Boron-Substituted Coronene: Intriguing Geometric and Electronic Properties, and Large Nonlinear Optical Response.

By substituting boron atoms for selected carbon atoms of a graphene quantum dot (GQD) model, namely a coronene molecule, the substituent effect on its geometric and electronic structure, as well as nonlinear optical response has been systemically investigated in theory. Our computations reveal that the boron substitution leads to a similar noncentrosymmetric apophysis structure for the boron-substituted coronene in singlet and triplet states. Noticeably, due to the small energy difference of 2.5 kcal mol-1 between the singlet and triplet states, the boron-substituted molecule can easily be switched between the antiferromagnetic (singlet state) and ferromagnetic (triplet state) state by slightly changing the external conditions. Notably, the boron-substituted coronene exhibits a considerably large first hyperpolarizability of 36241 au, because boron substitution yields a raised structure with an intermediate singlet diradical character. Hence, it is expected that this study not only provides new insights for the boron-substituent effect on the structure and properties of graphene but also may promote practical applications of GQDs in the fields of spintronics and nonlinear optics.