Engineering Triangulene Building Blocks with Tunable Magnetic Exchange Coupling for All-Carbon-Based Molecular Spintronics

Nanographenes are prospective candidates for spintronicmaterialsthat feature spin-polarization at zigzag edges. Triangulenes possessa distinct rule of large total spins analogous to transition metalelements and may be regarded as artificial atoms. In this work, weexplore design principles using triangulene building blocks to constructnanographene fragments with various shapes and sizes including simpledimeric systems, rhombenes, double-arrow systems, and superzethrenes.Empirical rules for each system relating their sizes and the moststable high spin states are derived, which correspond to the ferromagneticarrangement of their constituent triangulene units. Coupling mechanismsconstituting effective triangulene units are proposed for each systemrationalized by Clar sextet Lewis structures. We find that both thespin multiplicities and exchange energies within 10(0)-l0(2) meV can be modulated by the connection scheme and the bridgegeometry. Our results provide numerical references and valuable empiricalrules of molecular design models for future all-carbon-based spintronics.

Automated summary

In this study, we used triangulene building blocks to design nanographene fragments with different shapes and sizes. We found that these fragments have stable high spin states corresponding to the ferromagnetic arrangement of their constituent triangulene units. By analyzing the structure and bridge geometry, we can modulate the spin multiplicities and exchange energies. These results provide numerical references and valuable empirical rules for the design of all-carbon-based spintronics in the future.