Electronic, Vibrational, and Structural Study of Polysaccharide Agar-Agar Biopolymer

2021 ◽  
Vol 33 ◽  
pp. 35-46
Author(s):  
Ankita Pandey ◽  
Abhishek Kumar Gupta ◽  
Shivani Gupta ◽  
Sarvesh Kumar Gupta ◽  
Rajesh Kumar Yadav
Keyword(s):  
Charge Distribution ◽  
Molecular Orbital ◽  
Structural Study ◽  
Density Functional ◽  
Vibrational Analysis ◽  
Chemical Properties ◽  
Atomic Charge ◽  
Dft Method ◽  
Basis Set ◽  
Mulliken Charge

Polysaccharide biopolymer Agar-Agar extracted from red algae is a natural and biodegradable polymer. It is a combination of agarose (a neutral and linear polymer, with repeated units of agarobiose) and a heterogeneous mixture of agaropectin (a charged sulfated polymer). In this study, a comparative study of structural vibrational and electrochemical properties of agar-agar biopolymer with two different methods HF (Hartree-Fock) and DFT (Density Functional Theory) using a basis set 631+G (d, p) is performed. The comparative structural study of agar-agar biopolymer by HF and DFT method has been carried out to calculate the stability of the molecule. The thermionic properties and Mulliken charge distribution are analysed to deliver a quantitative study of partial atomic charge distribution. The overall vibrational analysis of primal modes of the biopolymer has been studied using FTIR analysis. Based on highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) composition and energies, various chemical parameters of the biopolymer have been evaluated. The Physico-chemical properties of this polysaccharide show a strong correlation with its optimized structure. Agar-agar has its application in the electrochemical, biotechnological, and pharmaceutical fields, as a stabilizer and gelling material.

scholarly journals Corrosion Inhibitive Potentials of some 2H-1-benzopyran-2-one Derivatives- DFT Calculations

2021 ◽  
Vol 11 (6) ◽  
pp. 13968-13981
Keyword(s):  
Charge Distribution ◽  
Metal Surface ◽  
Electrostatic Potential ◽  
Density Functional ◽  
Effective Interaction ◽  
Basis Set ◽  
Mulliken Charge ◽  
Surface Mode ◽  
Adsorption Sites ◽  
Fukui Indices

There is an increased demand for metals and alloys because of their use in household appliances and industrial machines. However, they react with the environment and are consequently prone to loss of strength and durability owing to corrosion. In a bid to eradicate or control this, the use of corrosion inhibitors has been employed. Quantum chemical calculations have been used to predict the corrosion inhibitive potentials of novel molecules and probe into their metals' surface mode of action. Density functional theory was employed here with a polar basis set, 6-31G(d), to investigate the corrosion inhibitive potentials of some 2H-1- benzopyran-2-ones derivatives via their electronic properties, global reactivity descriptors, electrostatic potential maps, and Fukui indices. The energy gaps follow the order: c > e > a > d > b > g > f > h, indicative that compounds f and h would effectively protect metals’ surface against corrosion with the HOMO map essentially delocalized over the benzopyran-2-one moiety and the attached substituents while the LUMO plot shows a delocalization of the lowest vacant molecular orbitals over the entire benzopyran-2-one moiety. The asymmetric charge distribution on the inhibitors from the electrostatic potential maps indicates that each compound possesses reactive adsorption sites for bonding and back-bonding with the metal surface. The Mulliken charge distribution and the Fukui indices reveal that the adsorption of an inhibitor on a metal surface is not only via the heteroatoms like O, Cl, Br, and N. The contribution of carbon atoms as nucleophilic and electrophilic centers ensures effective interaction between a metal surface and the inhibitor and isolates the material from corroding environment.

scholarly journals Ultrasound Assisted Synthesis, Molecular Structure,UV-Visible Assignments, MEP and Mulliken Charges Study of (E)-3-(4-chlorophenyl)-1-(4-methoxyphenyl) prop-2-en-1-one: Experimental and DFT Correlational

2021 ◽  
Vol 18 (1) ◽  
pp. 86-96
Author(s):  
Rohit S. Shinde
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Density Functional Theory Method ◽  
Atomic Charge ◽  
Dft Method ◽  
Basis Set ◽  
Geometrical Parameters ◽  
Functional Theory ◽  
Vibrational Assignments ◽  
Uv Visible

