Addition of benzyne to carbon nanostructures can proceed via (4 + 2) (1,4-addition) or (2 + 2) (1,2-addition) cycloadditions depending on the species under consideration. In this work, we analyze by means of density functional theory (DFT) calculations the reaction mechanisms for the (4 + 2) and (2 + 2) cycloadditions of benzyne to nanostructures of different curvature, namely, C60 and a series of zigzag single-walled carbon nanotubes. Our DFT calculations reveal that, except for the concerted (4 + 2) cycloaddition of benzyne to zigzag single-walled carbon nanotubes, all cycloadditions studied are stepwise processes with the initial formation of a biradical singly bonded intermediate. From this intermediate, the rotation of the benzyne moiety determines the course of the reaction. The Gibbs energy profiles lead to the following conclusions: (i) except for the 1,4-addition of benzyne to a six-membered ring of C60, all 1,2- and 1,4-additions studied are exothermic processes; (ii) for C60 the (2 + 2) benzyne cycloaddition is the most favored reaction pathway; (iii) for zigzag single-walled carbon nanotubes, the (4 + 2) benzyne cycloaddition is preferred over the (2 + 2) reaction pathway; and (iv) there is a gradual decrease in the exothermicity of the reaction and an increase of energy barriers as the diameter of the nanostructure of carbon is increased. By making use of the activation strain model, it is found that the deformation of the initial reactants in the rate-determining transition state is the key factor determining the chemoselectivity of the cycloadditions with benzyne.

The amino imidazolin-2-imine ligand [HAmIm, 1,2-(DippNH)–C6H4–NC(NiPrCMe)2] is employed in the synthesis of the paramagnetic cobalt(I) arene complex Co(AmIm)(η 6 -C6H6). The latter was found to be a highly efficient (pre)catalyst in H/D exchange reactions with deuterium (D2) in hydrosilanes. The scope comprises primary to tertiary silanes at a low catalyst loading of 1 mol %. Additionally, the same cobalt(I) arene complex was able to catalyze hydrosilylation reactions of terminal olefins with primary to tertiary silanes at low catalyst loadings of 0.5 mol %. The scope of hydrosilylation includes intramolecular hydrosilylation to produce silacarbocycles and multiple hydrosilylation with primary silanes. The mechanistic investigation includes numerous control experiments for both H/D exchange and hydrosilylation. Isolated (trapped) cobalt(III) hydride silyl complexes (including X-ray crystallographic authentication) are presented for primary to tertiary Si–H entities, which demonstrates a wide scope of Si–H bond activation by the low-valent Co(AmIm) core. The experimental results are strongly corroborated by density functional theory calculations, which explore the possible reaction mechanisms of studied reactions.

A low proportion of mildly hypertensive patients attended in a primary care setting are microalbuminuric. In this population, UAE is an expression of BP values over 24 h and correlates with several risk factors.

Fullerene based molecular heterojunctions such as the [6,6]-pyrrolidine-C60 donor-acceptor conjugate containing triphenylamine (TPA) are potential materials for high-efficient dye-sensitized solar cells. In this work, we estimate the rate constants for the photoinduced charge separation and charge recombination processes in TPA-C60 using the unrestricted and time-dependent DFT methods. Different schemes are applied to evaluate excited state properties and electron transfer parameters (reorganization energies, electronic couplings, and Gibbs energies). The use of open-shell singlet or triplet states, several density functionals and continuum solvation models is discussed. Strengths and limitations of the computational approaches are highlighted. The present benchmark study provides an overview of the expected performance of DFT-based methodologies in the description of photoinduced charge transfer reactions in fullerene heterojunctions.2

