BOREPIN, BORANORBORNADIENE AND BORANORCARADIENE: SUBSTITUENT EFFECTS ON INTERCONVERSIONS AT THEORETICAL LEVELS

2010 ◽  
Vol 09 (01) ◽  
pp. 379-392 ◽  
Author(s):  
M. Z. KASSAEE ◽  
S. M. MUSAVI ◽  
E. MOTAMEDI
Keyword(s):  
Gas Phase ◽  
Relative Stability ◽  
Density Functional ◽  
Substituent Effects ◽  
Basis Set ◽  
Electronic Effects ◽  
Bond Length Alternation ◽  
Ab Initio Hf ◽  
Rule Out ◽  
Hf Calculations

Density-functional B3LYP and ab initio HF calculations are used to study three isomeric systems including: borepin I, boranorbornadiene II, and boranorcaradiene III as well as their X-substituted analogues at two different positions ( X = F, Cl, Br, CH3, OCH3, CF3, CN , and NH2 ). Geometries, enthalpies, and energy barriers for two series of interconversions, IIIX → IX and IIIX → IIX, are calculated using 6-311G* basis set. The B3LYP calculated relative stability is in the order: I (0.00 kcal/mol) > II (23.33 kcal/mol) > III (39.07 kcal/mol). Except for NH2 , the electronic effects of the substituents are generally insignificant on the relative stability. At B3LYP, the gas-phase activation enthalpies for III → I and III → II interconversions are estimated to be very small (0.6 and 0.75 kcal/mol, respectively). The reverse conversions, I → III and II → III, have activation energies of 39.67 and 16.49 kcal/mol, respectively. These energies rule out the possibility of a rapid interconversion of the isomers in the gas phase. Again, none of the substituents, X, can change this situation. Two pathways are proposed for the possible [1, 3]-suprafacial sigmatropic shifts of IIIX → IIX. The partial aromatic characters of planar borepins are estimated using magnetic (NICS) and structural criteria (bond length alternation).

Theoretical calculations of intramolecular hydrogen bond of the 2-Amino-2, 4, 6-cycloheptatrien-1-one in the gas phase and solution: Substituent effects and their positions

2016 ◽  
Vol 15 (07) ◽  
pp. 1650063 ◽  
Author(s):  
Narges Khatoon Attaran Toosy ◽  
Heidar Raissi ◽  
Maryam Zaboli
Keyword(s):  
Hydrogen Bond ◽  
Gas Phase ◽  
Intramolecular Hydrogen Bond ◽  
Density Functional ◽  
Theoretical Calculations ◽  
Substituent Effects ◽  
Dft Method ◽  
Basis Set ◽  
Parent Molecule ◽  
Intramolecular Hydrogen

The density functional theory (DFT) method with 6-311[Formula: see text]G[Formula: see text] basis set has been used to calculate the intramolecular hydrogen bond, molecular structure, vibrational frequencies, nuclear quadrupole resonance (NQR) parameters, 1HNMR, and resonance parameters of 2-Amino-2, 4, 6-cycloheptatrien-1-one (2-amino tropone) and its 18 derivatives in 5 positions. The natural bonding orbital (NBO) and quantum theory of atoms in molecules (QTAIM) analyses have been studied. The strongest and weakest hydrogen bonds exist for NO2 substituent in R3 position and OH in R7 position, respectively. In general, the substituted systems in position 3 indicate the stronger hydrogen bond in comparison with the parent molecule (R[Formula: see text]H), while, it is comparatively weaker for position 5. The energy of the N-H[Formula: see text]O interaction is found to be medium in strength ([Formula: see text][Formula: see text]kJ mol[Formula: see text] to [Formula: see text][Formula: see text]kJ mol[Formula: see text]). The low [Formula: see text], positive [Formula: see text] values and [Formula: see text] show that the nature of O [Formula: see text] H bonding is electrostatic. Also, our theoretical results show that the hydrogen bond strength in solution phase and the first singlet excited state is weaker in comparison with the gas phase ground state.