Present investigation deals with the synthesis and density functional theory study (DFT) of a chalcone derivative; (E)-3-(4-chlorophenyl)-1-(4-methoxyphenyl)prop-2-en-1-one (CPMPP). The synthesis of a CPMPP has been carried out by the reaction of 4-methoxyacetophenone and 4-chlorobenzalehyde in ethanol at 30 ℃ under ultrasound irradiation. The structure of a synthesized chalcone is affirmed on the basis of FT-IT, 1H NMR and 13C NMR. The geometry of a CPMPP is optimized by using the density functional theory method at the B3LYP/6-31G(d,p) basis set. The optimized geometrical parameters like bond length and bond angles have been computed. The absorption energies, oscillator strength, and electronic transitions have been derived at the TD-DFT method at the B3LYP/6-31G(d,p) level of theory for B3LYP/6-31G(d p) optimized geometries. The effect of polarity on the absorption energies is discussed by computing UV-visible results in dichloromethane (DCM). Since theoretically obtained wavenumbers are typically higher than experimental wavenumbers, computed wavenumbers were scaled with a scaling factor, and vibrational assignments were made by comparing experimental wavenumbers to scaled theoretical wavenumbers. Quantum chemical parameters have been determined and examined. Molecular electrostatic potential (MEP) surface plot analysis has been carried out at the same level of theory. Mulliken atomic charge study is also discussed in the present study.

Spectroscopic investigation, HOMO–LUMO energies, natural bond orbital (NBO) analysis and thermodynamic properties of two-armed macroinitiator containing coumarin with DFT quantum chemical calculations

2016 ◽  
Vol 94 (6) ◽  
pp. 583-593 ◽  
Author(s):  
Feride Akman
Keyword(s):  
Density Functional Theory ◽  
Molecular Orbital ◽  
Electrostatic Potential ◽  
Density Functional ◽  
Natural Bond Orbital ◽  
Dft Method ◽  
Basis Set ◽  
Orbital Method ◽  
Functional Theory ◽  
Homo Lumo

In the present work, two-armed macroinitiator containing coumarin were synthesized, characterized by Fourier transform infrared spectroscopy and 1H nuclear magnetic resonance techniques and investigated theoretically using density functional theory (DFT) calculations. The molecular geometry, fundamental vibrational frequencies, atomic charges obtained from atomic polar tensors and Mulliken were analyzed by means of structure optimizations based on the DFT method with 6-31G+(d, p) as a basis set. The 1H chemical shifts were calculated by the gauge-including atomic orbital method and compared with available experimental data. The electronic properties, such as highest occupied molecular orbital – lowest unoccupied molecular orbital (HOMO–LUMO) energies, electron affinity, electronegativity, ionization energy, hardness, chemical potential, global softness, and global electrophilicity were calculated by using the DFT method. The electrostatic potential and molecular electrostatic potential surfaces were performed to predict the reactive sites of the two-armed macroinitiator. The energy difference between acceptor and donor and stabilization energy were determined using natural bond orbital analysis. The results show that the occurrence of intramolecular charge transfers within the polymer. Time-dependent density functional theory calculations of visible spectra were analyzed at different solvents. Finally, thermodynamic functions, such as enthalpy, heat capacity, and entropy, of the two-armed macroinitiator at different temperatures were calculated and the relationship with temperature was investigated.

DENSITY FUNCTIONAL THEORY STUDY OF THE INTERACTION BETWEEN 3-NITRO-1,2,4-TRIAZOLE-5-ONE AND WATER

2005 ◽  
Vol 04 (03) ◽  
pp. 849-856 ◽  
Author(s):  
GUO-YONG FANG ◽  
LI-NA XU ◽  
XIN-GEN HU ◽  
XIN-HUA LI ◽  
HE-MING XIAO ◽  
...  
Keyword(s):  
Intermolecular Interaction ◽  
Density Functional ◽  
Vibrational Analysis ◽  
Zero Point ◽  
Dft Method ◽  
Basis Set ◽  
Statistical Thermodynamic ◽  
Intermolecular Interaction Energy ◽  
Point Energy ◽  
Basis Set Superposition Error

Three fully optimized geometries of 3-nitro-1,2,4-triazol-5-one (NTO)-H2O complexes have been obtained with density function theory (DFT) method at the B3LYP/6-311++G** level. The intermolecular interaction energy is calculated with zero point energy (ZPE) correction and basis set superposition error (BSSE) correction. The greatest corrected intermolecular interaction of the NTO–H2O complexes is -30.14 KJ/mol. Electrons in complex systems transfer from H2O to NTO . The strong hydrogen bonds contribute to the interaction energies dominantly. Natural bond orbital (NBO) analysis is performed to reveal the origin of the interaction. Based on the vibrational analysis, the changes of thermodynamic properties from the monomer to complexes with the temperature ranging from 200 K to 800 K have been obtained using the statistical thermodynamic method. It is found that three NTO –water complexes can be produced spontaneously from NTO and H2O at lower temperature.

