Open-shell nanographenes appear as promising candidates for future applications in spintronics and quantum technologies. A critical aspect to realize this potential is to design and control the magnetic exchange. Here, we reveal the effects of frontier orbital symmetries on the magnetic coupling in diradical nanographenes through scanning probe microscope measurements and different levels of theoretical calculations. In these open-shell nanographenes, the exchange energy exhibits a remarkable variation between 20 and 160 meV. Theoretical calculations reveal that frontier orbital symmetries play a key role in affecting the magnetic coupling on such a large scale. Moreover, a triradical nanographene is demonstrated for investigating the magnetic interaction among three unpaired electrons with unequal magnetic exchange, in agreement with Heisenberg spin model calculations. Our results provide insights into both theoretical design and experimental realization of nanographene materials with different exchange interactions through tuning the orbital symmetry, potentially useful for realizing magnetically operable graphene-based nanomaterials.

开壳纳米石墨烯似乎是自旋电子学和量子技术未来应用的有希望的候选者。实现这一潜力的一个关键方面是设计和控制磁交换。在这里，我们通过扫描探针显微镜测量和不同水平的理论计算揭示了前沿轨道对称性对双自由基纳米石墨烯磁耦合的影响。在这些开壳纳米石墨烯中，交换能在 20 至 160 meV 之间表现出显着变化。理论计算表明，前沿轨道对称性在影响如此大范围的磁耦合方面发挥着关键作用。此外，三基纳米石墨烯被证明可用于研究具有不等磁交换的三个不成对电子之间的磁相互作用，与海森堡自旋模型计算一致。我们的研究结果为通过调整轨道对称性具有不同交换相互作用的纳米石墨烯材料的理论设计和实验实现提供了见解，这对于实现可磁性操作的石墨烯基纳米材料可能有用。