Electronic Structure Of Molecules Research Articles

A Quantum Mechanical MP2 Study of the Electronic Effect of Nonplanarity on the Carbon Pyramidalization of Fullerene C60.

Among C60's diverse functionalities, its potential application in CO2 sequestration has gained increasing interest. However, the processes involved are sensitive to the molecule's electronic structure, aspects of which remain debated and require greater precision. To address this, we performed structural optimization of fullerene C60 using the QM MP2/6-31G* method. The nonplanarity of the optimized icosahedron is characterized by two types of dihedral angles: 138° and 143°. The 120 dihedrals of 138° occur between two hexagons intersecting at C-C bonds of 1.42 Å, while the 60 dihedrals of 143° are observed between hexagons and pentagons at C-C bonds of 1.47 Å. NBO analysis reveals less pyramidal sp1.78 hybridization for carbons at the 1.42 Å bonds and more pyramidal sp2.13 hybridization for the 1.47 Å bonds. Electrostatic potential charges range from -0.04 a.u. to 0.04 a.u. on the carbon atoms. Second-order perturbation analysis indicates that delocalization interactions in the C-C bonds of 1.42 Å (143.70 kcal/mol) and 1.47 Å (34.98 kcal/mol) are 22% and 38% higher, respectively, than those in benzene. MP2/Def2SVP calculations yield a correlation energy of 13.49 kcal/mol per electron for C60, slightly higher than the 11.68 kcal/mol for benzene. However, the results from HOMO-LUMO calculations should be interpreted with caution. This study may assist in the rational design of fullerene C60 derivatives for CO2 reduction systems.

Stereo-Active Lone Pairs Induced Second Harmonic Generation Responses and Electrocatalytic Activity in Hybrid Material.

The lone pair electrons in the electronic structure of molecules have been a prominent research focus in chemistry for more than a century. Stable s2 lone pair electrons significantly influence material properties, including thermoelectric properties, nonlinear optical properties, ferroelectricity, and electro(photo)catalysis. While major advances have been achieved in understanding the influence of lone pair electrons on material characteristics, research on this effect in organic-inorganic hybrid materials is in its initial stage. In this work, we successfully obtained a novel organic-inorganic hybrid multifunctional material incorporating Ge with 4s2 lone pair electrons, (MeHDabco)2[GeBr3]4-H2O (MeHDabco=N-methyl-1,4-diazabicyclo[2.2.2]octane) (1). Driven by the stereochemically active lone pair electrons on the Ge2+, 1 crystallizes in the noncentrosymmetric space group P21 at room temperature and exhibits good second harmonic generation (SHG) responses. Interestingly, 1 also shows electrocatalytic activity for the hydrogen evolution reaction (HER) due to the existence of lone pair electrons on Ge2+ cations. The electrochemical experiment combined with the density functional theory (DFT) calculations revealed that the lone pair electrons act as both an active site for proton adsorption and facilitate the ionization of water. This work not only emphasizes the important role of lone pair electrons in material properties and functions but also provides new insight for designing novel Ge-based multifunctional hybrid materials.

Effect of intermolecular interactions and pharmacokinetic profile of antidiabetic agent (E)-N,N‑diethyl-2-(5(3‑hydroxy-4-methoxybenzylidene)-2,4-dioxothiazolidin-3-yl) acetamide

