Exploring Organic Chemistry with DFT: Radical, Organo‐metallic, and Bio‐organic Applications

In this review we report the results of DFT investigations which have been carried out in different fields of organic and organometallic chemistry, including radical reactivity, structure and reactivity of organometallic compounds, and biochemical/biophysical properties of long chain unsaturated systems. Many of the most popular non-local corrected functionals (e.g. B3LYP, BHLYP, BLYP, BP86) have been benchmarked both versus experimental and high level ab initio (e.g. MP2, MP4, CAS-SCF/CAS-PT2) data, resulting in an impressive agreement. The DFT approach appears to be a powerful tool, which can be used as a valid alternative to more traditional correlated methods, to achieve mechanistic information of chemical/ physical interest in the modelling of organic and biochemical systems. In particular, in the examples selected in this review, we discuss the results obtained for the addition reaction of alkyl radicals to double bonds and for the hydrogen/ chlorine abstraction reaction by alkyl and silyl radicals from various organic substrates. Moreover, binding interactions (i.e. geometries and energies) in organometallic compounds are shown to be satisfactorily reproduced via DFT and examples of nickel-catalyzed [2 + 2] cycloaddition reaction and homogeneous Ziegler-Natta catalysis are investigated. Finally, a DFT modelling for the singlet-oxygen quenching ability and radical trapping activity of carotenes is presented. The simulated data provide a rationale for the protective action of carotenes observed in biological tissues and elucidates the physical and chemical mechanisms involved in the reactivity of carotenes versus oxygen and radicals.