Preserving the Edge Magnetism of Zigzag Graphene Nanoribbons by Ethylene Termination: Insight by Clar's Rule

By means of density functional theory computations, we demonstrated that C(2)H(4) is the ideal terminal group for zigzag graphene nanoribbons (zGNRs) in terms of preserving the edge magnetism with experimental feasibility. The C(2)H(4) terminated zGNRs (C(2)H(4)-zGNRs) with pure sp(2) coordinated edges can be stabilized at rather mild experimental conditions, and meanwhile reproduce the electronic and magnetic properties of those hydrogen terminated zGNRs. Interestingly, the electronic structures and relative stability of C(2)H(4)-zGNRs with different edge configurations can be well interpreted by employing the Clar's rule. The multiple edge hyperconjugation interactions are responsible for the enhanced stability of the sp(2) coordinated edges of C(2)H(4)-zGNRs. Moreover, we demonstrated that even pure sp(2) termination is not a guarantee for edge magnetism, for example, C(2)H(2) termination can couple to the π-electron system of zGNRs, and destroy the magnetism. Our studies would pave the way for the application of zGNRs in spintronics.