Diabetes is a prevalent disease in South India, posing a severe threat to public health. To tackle this issue, researchers are focusing on developing multi-targeted ligands, and one promising candidate is (E)-N,N‑diethyl-2-(5(3‑hydroxy-4-methoxybenzylidene)-2,4-dioxothiazolidin-3-yl)acetamide (DMDA). Geometry optimization of DMDA was carried out using density functional theory with 6–311+G(d, p) basis set to develop a theoretical model close to the previously synthesized and reported DMDA. Natural Bond Orbital analysis was conducted to scrutinize the phenomena of charge delocalization and electronic exchange interactions governing both intermolecular and intramolecular associations. Moreover, the vibrational characteristics of the molecule were elucidated through FT-IR and FT-Raman spectra. Lowest Unoccupied Molecular Orbital and Highest Occupied Molecular Orbital have also been explored to enhance understanding of the molecule's electronic structure and reactivity. Hirshfeld surface analysis was utilized to investigate the interactions between molecules within the crystalline lattice. Absorption, distribution, metabolism, excretion, and toxicity (ADMET) analysis elucidates the potential pharmacokinetic profile of DMDA. Molecular docking was performed to predict the binding site responsible for various interactions with the targeted protein. By combining these techniques, a comprehensive molecular description of DMDA has been generated.There are three prominent intramolecular interactions within the ambit of van der Waals radii, leading to stability of the molecule. The presence of a broad and shallow band with a significant red shift provides evidence for the strong intermolecular OH hydrogen bonding. DMDA complies with Lipinski's Rule of Five, highlighting its favorable characteristics for pharmaceutical efficacy. The negative binding energies determined by docking studies ascertain the potential sites of ligand-protein interaction leading to inhibition of α-amylase and α-glucosidase enzyme.

APOST-3D: Chemical concepts from wavefunction analysis.

Open-source APOST-3D software features a large number of wavefunction analysis tools developed over the past 20 years, aiming at connecting classical chemical concepts with the electronic structure of molecules. APOST-3D relies on the identification of the atom in the molecule (AIM), and several analysis tools are implemented in the most general way so that they can be used in combination with any chosen AIM. Several Hilbert-space and real-space (fuzzy atom) AIM definitions are implemented. In general, global quantities are decomposed into one- and two-center terms, which can also be further grouped into fragment contributions. Real-space AIM methods involve numerical integrations, which are particularly costly for energy decomposition schemes. The current version of APOST-3D features several strategies to minimize numerical error and improve task parallelization. In addition to conventional population analysis of the density and other scalar fields, APOST-3D implements different schemes for oxidation state assignment (effective oxidation state and oxidation states localized orbitals), molecular energy decomposition schemes, and local spin analysis. The APOST-3D platform offers a user-friendly interface and a comprehensive suite of state-of-the-art tools to bridge the gap between theory and experiment, representing a valuable resource for both seasoned computational chemists and researchers with a focus on experimental work. We provide an overview of the code structure and its capabilities, together with illustrative examples.

Synthesis, Spectral Characterization and Photoluminescence of 3-chloro-6-methoxy-2-(methylsulfanyl)quinoxaline in Different Solvents: An Experimental and Theoretical Investigation Using DFT.

In the present work, we synthesized 3-chloro-6-methoxy-2-(methyl sulfanyl) quinoxaline (3MSQ) using a microwave-assisted synthesis method. The physicochemical structural analysis of the synthesized compound utilizing 1H-NMR, 13C-NMR, and FT-IR spectroscopy techniques. The photophysical properties of 3MSQ was examined through absorption and fluorescence spectroscopy. Spectroscopic analyses revealed a bathochromic shift in both absorption and fluorescence spectra, attributed to the π → π* transition. Ground and excited state dipole moments was experimentally determined using the solvatochromic shift method, employing various correlations such as Lippert's, Bakhshiev's, Kawski-Chamma-Viallet's equations, and solvent polarity parameters. Our findings indicate that the excited state dipole moments exceed those of the ground state, suggesting increased polarity in the excited state. Further, the while detailed bond length, bond angles, dihedral angles, Mulliken charge distribution, ground state dipole moments and HOMO-LUMO energy gap estimated through ab initio computations using Gaussian-09W. The value of energy band gap obtained from both the methods are in good agreement. Furthermore, employing DFT computational analysis, we identified reactive centers such as electrophilic and nucleophilic sites using molecular electrostatic potential (MESP) 3D plots. Additionally, CIE chromaticity analysis was performed to understand the photoluminescent properties of 3MSQ. The insights derived from these analyses contribute to a better understanding of the molecule's electronic structure, photophysical properties, and solute-solvent interactions, thus providing valuable information regarding its behaviour and characteristics under diverse conditions. These results contribute to a comprehensive understanding of the molecular structure and properties of 3-chloro-6-methoxy-2-(methyl sulfanyl) quinoxaline (3MSQ).

