A New Approach to Design High Spin Organic Systems: Aromatic Stabilization with Exo‐cyclic π Electrons Plays Crucial Role

Abstract

Radicals are important because of their diverse applications. Here we have modelled three systems, BC6F2H5, B2C6F4H4 and B2C5F4NH4. Each of them contain −CF2 unit (s) with one pz electron on carbon atom exo‐cyclic to the six membered ring. First two systems have 6π electrons and the last one contains 7π electrons in total. Stability of these systems are computationally investigated through Energy Decomposition Analysis (EDA), Molecular Dynamics Simulation, HOMO‐LUMO energy gap and minimum frequency analysis. Aromaticity is quantified through Nucleus Independent Chemical Shift (NICS), Aromatic Stabilization Energy (ASE), Adaptive Natural Density Partitioning (AdNDP) and Multi‐Centre Bond Order (MCBO). Isolated −CF2 unit can be considered as monoradical entity. From this computational study we observe that the pz electron on exo‐cyclic carbon atom participates in aromatic conjugation which in turn imparts stability to the designed systems. We found that exo‐cyclic conjugation is strong enough to force BC6F2H5 and B2C6F4H4 to be closed shell singlet. On the other hand, B2C5F4NH4 is in doublet state where formation of aromatic sextet of electrons stabilizes the system, and the extra spin is delocalized over the whole ring and thus forming a stable radical.