Density functional theory calculations have been used to explore the potential of Ru-based complexes with 1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene (SIMes) ligand backbone (A) being modified in silico by the insertion of a C60 molecule (B and C), as olefin metathesis catalysts. To this end, we investigated the olefin metathesis reaction catalyzed by complexes A, B, and C using ethylene as the substrate, focusing mainly on the thermodynamic stability of all possible reaction intermediates. Our results suggest that complex B bearing an electron-withdrawing N-heterocyclic carbene improves the performance of unannulated complex A. The efficiency of complex B is only surpassed by complex A when the backbone of the N-heterocyclic carbene of complex A is substituted by two amino groups. The particular performance of complexes B and C has to be attributed to electronic factors, that is, the electronic-donating capacity of modified SIMes ligand rather than steric effects, because the latter are predicted to be almost identical for complexes B and C when compared to those of A. Overall, this study indicates that such Ru-based complexes B and C might have the potential to be effective olefin metathesis catalysts.

We present a theoretical study on the role of van der Waals (vdW) interactions on the structure and, as a consequence, the photoinduced charge separation (CS) of a series of dimer complexes formed by the polymer P3HT and the fullerene derivative PCBM. CS rate constants for P3HT/PCBM dimer structures in which vdW interactions are taken into account agree well with experimental data. Without proper treatment of vdW interactions during geometry optimizations, the predicted CS rates can be too low by up to 3 orders of magnitude. These variations in computed CS rates are not due to changes in the Gibbs energy for CS. Instead, the electronic coupling increases by up to 2 orders of magnitude for structures obtained with dispersion-corrected density functionals that lead to deformations in the P3HT oligomer with pronounced π–π stacking interactions with PCBM.

We quantum chemically explore the thermodynamics and kinetics of all 65 possible mechanistic pathways of the Bingel-Hirsch addition of dimethyl bromomalonate to the endohedral metallofullerene La@C2v -C82 that result from the combination of 24 nonequivalent carbon atoms and 35 different bonds present in La@C2v -C82 by using dispersion-corrected DFT calculations. Experimentally, this reaction leads to four singly bonded derivatives and one fulleroid adduct. Of these five products, only the singly bonded derivative on C23 could be experimentally identified unambiguously. Our calculations show that La@C2v -C82 is not particularly regioselective under Bingel-Hirsch conditions. From the obtained results, however, it is possible to make a tentative assignment of the products observed experimentally. We propose that the observed fulleroid adduct results from the attack at bond 19 and that the singly bonded derivatives correspond to the C2, C19, C21, and C23 initial attacks. However, other possibilities cannot be ruled out completely.

This study is a cytogenetic characterization by karyotyping and a determination of the DNA content by flow cytometry of wild populations of Agave cupreata from the Guerrero State, Mexico. Three of the studied populations were diploids (2n = 2x =60) and one population had tetraploid (2n = 4x = 120), pentaploid (2n = 5x = 150) and hexaploid (2n = 6x = 180) plants. Diploid populations had three different structural cytotypes. One population showed polyploid cytotypes. A. cupreata showed a bimodal karyotype of 10 large + 50 small chromosomes in diploids; 20 large + 100 small chromosomes in tetraploids and 25 large + 125 small chromosomes in pentaploids. In diploids, they had secondary constriction in one pair of the large chromosomes and, in the fourth or fifth large homologous chromosome groups, in polyploid plants. The arm ratio, the proportion of different types of large and small chromosomes, the mean of genome length and the asymmetry index of karyotypes clearly varied among diploid and polyploid cytotypes. The pattern of variation among Agave cupreata populations is probably due to rearrangements in the large and small chromosomes of the complement. The diploid populations displayed a 0.63% variation in 2C DNA content. The mean 2C DNA content was 7.88 pg; 1Cx value = 3.94 pg in diploids of Agave cupreata. Tetraploids had 2C = 16.54 pg DNA, i.e. approximately four times the 1Cx value; 2C DNA amounts of pentaploid and hexaploid were equal to 20.42 and 23.92 pg DNA, respectively. These values are also multiples of 1Cx value, indicating a relationship between the ploidy level and the 2C DNA content. The results shown are basic and useful information to develop biotechnology and breeding approaches for Agave cupreata.