Scalable approach to quantum simulation via projection-based embedding

Owing to the computational complexity of electronic structure algorithms running on classical digital computers, the range of molecular systems amenable to simulation remains tightly circumscribed even after many decades of work. Many believe quantum computers will transcend such limitations although in the current era the size and noise of these devices militates against significant progress. Here we describe a chemically intuitive approach that permits a subdomain of a molecule's electronic structure to be calculated accurately on a quantum device, while the rest of the molecule is described at a lower level of accuracy using density functional theory running on a classical computer. We demonstrate that this approach produces improved results for molecules that cannot be simulated fully on current quantum computers but which can be resolved classically at a cheaper level of approximation. The algorithm is tunable, so that the size of the quantum simulation can be adjusted to run on available quantum resources. Therefore, as quantum devices become larger, this method will enable increasingly large subdomains to be studied accurately. Published by the American Physical Society 2024

Unravelling the effects of functional groups on the adsorption of 2-mercaptobenzothiazole on a copper surface: a DFT study.

The adsorption of organic compounds onto metal surfaces holds significant importance across various applications, where understanding the intricate interactions between the compounds and the metal surfaces is indispensable. By using density functional theory calculations, this study investigated the impact of functional groups on the interaction between the thione form of 2-mercaptobenzothiazole (MBT) and the Cu(111) surface. The results indicated that substituting functional groups at the C6 position exerts a dual influence on the covalent and non-covalent interactions (NCI). Electron-donating groups enhanced both covalent and non-covalent interactions, whereas electron-withdrawing groups decreased covalent while increasing non-covalent interactions. The covalent interaction between MBTs and Cu(111) is mainly governed by the electron donation from the occupied orbitals of the molecules to the conduction band of copper, with the absolute interaction energies (eV) increasing in the order of MBT-NO2 (0.629) < MBT-COOH (0.660) < MBT-Cl (0.699) < MBT (0.715) < MBT-SH (0.727) < MBT-OH (0.733) < MBT-CH3 (0.735) < MBT-OCH3 (0.749) < MBT-NH2 (0.781) < MBT-NHCH3 (0.792). The influence of functional groups on covalent interactions is clarified by examining changes in the molecule's electronic structure, revealing a linear relationship between covalent interaction energy and HOMO energy, or the Hammett substituent constant. However, the impact of functional groups on non-covalent interactions is more complex and cannot be described by changes in the electronic structure. A novel parameter, the substitution interaction energy, was proposed to capture the effect of functional groups on the NCI-included adsorption energy of MBT derivatives on the Cu(111) surface. The stronger the substitution interaction, the stronger the NCI-included interaction of MBTs on Cu(111). The absolute NCI-included interaction energies follow the order of MBT (2.141) < MBT-Cl (2.213) < MBT-COOH (2.266) < MBT-CH3 (2.294) < MBT-OH (2.331) < MBT-OCH3 (2.379) < MBT-NO2 (2.461) = MBT-NH2 (2.461) < MBT-SH (2.530) < MBT-NHCH3 (2.565). These insights offer valuable guidance for manipulating the adsorption of organic substances on metal surfaces through functional groups in diverse applications.

