Solvent influence on intramolecular interactions and aromaticity in meta and para nitroanilines

Pyrrole and Pyridine in the Water Environment-Effect of Discrete and Continuum Solvation Models

Properties of pyrrole and pyridine molecules upon different hydrations were investigated through density functional theory. Complexes of studied molecules with a cluster of 50 water molecules were considered, and the polarizable continuum model of solvation (PCM) was also taken into account. For comparative purposes, all mentioned calculations were repeated for single pyrrole and pyridine molecules and their complexes with one water molecule. Aromaticities of solvated pyrrole and pyridine rings were studied using several geometric- and electronic-based aromaticity criteria. Special attention was paid to studying the properties of formed hydrogen bonds between pyrrole or pyridine and either a single water molecule or several water molecules of the cluster. Overall, a comprehensive description of two very important heterocyclic compounds, that is, pyrrole and pyridine, in both discrete and continuum water solutions, is extensively presented.

Aromaticity in catalysis: metal ligand cooperation via ligand dearomatization and rearomatization

Unlike the conventional model of transition metal catalysis, ligands in metal-ligand cooperative (or bifunctional) catalysis are involved in the substrate activations. Such processes have offered unique mechanistic understandings and led to new concepts for the catalyst design. In particular, unprecedented activities were discovered when the ligand could undergo dearomatization-rearomatization reactions during the catalytic cycle. Aromatization can provide an extra driving force to thermodynamics; consequently, it brings a new perspective to ligand platform design for catalysis. While numerous applications were demonstrated, the influences of changing ligand aromatic properties were often overlooked. In this article, representative ligand systems will be highlighted and a comparison between the Milstein and the Huang pincer systems will be discussed to provide theoretical and conceptual insights.