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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 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 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: 3Citation - Scopus: 2Antiproliferative Activity of Platinum(ii) and Copper(ii) Complexes Containing Novel Biquinoxaline Ligands(Oxford Univ Press, 2024) El-Beshti, Hager Sadek; Gercek, Zuhal; Kayi, Hakan; Yildizhan, Yasemin; Cetin, Yuksel; Adiguzel, Zelal; Ozalp-Yaman, SenizNowadays, cancer represents one of the major causes of death in humans worldwide, which renders the quest for new and improved antineoplastic agents to become an urgent issue in the field of biomedicine and human health. The present research focuses on the synthesis of 2,3,2MODIFIER LETTER PRIME,3MODIFIER LETTER PRIME-tetra(pyridin-2-yl)-6,6MODIFIER LETTER PRIME-biquinoxaline) and (2,3,2MODIFIER LETTER PRIME,3MODIFIER LETTER PRIME-tetra(thiophen-2-yl)-6,6MODIFIER LETTER PRIME-biquinoxaline) containing copper(II) and platinum(II) compounds as prodrug candidates. The binding interaction of these compounds with calf thymus DNA (CT-DNA) and human serum albumin were assessed with UV titration, thermal decomposition, viscometric, and fluorometric methods. The thermodynamical parameters and the temperature-dependent binding constant (KMODIFIER LETTER PRIMEb) values point out to spontaneous interactions between the complexes and CT-DNA via the van der Waals interactions and/or hydrogen bonding, except Cu(ttbq)Cl2 for which electrostatic interaction was proposed. The antitumor activity of the complexes against several human glioblastomata, lung, breast, cervix, and prostate cell lines were investigated by examining cell viability, oxidative stress, apoptosis-terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling, in vitro migration and invasion, in vitro-comet DNA damage, and plasmid DNA interaction assays. The U87 and HeLa cells were investigated as the cancer cells most sensitive to our complexes. The exerted cytotoxic effect of complexes was attributed to the formation of the reactive oxygen species in vitro. It is clearly demonstrated that Cu(ttbq)Cl2, Pt(ttbq)Cl2, and Pt(tpbq)Cl2 have the highest DNA degradation potential and anticancer effect among the tested complexes by leading apoptosis. The wound healing and invasion analysis results also supported the higher anticancer activity of these two compounds. Graphical Abstract Antitumor activity of biqunoxaline complexes.
