Designer polyradical nanographenes with strong spin entanglement and perturbation resilience via Clar's goblet extension

TL;DR

This study demonstrates the design and synthesis of polyradical nanographenes with strong spin entanglement and resilience, advancing molecular quantum technologies and understanding correlated spin states.

Contribution

It introduces a predictive design strategy for creating highly entangled polyradical nanographenes with tunable spin properties and robustness against external perturbations.

Findings

Synthesized two homologues of Clar goblet nanographenes via surface chemistry.

Both structures exhibit correlated tetraradical character and a many-body singlet ground state.

Magnetic states show resilience to external magnetic perturbations, validated experimentally.

Abstract

Polyradical nanographenes featuring strong spin entanglement and robust many-body spin states against external magnetic perturbations not only enable the exploration of correlated quantum magnetism at the molecular scale, but also constitute promising candidates for developing molecular qubits with chemical tunability and building scalable quantum networks. Here, we employed a predictive design strategy to achieve the on-surface synthesis of two homologues of Clar goblet, C62H22 and C76H26, via lateral and vertical extensions of the parent structure, respectively. Vertical extension increases the number of topologically frustrated zero-energy modes, which scale linearly with the total number of benzene ring rows. In contrast, the lateral extension enhances electron-electron interactions, leading to the emergence of additional radical states beyond those predicted by the topological zero-energy modes. Consequently, both structures exhibit correlated tetraradical character and a many-body singlet ground state as confirmed by multireference theoretical calculations. These magnetic states arise from unique magnetic origins and also display distinct resilience to external perturbations, which can be experimentally validated using nickelocene-functionalized scanning probe techniques. Our work presents a general strategy for rational design of highly entangled polyradical nanographenes with tunable spin numbers and resilience of their many-body spin states to perturbations, opening exciting possibilities for exploring novel correlated spin phases in molecular systems and advancing quantum information technologies.