SON KULLANMA TARİHİ GEÇMİŞ BİR İLACIN İNHİBİSYON ETKİNLİĞİ ÜZERİNE PROTONASYONUNUN DEĞERLENDİRİLMESİNE YÖNELİK TEORİK BİR YAKLAŞIM

The quantum theoretical calculations were performed to elucidate the corrosion inhibition efficiency of an expired drug. For this purpose, molecular orbital analysis, which is used in the analysis of chemical interactions and gives detailed data about the electronic structure of molecules, was used to gain insight into the electronic properties of the selected drug molecule in neutral and aqueous form. The calculations were carried out at the (B3LYP) 6-311G**(d,p) basis set level utilizing density functional theory (DFT) to examine the relationship between the molecular structure and inhibition efficiency of the corresponding drug molecule. Various quantum chemical descriptors such as highest occupied molecular orbital energy (HOMO), lowest unoccupied molecular orbital energy (LUMO), energy gap (ΔE), dipole moment (μ), ionization potential (I), electron affinity (A), electronegativity (χ), hardness (η), softness (σ), back donation (ΔEback- donation) and fraction of electrons transferred (ΔN) were calculated and correlated to the inhibition efficiency. The most probable nucleophilic and electrophilic reactive sites of studied drug molecule were analyzed through computed Fukui indices. Overall, obtained theoretical data indicate that the quantum chemical parameters correlate well with the inhibition performance.

Computational Discovery of Marine Molecules of the Cyclopeptide Family with Therapeutic Potential.

Stellatolides are natural compounds that have shown promising biological activities, including antitumor, antimicrobial, and anti-inflammatory properties, making them potential candidates for drug development. Chemical Reactivity Theory (CRT) is a branch of chemistry that explains and predicts the behavior of chemical reactions based on the electronic structure of molecules. Conceptual Density Functional Theory (CDFT) and Computational Peptidology (CP) are computational approaches used to study the behavior of atoms, molecules, and peptides. In this study, we present the results of our investigation of the chemical reactivity and ADMET properties of Stellatolides A-H using a novel computational approach called Conceptual DFT-based Computational Peptidology (CDFT-CP). Our study uses CDFT and CP to predict the reactivity and stability of molecules and to understand the behavior of peptides at the molecular level. We also predict the ADMET properties of the Stellatolides A-H to provide insight into their effectiveness, potential side effects, and optimal dosage and route of administration, as well as their biological targets. This study sheds light on the potential of Stellatolides A-H as promising candidates for drug development and highlights the potential of CDFT-CP for the study of other natural compounds and peptides.

Novel phenoxyacetylthiosemicarbazide derivatives as novel ligands in cancer diseases

Numerous epidemiological studies report an increased risk of developing prostate cancer in patients with melanoma and an increased risk of developing melanoma in patients with prostate cancer. Based on our previous studies demonstrating the high anticancer activity of thiosemicarbazides with a phenoxy moiety, we designed nineteen phenoxyacetylthiosemicarbazide derivatives and four of them acting as potential dual-ligands for both cancers. All of the compounds were characterized by their melting points and 1H, 13C NMR and IR spectra. For selected compounds, X-ray investigations were carried out to confirm the synthesis pathway, identify the tautomeric form and intra- and intermolecular interaction in the crystalline state. The conformational preferences and electronic structure of molecules were investigated by theoretical calculation method. Lipophilicity of compounds (log kw) was determined using isocratic reversed phase/high pressure liquid chromatography RP-18. For the obtained compounds, in vitro tests were carried out on four melanoma cell lines (A375, G-361, SK-MEL2, SK-MEL28), four prostate cancer cell lines (PC-3, DU-145, LNCaP, VcaP) and a normal human fibroblast cell line (BJ). The most active compounds turned out to be F6. Cell cycle analysis, apoptosis detection, CellROX staining and mitochondrial membrane potential analysis were performed for the most sensitive cancer cells treated with most active compounds. DSC analysis was additionally performed for selected compounds to determine their purity, compatibility, and thermal stability. The process of prooxidation was proposed as a potential mechanism of anticancer activity.

Core Excitations of Uranyl in Cs2UO2Cl4 from Relativistic Embedded Damped Response Time-Dependent Density Functional Theory Calculations.

