Chapter 5 - Conceptual density functional theory and all metal aromaticity

Abstract

Aromaticity of various systems consisting of metals has been reviewed here briefly. Here, we have discussed about different approaches of aromaticity which through light on the aromatic characteristics of a system. This work begins with a short presentation on density functional theory and conceptual density functional theory followed by chemical reactivity parameters. In addition, history as well as origin of aromaticity along with the criteria to describe the system’s aromaticity have been analyzed. Aromaticity of alkali metals, alkaline earth metals, and transition metal complexes has been reviewed. Concept of aromaticity on all-metal aromatic systems was first shown on the prototypical cluster Al42−, which is doubly aromatic in nature. Furthermore, aluminum clusters in different isomeric forms are also studied. Aromaticity of sodium, potassium, beryllium, and magnesium clusters is also discussed here. Aromaticity of mixed metal clusters as done in earlier works has been presented. Transition metals clusters’ participation in aromaticity is first reported for Hg46−. Thereafter, other works on the aromaticity or antiaromaticity of the transition metal complexes have grown significantly. By adopting various methods of calculation like nucleus-independent chemical shift, gauge-including magnetically induced current, etc., the aromaticity (σ or ᴨ) determined in different works has been presented in this study.