ALBERT

Description: Diels–Alder (DA) reaction is one of the most commonly tools in functionalizing organic semiconductor crystals. The DA reactions of two organic semiconductors, i.e. tetracene ( ) and rubrene ( ), to several dienophiles ( to ) were performed experimentally recently. But the kinetics and mechanism of stereoselectivity and regioselectivity remain unknown. In the current study, all related 20 DA reactions (totally 32 possible pathways) were investigated by density functional theory. It was found that the reaction of and a–b position of is the most favorable one. The c–d position of is more reactive than its a–b position when combines with , but is less reactive when combines with to . The endo and exo pathways have similar activation barriers in each reaction. The rate coefficients were calculated using the canonical variational transition state theory and their Arrhenius expressions were fitted. The theoretical conclusion agrees with the experimental observations and is of general importance for similar reactions. Solvent has a slight effect on these reactions. Copyright © 2016 John Wiley & Sons, Ltd. The mechanisms of Diels–Alder reactions between two organic semiconductors and five small molecules were investigated by hybrid density functional calculations. All possible pathways of these reactions (32 pathways) were considered. The mechanisms of these reactions were analyzed with distortion/interaction energy model. The temperature-dependent rate coefficients were calculated using canonical variational transition state theory, and the three-parameter Arrhenius expressions were fitted.

Description: All possible types of Diels–Alder cycloadditions of 1,3- cis -butadiene to C 60 (2 in total) and to C 70 (8 in total) were theoretically investigated by the M06-2X density functional method in gas phase and solutions. An intermediate between the reactant and the transition state was located for each reaction. These intermediates except one have not been experimentally or theoretically reported before. The reactivities of the 10 reactions in both the gas phase and solutions were systematically compared based on the calculated results. The present conclusion agrees with the experimental observations and partly disagrees with the previously theoretical conclusion. Copyright © 2012 John Wiley & Sons, Ltd. All possible types of Diels-Alder (DA) cycloadditions of 1,3-cis-butadiene to C60 and C70 were theoretically investigated by the M06-2X density functional method in gas phase and solutions. An intermediate between the reactant and the transition state was located for each reaction. The present conclusion agrees with the experimental observations and partly disagrees with the previously theoretical conclusion.

Description: All possible types of Diels–Alder cycloadditions of 1,3- cis -butadiene to C 60 (2 in total) and to C 70 (8 in total) were theoretically investigated by the M06-2X density functional method in gas phase and solutions. An intermediate between the reactant and the transition state was located for each reaction. These intermediates except one have not been experimentally or theoretically reported before. The reactivities of the 10 reactions in both the gas phase and solutions were systematically compared based on the calculated results. The present conclusion agrees with the experimental observations and partly disagrees with the previously theoretical conclusion. Copyright © 2012 John Wiley & Sons, Ltd. All possible types of Diels-Alder (DA) cycloadditions of 1,3-cis-butadiene to C60 and C70 were theoretically investigated by the M06-2X density functional method in gas phase and solutions. An intermediate between the reactant and the transition state was located for each reaction. The present conclusion agrees with the experimental observations and partly disagrees with the previously theoretical conclusion.

Description: The Diels–Alder (DA) reaction is one of the most important reactions in organic chemistry. The controversy surrounding this reaction as to whether it follows a concerted or stepwise mechanism has existed for a long time. The reaction of 1,3-butadiene and ethylene is the paradigmatic example of the DA reaction. We have reinvestigated the mechanism of this reaction using density functional theory. The theoretical study considered all types of possible pathways for the reaction of 1,3-butadiene and ethylene using six functionals at different rungs of Jacob's ladder. Therefore, a complete picture is given for a thorough understanding of the iconic DA reaction, and a new stationary point during the reaction processes has been reported for the first time. The calculated results indicated that three functionals, ωB97X-D, M06-2X, and B2-PLYP, of the fourth and fifth rungs of Jacob's ladder performed well in the investigation of the mechanism of this reaction and that the reliable basis set should be larger than 6-311+G(2d,p). The cis -1,3-butadiene more easily reacted with ethylene compared with 1,3-butadiene in the trans conformation. The concerted mechanism was found to be energetically favorable, whose energy barrier is around 10 kcal/mol lower than that of the stepwise mechanism. Two investigated solvents, toluene and CH 3 CN, had little impact on this simple DA reaction. Copyright © 2014 John Wiley & Sons, Ltd. The reaction of 1,3-butadiene and ethylene is the paradigmatic example of the Diels–Alder reaction. Whether this reaction follows a concerted or stepwise mechanism has existed for a long time. We have reinvestigated all types of possible pathways of this reaction via density functional theory using six functionals at different rungs of Jacob's ladder. A complete picture is given for a thorough understanding of this iconic DA reaction.