X-ray spectroscopies, by their high selectivity and sensitivity to the chemical environment around the atoms probed, provide significant insights into the electronic structures of molecules and materials. Interpreting experimental results requires reliable theoretical models, accounting for environmental, relativistic, electron correlation, and orbital relaxation effects in a balanced manner. In this work, we present a protocol for the simulation of core excited spectra with damped response time-dependent density functional theory based on the Dirac-Coulomb Hamiltonian (4c-DR-TD-DFT), in which environmental effects are accounted for through the frozen density embedding (FDE) method. We showcase this approach for the uranium M4- and L3-edges and oxygen K-edge of the uranyl tetrachloride (UO2Cl42-) unit as found in a host Cs2UO2Cl4 crystal. We have found that the 4c-DR-TD-DFT simulations yield excitation spectra that very closely match the experiment for the uranium M4-edge and the oxygen K-edge, with good agreement for the broad experimental spectra for the L3-edge. By decomposing the complex polarizability in terms of its components, we have been able to correlate our results with angle-resolved spectra. We have observed that for all edges, but in particular the uranium M4-edge, an embedded model in which the chloride ligands are replaced by an embedding potential reproduces rather well the spectral profile obtained for UO2Cl42-. Our results underscore the importance of the equatorial ligands to simulating core spectra at both uranium and oxygen edges.

Simulation of the VUV Absorption Spectra of Oxygenates and Hydrocarbons: A Joint Theoretical–Experimental Study

Vacuum UV absorption spectroscopy is regularly used to provide unambiguous identification of a target species, insight into the electronic structure of molecules, and quantitative species concentrations. As molecules of interest have become more complex, theoretical spectra have been used in tandem with laboratory spectroscopic analysis or as a replacement when experimental data is unavailable. However, it is difficult to determine which theoretical methodologies can best simulate experiment. This study examined the performance of EOM-CCSD and 10 TD-DFT functionals (B3LYP, BH&HLYP, BMK, CAM-B3LYP, HSE, M06-2X, M11, PBE0, ωB97X-D, and X3LYP) to produce reliable vacuum UV absorption spectra for 19 small oxygenates and hydrocarbons using vertical excitation energies. The simulated spectra were analyzed against experiment using both a qualitative analysis and quantitative metrics, including cosine similarity, relative integral change, mean signed error, and mean absolute error. Based on our ranking system, it was determined that M06-2X was consistently the top performing TD-DFT method with BMK, CAM-B3LYP, and ωB97X-D also producing reliable spectra for these small combustion species.

Third-order nonlinear response of a novel organic acetohydrazide derivative: Experimental and theoretical approach

A novel nonlinear optical (NLO) organic material of N'-[(E)-(5-bromofuran-2-yl)methylidene]-2-(6-chloropyridin-3-yl)acetohydrazide (BCA) was synthesized by reflux method. The synthesized material was characterized using various analytical techniques, including spectroscopic methods (NMR, FTIR, PXRD). The UV–Vis absorption spectrum of BCA was recorded in different solvents. A strong absorption peak was observed in the 280–350 nm range, indicating its potential for UV-based optoelectronic applications. BCA shows good NLO responses (αCT, βCT, γCTvalues) with different solvents. The dielectric measurements were performed using impedance spectroscopy with varying temperatures as a function of frequency. Thermal stability of the material was evaluated using thermogravimetric analysis, indicating high thermal stability up to 153.28°C. The FMO, MEP, and NBO analyses were implemented using density functional theory (DFT) calculations to investigate the BCA molecule's electronic structure and charge distribution. The topology studies were carried out using the QTAIM and NCI to understand the structure's chemical bonding and intermolecular interactions and the structure's chemical bonding and intermolecular interactions. NLO properties of the BCA material were investigated using the Z-scan technique with a continuous wave (CW) laser, revealing a strong third-order nonlinear susceptibility (χ(3)) value of 2.44 × 10−6 e.s.u. and potential optical limiting behavior (OL threshold = 3.437 × 103 Wcm−2). The TD-HF method performed the calculated molecular static and dynamic of NLO parameters with frequency. The computed γ value of 6.2 × 10−36 e.s.u. was found to be consistent with the experimental value. The results of this study recommend that the synthesized hydrazide derivative material has potential NLO applications.

