报告题目：“化学成键理论及其应用”系列三：Short Course on “Chemical Bonding Theories and Applications”
报告人： 莫亦荣 教授
Chemical bonding theory has been playing the central role in chemistry ever since the proposal of the electron-pair bond by Lewis in 1916. While it is important to develop high-level quantum methods with as much as possible electron correlations recovered and extend these methods to larger molecular systems by employing more efficient scaling algorithms, it is equally valuable and important to develop reliable and quantitative approaches which can assist the understanding and interpretation of accurate numerical data in chemical senses and concepts. There is no science without concepts. To better understand the physical forces governing molecular bonding and reactivity, we often resort to various bonding analysis schemes. For instances, a variety of energy decomposition approaches (EDAs) have been developed to decompose the intermolecular energy into several physically meaningful components based on electronic and steric effects. The importance of intermolecular EDAs can be highlighted with the example of electrophilic aromatic nitrosation and nitration. Both electrophiles (NO+ and NO2+) have similar inherent physical properties, but their chemical reactivities toward various aromatic donors are dramatically different. EDA studies showed that NO2+ has seemingly lower binding energy than NO+ to benzene, but it has much higher charge transfer stabilization energy thus much higher chemical reactivity than NO+.
In this short course, I will review the major approaches used in current computational chemistry and introduce our block-localized wavefunction (BLW) method which is the simplest variant of ab initio VB theory with the MO or DFT computational efficiency. Focuses will be on the applications of the BLW method to the adsorption and activation of small molecules like CO and N2 by earth-abound main group compounds, and the interpretation of non-covalent interactions. For instance, Braunschweig et al. not only showed that diboryne (B≡B) stabilized by N-heterocyclic carbenes (B2(NHCR)2) can bind and activate CO molecules to forge C-C bonds, but also found that borylene (CAAC)DurB, where CAAC is a cyclic alkyl(amino) carbene and Dur refers to 2,3,5,6-tetramethylphenyl, can bind and activate N2. I will show how we can use the BLW method to derive novel insights into the chemical reactions.