molecule are represented as logic `0' and logic `1', respectively. This p and n regions of this switch has been made using electrical doping process. The current through the twisted form of the cytosine biomolecule is ~1000 times higher than the straightened form. The maximum switching ratio 62.1 is obtained at 1 V bias. The origin of the switching behaviour of the biomolecule can be interpreted by quantum-ballistic transport model along with HOMO-LUMO gaps.

Investigation of spectroscopic studies and DFT calculations on glucofuranose derivatives of dithiophosphonates

2,4-Bis(4-methoxyphenyl)-1,3,2,4-dithiadiphosphetane-2,4-disulfide (Lawesson’s reagent: LR) was reacted with 1,2:5,6-di-O-cyclohexylidene-α-D-glucofuranose and 1,2:5,6-di-O-isopropylidene-α-D-glucofuranose in toluene and gave rise to crude dithiophosphonic acids. The crude dithiophosphonic acids were treated with excess triethylamine and the triethylammonium salts of dithiophosphonic acids (1) and (2) were isolated by crystallization method. Compounds 1 and 2 were characterized by elemental analysis, IR, and NMR (1H-, 13C- and 31P-) spectroscopies and mass spectrometry. In addition, NMR spectra, the electronic properties (the electronic chemical potential, electronegativity, chemical hardness and the global electrophilicity index) and NBO analysis of compound 2 have been calculated by using the Gaussian 16 W program. The electronic properties were calculated using Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) energies by density functional method (DFT/B3LYP) at 6-31G(d,p) level. The HOMO and LUMO energies are −5.9 and −0.72 eV, respectively. The HOMO–LUMO energy difference is 5.18 eV and this value shows that compound 2 has a high stability and low reactivity.

Investigating metal-organic framework based on nickel (II) and benzene 1,3,5-tri carboxylic acid (H3BTC) as a new photocatalyst for degradation of 4-nitrophenol

ABSTRACTMetal-organic framework nickel (II) benzene tricarboxylate Ni3(BTC)2·12H2O (MOF-Ni) has been synthesised under solvothermal conditions and characterised by single crystal X-ray diffraction, Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA). The photocatalytic degradation of 4-nitrophenol (4-NP) using MOF-Ni under UV light irradiation was investigated and showed satisfactory results. A catalytic mechanism is proposed in terms of the HOMO-LUMO (highest occupied molecular orbital-lowest unoccupied molecular orbital) gap and the associated light-induced transition. The results showed that the studied MOF-based photocatalyst can be reused three to five times in the photocatalysis process and can degrade and mineralise 74% and 48% of 4-NP, respectively.

Spectroscopic (FTIR, FT-Raman, 1H NMR and UV–Vis) and DFT/TD-DFT studies on cholesteno [4,6-b,c]-2′,5′-dihydro-1′,5′-benzothiazepine

The density functional theory calculations and spectroscopic characterization (FTIR, FT-Raman, 1H NMR and ultraviolet–visible) of the pharmaceutically active compound Cholesteno [4,6-b,c]-2′,5′-dihydro-1′,5′-benzothiazepine (CHBT) have been carried out. The recorded Vibrational, proton NMR and electronic spectra have been compared with the simulated one and they are found in well agreement. The bands appearing in FTIR and FT-Raman spectra are assigned with great accuracy using animated modes. The ultraviolet–visible (UV–Vis) absorption bands are assigned using molecular orbitals data obtained by TD-B3LYP/PCM calculations with 6-311G(d,p) basis set. Proton NMR signal peaks have been assigned using GIAO-B3LYP/6-311G(d,p)/PCM method. The hyperconjugative interactions and charge delocalization within the molecule have been studied using natural bond orbital (NBO) analysis. The non-linear optical (NLO) behavior of the present compound has been investigated using theoretical dipole moment, polarizability and first static hyperpolarizability values. The thermodynamic functions (entropy, heat capacity and enthalpy) obtained from harmonic force field calculations for the range of temperature 100–1000 K are reported. Moreover, highest occupied molecular orbital – lowest unoccupied molecular orbital (HOMO-LUMO) analysis, molecular electrostatic potential (MEP) diagram, global reactivity descriptors and condensed or atomic Fukui Functions have been also presented.

Structural and Electronic Effects Due to Fluorine Atoms on Dibenzotetraaza-Annulenes Complexes.

The preparation and characterization of Ni(II) (1F) and Cu(II) (2F) complexes of the ligand 15,16,17,18,19,20,21,22-octafluoro-dibenzotetraaza[14]annulene (LF) are here reported. These compounds have been characterized by elemental analysis, mass and UV–vis spectroscopies, single-crystal X-ray diffraction, and computational studies. The effects due to the presence of fluorine atoms have been highlighted by comparison with the analogous complexes of the ligand LH (Ni: 1H; Cu: 2H), which bears hydrogen atoms at the benzenoid rings instead of fluorine. 1F and 2F are isostructural, with the metal ions bound to the four nitrogen atoms in a square-planar geometry and where the planar molecules are arranged in a herringbone motif in the crystal lattice. Remarkable differences in the intermolecular interactions between 1F and 2F and the corresponding H-complexes are shown by Hirshfeld surface calculations. Moreover, the effects of fluorination on the electronic structures have been investigated by density functional theory (DFT) and time-dependent DFT calculations. The compounds with LF and LH ligands present corresponding molecular orbitals (MOs) with similar shapes. Furthermore, while the presence of F-atoms lowers the energy of the MOs in comparison with those of the LH complexes, it does not remarkably affect the highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) and HOMO–LUMO + 1 gaps, in agreement with the UV–vis results.

