Adjacent Lone Pair (ALP) Effect: A Computational Approach for Its Origin

作者：Zhang, Huaiyu; Wu, Wei^*; Ahmed, Basil M.; Mezei, Gellert; Mo, Yirong^*

来源：Chemistry - A European Journal, 2016, 22(22): 7415-7421.

DOI：10.1002/chem.201600509

• adjacent lone pair effect
• conjugation
• electrostatic interactions
• energy decomposition
• valence bond theory

The adjacent lone pair (ALP) effect is an experimental phenomenon in certain nitrogenous heterocyclic systems exhibiting the preference of the products with lone pairs separated over other isomers with lone pairs adjacent. A theoretical elucidation of the ALP effect requires the decomposition of intramolecular energy terms and the isolation of lone pair-lone pair interactions. Here we used the block-localized waveBLW) method within the ab initio valence bond (VB) theory to derive the strictly localized orbitals which are used to accommodate one-atom centered lone pairs and two-atom centered sigma or pi bonds. As such, interactions among electron pairs can be directly derived. Two-electron integrals between adjacent lone pairs do not support the view that the lone pair-lone pair repulsion is responsible for the ALP effect. Instead, the disabling of pi conjugation greatly diminishes the ALP effect, indicating that the reduction of pi conjugation in deprotonated forms with two s lone pairs adjacent is one of the major causes for the ALP effect. Further electrostatic potential analysis and intramolecular energy decomposition confirm that the other key factor is the favorable electrostatic attraction within the isomers with lone pairs separated.

• 出版日期2016-5-23
• 单位厦门大学