In the current study, the interactions of carbon nanotube and sulfur-doped carbon nanotubes (SCNTs) with methanol, methanethiol, water and dihydrogen sulfide at on-body and dead-end positions of nanotubes have been studied. Interaction energies in the gas and solvent (via PCM model) were calculated using density functional theory calculations. Atomic charges, interaction energies, electron densities and their Laplacians at bond critical points have been calculated. Moreover, noncovalent interaction isosurfaces have been visualized using NCI index calculations. Interactions in gaseous phase were more favorable than those in solvent phase, and among considered solvents (benzene, chloroform and cyclohexane), cyclohexane showed the most preferred interactions. In addition, oxygen-bearing molecules (methanol and water) showed more favorable interactions compared with sulfurbearing ones. NBO analyses revealed the stronger donoracceptor interactions with methanol and methanethiol. QTAIM calculation results indicated the reasonable electron densities at BCPs, and the Laplacians of electron densities showed ionic-like (closed shell) interactions. Moreover, isosurfaces of these interactions were also studied to depict the interaction surfaces, and DOS plots for SCNTs were obtained to define their HOMO-LUMO levels and electric conduction properties. The increasing of the global softness and decreasing of total hardness was resulted by sulfur doping of nanotubes, which causes the heterodoped nanotubes to become less electrophilic species.
This work reports study on the interactions of sulfur-doped fullerenes with halogens and halides (except iodine and iodide) to gain an enlightened vision to such interactions for employing them in possible applications such as sensor and surface adsorption. The ωB97XD DFT code has utilized in this study to obtain adsorption energies in the gas phase and solvent. The energy outcomes showed proper results for adsorptions in both gas and solvent (using PCM model). However, the gas phase interactions are more favorable thermodynamically. The formation of halide complexes releases more energy than the formation of halogen complexes and the strongest interaction is belong to the interactions of disulfur-doped fullerenes with halides. Donor-Acceptor transitions mostly affected by sulfur doping, which made C-S bond as auxiliary tool for the absorption process. The density of states (DOS) plots demonstrated better modification of conductivity properties upon sulfur-doping on fullerene structures. Electron densities and their Laplacians at bond critical points (BCPs) of interaction sites, NCI calculations and further visualizations proved the existence of such these interactions, clearly indeed. It's worthy to point that, in some cases, something like partial functionalization of fullerene have seen and these observations were approved via QTAIM, NCI and energy data. In these cases, the stable and thermodynamically favorable cation of halogenated doped fullerene (along with X3ˉ as counter ion) could be produced from the interaction of double-doped fullerene with two molecular halogens.Please do not adjust margins Please do not adjust margins noncovalent interaction isosurface for one halogen atom in S2F1-DP-X 2 (X=F, Cl, Br) which refer to lack of such interaction in this case (and existing covalent bond). Although, there are much more troughs in negative area of electron density for S2F1-DP-X 2 (X=F, Cl, Br) complexes in figure 6 that could assign to more attractive interactions in those models.
In this study, using a computational approach, we are pursuing to find a proper answer about the possible application of fused TIs as superbases through the calculation and discussion of standard thermochemistry parameters, like gas-phase basicity (GB) and proton affinity (PA). In some studied cases, the role of aromaticity/antiaromaticity fluctuations supposed to be more important than mesomeric effects. In this sense, nucleus-independent chemical shift (NICS) and anisotropy of the induced current density (ACID) were utilized in this study to probe into the aromaticity-related parameters of the proposed molecules. Results revealed the highest GB/PA values for the molecules having cyclobutadiene in between two troponimines. Additional investigation was performed into the other candidates of cyclobutadiene-fused troponimines by substituting several electron donors along with the changing position of donors. Some novel superbases offered record-holding GB/PA values so that PA magnitudes higher than 300 kcal mol −1 are now feasible for nonphosphorous neutral organic superbases (NOS).
The reaction of 2,4-dichloro-5-(chloromethyl)-6-methylpyrimidine with 4,5-dihydrothiazol-2-amine in chloroform led to the formation of 2-chloro-4-methyl-7,8-dihydro-5H-pyrimido[4,5-d]thiazolo[3,2-a]pyrimidine (3). The true structure of the target compound was confirmed by density functional theory calculations of condensed Fukui indices. The substitution of the 2-Cl function in compound 3 with different secondary amines yielded 2-substituted-4-methyl-7,8-dihydro-5H-pyrimido[4,5-d]thiazolo[3,2-a]pyrimidines in good yields. The assigned products were tested for their potential antibacterial activity and the results indicated that a few derivatives are valuable compounds with great potential to be used as antibacterial agents.
Several 3H-[1,2,3]triazolo[4,5-d][1,2,4]triazolo[4,3-a]pyrimidine derivatives of a novel ring system have been synthesised. The initial substitution of the 4-Cl function of 2,4-dichloro-6-methylpyrimidin-5-amine with benzylamine followed by treatment with sodium nitrite generated 3-benzyl-5-chloro-7-methyl-3H-[1,2,3]triazolo[4,5-d]pyrimidine. Nucleophilic substitution of the 5-Cl moiety of the latter compound with hydrazine hydrate and subsequent treatment with carbon disulfide in boiling pyridine gave, quantitatively, the corresponding [1,2,3]triazolo[4,5-d][1,2,4]triazolo[4,3-a]pyrimidine derivatives. Density functional theory (DFT) studies were also performed to reveal regioselectivity of the ring closure via Gauge-Independent Atomic Orbital (GIAO) 1H NMR calculations. The WP04 method was used as the DFT code to yield accurate chemical shift values. Theoretical results correlated well with the expected regioisomer and aided assignment of the final structure.
The paradigmatic electrocyclic ring opening of monosubstituted cyclobutenes has been used to diagnose possible solvation effects tuning the torquoselectivity observed in these reactions.
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