Design and Synthesis of Functional π Molecules and Their Application to Near-IR Materials

The combination of several aromatic rings and/or heterocycles can induce novel functions. This phenomenon is observed in porphyrin derivatives, commonly found in hemoglobin, in the active sites of P-450, etc. The ability of these structures to interact strongly with visible light accounts for today's increased interest in the development of rationally designed porphyrinoid-based optical materials. In the pharmaceutical sciences, designing near-IR materials can be a challenge due to the high transparency of near-IR light in biological samples. Phthalocyanines (Pcs) are robust organic dyes that are absorbed in visible light. A theoretical investigation of molecular orbitals of Pcs has revealed that the introduction of a phosphorus(V) atom into a macrocyclic core leads to a narrower highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gap. Following these studies, we found that certain types of Pc phosphorus(V) complexes display main absorptions beyond 1000 nm. Additionally, phosphorus(V) complexes with other azaporphyrinoids have been designed and synthesized via a relatively simple procedure. These complexes showed novel optical properties which are potentially useful in the pharmaceutical and material sciences. Furthermore, we have overcome the problem of organic radicals and antiaromatic compounds, which are generally considered to be unstable, by using a combination of serendipitous synthetic methodologies and spectroscopic techniques. These novel azaporphyrin compounds are robust and free from transition metals. They are relatively easy to synthesize and also exhibit predictable properties.

Synthesis and vibrational spectral (FT-IR, FT-Raman) studies, NLO properties & NBO analysis of (E)-N'(thiophen-2yl methylene)isonicotinohydrazide using quantum chemical method

FT-IR (4000-400 cm-1) and FT-Raman (3500-50 cm-1) spectra of (E)-N'(thiophen-2yl methylene)isonicotinohydrazide (TMINH) molecule was recorded in solid phase. The optimized geometry was calculated by B3LYP method with 6-311++G(d,p) basis set. The harmonic vibrational frequencies, infrared (IR) intensities and Raman scattering activities of the title compound were performed at same level of theory. The complete vibrational assignments were performed on the basis of the Total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanical (SQM) method. The calculated first hyperpolarizability may be attractive for further studies on non-linear optical (NLO) properties of material. Stability of the molecule arising from hyperconjugative interaction and charge delocalization was analyzed using natural bond orbital (NBO) analysis. Highest occupied molecular orbital-Lowest unoccupied molecular orbital (HOMO-LUMO) energy gap explains the eventual charge transfer interactions taking place within the title molecule. A study on the electronic properties, such as excitation energies and wavelengths, were performed by time-dependent (TD-DFT) approach. Molecular electrostatic potential (MEP) provides the information on the electrophilic, nucleophilic and free radical prone reactive sites of the molecule. The thermodynamic properties such as heat capacity, entropy and enthalpy of the title compound were calculated at different temperatures in gas phase. 1H and 13C-NMR chemical shifts of the molecule were calculated using Gauge-independent atomic orbital (GIAO) method.To establish information about the interactions between human cytochrome protein and this novel compound theoretically, docking studies were carried out using Schrödinger software.

Modification on C217 by auxiliary acceptor toward efficient sensitiser for dye-sensitised solar cells: a theoretical study

ABSTRACTIn this work, to develop efficient organic dye sensitisers, a series of novel donor–acceptor–π–acceptor metal-free dyes were designed based on the C217 dye by means of modifying different auxiliary acceptors, and their photovoltaic performances were theoretically investigated with systematic density functional theory calculations coupled with the incoherent charge-hopping model. Results showed that the designed dyes possess lower highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels as well as narrower HOMO–LUMO gaps compared to C217, which indicate their higher light-harvesting efficiency. In addition, using the (TiO2)38 cluster and bidentate bridging model, we predicted that the photoelectric conversion efficiency (PCE) for the C217 dye is as high as 9.92% under air mass (AM) 1.5 illumination (100 mW·cm−2), which is in good agreement with its experimental value (9.60%–9.90%). More interestingly, the cell sensitised by the dye 7 designed in this work exhibits a middle-sized open-circuit voltage of 0.737 V, large short-circuit photocurrent density of 21.16 mAˑcm−2 and a fill factor of 0.801, corresponding to a quite high PCE of 12.49%, denoting the dye 7 is a more promising sensitiser candidate than the C217, and is worth further experimental study.

Energy Gap Law for Exciton Dynamics in Gold Cluster Molecules.

The energy gap law relates the nonradiative decay rate to the energy gap separating the ground and excited states. Here we report that the energy gap law can be applied to exciton dynamics in gold cluster molecules. Size-dependent electrochemical and optical properties were investigated for a series of n-hexanethiolate-protected gold clusters ranging from Au25 to Au333. Voltammetric studies reveal that the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gaps of these clusters decrease with increasing cluster size. Combined femtosecond and nanosecond time-resolved transient absorption measurements show that the exciton lifetimes decrease with increasing cluster size. Comparison of the size-dependent exciton lifetimes with the HOMO-LUMO gaps shows that they are linearly correlated, demonstrating the energy gap law for excitons in these gold cluster molecules.