Graphic Characterization and Clustering Configuration Descriptors of Determinant Space for Molecules.

Quantum Monte Carlo approaches based on stochastic sampling of determinant space have evolved to be powerful methods to compute the electronic states of molecules. These methods not only calculate the correlation energy at an unprecedented accuracy but also provide insightful information on the electronic structures of computed states, for example, the population, connection, and clustering of determinants, which have not been fully explored. In this work, we devise a configuration graph for visualizing determinant space, revealing the nature of the molecule's electronic structure. In addition, we propose two analytical descriptors to quantify the extent of configuration clustering of multideterminant wave functions. The graph and descriptors provide us with a fresh perspective of the electronic structures of molecules and can assist with further development of configuration interaction-based electronic structure methods.

Reference interaction site model self-consistent field with constrained spatial electron density approach for nuclear magnetic shielding in solution.

We propose a new hybrid approach combining quantum chemistry and statistical mechanics of liquids for calculating the nuclear magnetic resonance (NMR) chemical shifts of solvated molecules. Based on the reference interaction site model self-consistent field with constrained spatial electron density distribution (RISM-SCF-cSED) method, the electronic structure of molecules in solution is obtained, and the expression for the nuclear magnetic shielding tensor is derived as the second-order derivative of the Helmholtz energy of the solution system. We implemented a method for calculating chemical shifts and applied it to an adenine molecule in water, where hydrogen bonding plays a crucial role in electronic and solvation structures. We also performed the calculations of 17O chemical shifts, which showed remarkable solvent dependence. While converged results could not be sometimes obtained using the conventional method, in the present framework with RISM-SCF-cSED, an adequate representation of electron density is guaranteed, making it possible to obtain an NMR shielding constant stably. This introduction of cSED is key to extending the method's applicability to obtain the chemical shift of various chemical species. The present demonstration illustrates our approach's superiority in terms of numerical robustness and accuracy.

Comparison of Born–Oppenheimer approximation and electron-nuclear correlation

ABSTRACT The electronic structure of molecules is routinely examined for static arrangements of point nuclei, which is a highly useful premise but not without certain limitations. Here, the electron-nuclear correlation energy is analysed in the context of the quantised nuclear energy associated with the chemical bond vibrations. To this end, accurate calculations of the ground state of a hydrogen atom (including basis functions in the energy continuum) whose nucleus is confined by a quadratic potential well, are performed for all values of the spring constant. The numerically exact ground state energy is compared to the results obtained within the Born–Oppenheimer approximation and within the uncorrelated product wavefunction ansatz. The electron-nuclear correlation energy is found to be smaller in magnitude than the electron correlation in two-electron atomic systems, in the limit of weak nuclear confinement, and is further reduced by at least an order of magnitude in the limit of strong confinement. In all cases, however, the electron-nuclear correlation energy is found to be significantly larger than the error of the Born–Oppenheimer approximation. Moreover, the error of the Born–Oppenheimer approximation is found to persist within the limit of infinite nuclear confinement. Insight into the electron-nuclear correlation energy from this study will help incorporate the nuclear quantum effects into the electronic structure theories.

Theoretical study of the effect of nonlocal short-range exchange on calculations of molecular excitation energies in the dielectric screened-exchange method

We have previously proposed a dielectric screened-exchange approach in which the dielectric constant is used to describe system-dependent features of the electronic structures of materials (Chem. Phys. Lett., 466, pp. 91–94, 2008). In the present paper, we discuss the theoretical effects of the nonlocal short-range exchange term on molecular excitations and compare them with the effects of the local Slater approximation. We show that the nonlocal short-range term is useful in describing precisely the (excited) electronic structures of molecules with large HOMO–LUMO gaps. Conversely, the local Slater approximation works effectively for systems with small HOMO–LUMO gaps.