Donor Functionalized Perylene and Different π-Spacers Based Sensitizers for DSSC Applications - A Theoretical Approach

2021 ◽  
Author(s):  
D. Nicksonsebastin ◽  
P. Pounraj ◽  
Prasath M
Keyword(s):  
Density Functional Theory ◽  
Solar Cell ◽  
Gas Phase ◽  
Density Functional ◽  
Basis Set ◽  
Dye Sensitized Solar Cell ◽  
Functional Theory ◽  
Dye Sensitized ◽  
Td Dft ◽  
Organic Sensitizers

Abstract Perylene based novel organic sensitizers for the Dye sensitized solar cell applications are investigated by using Density functional theory (DFT) and time dependant density functional theory (TD-DFT).The designed sensitizers have perylene and dimethylamine (DM) and N-N-dimethylaniline(DMA) functionalized perylene for the dssc applications.π-spacers are thiophene andcyanovinyl groups and cyanoacrylic acid is chosen as the acceptor for the designed sensitizers. The studied sensitizers were fully optimized by density functional theory at B3LYP/6-311G basis set on gas phase and DMF phase. The electronic absorption of the sensitizers is analyzed by TD-DFT at B3LYP/6-311G basis set in both gas and DMF phase.

SOLVENT EFFECTS ON THE ELECTRONIC STRUCTURE AND NON-LINEAR OPTICAL PROPERTIES OF PYRENE AND SOME OF ITS DERIVATIVES BASED ON DENSITY FUNCTIONAL THEORY

2021 ◽  
Vol 4 (4) ◽  
pp. 236-251
Author(s):  
A. S. Gidado ◽  
L. S. Taura ◽  
A. Musa
Keyword(s):  
Density Functional Theory ◽  
Gas Phase ◽  
Density Functional ◽  
Energy Gap ◽  
Chemical Reactivity ◽  
Basis Set ◽  
Lumo Energy ◽  
Functional Theory ◽  
Organic Optoelectronic ◽  
Homo Lumo

Pyrene (C16H10) is an organic semiconductor which has wide applications in the field of organic electronics suitable for the development of organic light emitting diodes (OLED) and organic photovoltaic cells (OPV). In this work, Density Functional Theory (DFT) using Becke’s three and Lee Yang Parr (B3LYP) functional with basis set 6-311++G(d, p) implemented in Gaussian 03 package was  used to compute total energy, bond parameters, HOMO-LUMO energy gap, electron affinity, ionization potential, chemical reactivity descriptors, dipole moment, isotropic polarizability (α), anisotropy of polarizability ( Δ∝) total first order hyper-polarizability () and second order hyperpolarizability (). The molecules used are pyrene, 1-chloropyrene and 4-chloropyrene  in gas phase and in five different solvents: benzene, chloroform, acetone, DMSO and water. The results obtained show that solvents and chlorination actually influenced the properties of the molecules. The isolated pyrene in acetone has the largest value of HOMO-LUMO energy gap of and is a bit closer to a previously reported experimental value of  and hence is the most stable. Thus, the pyrene molecule has more kinetic stability and can be described as low reactive molecule. The calculated dipole moments are in the order of 4-chloropyrene (1.7645 D) < 1-chloropyrene (1.9663 D) in gas phase. The anisotropy of polarizability ( for pyrene and its derivatives were found to increase with increasing polarity of the solvents.  In a nutshell, the molecules will be promising for organic optoelectronic devices based on their computed properties as reported by this work.

Theoretical Analysis of the Unusual Vicinal Effects on Electronic Circular Dichroism Spectra of Cobalt(III) Complexes with ED3A-Type and Related Ligands

2014 ◽  
Vol 69 (7) ◽  
pp. 371-384
Author(s):  
Yuekui Wang ◽  
Chunxia Zhang
Keyword(s):  
Circular Dichroism ◽  
Optical Activity ◽  
Density Functional ◽  
Substituent Effects ◽  
Basis Set ◽  
Excitation Energies ◽  
Electronic Circular Dichroism ◽  
Special Cases ◽  
Circular Dichroïsm ◽  
Optimized Geometries