Description: Investigation of the relative reactivity of bonds in fullerenes will provide fundamental theory for the design of fullerene-based materials. We have theoretically investigated the reactivity of the Diels–Alder (DA) cycloaddition of cis -1,3-butadiene to all types of bonds in C 60 and C 70 using the M06-2X hybrid density functional theory (DFT) calculations ( J. Phys. Org. Chem . 2012, 25 850–855) and have pointed out that the DA cycloadditions of cis and trans forms of 1,3-butadiene to ethylene have a specially intimate relationship ( J. Phys. Org. Chem . 2014, 27 652–660). For the aim of telling a whole story of the DA cycloaddition concerning C 60 and C 70 , the DA cycloadditions of trans -1,3-butadiene to all types of bonds in C 60 and C 70 were explored at the same theoretical level as those of the cis -1,3-butadiene. The calculated results related with the trans - and cis -1,3-butadienes were compared. The potential energy curves of DA cycloadditions of trans - and cis -1,3-butadiene to C 60 and C 70 were discussed. The distortion–interaction energy model was employed to elucidate the origin of different reactivity of all kinds of C C bonds. The solvent effects were examined using the continuum solvent model. These current results, along with our previous research, will help to obtain an overall view of the DA cycloadditions of 1,3-butadiene to C 60 and C 70 . Copyright © 2014 John Wiley & Sons, Ltd. All possible types of Diels-Alder cycloadditions of trans -1,3-butadiene to C 60 and C 70 were theoretically investigated by the M06-2X density functional method in gas phase and solutions. An intermediate between the reactant and the transition state was located for each reaction. The calculated results related with the trans -1,3-butadiene and cis -1,3-butadiene were compared. The present conclusion will help to obtain an overall view of the Diels-Alder cycloadditions of 1,3-butadiene to C 60 and C 70 .

Description: The 1,3-dipolar cycloaddition (1,3-DPCA) reaction plays a crucial role during the functionalization of fullerenes, which have broad applications in the materials and pharmaceutical fields. In concert with previous experiments, we theoretically investigated the mechanisms of 1,3-DPCA of diphenyldiazomethane (DDMf) to two fullerenes (C 60 and C 70 ) using the M06-2X density functional method under vacuum and in solvents. To understand the influence of the dipolarophile on these reactions, the 1,3-DPCA of DDMf to three common acceptors, specifically tetracyanoethylene (TCNE), 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), and chloranil (CA), was also studied at the same computational level. The substituent effects on the five reactions were investigated by modeling 1,3-DPCA reactions with 12 different substituted DDMf (DDMs) with five dipolarophiles, totaling 60 reactions. Including the five unsubstituted DDMf reactions, 65 1,3-DPCA reactions were studied. The stereoselectivity, relative reactivity, solvent effects, and distortion/interaction energy model were carefully considered and analyzed based on their corresponding electronic structures, electrostatic potential surfaces, interaction models, solvent models, and thermodynamic data. An intermediate was identified for each of the 65 reactions. A possible biradical pathway for the reactions between DDMf and the two fullerenes was also investigated. The calculated results corroborate and enrich the experimental observations. The conclusion and detailed discussion are generally important for understanding the 1,3-DPCA reactions to fullerenes. Copyright © 2014 John Wiley & Sons, Ltd. We located one Int between the reactant and the TS for all 65 of the 1,3-DPCA reactions. We found that the distortion of the reactants toward their structures in the TS is a hindering factor, but the interaction energy promotes the reaction. We concluded that EDGs promote and EWGs hinder the five unsubstituted reactions.

Description: Complete solid solutions between Mg 2 SiO 4 and LiMgPO 4 are confirmed by the XRD results. The phase constitution of 0.5Mg 2 SiO 4 -0.5LiMgPO 4 is found to be dependent on firing temperature. The chemical compatibility between Mg 2 SiO 4 and rutile phase at sintering temperature is modified by incorporating LiMgPO 4 . The microwave dielectric properties of (1− y )(0.5Mg 2 SiO 4 -0.5LiMgPO 4 )- y TiO 2 ( y = 0–0.3) composite ceramics have been investigated. The optimized microwave dielectric properties for 0.35Mg 2 SiO 4 -0.35LiMgPO 4 -0.3TiO 2 ceramics sintered at 1050°C show low dielectric constant (11.4), high-quality factor (31 800 GHz), and low-temperature coefficient of resonant frequency (−4 ppm/°C).

Description: Neonatal mouse hearts have completely regenerative capability after birth, but the ability to regenerate rapidly lost after 7 days, the mechanism has not been clarified. Previous studies have shown that mRNA profile of adult mouse changed greatly compared to neonatal mouse. So far, there is no research of peptidomics related to heart regeneration. In order to explore the changes of proteins, enzymes and peptides related to the transient regeneration, we used comparative petidomics technique to compare the endogenous peptides in the mouse heart of postnatal 1 and 7 days. In final, we identified 236 differentially expressed peptides, 169 of which were up-regulated and 67 were down-regulated in the postnatal 1day heart, and also predicted 36 functional peptides associated with transient regeneration. The predicted 36 candidate peptides are located in the important domains of precursor proteins and / or contain the post-transcriptional modification (PTM) sites, which are involved in the biological processes of cardiac development, cardiac muscle disease, cell proliferation, necrosis and apoptosis. In conclusion, for the first time, we compared the peptidomics profiles of neonatal heart between postnatal one day and postnatal seven day. This study provides a new direction and an important basis for the mechanism research of transient regeneration in neonatal heart. This article is protected by copyright. All rights reserved