Position of Biphenyl Group Turning the Structure and Photophysical Property of D-π- π -A Prototype Fluorescent Material.

Three novel D-π-π-A prototype compounds, namely, (E)-2-(3-([1,1'-biphenyl]-2-yl)-1-(9H-fluoren-2-yl)allylidene)malononitri-le (2-BAM), (E)-2-(3-([1,1'-biphenyl]-3-yl)-1-(9H-fluoren-2-yl)allylidene)malononitri-le (3-BAM), and (E)-2-(3-([1,1'-biphenyl]-4-yl)-1-(9H-fluoren-2-yl)allylidene)malononitri-le (4-BAM) were synthesized. Furthermore, the structures and photophysical properties of three compounds were compared. Molecules of 2-BAM were packed into a 1D column structure with H-aggregation. However, both of 3-BAM and 4-BAM were packed into 3D layer structures with J-aggregation, respectively. Although all three compounds showed highly twisted molecular geometries, their respective molecular packing and intermolecular interactions were different. Because of the differences in electronic structures of molecules, three compounds displayed different emission behaviors in solid and dilute solution states. This study indicated that changing the position of biphenyl groups is an effective way for turning the structures and photophysical properties of such D-π-π-A prototype fluorescent materials.

Excited states of chlorophyll a and b in solution by time-dependent density functional theory.

The ground state and excited state electronic properties of chlorophyll (Chl) a and Chl b in diethyl ether, acetone, and ethanol solutions are investigated using quantum mechanical and molecular mechanical calculations with density functional theory (DFT) and time-dependent DFT (TDDFT). Although the DFT/TDDFT methods are widely used, the electronic structures of molecules, especially large molecules, calculated with these methods are known to be strongly dependent on the functionals and the parameters used in the functionals. Here, we optimize the range-separated parameter, μ, of the CAM-B3LYP functional of Chl a and Chl b to reproduce the experimental excitation energy differences of these Chl molecules in solution. The optimal values of μ for Chl a and Chl b are smaller than the default value of μ and that for bacteriochlorophyll a, indicating the change in the electronic distribution, i.e., an increase in electron delocalization, within the molecule. We find that the electronic distribution of Chl b with an extra formyl group is different from that of Chl a. We also find that the polarity of the solution and hydrogen bond cause the decrease in the excitation energies and the increase in the widths of excitation energy distributions of Chl a and Chl b. The present results are expected to be useful for understanding the electronic properties of each pigment molecule in a local heterogeneous environment, which will play an important role in the excitation energy transfer in light-harvesting complex II.

Calculation of the ionization potential of zinc and graphene phthalocyaninates on the surface of dielectrics

A mathematical model is proposed for calculating the ionization potentials of molecules on the surface of dielectrics in order to quantify changes in the electronic characteristics of materials on a substrate. The semiconductor and photoelectronic properties of nanosystems based on phthalocyanine derivatives are determined by the electronic structure of molecules. Based on the zinc phthalocyaninate molecule ZnC32N8H16, model structures are constructed that increase this molecule by attaching benzene rings ZnC48N8H24, ZnC64N8H32 and a model simulating the film structure of Zn4C120N32 H48. Graphene was considered as a nanostructure modeling a fragment of a monomer lm. The ionization potentials of these compounds on the surface of magnesium oxide, sodium chloride and silicon are calculated. In the presence of a substrate, the ionization potentials of all nanostructures decrease, while the values of the surface ionization potentials remain fundamentally dierent in their magnitude for all compounds. The compound ZnC64N8H32 sprayed onto the surface exhibits the best photoelectronic properties, its surface ionization potential is comparable to graphene.