To investigate the origin of unusual N-vicinal effects, the geometries of the two series of cobalt(III) complexes, [Co(ED3A-type)(X)]-(X = CN-, NO2-) and [Co(EDDS-type)]-, with the pentadentate ethylenediamine-N;N;N0-triacetate (ED3A), hexadentate (S,S)-ethylenediamine-N;N0-dissuccinate (EDDS), and their N-alkyl-substituted ligands in aqueous solution have been optimized at the DFT/B3P86/6-311++G(2d,p) level of theory. Based on the optimized geometries, the excitation energies and rotational strengths have been calculated using the time dependent density functional theory (TDDFT) method with the same functional and basis set. The optimized geometries and calculated electronic circular dichroism (ECD) curves are in good agreement with the observed ones. Based on this agreement, the characteristics of usual and unusual N-vicinal effects as well as the related chiral stereochemistry phenomena have been discussed. To reveal the origin of the unusual N-vicinal effects, a novel calculation scheme has been proposed, which permits efficiently assessing the contribution of the octahedral core to the optical activities of the chelates. The results show that the substituent effects and conformational relaxation effects make opposite contributions to the overall N-vicinal effects with the former being dominant. The unusual N-vicinal effects originate from the negligible chirality of the octahedral core in the unsubstituted [Co(ED3A)(X)]-chelates. For this reason, their optical activity is dominated by the asymmetric nitrogens and behaves different from the normal cases. The unusual vicinal effects observed in the N-alkyl-substituted ED3A-type chelates reflect an increase in the contribution of the octahedral core to their optical activity, which recovers the ECD spectra from the special cases to the normal ones. These findings provide some insight into the unusual N-vicinal effects as well as the chiroptical properties of the chelates.

scholarly journals Protonated heterocyclic derivatives of cyclopropane and cyclopropanone: classical species, alternate sites, and ring fragmentation

2015 ◽  
Vol 93 (7) ◽  
pp. 708-714 ◽  
Author(s):  
Margarida S. Miranda ◽  
Darío J.R. Duarte ◽  
Joaquim C.G. Esteves da Silva ◽  
Joel F. Liebman
Keyword(s):  
Density Functional Theory ◽  
Gas Phase ◽  
Density Functional ◽  
Computational Study ◽  
Basis Set ◽  
Proton Affinities ◽  
Functional Theory ◽  
Heterocyclic Derivatives ◽  
Gas Phase Basicities ◽  
Derivatives Of

A computational study has been performed for protonated oxygen- or nitrogen-containing heterocyclic derivatives of cyclopropane and cyclopropanone. We have searched for the most stable conformations of the protonated species using density functional theory with the B3LYP functional and the 6-31G(2df,p) basis set. More accurate enthalpy values were obtained from G4 calculations. Proton affinities and gas-phase basicities were accordingly derived.

Gas-phase reaction of ClO− with CHnCl4-n (n = 0, 1, 2, 3) and CX3H (X = F, Cl and Br): Substituent effect from a comparative study

2014 ◽  
Vol 92 (9) ◽  
pp. 868-875 ◽  
Author(s):  
Liang Junxi ◽  
Su Qiong ◽  
Li Yu ◽  
Zhang Qiang ◽  
Geng Zhiyuan
Keyword(s):  
Density Functional ◽  
Substituent Effects ◽  
Bond Distance ◽  
State Theory ◽  
Basis Set ◽  
Phase Reaction ◽  
Chemical Research ◽  
Functional Theory ◽  
Deprotonation Reaction ◽  
Strain Model

Substituent effects on reactivity are studied using the hybrid B3LYP and BHandHLYP methods of density functional theory with the aug-cc-pVDZ basis set. The chosen testing models includes two very representative reactions in chemical research, the bimolecular nucleophilic substitution (SN2) reaction and the deprotonation reaction, in which the former is represented by ClO− + CHnCl4-n (n = 0, 1, 2, 3), and the latter is based on reactions of ClO− with CX3H (X = F, Cl, and Br). Our theoretical findings suggest that a heavier substituent X in substrate results in a higher activation energy, a slower SN2 reaction, but a faster deprotonation reaction. Those are well confirmed by some presented results from bond orders, second-order perturbative energy E(2), and activation strain model analysis. Moreover, we have further explored the reactivity difference derived from substituent effects in term of the relationships of reactive barrier with the charges transferred and the leaving-bond distance in TSs, respectively, especially the TSs in SN2 reactions. Again, the rate constants at 298–1000 K are also evaluated for the SN2 reactions presented through the transition state theory.

