8 results
Search Results
Now showing 1 - 8 of 8
Article A computational study on 4,7-di(furan-2-yl)benzo[c][1,2,5] thiadiazole monomer and its oligomers(Journal of Molecular Modeling, 2014) Kayı, HakanThe energy gap, Eg, between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molec ular orbital (LUMO) energy levels that determines the elec tronic and optical properties of 4,7-di(furan-2- yl)benzo[c][1,2,5]thiadiazole (FSF) polymer is calculated by performing quantum chemical calculations. First, we theoret ically investigated the most stable conformers of FSF mono mer and its corresponding oligomers at the B3LYP/6-31G(d) and B3LYP/LANL2DZ levels of theory. We reveal the theoret ical molecular structure of this very recently synthesized novel monomer and its oligomers for the first time in the literature. Our results from the B3LYP/6-31G(d) calculations indicated that FSF polymer has a low HOMO-LUMO gap of 1.55 eV to be in good agreement with the experiments. Experimental design and synthesis of novel conjugated polymers require time-consuming and expensive procedures. The findings from this study are promising for the use of computational methods in the design of the novel conjugated polymers, and help to narrow the materials to be used in design and synthesis of conjugated polymers with desired properties.Article Conformational Behaviors of Trans-2,3 and Trans-2,5 1,4-Diselenanes. a Complete Basis Set, Hybrid-Density Functional Theory Study and Natural Bond Orbital Interpretations(Journal of Molecular Modeling, 2014) Nori-shargh, Davood; Mousavı, Seiedeh Negar; Kayı, HakanComplete basis set CBS-4, hybrid-density func tional theory (hybrid-DFT: B3LYP/6-311+G**) based methods and natural bond orbital (NBO) interpretations have been used to examine the contributions of the hyperconjugative, electrostatic, and steric effects on the con formational behaviors of trans-2,3-dihalo-1,4-diselenane [halo=F (1), Cl (2), Br (3)] and trans-2,5-dihalo-1,4- diselenane [halo = F (4), Cl (5), Br (6)]. Both levels of theory showed that the axial conformation stability, compared to its corresponding equatorial conformation, decreases from com pounds 1→3 and 4→6. Based on the results obtained from the NBO analysis, there are significant anomeric effects for compounds 1-6. The anomeric effect associated with the electron delocalization is in favor of the axial conformation and increases from compounds 1→3 and 4→6. On the other hand, dipole moment differences between the axial and equa torial conformations [Δ(μeq - μax)] decrease from compounds 1→3. Although Δ(μeq-μax) parameter decreases from com pound 1 to compound 3, the dipole moment values of the axial conformations are smaller than those of their corresponding equatorial conformations. Therefore, the anomeric effect as sociated with the electron delocalizations (for halogen-C-Se segments) and the electrostatic model associated with the dipole-dipole interactions fail to account for the increase of the equatorial conformations stability on going from com pound 1 to compound 3. Since there is no dipole moment for the axial and equatorial conformations of compounds 4-6, consequently, the conformational preferences in compounds 1-6 is in general dictated by the steric hindrance factor asso ciated with the 1,3-syn-axial repulsions. Importantly, the CBS-4 results show that the entropy difference (ΔS) between the equatorial axial conformations increases from compounds 1→3 and 4→6. This fact can be explained by the anomeric effect associated with the electron delocalization which affects the C2-Se bond orders and increase the rigidity of the corre sponding rings. The Gibbs free energy difference values be tween the axial and equatorial conformations (i.e. ΔGax-ax and ΔGeq-eq) of compounds 1 and 4, 2 and 5 and also 3 and 6 have been calculated. The correlations between the anomeric effect, electrostatic model, ΔGeq-ax, ΔGax-ax, ΔGeq-eq, bond orders, dipole-dipole interactions, structural parameters and confor mational behaviors of compounds 1-6 have been investigated.Article Citation - WoS: 8Citation - Scopus: 9Conformational Behaviors of Trans-2,3 Trans-2,5 a Complete Basis Set, Hybrid-Density Functional Theory Study and Natural Bond Orbital Interpretations(Springer, 2014) Nori-Shargh, Davood; Kayı, Hakan; Mousavi, Seiedeh Negar; Kayi, Hakan; Kayı, Hakan; Chemical Engineering; Chemical EngineeringComplete basis set CBS-4, hybrid-density functional theory (hybrid-DFT: B3LYP/6-311+G**) based methods and natural bond orbital (NBO) interpretations have been used to examine the contributions of the hyperconjugative, electrostatic, and steric effects on the conformational behaviors of trans-2,3-dihalo-1,4-diselenane [halo = F (1), Cl (2), Br (3)] and trans-2,5-dihalo-1,4-diselenane [halo = F (4), Cl (5), Br (6)]. Both levels of theory showed that the axial conformation stability, compared to its corresponding equatorial conformation, decreases from compounds 1 -> 3 and 4 -> 6. Based on the results obtained