Magnetic Coupling Control in Triangulene Dimers

Triangulenes with inherent spin polarization are promising candidates for realizing metal-free magnetism. However, controlling and enhancing the magnetic interactions between the monomers are required for their application in molecular spintronics. Herein, we investigate 24 triangulene dimers using first-principles calculations and demonstrate their tunable magnetic coupling (J), achieving strong J values of up to -128 meV. We further establish a positive correlation between bandgap, electronic coupling and antiferromagnetic interaction. By twisting the molecular fragments, we regulate and boost the J at planar configurations. We realize ferromagnetic coupling in nitrogen-doped triangulene dimers at both planar and largely twisted configurations, representing the first example of ferromagnetic triangulene dimers. We provide a practical strategy for enhancing magnetic coupling and open up new avenues for metal-free ferromagnetism.