Charge transfer complexes between 2-, 3- and 4-aminopyridines and some π-acceptors in the gas phase and in chloroform: DFT calculations

2016 ◽  
Vol 15 (04) ◽  
pp. 1650029 ◽  
Author(s):  
Nuha Ahmed Wazzan
Keyword(s):  
Charge Transfer ◽  
Dft Calculations ◽  
Gas Phase ◽  
Density Functional ◽  
Molecular Structures ◽  
Basis Set ◽  
Charge Transfer Complexes ◽  
Good Correspondence ◽  
Electronic Distribution ◽  
Picryl Chloride

This work reports density functional theory (DFT) calculations on the molecular structures, electronic distribution, and UV-Vis and IR spectroscopy analysis of charge transfer complexes between aminopyridines (APYs), namely 2-APY, 3-APY and 4-APY, as electron-donors and some [Formula: see text]-electron-acceptors, namely chloranil (CHL), tetracyanoethylene (TCNE) and picryl chloride (PC), formed in the gas phase at the B3LYP/6-31[Formula: see text]G(d,p) method/basis set, and in chloroform at the same method/basis set using PCM as solvation model. Good correspondence was generally obtained between the calculated parameters and the experimental ones.

scholarly journals Tautomeric Equilibrium Revisited: proton-tautomerism in solvent and the fundamentals of molecular stability prediction.

2019 ◽  
Author(s):  
Andre Ricardo Carvalho
Keyword(s):  
Gas Phase ◽  
Relative Stability ◽  
Density Functional ◽  
Software Tool ◽  
Tautomeric Equilibrium ◽  
Consistent Estimate ◽  
Methods Development ◽  
Functional Methods ◽  
Molecular Stability ◽  
Molecular Orbital Analysis

Understanding the molecular stability is important for predicting the relative reactivity of chemical agents and the relative yields of desirable products. However, over decades, a consistent estimate of a particular chemical equilibrium (proton-tautomerism) has proven challenging. We revisit the molecular orbital analysis in the classic tautomeric oxo-hydroxy case, i.e., 2-pyridone/2-hydroxypyridine in gas-phase and solution, (Wong et al. 1992). Our results indicate the possibility of tuning the tautomeric equilibrium through directing groups. Our findings also reveal the lack of <a></a>reproducibility of orbital energies as responsible for the remarkable contrast between the results of the wavefunction and density functional methods. Our proposal leads the correction in the estimation of relative stability in excellent agreement with experiments in gas-phase and solution. The analogous approach for different compounds corroborates the reliability of our description on the molecular stability and its potential application, e.g., a guide to estimate the relative stability of molecules, to measure the confidence of the proposed reaction mechanisms by different theoretical methods, development of the molecular switches and computer-aided drug design. A software tool for Gaussian 09 package, in the support information, is available on the author's ORCiD page.<br>

scholarly journals Potential Energy Surface (PES) Scan of Gas-Phase L-Proline

2014 ◽  
Vol 38 ◽  
pp. 26-34
Author(s):  
Anouar el Guerdaoui ◽  
Yassine el Kahoui ◽  
Malika Bourjila ◽  
Rachida Tijar ◽  
Abderrahman el Gridani
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Gas Phase ◽  
Density Functional ◽  
Energy Surface ◽  
Conformational Stability ◽  
Geometry Optimization ◽  
Basis Set ◽  
Absolute Minimum ◽  
Pes Scan

We performed here a systematic ab initio calculations on neutral gas-phase L-proline. A total of 8 local minima were located by geometry optimization of the trial structures using density functional theory (DFT) with B3LYP three parameter hybrid potential coupled with the 6-31G)d( basis set. The absolute minimum obtained will be subject to a rigid potential energy surface (PES) scan by rotating its carboxylic group using the same method with more accurate basis set B3LYP/6-311++G(d,p), to get a deeper idea about its conformational stability. The main aim of the present work was the study of the rigidity of the L-proline structure and the puckering of its pyrrolidine ring.

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