THEORETICAL STUDY ON PHOTOINDUCED INTRAMOLECULAR CHARGE TRANSFER IN A NOVEL ORGANIC SENSITIZER C201

2011 ◽  
Vol 10 (05) ◽  
pp. 641-649 ◽  
Author(s):  
FENGJIE ZHOU ◽  
YAPING ZHANG ◽  
SHUO CAO ◽  
YONG DING ◽  
SHASHA LIU
Keyword(s):  
Charge Transfer ◽  
Molecular Orbital ◽  
Density Functional ◽  
Intramolecular Charge Transfer ◽  
Transition Density ◽  
Dft Method ◽  
Transition Dipole Moment ◽  
Transition Dipole ◽  
Level Densities ◽  
Charge Difference Density

A new organic dye (C201) composed of triarylamine unit as electron donor and anchoring unit as electron acceptor, was theoretically investigated by quantum chemical methods. We optimized the geometry of C201 with density functional theory (DFT) at B3LYP/6-311G (d) level. Densities of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), as well as the energies are listed. The excited states of the dye molecules C201 were calculated by time dependent-DFT (TD-DFT) method. Two main visible bands at 572 nm and 407 nm were mainly attributed to the electronic transition from HOMO→LUMO and HOMO-1→LUMO, respectively. 3D cube representations including transition density (TD) and charge difference density (CDD) directly visualized the character of intramolecular charge transfer of C201. The orientation and strength of transition dipole moment were showed visually using TD. Furthermore, we illustrate the orientation and results of the intramolecular charge transfer by CDD.

scholarly journals Computational Aspects of (E)-O-Carbomethoxy Methyl Oxime Ether of 1,3-Dimethyl-2,6-Diphenylpiperidin-4-One

2019 ◽  
Vol 9 (2S2) ◽  
pp. 701-706
Keyword(s):  
Molecular Orbital ◽  
Density Functional ◽  
Atomic Charge ◽  
Molecular Geometry ◽  
Biologically Active ◽  
Oxime Ether ◽  
Structure And Property ◽  
Highest Occupied Molecular Orbital ◽  
Computational Aspects ◽  
Lowest Unoccupied Molecular Orbital

Density Functional Theoretical (DFT) studies on the biologically active oxime ether derived from 1,3-dimethyl-2,6-diphenylpiperidin-4-one has been carried out. Various quantum chemical parameters of the molecule viz. molecular geometry, Highest Occupied Molecular Orbital – Lowest Unoccupied Molecular Orbital (HOMO–LUMO) energies, Non-Linear Optical (NLO) properties, Mulliken atomic charge distribution were obtained theoretically and compared with the single crystal data. An insight into the structure and property correlation revealed the probable behavior of the molecule studied

Multiplicity spin, structure, and charge of iron-verdohemeoxygenase complex: A comparison study by the DFT method

2020 ◽  
Vol 24 (10) ◽  
pp. 1208-1214
Author(s):  
Hamideh Tasharofi ◽  
Maryam Daghighi Asli ◽  
Parisa Rajabali Jamaat
Keyword(s):  
Heme Oxygenase ◽  
Density Functional ◽  
Complex Structure ◽  
Three Dimensional ◽  
Dft Method ◽  
Basis Set ◽  
Dimensional Structure ◽  
Central Metal ◽  
Stable States ◽  
And Function

Recently the three-dimensional structure of verdoheme heme oxygenase complex was revealed. However, many parameters of verdoheme heme oxygenase’s complex structure and their role and function on Heme degradation were unknown. In this work the structure of iron verdoheme in complex with heme oxygenase was compared by the density functional theory (DFT)-based B3LYP method using the 6-31G basis set. Many parameters such as charge of verdoheme and iron as central metal, electron distribution, spin multiplicity of the molecule and proximal substituents effects on verdoheme ring stabilization and their arrangement are discussed and compared for twelve different conformations of the molecules to find the most energetically stable states.

scholarly journals Substitution Effects on the Optoelectronic Properties of Coumarin Derivatives