from the NBO analysis, there are significant anomeric effects for compounds 1-6. The anomeric effect associated with the electron delocalization is in favor of the axial conformation and increases from compounds 1 -> 3 and 4 -> 6. On the other hand, dipole moment differences between the axial and equatorial conformations [Delta(mu(eq) - mu(ax))] decrease from compounds 1 -> 3. Although Delta(mu(eq)-mu(ax)) parameter decreases from compound 1 to compound 3, the dipole moment values of the axial conformations are smaller than those of their corresponding equatorial conformations. Therefore, the anomeric effect associated with the electron delocalizations (for halogen-C-Se segments) and the electrostatic model associated with the dipole-dipole interactions fail to account for the increase of the equatorial conformations stability on going from compound 1 to compound 3. Since there is no dipole moment for the axial and equatorial conformations of compounds 4-6, consequently, the conformational preferences in compounds 1-6 is in general dictated by the steric hindrance factor associated with the 1,3-syn-axial repulsions. Importantly, the CBS-4 results show that the entropy difference (Delta S) between the equatorial axial conformations increases from compounds 1 -> 3 and 4 -> 6. This fact can be explained by the anomeric effect associated with the electron delocalization which affects the C-2-Se bond orders and increase the rigidity of the corresponding rings. The Gibbs free energy difference values between the axial and equatorial conformations (i.e. Delta G(ax-ax) and Delta G(eq-eq)) of compounds 1 and 4, 2 and 5 and also 3 and 6 have been calculated. The correlations between the anomeric effect, electrostatic model, Delta G(eq-ax), Delta G(ax-ax), Delta G(eq-eq), bond orders, dipole-dipole interactions, structural parameters and conformational behaviors of compounds 1-6 have been investigated.Article Citation - WoS: 10Citation - Scopus: 9A Computational Study on 4,7-Di(furan Monomer and Its Oligomers(Springer, 2014) Kayi, Hakan; Kayı, Hakan; Kayı, Hakan; Chemical Engineering; Chemical EngineeringThe energy gap, Eg, between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels that determines the electronic and optical properties of 4,7-di(furan-2yl)benzo[c][1,2,5]thiadiazole (FSF) polymer is calculated by performing quantum chemical calculations. First, we theoretically investigated the most stable conformers of FSF monomer and its corresponding oligomers at the B3LYP/6-31G(d) and B3LYP/LANL2DZ levels of theory. We reveal the theoretical molecular structure of this very recently synthesized novel monomer and its oligomers for the first time in the literature. Our results from the B3LYP/6-31G(d) calculations indicated that FSF polymer has a low HOMO-LUMO gap of 1.55 eV to be in good agreement with the experiments. Experimental design and synthesis of novel conjugated polymers require time-consuming and expensive procedures. The findings from this study are promising for the use of computational methods in the design of the novel conjugated polymers, and help to narrow the materials to be used in design and synthesis of conjugated polymers with desired properties.Article Theoretical Investigation of Carbon Dioxide Capture by Aqueous Boric Acid Solution: a Termolecular Reaction Mechanism(2018) Kayı, HakanHitherto, boric is suggested and used as a promoter or catalyst for carbondioxide capture in various chemical absorption reactions, such as, absorptionby aqueous potassium carbonate solution to increase mass transfer rate. Butin this study, a single step termolecular reaction mechanism is suggested forthe chemical absorption of carbon dioxide directly by boric acid and water. Thereaction thermochemistry and reaction kinetics for termolecular mechanism areinvestigated by using density functional theory calculations at the B3LYP/6-31G(d)level of theory by taking into account of the implicit solvent effects of water throughthe polarizable continuum model and dispersion corrections. The findings obtainedfrom theoretical calculations indicate that it is possible to capture carbon dioxidewith boric acid in the form of B(OH)2OCOOH.Article Citation - WoS: 6Citation - Scopus: 7Natural Bond Orbital, Nuclear Magnetic Resonance Analysis and Hybrid-Density Functional Theory Study of Σ-Aromaticity in Al2f6< Al2cl6< Al2br6< and Al2i6<(Springer, 2013) Nori-Shargh, Davood; Kayı, Hakan; Yahyaei, Hooriye; Mousavi, Seiedeh Negar; Maasoomi, Akram; Kayi, Hakan; Kayı, Hakan; Chemical Engineering; Chemical EngineeringNatural bond orbital (NBO), nuclear magnetic resonance (NMR) analysis and hybrid-density functional theory based method (B3LYP/Def2-TZVPP) were used to investigate the correlation between the nucleus-independent chemical shifts [NICS, as an aromaticity criterion], sigma (Al(1)-X2(b)) -> sigma*(Al(3)-X4(b)) electron delocalizations and the dissociation energies of Al2F6, Al2Cl6, Al2Br6 and Al2I6 to 2AlX(3) (X = F, Cl, Br, I). The results