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The first experimental examples of Diels-Alder (DA) reactions of diazo compounds as heterodienophiles with dienes have been studied with density functional theory (DFT) using the M06-2X functional. For comparison, the reactivities of diazo esters as dienophiles or 1,3-dipoles with 1,3-dienes in intermolecular model systems have been analyzed by the distortion/interaction model. The 1,3-dipolar cycloaddition is strongly favored for the intermolecular system. The intramolecular example is unique because the tether strongly favors the (4 + 2) cycloaddition. [ABSTRACT FROM AUTHOR]

Se--N dynamic covalent bond is a new dynamic covalent bond which has applications in the fabrication of stimuli responsive and self-healing functional materials. Although recent advances have been achieved in the experimental aspect, little is known about the formation mechanism of Se--N dynamic covalent bond. Here the structures and nature of Se--N dynamic covalent bond between three kinds of pyridine derivatives R-C5H4N, [pyridine (R = H), 4-methylpyridine (R = CH3), 4-dimethylamino-pyridine (R = N(CH3)2)] and phenylselenyl bromine (PhSeBr) have been analyzed using density functional theory. The interactions between Se atom in PhSeBr and N atom in pyridine or pyridine derivatives can be divided into three models: dissociation, nonbonding interaction and covalent bond interaction. Quantum chemical calculations on three series compounds show that these three models can convert mutually, which results in the generation of Se--N dynamic covalent bond. Solvent effects produced in polar solvents such as CH2Cl2 can make the conversion between Se--N covalent bond and Se...N nonbonding interactions easier. The kind of the substituents in pyridine ring can affect the conversion process: the stronger the electron-donating ability of the substituent, the easier the structure transformation. [ABSTRACT FROM AUTHOR]

Redox-active organic molecules have attracted much attention as alternatives to transition-metal-based electrodes for lithium-ion batteries due to their low cost and large abundance. However, the relatively low cycling stability still prevents some of the most promising molecules to be used as lithium-ion electrodes. Herein, we used 1,4,5,8-naphthalene diimide (NDI) as a model molecule to systematically investigate its intrinsic electrochemical property, including its electrolyte compatibility, maximum capacity, cycling stability, and rate capability in different organic electrolytes. Extensive physicochemical characterization, electrochemical measurement, and density function theory (DFT) calculation together show that the electrode-electrolyte interaction is the key factor determining its specific capacity and cycling stability. With a proper selection of electrolytes, NDI molecule, which was considered to be not stable for lithium storage, can achieve near theoretical capacity (based on two-electron reaction), very high rate capability, and high cycling stability. This study suggests the importance of understanding the fundamental electrode-electrolyte interactions in designing high-performance organic electrodes. [ABSTRACT FROM AUTHOR]