2019 ◽  
Vol 10 (1) ◽  
pp. 144
Author(s):  
Amit Kumar ◽  
Roberto Baccoli ◽  
Antonella Fais ◽  
Alberto Cincotti ◽  
Luca Pilia ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Binding Energy ◽  
Molecular Orbital ◽  
Density Functional ◽  
Optoelectronic Properties ◽  
Exciton Binding Energy ◽  
Basis Set ◽  
Substitution Effects ◽  
Coumarin Derivatives ◽  
Functional Theory

Coumarin derivatives have gathered major attention largely due to their versatile utility in a wide range of applications. In this framework, we report a comparative computational investigation on the optoelectronic properties of 3-phenylcoumarin and 3-heteroarylcoumarin derivatives established as enzyme inhibitors. Specifically, we concentrate on the variation in the optoelectronic characteristics for the hydroxyl group substitutions within the coumarin moiety. In order to realize our aims, all-electron density functional theory and time dependent density functional theory calculations were performed with a localized Gaussian basis-set matched with a hybrid exchange–correlation functionals. Molecular properties such as highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies, vertical ionization (IEV) and electron affinity energies, absorption spectra, quasi-particle gap, and exciton binding energy values are examined. Furthermore, the influence of solvent on the optical properties of the molecules is considered. We found a good agreement between the experimental (8.72 eV) and calculated (8.71 eV) IEV energy values for coumarin. The computed exciton binding energy of the investigated molecules indicated their potential optoelectronics application.

scholarly journals Theoretical Study of a Class of Organic D-π-A Dyes for Polymer Solar Cells: Influence of Various π-Spacers

Crystals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 163
Author(s):  
Nguyen Van Trang ◽  
Tran Ngoc Dung ◽  
Ngo Tuan Cuong ◽  
Le Thi Hong Hai ◽  
Daniel Escudero ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Solar Cells ◽  
Molecular Orbital ◽  
Density Functional ◽  
Energy Gap ◽  
Polymer Solar Cells ◽  
Basis Set ◽  
Structure Theory ◽  
Functional Theory ◽  
Alkyl Groups

A class of D-π-A compounds that can be used as dyes for applications in polymer solar cells has theoretically been designed and studied, on the basis of the dyes recently shown by experiment to have the highest power conversion efficiency (PCE), namely the poly[4,8-bis(5-(2-butylhexylthio)thiophen-2-yl)benzo[1,2-b:4,5-b’]dithiophene-2,6-diyl-alt-TZNT] (PBDTS-TZNT) and poly[4,8-bis(4-fluoro-5-(2-butylhexylthio)thiophen-2-yl)benzo[1,2-b:4,5-b’]dithiophene-2,6-diyl-alt-TZNT] (PBDTSF-TZNT) substances. Electronic structure theory computations were carried out with density functional theory and time-dependent density functional theory methods in conjunction with the 6−311G (d, p) basis set. The PBDTS donor and the TZNT (naphtho[1,2-c:5,6-c]bis(2-octyl-[1,2,3]triazole)) acceptor components were established from the original substances upon replacement of long alkyl groups within the thiophene and azole rings with methyl groups. In particular, the effects of several π-spacers were investigated. The calculated results confirmed that dithieno[3,2-b:2′,3′-d] silole (DTS) acts as an excellent π-linker, even better than the thiophene bridge in the original substances in terms of well-known criteria. Indeed, a PBDTS-DTS-TZNT combination forms a D-π-A substance that has a flatter structure, more rigidity in going from the neutral to the cationic form, and a better conjugation than the original compounds. The highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) energy gap of such a D-π-A substance becomes smaller and its absorption spectrum is more intense and red-shifted, which enhances the intramolecular charge transfer and makes it a promising candidate to attain higher PCEs.

Electronic Structure, Nonlinear Optical Properties, and Vibrational Analysis of Ethyl benzoate by Density Functional Theory

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
Tanveer Hasan ◽  
P. K. Singh
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Vibrational Analysis ◽  
Ethyl Benzoate ◽  
Computational Method ◽  
Basis Set ◽  
Vibrational Modes ◽  
Normal Coordinate ◽  
Functional Theory ◽  
Vibrational Bands

This work deals with the vibrational spectroscopy of Ethyl benzoate (C9H10O2). The fundamental vibrational frequencies and intensity of vibrational bands were evaluated using density functional theory (DFT) using standard HF/6-31G(d,p) and B3LYP/6-31G(d,p) methods and basis set combinations. The vibrational spectra were interpreted, with the aid of normal coordinate analysis based on a scaled quantum mechanical force field. The infrared and Raman spectra were also predicted from the calculated intensities. Comparison of simulated spectra with the experimental spectra provides important information about the ability of the computational method to describe the vibrational modes.

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