obtained showed that the dissociation energies of Al2F6, Al2Cl6, Al2Br6 and Al2I6 decrease from Al2F6 to Al2I6. Like aromatic molecules, these compounds have relatively significant negative NICSiso(0) values. Clearly, based on magnetic criteria, they exhibit aromatic character and make it possible to consider them as sigma-delocalized aromatic species, such as Mobius sigma-aromatic species. The sigma-aromatic character which is demonstrated by their NICSiso(0) values decreases from Al2F6 to Al2I6. The NICSiso values are dominated by the in-plane sigma(22) (i.e., sigma(yy,) the plane containing halogen atoms bridged) chemical shift components. The increase of the NICSiso values explains significantly the decrease of the corresponding dissociation energies of Al2F6, Al2Cl6, Al2Br6 and Al2I6. Importantly, the NBO results suggest that in these compounds the dissociation energies are controlled by the stabilization energies associated with sigma (Al(1)-X2(b)) ->sigma*(Al(3)-X4(b)) electron delocalizations. The decrease of the stabilization energies associated with sigma (Al(1)-X2(b)) ->sigma*(Al(3)-X4(b)) electron delocalizations is in accordance with the variation of the calculated NICSiso values. The correlations between the dissociation energies of Al2F6, Al2Cl6, Al2Br6 and Al2I6, sigma (Al(1)-X2(b)) ->sigma*(Al(3)-X4(b)) electron delocalizations, natural atomic orbitals (NAOs) and NICSiso values have been investigated.Article Natural Bond Orbital, Nuclear Magnetic Resonance Analysis and Hybrid-Density Functional Theory Study of Σ-Aromaticity in Al2f6, Al2cl6, Al2br6 and Al2i6(Journal of Molecular Modeling, 2013) Norı-shargh, Davood; Yahyaeı, Hooriye; Mousevı, Seiedeh Negar; Maasoomı, Akram; Kayı, HakanNatural bond orbital (NBO), nuclear magnetic res onance (NMR) analysis and hybrid-density functional theory based method (B3LYP/Def2-TZVPP) were used to investigate the correlation between the nucleus-independent chemical shifts [NICS, as an aromaticity criterion], σAl(1)-X2(b) → σ*Al(3)-X4(b) electron delocalizations and the dissociation ener gies of Al2F6, Al2Cl6, Al2Br6 and Al2I6 to 2AlX3 (X=F, Cl, Br, I). The results obtained showed that the dissociation energies of Al2F6, Al2Cl6, Al2Br6 and Al2I6 decrease from Al2F6 to Al2I6. Like aromatic molecules, these compounds have relatively significant negative NICSiso(0) values. Clearly, based on mag netic criteria, they exhibit aromatic character and make it possible to consider them as σ-delocalized aromatic species, such as Möbius σ-aromatic species. The σ-aromatic character which is demonstrated by their NICSiso(0) values decreases from Al2F6 to Al2I6. The NICSiso values are dominated by the in-plane σ22 (i.e., σyy, the plane containing halogen atoms bridged) chemical shift components. The increase of the NICSiso values explains significantly the decrease of the corre sponding dissociation energies of Al2F6, Al2Cl6, Al2Br6 and Al2I6. Importantly, the NBO results suggest that in these compounds the dissociation energies are controlled by the stabilization energies associated with σAl(1)-X2(b) →σ*Al(3)- X4(b) electron delocalizations. The decrease of the stabilization energies associated with σAl(1)-X2(b) →σ*Al(3)-X4(b) electron delocalizations is in accordance with the variation of the calculated NICSiso values. The correlations between the dis sociation energies of Al2F6, Al2Cl6, Al2Br6 and Al2I6, σAl(1)- X2(b) →σ*Al(3)-X4(b) electron delocalizations, natural atomic orbitals (NAOs) and NICSiso values have been investigated.Article Experimental and Theoretical Investigation of the Reaction Between Co2andcarbon Dioxide Binding Organic Liquids(2016) Tankal, Hilal; Orhan, Özge Yüksel; Alper, Erdoğan; Özdoğan, Telhat; Kayı, HakanThe reaction kinetics of CO2absorption into new carbon dioxide binding organic liquids (CO2BOLs) was com-prehensively studied to evaluate their potential for CO2removal. A stopped- ow apparatus with conductivity detectionwas used to determine the CO2absorption kinetics of novel CO2BOLs composed of DBN (1,5-diazabicyclo[4.3.0]non-5-ene)/1-propanol and TBD (1,5,7-triazabicyclo[4.4.0]dec-5-ene)/1-butanol. A modi ed termolecular reaction mechanismfor the reaction of CO2with CO2BOLs was used to calculate the observed pseudo- rst{order rate constant k0(s1)and second-order reaction rate constant k2(m3/kmol.s). Experiments were performed by varying organic base (DBN orTBD) weight percentage in alcohol medium for a temperature range of 288{308 K. It was found that k0increased withincreasing amine concentration and temperature. By comparing using two different CO2BOL systems, it was observedthat the TBD/1-butanol system has faster reaction kinetics than the DBN/1-propanol system. Finally, experimentaland theoretical activation energies of these CO2BOL systems were obtained and compared. Quantum chemical calcula-tions using spin restricted B3LYP and MP2 methods were utilized to reveal the structural and energetic details of thesingle-step termolecular reaction mechanism.
